Straw mulching is a widespread practice for reducing the soil carbon loss caused by erosion.However,the effects of straw mulching on dissolved organic matter(DOM)runoff loss from black soil are not well studied.How st...Straw mulching is a widespread practice for reducing the soil carbon loss caused by erosion.However,the effects of straw mulching on dissolved organic matter(DOM)runoff loss from black soil are not well studied.How straw mulching affects the composition and loss of runoff DOM by changing soil aggregates remains largely unclear.Here,a straw mulching treatment was compared to a no mulching treatment(as a control)on sloping farmland with black soil erosion in Northeast China.We divided the soil into large macroaggregates(>2 mm),small macroaggregates(0.25-2 mm),and microaggregates(<0.25 mm).After five rain events,the effects of straw mulching on the concentration(characterized by dissolved organic carbon(DoC)and composition(analyzed by fluorescence spectroscopy)of runoff and soil aggregate DOM were studied.The results showed that straw mulching reduced the runoff amount by 54.7%.Therefore,although straw mulching increased the average DOc concentration in runoff,it reduced the total runoff DOM loss by 48.3%.The composition of runoff DOM is similar to that of soil,as both contain humic-like acid and protein-like components.With straw mulching treatment,the protein-like components in small macroaggregates accumulated and the protein-like components in runoff declined with rain events.Fluorescence spectroscopy technology may help in understanding the hydrological paths of rain events by capturing the dynamic changes of runoff and soil DOM characteristics.A variation partitioning analysis(VPA)indicated that the DOM concentration and composition of microaggregates explained 68.2%of the change in runoff DOM from no mulching plots,while the change in runoff DOM from straw mulching plots was dominated by small macroaggregates at a rate of 55.1%.Taken together,our results demonstrated that straw mulching reduces the fragmentation of small macroaggregates and the loss of microaggregates,thus effecting DOM compositions in soil and reducing the DOM loss in runoff.These results provide a theoretical basis for reducing carbon loss in sloping farmland.展开更多
Rapid and accurate acquisition of soil organic matter(SOM)information in cultivated land is important for sustainable agricultural development and carbon balance management.This study proposed a novel approach to pred...Rapid and accurate acquisition of soil organic matter(SOM)information in cultivated land is important for sustainable agricultural development and carbon balance management.This study proposed a novel approach to predict SOM with high accuracy using multiyear synthetic remote sensing variables on a monthly scale.We obtained 12 monthly synthetic Sentinel-2 images covering the study area from 2016 to 2021 through the Google Earth Engine(GEE)platform,and reflectance bands and vegetation indices were extracted from these composite images.Then the random forest(RF),support vector machine(SVM)and gradient boosting regression tree(GBRT)models were tested to investigate the difference in SOM prediction accuracy under different combinations of monthly synthetic variables.Results showed that firstly,all monthly synthetic spectral bands of Sentinel-2 showed a significant correlation with SOM(P<0.05)for the months of January,March,April,October,and November.Secondly,in terms of single-monthly composite variables,the prediction accuracy was relatively poor,with the highest R^(2)value of 0.36 being observed in January.When monthly synthetic environmental variables were grouped in accordance with the four quarters of the year,the first quarter and the fourth quarter showed good performance,and any combination of three quarters was similar in estimation accuracy.The overall best performance was observed when all monthly synthetic variables were incorporated into the models.Thirdly,among the three models compared,the RF model was consistently more accurate than the SVM and GBRT models,achieving an R^(2)value of 0.56.Except for band 12 in December,the importance of the remaining bands did not exhibit significant differences.This research offers a new attempt to map SOM with high accuracy and fine spatial resolution based on monthly synthetic Sentinel-2 images.展开更多
Lacustrine shale oil and gas are important fields for unconventional exploration and development in China,and organic-rich shale deposition lays down the critical foundation for hydrocarbon generation.There are two se...Lacustrine shale oil and gas are important fields for unconventional exploration and development in China,and organic-rich shale deposition lays down the critical foundation for hydrocarbon generation.There are two sets of shale,the Dongyuemiao and Da’anzhai Members,in the Ziliujing Formation in the Sichuan Basin.To identify the differential enrichment characteristics of organic matter and clarify its controlling factors,geochemical analyses of organic and inorganic geochemical analyses were performed.The results showed that the total organic carbon content of the Dongyuemiao shale(1.36%)is slightly higher than that of the Da’anzhai shale(0.95%).The enrichment of organic matter in the two shales resulted from the comprehensive controls of paleoproductivity,paleoenvironment,and terrigenous input,but different factors have different effects.In addition,driven by climate,the change in the sulfate concentration in the bottom water further led to the different intensities of bacterial sulfate reduction in early diagenesis.This made a great difference regarding organic matter accumulation in the two members.In general,climate may have played a dominant role in organic matter enrichment in the two sets of shale.展开更多
As a river with more than 3000 reservoirs in its watershed,the Yellow River has been affected by dams not only on the sediment load,but also on the water quality.Water-sediment regulation scheme(WSRS),which has been c...As a river with more than 3000 reservoirs in its watershed,the Yellow River has been affected by dams not only on the sediment load,but also on the water quality.Water-sediment regulation scheme(WSRS),which has been carried out annually in the Yellow River since 2002,is a typical human activity affecting river water quality.Chromophoric dissolved organic matter(CDOM)in river is susceptible to changes in ecological and environmental conditions as well as human activities.Here,we report variations in dissolved organic carbon concentrations,compositions and sources of CDOM in time series samples in the lower Yellow River during WSRS.In addition,a parallel factor fluorescence analysis(PARAFAC)method is applied to identify different fluorescent components in water samples during WRSR,showing four major components including tryptophan-like component(C1),microbial humic-like component(C2),terrestrial humic-like component(C3)and tyrosine-like component(C4).In general,C1 increased after water regulation,while C2 and C3 increased after sediment regulation,indicating that the water and sediment released by the dam have different effects on CDOM compositions.Under the impacts of the dam,source of CDOM in the lower Yellow River is mainly autochthonous related to microbial activities,and is regulated by the terrestrial input during WSRS period.Sediment resuspension inhibits microbial activities and reduces the production of autochthonous CDOM.Overall,human activities especially WSRS,as exemplified here,significantly alter the quality and quantity of CDOM in the lower Yellow River,affecting CDOM dynamics and biogeochemical processes in the estuarine environment.展开更多
The lacustrine organic-rich shale in the Permian Lucaogou(LCG)Formation of the Jimsar Sag,Junggar Basin,is one of the main shale oil plays in China.In this paper,geological and geochemical research techniques were emp...The lacustrine organic-rich shale in the Permian Lucaogou(LCG)Formation of the Jimsar Sag,Junggar Basin,is one of the main shale oil plays in China.In this paper,geological and geochemical research techniques were employed to evaluate the geochemical variability of the lacustrine shale and the pro-duction of organic matter and its preservation conditions.The LcG Formation is characterized by its complex mineral compositions and a wide range of organic matter richness and quality.The presence of high proportions ofβ-carotane and C2g steranes,indicates that the organic matter mainly originated from phytoplankton and aquatic algal-bacterial organisms,especially cyanobacteria.This study found that the productivity of the Lower LCG Member(P2li)was highest,and the Middle LCG Member(P_(2)l_(2))was the lowest.During the deposition of the Lower LCG Member,the lake's bottom water was predominantly a reducing environment,and the degradation of organic matter was largely a result of bacterial sulfate reduction.During the deposition of the Middle and Upper LCG members,the lake's bottom water was mainly oxidizing,and the degradation of organic matter was likely to be caused by aerobic processes.Based on a comprehensive analysis of the origin and production of organic matter,as well as its depo-sitional environment and preservation conditions,two organic matter accumulation models were pro-posed to explain the distribution of the organic-rich shale.In model A,the high influx of volcanic ash released nutrients and brought abundant sulfate into the water,the accumulation of organic matter was mainly controlled by the preservation of organic matter,which was mainly controlled by BsR.In the model B,the influx of volcanic ash was small,organic matter was mainly degraded by oxygen and the accumulation of organic matter is mainly determined by the production of organic matter.展开更多
