The toxic heavy metal mercury(Hg)has significantly enhanced the global Hg cycle influenced by human activities over the last century.In this study,we presented a high-resolution Hg deposition history between∼1780 and...The toxic heavy metal mercury(Hg)has significantly enhanced the global Hg cycle influenced by human activities over the last century.In this study,we presented a high-resolution Hg deposition history between∼1780 and 2015 AD in a sediment core from Xincun Lagoon,located in the southeastern Hainan Island,South China,and analyzed it in conjunction with geochemical elements,grain-size distribution,organic matter,and HYSPLIT backward trajectory simulation.The objective was to investigate the influencing factors affecting historical Hg deposition in relatively remote regions and assess the extent of the effects of natural background and human activities.The results showed that the Hg in the sediment was deposited primarily through atmospheric deposition,which was closely related to regional and even global human activities.Anthropogenic Hg contamination increased gradually from the 1830s to 1850s,possibly due to Hg emissions from Opium Wars I and II occurring in southeastern China.High broad peaks of anthropogenic Hg were observed during the 1910s to 1950s and in the 1980s,likely associated with the two world wars and modern Chinese wars.In addition,a further sharp increase in anthropogenic Hg from the mid-1970s to the present occurred,likely originating from the intense industrial activities in China triggered by the reform and opening-up policy of China in 1978 and some countries in Southeast Asia.展开更多
The coast of the Dapeng Peninsula has been honored as one of "the eight most beautiful coasts in China". The most precious tourism resource for the peninsula is headland bay beaches, among which the beach at...The coast of the Dapeng Peninsula has been honored as one of "the eight most beautiful coasts in China". The most precious tourism resource for the peninsula is headland bay beaches, among which the beach at Xichong on the southern coast of the peninsula is the longest and the most important one. The information of the stability, sedimentary source and shape change of the beach is very important for maintaining the beach in terms of sustainable development of the peninsula. Heavy minerals in the sand of the beach and the inland stream at Xichong are compared with those of a nearby beach on the same coast to determine the beach sand source; with help of a computer software, MEPBAY, the equilibrium planforms of the beaches on the peninsula are compared with those of an island without rivers to evaluate the stream's effects on the beach stability; cross shore profiles along the Xichong beach are also surveyed in different seasons of a year to assess the annual shore normal beach changes affected by the stream input, and the relation between the equilibrium planform state and cross shore changes of the beach. It is shown that(1) stream is the main sedimentary source of the beach and the weathering materials of the rocky headlands on both sides of the bay transported by waves are the second source for the beach but it is limited, sand from an inner shelf is not the sedimentary source for the beach at present and was not even during the Holocene transgression;(2) the Xichong beach cannot reach static equilibrium around the entire bay shoreline, the segment of the shoreline where a stream outlet is located is in dynamic equilibrium, and the unstable section occurs in the wave shadow region in the lee of an offshore island;(3) no matter whether the section of the beach shoreline at Xichong is in an equilibrium state or not, it is eroded in the typhoon season and recovered after the season, the maximum change in erosion and accretion occurs in the unstable segment;(4) the Xichong beach can only have small sand body since it is supplied with sand mainly form inland streams, resulting in a possible danger in which sand loss induced by human activities or huge storms cannot be replenished naturally.展开更多
Quercus is the largest genus within the Fagaceae and has a rich fossil record.Most of the fossil material is attributed to the subgenus Quercus based on leaves,pollen or rarely acorns and nuts.Fossil records of Q.sect...Quercus is the largest genus within the Fagaceae and has a rich fossil record.Most of the fossil material is attributed to the subgenus Quercus based on leaves,pollen or rarely acorns and nuts.Fossil records of Q.section Cyclobalanopsis characterized by ring-cupped acorns are relatively few and especially those described based on nuts are scant.In this study,we described four new species of Quercus section Cyclobalanopsis based on mummified acorns and nuts:Q.paleodisciformis X.Y.Liu et J.H.Jin sp.nov.,Q.paleohui X.Y.Liu et J.H.Jin sp.nov.,Q.nanningensis X.Y.Liu et J.H.Jin sp.nov.and Q.yongningensis X.Y.Liu et J.H.Jin sp.nov.These species closely resemble the extant species Q.disciformis,Q.hui,Q.kerrii,and Q.dinghuensis.The occurrence of Q.section Cyclobalanopsis in the Oligocene stratum of Guangxi,South China,suggests that the section has diversified within its extant distribution center since the Oligocene.By combining records from other areas,we propose that the section first appeared in the middle Eocene of East Asia(Sino-Japan),has diversified in situ with a few elements scattering into West Asia and southern Europe since the Oligocene and Pliocene,respectively,and finally became restricted in East Asia since the Pleistocene.This indicates that the section originated and diversified in East Asia,before spreading into West Asia no later than the Oligocene and into southern Europe by the Pliocene.Subsequently it disappeared from South Europe and West Asia due to the appearance of the(summer dry)Mediterranean climate and widespread cooling during the Pleistocene.展开更多