The geochemical analysis and experimental simulation are comprehensively used to systematically study the hydrocarbon generation material,organic matter enrichment and hydrocarbon generation model of Paleogene source ...The geochemical analysis and experimental simulation are comprehensively used to systematically study the hydrocarbon generation material,organic matter enrichment and hydrocarbon generation model of Paleogene source rock in the Western Qaidam Depression,Qaidam Basin,NW China.Three main factors result in low TOC values of saline lacustrine source rock of the Qaidam Basin:relatively poor nutrient supply inhibits the algal bloom,too fast deposition rate causes the dilution of organic matter,and high organic matter conversion efficiency causes the low residual organic carbon.For this type of hydrogen-rich organic matter,due to the reduction of organic carbon during hydrocarbon generation,TOC needs to be restored based on maturity before evaluating organic matter abundance.The hydrocarbon generation of saline lacustrine source rocks of the Qaidam Basin is from two parts:soluble organic matter and insoluble organic matter.The soluble organic matter is inherited from organisms and preserved in saline lacustrine basins.It generates hydrocarbons during low-maturity stage,and the formed hydrocarbons are rich in complex compounds such as NOS,and undergo secondary cracking to form light components in the later stage;the hydrocarbon generation model of insoluble organic matter conforms to the traditional“Tissot”model,with an oil generation peak corresponding to Ro of 1.0%.展开更多
The hydrocarbon generation effectiveness of lacustrine limestone has been gradually proven. The Da'anzhai Member limestone is the most important Jurassic oil-producing layer in the central Sichuan Basin, and the c...The hydrocarbon generation effectiveness of lacustrine limestone has been gradually proven. The Da'anzhai Member limestone is the most important Jurassic oil-producing layer in the central Sichuan Basin, and the characteristics of limestone organic matter are often overlooked. 175 typical samples of different lithologies from 19 wells were systematically analyzed to determine hydrocarbon generation, controlling factors and formation models by analyses of organic matter, minerals, elements, isotopes and petrography. (1) Lacustrine paleoenvironments can be beneficial for the enrichment of organic matter in limestone. A favorable environment would be a quiet, low-energy zone in a warm and humid climate with an appropriate supply of terrestrial inputs. (2) Lacustrine limestone has a higher organic matter conversion rate, and a lower hydrocarbon generation threshold than argillaceous source rocks, and can be effective source rock. (3) The mud-bearing shell limestone from the forebeach to the lake slope is thick, with a relatively high abundance of organic matter, and its hydrocarbon generation is effective. This study can clarify the effectiveness and enrichment of the limestone organic matters in the study area, and contribute to an understanding of hydrocarbon generation for full-rock system in a lacustrine mixed sedimentary environment.展开更多
The main objective of our study has been to determine the role of deadwood in the shaping of the amount of soil organic matter fractions in mountain forest soils.For this purpose,a climosequence approach comprising no...The main objective of our study has been to determine the role of deadwood in the shaping of the amount of soil organic matter fractions in mountain forest soils.For this purpose,a climosequence approach comprising north(N)and south(S)exposure along the altitudinal gradient(600,800,1000 and 1200 m a.s.l.)was set up.By comparing the properties of decomposing deadwood and those of the soils located directly beneath the decaying wood we drew conclusions about the role of deadwood in the shaping of soil organic matter fractions and soil carbon storage in different climate conditions.The basic properties,enzymatic activity and fractions of soil organic matter(SOM)were determined in deadwood and affected directly by the components released from decaying wood.Heavily decomposed deadwood impacts soil organic matter stabilization more strongly than the less decayed deadwood and the light fraction of SOM is more sensitive to deadwood effects than the heavy fraction regardless of the location in the altitude gradient.Increase in SOM mineral-associated fraction C content is more pronounced in soils under the influence of deadwood located in lower locations of warmer exposure.Nutrients released from decaying wood stimulate the enzymatic activity of soils that are within the range of deadwood influence.展开更多
A set of organic-rich shales of the upper Permian Longtan Formation,which is widely developed in the northeastern part of the Sichuan Basin,is a key formation for the next step of exploration and development.At presen...A set of organic-rich shales of the upper Permian Longtan Formation,which is widely developed in the northeastern part of the Sichuan Basin,is a key formation for the next step of exploration and development.At present,most studies on this set of formations have focused on the reservoir characteristics and reservoir formation mechanism of the shales,and basic studies on the palaeoenvironment and organic matter(OM)enrichment mechanism have not been fully carried out.In this paper,we recovered the sedimentary palaeoenvironment by mineralogical,elemental geochemical and organic geochemical analyses,and explored the enrichment mechanism of OM under the constraints of palaeoenvironmental evolution.The shales can be divided into two stages of sedimentary evolution:compared with the shales of the Lower Longtan Formation,the shales of the Upper Longtan Formation are relatively rich in quartz,poor in clay and carbonate minerals,and the OM type changes from typeⅢto typeⅡ_(2).The depositional environment has undergone a change from sea level rise,from warm and wet climate to dry and cold climate,and from oxygen-poor condition restricted to open reduction environment;the land source input has decreased,the siliceous mineral content has increased,the biological productivity has improved,and the deposition rate has changed from high to low.A depositional model was established for the shales of the Longtan Formation,reflecting the differential reservoir formation pattern of organic matter.For the Lower Longtan Formation shales,the most important factors controlling OM content are terrestrial source input and deposition rate,followed by paleoclimate and paleooxygen conditions.For the Upper Longtan Formation shales,the most important controlling factor is paleo-productivity,followed by sedimentation rate.The depositional model constructed for the Upper and Lower Longtan Formation shales can reproduce the enrichment of organic matter and provide a basis for later exploration and development.展开更多
Early Cambrian shale is an important petroleum source rock around the world.Because of little drilling data and poor seismic data,until recently,organic matter enrichment of the Lower Cambrian Yuertusi and Xishanbulak...Early Cambrian shale is an important petroleum source rock around the world.Because of little drilling data and poor seismic data,until recently,organic matter enrichment of the Lower Cambrian Yuertusi and Xishanbulake formations shale is still an enigma in the Tarim Basin,northwestern China.Total organic carbon(TOC),major and trace element data of Cambrian shale samples from five boreholes have been analyzed to decipher the mechanism of the organic matter enrichment.The results show that the shales deposited in the western restricted intraplatform have much higher TOC contents(3.2%-19.8%,on average 11.0%)than those from the eastern basin(2.2%-10.2%,on average 4.5%).The paleoproductivity proxies(Ba,Ba/Al,P/Al)in the western restricted platform are much higher than those in the eastern basin.The trace element indicators such as V/Cr,Ni/Co,Mo-TOC and Mo_(EF)-U_(EF)suggest an anoxic environment across the basin,but a more restricted environment in the western intraplatform.The paleoproductivity rather than anoxic condition and hydrothermal activity are concluded to have resulted in the differentiation of the organic matter enrichment from the western intraplatform to eastern basin in the early Cambrian shales;the restricted environment was favorable for paleoproductivity and preservation of organic matter.展开更多
The late Paleozoic Fengcheng Formation shale(LPF shale)in the Junggar Basin,NW China,is the oldest alkaline source rock discovered in the world,providing a unique perspective with which to explore organic matter(OM)en...The late Paleozoic Fengcheng Formation shale(LPF shale)in the Junggar Basin,NW China,is the oldest alkaline source rock discovered in the world,providing a unique perspective with which to explore organic matter(OM)enrichment in alkaline lake environments.Combined with the organic carbon isotope profile and paleoenvironmental proxies,this study reveals that the LPF shale was deposited in an arid climate with high salinity and a strong reducing environment,accompanied by frequent volcanic activity.High TOC values are concentrated in two intervals with frequent fluctuations in OM types.A negative excursion due to changes in sedimentary OM source is found in the δ^(13)C_(org) profile.The excursion corresponds to the OM enrichment interval and is accompanied by abnormally high values of Sr/Ba and Sr/Cu.This implies that the extreme arid climate has led to high salinity,resulting in strong reducibility and changes in paleontological assemblages,which in turn controlled the differential enrichment of OM.The Fengcheng Fm.high-quality source rocks are the result of the combined action of climatic events,volcanism,high-salinity water environment and superior hydrocarbon-generating organisms.The results provide new insights into the formation conditions of terrestrial alkaline high-quality source rocks and the factors controlling alkaline OM enrichment.展开更多
Visible and near-infrared(vis-NIR)spectroscopy technique allows for fast and efficient determination of soil organic matter(SOM).However,a prior requirement for the vis-NIR spectroscopy technique to predict SOM is the...Visible and near-infrared(vis-NIR)spectroscopy technique allows for fast and efficient determination of soil organic matter(SOM).However,a prior requirement for the vis-NIR spectroscopy technique to predict SOM is the effective removal of redundant information.Therefore,this study aims to select three wavelength selection strategies for obtaining the spectral response characteristics of SOM.The SOM content and spectral information of 110 soil samples from the Ogan-Kuqa River Oasis were measured under laboratory conditions in July 2017.Pearson correlation analysis was introduced to preselect spectral wavelengths from the preprocessed spectra that passed the 0.01 level significance test.The successive projection algorithm(SPA),competitive adaptive reweighted sampling(CARS),and Boruta algorithm were used to detect the optimal variables from the preselected wavelengths.Finally,partial least squares regression(PLSR)and random forest(RF)models combined with the optimal wavelengths were applied to develop a quantitative estimation model of the SOM content.The results demonstrate that the optimal variables selected were mainly located near the range of spectral absorption features(i.e.,1400.0,1900.0,and 2200.0 nm),and the CARS and Boruta algorithm also selected a few visible wavelengths located in the range of 480.0–510.0 nm.Both models can achieve a more satisfactory prediction of the SOM content,and the RF model had better accuracy than the PLSR model.The SOM content prediction model established by Boruta algorithm combined with the RF model performed best with 23 variables and the model achieved the coefficient of determination(R2)of 0.78 and the residual prediction deviation(RPD)of 2.38.The Boruta algorithm effectively removed redundant information and optimized the optimal wavelengths to improve the prediction accuracy of the estimated SOM content.Therefore,combining vis-NIR spectroscopy with machine learning to estimate SOM content is an important method to improve the accuracy of SOM prediction in arid land.展开更多
The geochemical signatures of fifty-four rock samples and three supplementary drill stem test(DST)oils from the Yacheng-Sanya formations in the central Qiongdongnan Basin(CQB)were analysed.Reconstruction of the early ...The geochemical signatures of fifty-four rock samples and three supplementary drill stem test(DST)oils from the Yacheng-Sanya formations in the central Qiongdongnan Basin(CQB)were analysed.Reconstruction of the early Oligocene-early Miocene(36–16 Ma)palaeovegetation and source analyses of organic matter(OM)were conducted using aliphatic biomarkers in ancient sediments and DST oils.Both the interpreted aquatic and terrigenous OM contributed to the CQB source rocks(SRs)but had varying relative proportions.The four distribution patterns derived from n-alkanes,terpanes,and steranes are representative of four OM composition models of the Yacheng-Sanya SRs,including model A,model B,model C,and model D,which were classified based on the increasing contribution from terrigenous OM relative to aquatic OM.Some terrigenous higher plantderived biomarkers,including oleanane,des-A-oleanane,C_(29)ααα20R sterane,bicadinanes,the C_(19)/(C_(19)+C_(23))tricyclic terpane ratio,and other n-alkane-derived ratios suggest that angiosperms had increased proportions in the palaeoflora from early Oligocene to early Miocene,and the bloom of terrigenous higher plants was observed during deposition of upper Lingshui Formation to lower Sanya Formation.These findings are consistent with the incremental total organic carbon and free hydrocarbons+potential hydrocarbons(S_1+S_2)in the lower Lingshuilower Sanya strata with a significant enrichment of OM in the E_3l_1-N_1s_2 shales.The maturity-and environmentsensitive aliphatic parameters of the CQB SRs and DST oils suggest that all the samples have predominantly reached their early oil-generation windows but have not exceeded the peak oil windows,except for some immature Sanya Formation shales.In addition,most of the OM in the analysed samples was characterised by mixed OM contributions under anoxic to sub-anoxic conditions.Furthermore,terrestrial-dominant SRs were interpreted to have developed mainly in the Lingshui-Sanya formations and were deposited in sub-oxic to oxic environments,compared to the anoxic to sub-anoxic conditions of the Yacheng Formation.展开更多
In the context of global warming and rapid environment change in the Arctic,the supply of organic matter(OM)has increased significantly and a large amount of OM are buried on the Arctic shelf.Studying the fate of OM i...In the context of global warming and rapid environment change in the Arctic,the supply of organic matter(OM)has increased significantly and a large amount of OM are buried on the Arctic shelf.Studying the fate of OM in Arctic shelf sediments is crucial to understanding the global carbon sink.As a marginal sea of the Arctic Ocean,the Chukchi Sea is one of the most critical areas where OM is buried.Based on the surface sediment samples collected during the sixth Chinese National Arctic Research Expedition in the summer of 2014 and the SinoRussian joint Arctic Research Expedition in the summer of 2016,this study takes amino acids(AAs)as the primary tool to explore the source and degradation of OM in the surface sediments of the Chukchi Sea.This study shows that total hydrolyzable amino acid(THAA)concentrations(dry weight)are high,with a mean value of(32.7±15.8)μmol/g.Their spatial distribution is related to primary productivity,hydrodynamic conditions,sediment properties and other factors.The source of OM in the surface sediments of the Chukchi Sea is dominated by diatom-dominated marine productivity,with some input from terrestrial sources.Bacteria,as the main source of the D-enantiomer of AA(D-AA),not only have transforming effect on OM,but their cell walls and remnants likewise supply the OM pool.Based on a series of diagenetic indicators,we conclude that the OM in the surface sediments of the Chukchi Sea has undergone extensive degradation[DI(degradation index)=-0.59±0.44],and the degradation degree in the slope is higher than that in the shelf.This study uses AA to explore the sources and degradation of OM in the sediments of the Chukchi Sea,which facilitates our understanding of OM transport and transformation on the Arctic shelf.展开更多
Colored dissolved organic matter(CDOM)is a crucial constituent that affects the optical absorption properties of seawater.Owing to the relatively limited measured data on the spatial distribution characteristics of CD...Colored dissolved organic matter(CDOM)is a crucial constituent that affects the optical absorption properties of seawater.Owing to the relatively limited measured data on the spatial distribution characteristics of CDOM in the tropical eastern Indian Ocean,this study analyzes the optical absorption characteristics of CDOM in the southeast Indian Ocean using the data collected during four seasons from 2013 to 2017.This work also systematically describes the seasonal horizontal and vertical distribution characteristics of CDOM in this area and conducts a preliminary analysis of the relevant factors affecting CDOM absorption characteristics in this region.Results indicate that the CDOM ag(440)during summer was remarkably lower than that in the coastal waters of Europe and coastal waters of China but slightly higher than that in the western and southeast Pacific.The spatial distribution of surface CDOM shows remarkable seasonal differences,and the spatial distribution characteristics of CDOM in the 5°S,92°E region differ between spring/summer and autumn/winter.The values of ag(400)and ag(440)are weak/strong at a surface/subsurface level of 100 m,with differences found between summer and winter.The correlation of CDOM with temperature,salinity,and chlorophyll-a concentration is relatively low,indicating that CDOM is an independent driving mechanism influenced by phytoplankton degradation,photobleaching,and water mixing.展开更多
Colored dissolved organic matter(CDOM)is an important optically active substance in marine environment.Its biochemical conservatism makes it an important indicator to offshore pollution process.Monitoring the content,...Colored dissolved organic matter(CDOM)is an important optically active substance in marine environment.Its biochemical conservatism makes it an important indicator to offshore pollution process.Monitoring the content,composition,and diffusion process of CDOM is a good approach to analyze the terrestrial input,optical properties,and ecological environment of offshore areas.The spatiotemporal characteristics of CDOM around the Leizhou Peninsula were analyzed based on field observation data collected in the autumn 2020 and spring 2021,and an empirical inversion model of the ag(355)(absorption coefficient at 355 nm)and spectral slope(Sg)(g stands for gelbstoff/gilvin,which is called CDOM)based on Sentinel-3A ocean and land color instrument(OLCI)images was constructed.The results show(1)the order of average ag(355)value around the Leizhou Peninsula was east coast(0.503/m)>Qiongzhou Strait(0.502/m)>west coast(0.365/m);(2)the best band combinations of CDOM inversion in spring and autumn were(B4+B11)/B3 and(B7-B1)/B6(B stands for the band of spectral images),and the final inversion results are close to the measured results,indicating that the model has good accuracy;(3)the S_(g)value of the CDOM absorption spectrum was fitted to the hyperbolicexponential model.The fitting accuracy of the model was higher than those of the exponential model and the hyperbolic model,and the best S_(g)inversion model was constructed by selecting Sg(275-295)and Sg(250-295)in spring and autumn;(4)the spatial distributions of ag(355)and S_(g)were inverted,and CDOM in the waters around the Leizhou Peninsula originated from terrestrial organic matter carried by coastal aquaculture zones and runoff in the northeast Zhanjiang and the northern Beibu Gulf.展开更多
The terrigenously-dominated marine shales which were deposited in the lower Eocene Pinghu Formation were thought to be a potential source rock in the Xihu Depression of the East China Sea Shelf Basin.However,the excep...The terrigenously-dominated marine shales which were deposited in the lower Eocene Pinghu Formation were thought to be a potential source rock in the Xihu Depression of the East China Sea Shelf Basin.However,the exceptionally high total organic carbon content(TOC,>6%on average)of the tidal sand ridge samples was not compatible with their sedimentary environment,indicating coal-bearing sedimentary debris may have been transferred from the coast to the ocean.In this study,new sights into the origins and supply of organic materials in the coastal environment were proposed in the neritic organic matter of the Eocene Pinghu Formation.A discriminant model was developed using plynofacies analysis data to pinpoint the source of organic materials in marine source rocks.The discrimination results suggested that marine mudstones were associated with tidal flat mudstones rather than deltaic ones.The biomarker characteristics of mudstones deposited in various environments support this assertion,indicating that the supply of plant materials in tidal flats is the primary organic matter source for the marine environment.The organic matter abundance was elevated in tidal flats due to their superior preservation conditions.Additionally,the lithological assemblage of tidal flats suggests that tidal currents can scour marshes and then transport dispersed terrigenous organic materials to neritic areas.These findings indicate that coal-bearing sedimentary debris was likely transferred from the coast to the ocean,and tidal currents are thought to be the dominant mechanism driving organic matter from the tidal to the marine environment.展开更多
According to the theory of sequence stratigraphy based on continental transgressive-regressive(T-R)cycles,a 500 m continuous core taken from the second member of Kongdian Formation(Kong 2 Member)of Paleogene in Well G...According to the theory of sequence stratigraphy based on continental transgressive-regressive(T-R)cycles,a 500 m continuous core taken from the second member of Kongdian Formation(Kong 2 Member)of Paleogene in Well G108-8 in the Cangdong Sag,Bohai Bay Basin,was tested and analyzed to clarify the high-frequency cycles of deep-water fine-grained sedimentary rocks in lacustrine basins.A logging vectorgraph in red pattern was plotted,and then a sequence stratigraphic framework with five-order high-frequency cycles was formed for the fine-grained sedimentary rocks in the Kong 2 Member.The high-frequency cycles of fine-grained sedimentary rocks were characterized by using different methods and at different scales.It is found that the fifth-order T cycles record a high content of terrigenous clastic minerals,a low paleosalinity,a relatively humid paleoclimate and a high density of laminae,while the fifth-order R cycles display a high content of carbonate minerals,a high paleosalinity,a dry paleoclimate and a low density of laminae.The changes in high-frequency cycles controlled the abundance and type of organic matter.The T cycles exhibit relatively high TOC and abundant endogenous organic matters in water in addition to terrigenous organic matters,implying a high primary productivity of lake for the generation and enrichment of shale oil.展开更多
The major enrichment type of shale oil in the Chang 7_(3) shale of Upper Triassic Yanchang Formation in the Ordos Basin is unknown.This paper analyzes the organic matter transformation ratio,hydrocarbon expulsion effi...The major enrichment type of shale oil in the Chang 7_(3) shale of Upper Triassic Yanchang Formation in the Ordos Basin is unknown.This paper analyzes the organic matter transformation ratio,hydrocarbon expulsion efficiency and roof/floor sealing conditions of the Chang 7_(3) shale,and evaluates the major enrichment type of shale oil in this interval.The average organic matter transformation ratio of the Chang 7_(3) shale is about 45%;in other words,more than 50%of the organic matters have not transformed to hydrocarbons,and the lower the maturity,the greater the proportion of untransformed organic matters.The cumulative hydrocarbon expulsion efficiency of the transformed hydrocarbon is 27.5% on average,and the total proportion of untransformed organic matters plus retained hydrocarbons is greater than 70%.The relative hydrocarbon expulsion efficiency of the Chang 7_(3) shale is 60%on average,that is,about 40% of hydrocarbons retain in the shale.The Chang 7_(3) shale corresponds to Chang 7_(1+2) and Chang 8 sandstones as the roof and floor,respectively,and is further overlaid by Chang 6 shale,where extensive low porosity and low permeability–tight oil reservoirs have formed in the parts with relatively good porosity and permeability.Moreover,the Chang 7_(3) shale is tested to be in a negative pressure system(the pressure coefficient of 0.80–0.85).Therefore,the roof/floor sealing conditions of the Chang 7_(3) shale are poor.The retained hydrocarbons appear mostly in absorbed status,with low mobility.It is concluded that the medium–high mature shale oil is not the major enrichment type of shale oil in the Chang 7_(3) shale,but there may be enrichment opportunity for shale oil with good mobility in the areas where the sealing conditions are good without faults and fractures and oil reservoirs are formed off Chang 7_(1+2),Chang 6 and Chang 8.Furthermore,low–medium mature shale oil is believed to have great potential and is the major enrichment type of shale oil in the Chang 7_(3) shale.It is recommended to prepare relevant in-situ conversion technologies by pilot test and figure out the resource availability and distribution.展开更多
An improvised auger sediment sampler was used to collect sediments at shallow depths from two wetlands in the Northern Bida Basin for laboratory studies in order to ascertain the impact on the chemical quality of grou...An improvised auger sediment sampler was used to collect sediments at shallow depths from two wetlands in the Northern Bida Basin for laboratory studies in order to ascertain the impact on the chemical quality of groundwater within these two studied locations. The dissolved organic carbon content of water is an important component of the geochemical cycling of elements capable of affecting groundwater quality. The sediments which serve as a conduit and pathways for the elements’ transport depending on the characteristics of the particle sizes are to be considered in the evaluation of contaminant mobility within the pathways. Representative cored sediment samples were collected and their particle size characterization and chemical analysis for Organic Matter (OM), Organic Carbon (OC) and Moisture Content (MC) were carried out. The hydrometer results show that the sediment particle sizes are in the order of sand > clay > silt in both locations with few exceptions. This represents the geology of the area (sandstone). The Mean values of 1.14% and 1.98% of OC and OM respectively were recorded in the sediment samples collected in parts of Ebgako. In contrast, 1.72% and 2.97% mean values were recorded in sediments collected in part of Bida for OC and OM respectively. The values of the OC and OM in the sediments from the two wetlands are low and may have been dissolved along the groundwater pathways to the aquifer. Other physicochemical parameters analysed in the sediments showed poor correlation. OM and OC were strongly positively correlated and showed an R<sup>2</sup> value of 1 and 0.9 respectively for parts of the Bida and Egbako sheets. There is low acidity of the sediments from the two study locations with a mean pH value of 5.64 and 5.13 respectively for Egbako and Bida. The low acidic nature of the sediments and the OM and OC composition have the potential to influence biogeochemical processes in the sediments and can affect the chemical quality of the groundwater in these two study locations.展开更多
基金supported by the National Key Research and Development Project of China (2022YFD1601102)the Key R&D Plan of Heilongjiang Province, China (JD22B002)+1 种基金the Program on Industrial Technology System of National Soybean, China (CARS-04-PS17)the UNDP Project, China (cpr/21/401) and the National Natural Science Foundation of China (41771284)
文摘Straw mulching is a widespread practice for reducing the soil carbon loss caused by erosion.However,the effects of straw mulching on dissolved organic matter(DOM)runoff loss from black soil are not well studied.How straw mulching affects the composition and loss of runoff DOM by changing soil aggregates remains largely unclear.Here,a straw mulching treatment was compared to a no mulching treatment(as a control)on sloping farmland with black soil erosion in Northeast China.We divided the soil into large macroaggregates(>2 mm),small macroaggregates(0.25-2 mm),and microaggregates(<0.25 mm).After five rain events,the effects of straw mulching on the concentration(characterized by dissolved organic carbon(DoC)and composition(analyzed by fluorescence spectroscopy)of runoff and soil aggregate DOM were studied.The results showed that straw mulching reduced the runoff amount by 54.7%.Therefore,although straw mulching increased the average DOc concentration in runoff,it reduced the total runoff DOM loss by 48.3%.The composition of runoff DOM is similar to that of soil,as both contain humic-like acid and protein-like components.With straw mulching treatment,the protein-like components in small macroaggregates accumulated and the protein-like components in runoff declined with rain events.Fluorescence spectroscopy technology may help in understanding the hydrological paths of rain events by capturing the dynamic changes of runoff and soil DOM characteristics.A variation partitioning analysis(VPA)indicated that the DOM concentration and composition of microaggregates explained 68.2%of the change in runoff DOM from no mulching plots,while the change in runoff DOM from straw mulching plots was dominated by small macroaggregates at a rate of 55.1%.Taken together,our results demonstrated that straw mulching reduces the fragmentation of small macroaggregates and the loss of microaggregates,thus effecting DOM compositions in soil and reducing the DOM loss in runoff.These results provide a theoretical basis for reducing carbon loss in sloping farmland.
基金National Key Research and Development Program of China(2022YFB3903302 and 2021YFC1809104)。
文摘Rapid and accurate acquisition of soil organic matter(SOM)information in cultivated land is important for sustainable agricultural development and carbon balance management.This study proposed a novel approach to predict SOM with high accuracy using multiyear synthetic remote sensing variables on a monthly scale.We obtained 12 monthly synthetic Sentinel-2 images covering the study area from 2016 to 2021 through the Google Earth Engine(GEE)platform,and reflectance bands and vegetation indices were extracted from these composite images.Then the random forest(RF),support vector machine(SVM)and gradient boosting regression tree(GBRT)models were tested to investigate the difference in SOM prediction accuracy under different combinations of monthly synthetic variables.Results showed that firstly,all monthly synthetic spectral bands of Sentinel-2 showed a significant correlation with SOM(P<0.05)for the months of January,March,April,October,and November.Secondly,in terms of single-monthly composite variables,the prediction accuracy was relatively poor,with the highest R^(2)value of 0.36 being observed in January.When monthly synthetic environmental variables were grouped in accordance with the four quarters of the year,the first quarter and the fourth quarter showed good performance,and any combination of three quarters was similar in estimation accuracy.The overall best performance was observed when all monthly synthetic variables were incorporated into the models.Thirdly,among the three models compared,the RF model was consistently more accurate than the SVM and GBRT models,achieving an R^(2)value of 0.56.Except for band 12 in December,the importance of the remaining bands did not exhibit significant differences.This research offers a new attempt to map SOM with high accuracy and fine spatial resolution based on monthly synthetic Sentinel-2 images.
基金This work was funded by the National Natural Science Foundation of China(Grant No.42002139 and U20B6001)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA14010404).
文摘Lacustrine shale oil and gas are important fields for unconventional exploration and development in China,and organic-rich shale deposition lays down the critical foundation for hydrocarbon generation.There are two sets of shale,the Dongyuemiao and Da’anzhai Members,in the Ziliujing Formation in the Sichuan Basin.To identify the differential enrichment characteristics of organic matter and clarify its controlling factors,geochemical analyses of organic and inorganic geochemical analyses were performed.The results showed that the total organic carbon content of the Dongyuemiao shale(1.36%)is slightly higher than that of the Da’anzhai shale(0.95%).The enrichment of organic matter in the two shales resulted from the comprehensive controls of paleoproductivity,paleoenvironment,and terrigenous input,but different factors have different effects.In addition,driven by climate,the change in the sulfate concentration in the bottom water further led to the different intensities of bacterial sulfate reduction in early diagenesis.This made a great difference regarding organic matter accumulation in the two members.In general,climate may have played a dominant role in organic matter enrichment in the two sets of shale.
基金supported by the National Natural Science Foundation of China(Nos.41876077,41376085).
文摘As a river with more than 3000 reservoirs in its watershed,the Yellow River has been affected by dams not only on the sediment load,but also on the water quality.Water-sediment regulation scheme(WSRS),which has been carried out annually in the Yellow River since 2002,is a typical human activity affecting river water quality.Chromophoric dissolved organic matter(CDOM)in river is susceptible to changes in ecological and environmental conditions as well as human activities.Here,we report variations in dissolved organic carbon concentrations,compositions and sources of CDOM in time series samples in the lower Yellow River during WSRS.In addition,a parallel factor fluorescence analysis(PARAFAC)method is applied to identify different fluorescent components in water samples during WRSR,showing four major components including tryptophan-like component(C1),microbial humic-like component(C2),terrestrial humic-like component(C3)and tyrosine-like component(C4).In general,C1 increased after water regulation,while C2 and C3 increased after sediment regulation,indicating that the water and sediment released by the dam have different effects on CDOM compositions.Under the impacts of the dam,source of CDOM in the lower Yellow River is mainly autochthonous related to microbial activities,and is regulated by the terrestrial input during WSRS period.Sediment resuspension inhibits microbial activities and reduces the production of autochthonous CDOM.Overall,human activities especially WSRS,as exemplified here,significantly alter the quality and quantity of CDOM in the lower Yellow River,affecting CDOM dynamics and biogeochemical processes in the estuarine environment.
基金supported by National Science Foundation for Young Scientists of China(Grant 41702143)Major basic science and technology projects of CNPC(2021DJ0206-03)。
文摘The lacustrine organic-rich shale in the Permian Lucaogou(LCG)Formation of the Jimsar Sag,Junggar Basin,is one of the main shale oil plays in China.In this paper,geological and geochemical research techniques were employed to evaluate the geochemical variability of the lacustrine shale and the pro-duction of organic matter and its preservation conditions.The LcG Formation is characterized by its complex mineral compositions and a wide range of organic matter richness and quality.The presence of high proportions ofβ-carotane and C2g steranes,indicates that the organic matter mainly originated from phytoplankton and aquatic algal-bacterial organisms,especially cyanobacteria.This study found that the productivity of the Lower LCG Member(P2li)was highest,and the Middle LCG Member(P_(2)l_(2))was the lowest.During the deposition of the Lower LCG Member,the lake's bottom water was predominantly a reducing environment,and the degradation of organic matter was largely a result of bacterial sulfate reduction.During the deposition of the Middle and Upper LCG members,the lake's bottom water was mainly oxidizing,and the degradation of organic matter was likely to be caused by aerobic processes.Based on a comprehensive analysis of the origin and production of organic matter,as well as its depo-sitional environment and preservation conditions,two organic matter accumulation models were pro-posed to explain the distribution of the organic-rich shale.In model A,the high influx of volcanic ash released nutrients and brought abundant sulfate into the water,the accumulation of organic matter was mainly controlled by the preservation of organic matter,which was mainly controlled by BsR.In the model B,the influx of volcanic ash was small,organic matter was mainly degraded by oxygen and the accumulation of organic matter is mainly determined by the production of organic matter.
基金Supported by the PetroChina Science and Technology Project(2021DJ1808).
文摘The geochemical analysis and experimental simulation are comprehensively used to systematically study the hydrocarbon generation material,organic matter enrichment and hydrocarbon generation model of Paleogene source rock in the Western Qaidam Depression,Qaidam Basin,NW China.Three main factors result in low TOC values of saline lacustrine source rock of the Qaidam Basin:relatively poor nutrient supply inhibits the algal bloom,too fast deposition rate causes the dilution of organic matter,and high organic matter conversion efficiency causes the low residual organic carbon.For this type of hydrogen-rich organic matter,due to the reduction of organic carbon during hydrocarbon generation,TOC needs to be restored based on maturity before evaluating organic matter abundance.The hydrocarbon generation of saline lacustrine source rocks of the Qaidam Basin is from two parts:soluble organic matter and insoluble organic matter.The soluble organic matter is inherited from organisms and preserved in saline lacustrine basins.It generates hydrocarbons during low-maturity stage,and the formed hydrocarbons are rich in complex compounds such as NOS,and undergo secondary cracking to form light components in the later stage;the hydrocarbon generation model of insoluble organic matter conforms to the traditional“Tissot”model,with an oil generation peak corresponding to Ro of 1.0%.
基金supported by the National Natural Science Foundation of China(Grants 41902131 and 41821002 and 4169130014).
文摘The hydrocarbon generation effectiveness of lacustrine limestone has been gradually proven. The Da'anzhai Member limestone is the most important Jurassic oil-producing layer in the central Sichuan Basin, and the characteristics of limestone organic matter are often overlooked. 175 typical samples of different lithologies from 19 wells were systematically analyzed to determine hydrocarbon generation, controlling factors and formation models by analyses of organic matter, minerals, elements, isotopes and petrography. (1) Lacustrine paleoenvironments can be beneficial for the enrichment of organic matter in limestone. A favorable environment would be a quiet, low-energy zone in a warm and humid climate with an appropriate supply of terrestrial inputs. (2) Lacustrine limestone has a higher organic matter conversion rate, and a lower hydrocarbon generation threshold than argillaceous source rocks, and can be effective source rock. (3) The mud-bearing shell limestone from the forebeach to the lake slope is thick, with a relatively high abundance of organic matter, and its hydrocarbon generation is effective. This study can clarify the effectiveness and enrichment of the limestone organic matters in the study area, and contribute to an understanding of hydrocarbon generation for full-rock system in a lacustrine mixed sedimentary environment.
基金financed by the National Science Centre,Poland:decision no.DEC 2020/39/B/NZ9/00372
文摘The main objective of our study has been to determine the role of deadwood in the shaping of the amount of soil organic matter fractions in mountain forest soils.For this purpose,a climosequence approach comprising north(N)and south(S)exposure along the altitudinal gradient(600,800,1000 and 1200 m a.s.l.)was set up.By comparing the properties of decomposing deadwood and those of the soils located directly beneath the decaying wood we drew conclusions about the role of deadwood in the shaping of soil organic matter fractions and soil carbon storage in different climate conditions.The basic properties,enzymatic activity and fractions of soil organic matter(SOM)were determined in deadwood and affected directly by the components released from decaying wood.Heavily decomposed deadwood impacts soil organic matter stabilization more strongly than the less decayed deadwood and the light fraction of SOM is more sensitive to deadwood effects than the heavy fraction regardless of the location in the altitude gradient.Increase in SOM mineral-associated fraction C content is more pronounced in soils under the influence of deadwood located in lower locations of warmer exposure.Nutrients released from decaying wood stimulate the enzymatic activity of soils that are within the range of deadwood influence.
基金the General Fund of the National Natural Science Foundation of China(Grant No.42272184)National Natural Science Foundation of China(Grant Nos.42230311 and 91755215)for their support of this paper。
文摘A set of organic-rich shales of the upper Permian Longtan Formation,which is widely developed in the northeastern part of the Sichuan Basin,is a key formation for the next step of exploration and development.At present,most studies on this set of formations have focused on the reservoir characteristics and reservoir formation mechanism of the shales,and basic studies on the palaeoenvironment and organic matter(OM)enrichment mechanism have not been fully carried out.In this paper,we recovered the sedimentary palaeoenvironment by mineralogical,elemental geochemical and organic geochemical analyses,and explored the enrichment mechanism of OM under the constraints of palaeoenvironmental evolution.The shales can be divided into two stages of sedimentary evolution:compared with the shales of the Lower Longtan Formation,the shales of the Upper Longtan Formation are relatively rich in quartz,poor in clay and carbonate minerals,and the OM type changes from typeⅢto typeⅡ_(2).The depositional environment has undergone a change from sea level rise,from warm and wet climate to dry and cold climate,and from oxygen-poor condition restricted to open reduction environment;the land source input has decreased,the siliceous mineral content has increased,the biological productivity has improved,and the deposition rate has changed from high to low.A depositional model was established for the shales of the Longtan Formation,reflecting the differential reservoir formation pattern of organic matter.For the Lower Longtan Formation shales,the most important factors controlling OM content are terrestrial source input and deposition rate,followed by paleoclimate and paleooxygen conditions.For the Upper Longtan Formation shales,the most important controlling factor is paleo-productivity,followed by sedimentation rate.The depositional model constructed for the Upper and Lower Longtan Formation shales can reproduce the enrichment of organic matter and provide a basis for later exploration and development.
基金partly supported by the National Natural Science Foundation of China(Grant No.42241206,91955204)the Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(Grant No.4224100017,2020CX010101)。
文摘Early Cambrian shale is an important petroleum source rock around the world.Because of little drilling data and poor seismic data,until recently,organic matter enrichment of the Lower Cambrian Yuertusi and Xishanbulake formations shale is still an enigma in the Tarim Basin,northwestern China.Total organic carbon(TOC),major and trace element data of Cambrian shale samples from five boreholes have been analyzed to decipher the mechanism of the organic matter enrichment.The results show that the shales deposited in the western restricted intraplatform have much higher TOC contents(3.2%-19.8%,on average 11.0%)than those from the eastern basin(2.2%-10.2%,on average 4.5%).The paleoproductivity proxies(Ba,Ba/Al,P/Al)in the western restricted platform are much higher than those in the eastern basin.The trace element indicators such as V/Cr,Ni/Co,Mo-TOC and Mo_(EF)-U_(EF)suggest an anoxic environment across the basin,but a more restricted environment in the western intraplatform.The paleoproductivity rather than anoxic condition and hydrothermal activity are concluded to have resulted in the differentiation of the organic matter enrichment from the western intraplatform to eastern basin in the early Cambrian shales;the restricted environment was favorable for paleoproductivity and preservation of organic matter.
基金supported by the National Natural Science Foundation of China(Grant Nos.41872128,42202133)the Strategic Cooperation Technology Projects of the CNPC and CUPB(Grant No.ZLZX2020-01-05)。
文摘The late Paleozoic Fengcheng Formation shale(LPF shale)in the Junggar Basin,NW China,is the oldest alkaline source rock discovered in the world,providing a unique perspective with which to explore organic matter(OM)enrichment in alkaline lake environments.Combined with the organic carbon isotope profile and paleoenvironmental proxies,this study reveals that the LPF shale was deposited in an arid climate with high salinity and a strong reducing environment,accompanied by frequent volcanic activity.High TOC values are concentrated in two intervals with frequent fluctuations in OM types.A negative excursion due to changes in sedimentary OM source is found in the δ^(13)C_(org) profile.The excursion corresponds to the OM enrichment interval and is accompanied by abnormally high values of Sr/Ba and Sr/Cu.This implies that the extreme arid climate has led to high salinity,resulting in strong reducibility and changes in paleontological assemblages,which in turn controlled the differential enrichment of OM.The Fengcheng Fm.high-quality source rocks are the result of the combined action of climatic events,volcanism,high-salinity water environment and superior hydrocarbon-generating organisms.The results provide new insights into the formation conditions of terrestrial alkaline high-quality source rocks and the factors controlling alkaline OM enrichment.
基金supported by the Key Project of Natural Science Foundation of Xinjiang Uygur Autonomous Region,China(2021D01D06)the National Natural Science Foundation of China(41961059)。
文摘Visible and near-infrared(vis-NIR)spectroscopy technique allows for fast and efficient determination of soil organic matter(SOM).However,a prior requirement for the vis-NIR spectroscopy technique to predict SOM is the effective removal of redundant information.Therefore,this study aims to select three wavelength selection strategies for obtaining the spectral response characteristics of SOM.The SOM content and spectral information of 110 soil samples from the Ogan-Kuqa River Oasis were measured under laboratory conditions in July 2017.Pearson correlation analysis was introduced to preselect spectral wavelengths from the preprocessed spectra that passed the 0.01 level significance test.The successive projection algorithm(SPA),competitive adaptive reweighted sampling(CARS),and Boruta algorithm were used to detect the optimal variables from the preselected wavelengths.Finally,partial least squares regression(PLSR)and random forest(RF)models combined with the optimal wavelengths were applied to develop a quantitative estimation model of the SOM content.The results demonstrate that the optimal variables selected were mainly located near the range of spectral absorption features(i.e.,1400.0,1900.0,and 2200.0 nm),and the CARS and Boruta algorithm also selected a few visible wavelengths located in the range of 480.0–510.0 nm.Both models can achieve a more satisfactory prediction of the SOM content,and the RF model had better accuracy than the PLSR model.The SOM content prediction model established by Boruta algorithm combined with the RF model performed best with 23 variables and the model achieved the coefficient of determination(R2)of 0.78 and the residual prediction deviation(RPD)of 2.38.The Boruta algorithm effectively removed redundant information and optimized the optimal wavelengths to improve the prediction accuracy of the estimated SOM content.Therefore,combining vis-NIR spectroscopy with machine learning to estimate SOM content is an important method to improve the accuracy of SOM prediction in arid land.
基金The National Natural Science Foundation of China under contract No.41872131。
文摘The geochemical signatures of fifty-four rock samples and three supplementary drill stem test(DST)oils from the Yacheng-Sanya formations in the central Qiongdongnan Basin(CQB)were analysed.Reconstruction of the early Oligocene-early Miocene(36–16 Ma)palaeovegetation and source analyses of organic matter(OM)were conducted using aliphatic biomarkers in ancient sediments and DST oils.Both the interpreted aquatic and terrigenous OM contributed to the CQB source rocks(SRs)but had varying relative proportions.The four distribution patterns derived from n-alkanes,terpanes,and steranes are representative of four OM composition models of the Yacheng-Sanya SRs,including model A,model B,model C,and model D,which were classified based on the increasing contribution from terrigenous OM relative to aquatic OM.Some terrigenous higher plantderived biomarkers,including oleanane,des-A-oleanane,C_(29)ααα20R sterane,bicadinanes,the C_(19)/(C_(19)+C_(23))tricyclic terpane ratio,and other n-alkane-derived ratios suggest that angiosperms had increased proportions in the palaeoflora from early Oligocene to early Miocene,and the bloom of terrigenous higher plants was observed during deposition of upper Lingshui Formation to lower Sanya Formation.These findings are consistent with the incremental total organic carbon and free hydrocarbons+potential hydrocarbons(S_1+S_2)in the lower Lingshuilower Sanya strata with a significant enrichment of OM in the E_3l_1-N_1s_2 shales.The maturity-and environmentsensitive aliphatic parameters of the CQB SRs and DST oils suggest that all the samples have predominantly reached their early oil-generation windows but have not exceeded the peak oil windows,except for some immature Sanya Formation shales.In addition,most of the OM in the analysed samples was characterised by mixed OM contributions under anoxic to sub-anoxic conditions.Furthermore,terrestrial-dominant SRs were interpreted to have developed mainly in the Lingshui-Sanya formations and were deposited in sub-oxic to oxic environments,compared to the anoxic to sub-anoxic conditions of the Yacheng Formation.
基金The Open Research Fund of State Key Laboratory of Estuarine and Coastal Research under contract No.SKLECKF202109the National Natural Science Foundation of China under contract Nos 42076242,41906200,41941013,and 42176039+4 种基金the National Key Research and Development Program of China under contract No.2019YFE0120900the Oceanic Interdisciplinary Program of Shanghai Jiao Tong University under contract No.SL2021MS020the Shanghai Pilot Program for Basic Research—Shanghai Jiao Tong University under contract No.21TQ1400201the Shanghai Frontiers Science Center of Polar Science under contract No.SCOPSthe Ministry of Sciences and Education of the Russian Federation under contract No.project 121021700342-9。
文摘In the context of global warming and rapid environment change in the Arctic,the supply of organic matter(OM)has increased significantly and a large amount of OM are buried on the Arctic shelf.Studying the fate of OM in Arctic shelf sediments is crucial to understanding the global carbon sink.As a marginal sea of the Arctic Ocean,the Chukchi Sea is one of the most critical areas where OM is buried.Based on the surface sediment samples collected during the sixth Chinese National Arctic Research Expedition in the summer of 2014 and the SinoRussian joint Arctic Research Expedition in the summer of 2016,this study takes amino acids(AAs)as the primary tool to explore the source and degradation of OM in the surface sediments of the Chukchi Sea.This study shows that total hydrolyzable amino acid(THAA)concentrations(dry weight)are high,with a mean value of(32.7±15.8)μmol/g.Their spatial distribution is related to primary productivity,hydrodynamic conditions,sediment properties and other factors.The source of OM in the surface sediments of the Chukchi Sea is dominated by diatom-dominated marine productivity,with some input from terrestrial sources.Bacteria,as the main source of the D-enantiomer of AA(D-AA),not only have transforming effect on OM,but their cell walls and remnants likewise supply the OM pool.Based on a series of diagenetic indicators,we conclude that the OM in the surface sediments of the Chukchi Sea has undergone extensive degradation[DI(degradation index)=-0.59±0.44],and the degradation degree in the slope is higher than that in the shelf.This study uses AA to explore the sources and degradation of OM in the sediments of the Chukchi Sea,which facilitates our understanding of OM transport and transformation on the Arctic shelf.
基金The study has received support from the National Natural Science Foundation of China(No.41906182)the National Program on Global Change and Air-Sea Interactions(No.GASI-01-WIND-STwin)the Program of Shandong Key Laboratory of Marine Ecological Environment and Disaster Prevention and Mitigation(Nos.202102,202209 and 201901).
文摘Colored dissolved organic matter(CDOM)is a crucial constituent that affects the optical absorption properties of seawater.Owing to the relatively limited measured data on the spatial distribution characteristics of CDOM in the tropical eastern Indian Ocean,this study analyzes the optical absorption characteristics of CDOM in the southeast Indian Ocean using the data collected during four seasons from 2013 to 2017.This work also systematically describes the seasonal horizontal and vertical distribution characteristics of CDOM in this area and conducts a preliminary analysis of the relevant factors affecting CDOM absorption characteristics in this region.Results indicate that the CDOM ag(440)during summer was remarkably lower than that in the coastal waters of Europe and coastal waters of China but slightly higher than that in the western and southeast Pacific.The spatial distribution of surface CDOM shows remarkable seasonal differences,and the spatial distribution characteristics of CDOM in the 5°S,92°E region differ between spring/summer and autumn/winter.The values of ag(400)and ag(440)are weak/strong at a surface/subsurface level of 100 m,with differences found between summer and winter.The correlation of CDOM with temperature,salinity,and chlorophyll-a concentration is relatively low,indicating that CDOM is an independent driving mechanism influenced by phytoplankton degradation,photobleaching,and water mixing.
基金Supported by the Key Projects of the Guangdong Education Department(No.2019KZDXM019)the Fund of Southern Marine Science and Engineering Guangdong Laboratory(Zhanjiang)(No.ZJW-2019-08)+3 种基金the High-level Marine Discipline Team Project of Guangdong Ocean University(No.002026002009)the Guangdong Graduate Academic Forum Project(No.230420003)the“First Class”Discipline Construction Platform Project in 2019 of Guangdong Ocean University(No.231419026)the Innovation Projects of Colleges and Universities in Guangdong Province(No.2021KQNCX028)。
文摘Colored dissolved organic matter(CDOM)is an important optically active substance in marine environment.Its biochemical conservatism makes it an important indicator to offshore pollution process.Monitoring the content,composition,and diffusion process of CDOM is a good approach to analyze the terrestrial input,optical properties,and ecological environment of offshore areas.The spatiotemporal characteristics of CDOM around the Leizhou Peninsula were analyzed based on field observation data collected in the autumn 2020 and spring 2021,and an empirical inversion model of the ag(355)(absorption coefficient at 355 nm)and spectral slope(Sg)(g stands for gelbstoff/gilvin,which is called CDOM)based on Sentinel-3A ocean and land color instrument(OLCI)images was constructed.The results show(1)the order of average ag(355)value around the Leizhou Peninsula was east coast(0.503/m)>Qiongzhou Strait(0.502/m)>west coast(0.365/m);(2)the best band combinations of CDOM inversion in spring and autumn were(B4+B11)/B3 and(B7-B1)/B6(B stands for the band of spectral images),and the final inversion results are close to the measured results,indicating that the model has good accuracy;(3)the S_(g)value of the CDOM absorption spectrum was fitted to the hyperbolicexponential model.The fitting accuracy of the model was higher than those of the exponential model and the hyperbolic model,and the best S_(g)inversion model was constructed by selecting Sg(275-295)and Sg(250-295)in spring and autumn;(4)the spatial distributions of ag(355)and S_(g)were inverted,and CDOM in the waters around the Leizhou Peninsula originated from terrestrial organic matter carried by coastal aquaculture zones and runoff in the northeast Zhanjiang and the northern Beibu Gulf.
基金China Postdoctoral Science Foundation under contract No.2021M703619。
文摘The terrigenously-dominated marine shales which were deposited in the lower Eocene Pinghu Formation were thought to be a potential source rock in the Xihu Depression of the East China Sea Shelf Basin.However,the exceptionally high total organic carbon content(TOC,>6%on average)of the tidal sand ridge samples was not compatible with their sedimentary environment,indicating coal-bearing sedimentary debris may have been transferred from the coast to the ocean.In this study,new sights into the origins and supply of organic materials in the coastal environment were proposed in the neritic organic matter of the Eocene Pinghu Formation.A discriminant model was developed using plynofacies analysis data to pinpoint the source of organic materials in marine source rocks.The discrimination results suggested that marine mudstones were associated with tidal flat mudstones rather than deltaic ones.The biomarker characteristics of mudstones deposited in various environments support this assertion,indicating that the supply of plant materials in tidal flats is the primary organic matter source for the marine environment.The organic matter abundance was elevated in tidal flats due to their superior preservation conditions.Additionally,the lithological assemblage of tidal flats suggests that tidal currents can scour marshes and then transport dispersed terrigenous organic materials to neritic areas.These findings indicate that coal-bearing sedimentary debris was likely transferred from the coast to the ocean,and tidal currents are thought to be the dominant mechanism driving organic matter from the tidal to the marine environment.
基金Supported by the National Major Research and Development Project(2020YFA0710504,2022YFF0801204)PetroChina Science and Technology Major Project(2019E-26)。
文摘According to the theory of sequence stratigraphy based on continental transgressive-regressive(T-R)cycles,a 500 m continuous core taken from the second member of Kongdian Formation(Kong 2 Member)of Paleogene in Well G108-8 in the Cangdong Sag,Bohai Bay Basin,was tested and analyzed to clarify the high-frequency cycles of deep-water fine-grained sedimentary rocks in lacustrine basins.A logging vectorgraph in red pattern was plotted,and then a sequence stratigraphic framework with five-order high-frequency cycles was formed for the fine-grained sedimentary rocks in the Kong 2 Member.The high-frequency cycles of fine-grained sedimentary rocks were characterized by using different methods and at different scales.It is found that the fifth-order T cycles record a high content of terrigenous clastic minerals,a low paleosalinity,a relatively humid paleoclimate and a high density of laminae,while the fifth-order R cycles display a high content of carbonate minerals,a high paleosalinity,a dry paleoclimate and a low density of laminae.The changes in high-frequency cycles controlled the abundance and type of organic matter.The T cycles exhibit relatively high TOC and abundant endogenous organic matters in water in addition to terrigenous organic matters,implying a high primary productivity of lake for the generation and enrichment of shale oil.
基金Supported by the National Natural Science Foundation of China(U22B6004).
文摘The major enrichment type of shale oil in the Chang 7_(3) shale of Upper Triassic Yanchang Formation in the Ordos Basin is unknown.This paper analyzes the organic matter transformation ratio,hydrocarbon expulsion efficiency and roof/floor sealing conditions of the Chang 7_(3) shale,and evaluates the major enrichment type of shale oil in this interval.The average organic matter transformation ratio of the Chang 7_(3) shale is about 45%;in other words,more than 50%of the organic matters have not transformed to hydrocarbons,and the lower the maturity,the greater the proportion of untransformed organic matters.The cumulative hydrocarbon expulsion efficiency of the transformed hydrocarbon is 27.5% on average,and the total proportion of untransformed organic matters plus retained hydrocarbons is greater than 70%.The relative hydrocarbon expulsion efficiency of the Chang 7_(3) shale is 60%on average,that is,about 40% of hydrocarbons retain in the shale.The Chang 7_(3) shale corresponds to Chang 7_(1+2) and Chang 8 sandstones as the roof and floor,respectively,and is further overlaid by Chang 6 shale,where extensive low porosity and low permeability–tight oil reservoirs have formed in the parts with relatively good porosity and permeability.Moreover,the Chang 7_(3) shale is tested to be in a negative pressure system(the pressure coefficient of 0.80–0.85).Therefore,the roof/floor sealing conditions of the Chang 7_(3) shale are poor.The retained hydrocarbons appear mostly in absorbed status,with low mobility.It is concluded that the medium–high mature shale oil is not the major enrichment type of shale oil in the Chang 7_(3) shale,but there may be enrichment opportunity for shale oil with good mobility in the areas where the sealing conditions are good without faults and fractures and oil reservoirs are formed off Chang 7_(1+2),Chang 6 and Chang 8.Furthermore,low–medium mature shale oil is believed to have great potential and is the major enrichment type of shale oil in the Chang 7_(3) shale.It is recommended to prepare relevant in-situ conversion technologies by pilot test and figure out the resource availability and distribution.
文摘An improvised auger sediment sampler was used to collect sediments at shallow depths from two wetlands in the Northern Bida Basin for laboratory studies in order to ascertain the impact on the chemical quality of groundwater within these two studied locations. The dissolved organic carbon content of water is an important component of the geochemical cycling of elements capable of affecting groundwater quality. The sediments which serve as a conduit and pathways for the elements’ transport depending on the characteristics of the particle sizes are to be considered in the evaluation of contaminant mobility within the pathways. Representative cored sediment samples were collected and their particle size characterization and chemical analysis for Organic Matter (OM), Organic Carbon (OC) and Moisture Content (MC) were carried out. The hydrometer results show that the sediment particle sizes are in the order of sand > clay > silt in both locations with few exceptions. This represents the geology of the area (sandstone). The Mean values of 1.14% and 1.98% of OC and OM respectively were recorded in the sediment samples collected in parts of Ebgako. In contrast, 1.72% and 2.97% mean values were recorded in sediments collected in part of Bida for OC and OM respectively. The values of the OC and OM in the sediments from the two wetlands are low and may have been dissolved along the groundwater pathways to the aquifer. Other physicochemical parameters analysed in the sediments showed poor correlation. OM and OC were strongly positively correlated and showed an R<sup>2</sup> value of 1 and 0.9 respectively for parts of the Bida and Egbako sheets. There is low acidity of the sediments from the two study locations with a mean pH value of 5.64 and 5.13 respectively for Egbako and Bida. The low acidic nature of the sediments and the OM and OC composition have the potential to influence biogeochemical processes in the sediments and can affect the chemical quality of the groundwater in these two study locations.