Since China’s reform and opening-up,the growing disparity between urban and rural areas and regions has led to massive migration.With China’s Rural Revitalization Strategy and the industrial transfer from the easter...Since China’s reform and opening-up,the growing disparity between urban and rural areas and regions has led to massive migration.With China’s Rural Revitalization Strategy and the industrial transfer from the eastern coastal areas to the inland,the migration direction and pattern of the floating population have undergone certain changes.Using the 2017 China Migrants Dynamic Survey(CMDS),excluding Hong Kong,Macao,and Taiwan regions of China,organized by China’s National Health Commission,the relationship matrix of the floating population is constructed according to the inflow place of the interviewees and their outflow place(the location of the registered residence)in the questionnaire survey.We then apply the complex network model to analyze the migration direction and network pattern of China’s floating population from the city scale.The migration network shows an obvious hierarchical agglomeration.The first-,second-,third-and fourth-tier distribution cities are municipalities directly under the central government,provincial capital cities,major cities in the central and western regions and ordinary cities in all provinces,respectively.The migration trend is from the central and western regions to the eastern coastal areas.The migration network has‘small world’characteristics,forming nine communities.It shows that most node cities in the same community are closely linked and geographically close,indicating that the migration network of floating population is still affected by geographical proximity.Narrowing the urban-rural and regional differences will promote the rational distribution this population.It is necessary to strengthen the reform of the registered residence system,so that the floating population can enjoy urban public services comparable to other populations,and allow migrants to live and work in peace.展开更多
The Sonneratia apetala artificial mangroves in the intertidal zone of Da Wei Bay at Qi'ao Island of Zhuhai, South China were chosen as the macrofauna succession plots while bare tidal flats of the same size were e...The Sonneratia apetala artificial mangroves in the intertidal zone of Da Wei Bay at Qi'ao Island of Zhuhai, South China were chosen as the macrofauna succession plots while bare tidal flats of the same size were established as control plots in surrounding interference-free areas. Conventional change indicators of community structure, such as biomass and biodiversity, and indicators, such as exergy and specific exergy, which reflect the information change of overall communities, were used to analyze the succession of macrofauna communities in S. apetala artificial mangroves. The similarities and differences in variation tendency of the different ecological indicators and their reflected ecological principles were compared. The results showed that from D-1 to D-1275 after planting S. apetala, the biomass of the macrofauna communities first increased, which was then followed by an increase in the network relationship between the macrofauna communities(analysis of the Pielou evenness index and Shannon-Wiener diversity index). The system information(specific exergy) increased the slowest. Between D-1460 and D-2370 after planting S. apetala, there was a decrease in biomass, network structure, and system information in the succession plots. After the decrease in the system information(the specific exergy), there was a decline in the network relationships(Pielou evenness index and Shannon-Wiener diversity index). Biomass was the last indicator to decrease. The similarities and differences among the different ecological indicators varied during the succession process, which reflected the relativity and differences among the indicators. This study suggested that, although the species diversity index can be an effective indicator of two types of changes(network structure and system information), it was quite clear that species diversity measurement was not suitable for expressing the changes in biomass during the succession process. While exergy and specific exergy can provide useful information about the structural development of communities, they cannot identify the information state of the system. Therefore, when evaluating macrofaunal succession in S. apetala artificial mangrove wetlands, it would be better to apply a number of different ecological indicators, rather than just one single indicator.展开更多
Contents of heavy metals,polycyclic aromatic hydrocarbons (PAHs),dichlorodiphenyltrichloroethanes (DDTs) and hexachlorcyclohexanes (HCHs) in surface sediments from mangrove areas of the Leizhou Peninsula were analyzed...Contents of heavy metals,polycyclic aromatic hydrocarbons (PAHs),dichlorodiphenyltrichloroethanes (DDTs) and hexachlorcyclohexanes (HCHs) in surface sediments from mangrove areas of the Leizhou Peninsula were analyzed in July and November 2005. Risk assessment criteria applied by Long E R et al. (1995) and Long E D et al. (1998) (effects range low,ERL; effects range mean,ERM) of chemicals in sediments from the gulf or estuary were used to assess the potential ecological risks of heavy metals,PAHs,DDTs and HCHs to aquatic organisms in the studied area. The results indicated that the average contents of zinc,nickel,chromium,lead,copper,arsenic and mercury were (61.97 ± 55.87),(59.99 ± 39.01),(47.93 ± 28.37),(26.64 ± 13.00),(23.45 ± 41.96),(9.32 ± 3.62),(0.14 ± 0.18) mg/kg in dry weight in the sediment samples collected from five studied sites in the Leizhou Peninsula,respectively. Cadmium was not calculated due to its content being below the detection limit (< 0.3 mg/kg). The average levels of Cr,Cu,Ni,Pb,Zn and Hg exceed their background values. The average contents of Ni were higher than ERM. The contents of PAHs in the sediments from the five studied sites were (79.78 ± 43.70) ng/g in dry weight,far lower than ERL(4 022 ng/g). The contents of DDE,DDD and DDTs in the sediments from five studied sites were (2.60 ± 4.68),(17.52 ± 27.25),(27.78 ± 46.64) ng/g in dry weight respectively,clearly higher than ERL,and the average contents of DDT were (7.66 ± 15.93) ng/g in dry weight,much higher than ERM. HCHs could be detected in the sediments only from Gaoqiao sampling site,with the average contents (0.07 ± 0.08) ng/g in dry weight.展开更多
A 350-cm-long sediment core sequence from Dahu Swamp situated in the eastern Nanling Mountains was selected for high-resolution paleoclimatic reconstruction since the Late Glacial period. The multi-proxy records of th...A 350-cm-long sediment core sequence from Dahu Swamp situated in the eastern Nanling Mountains was selected for high-resolution paleoclimatic reconstruction since the Late Glacial period. The multi-proxy records of this paper reveal several evidently dry and cold events that may coincide with the Oldest Dryas, the Older Dryas, the Younger Dryas in the late deglacial period. Two relatively wetter and warmer phases occurred in ca. 15,000-14,400 cal yr B.P. and 13,500-12,800 cal yr B.P. respectively may correspond to the Blling and Allerd warming events. The Younger Dryas event (ca. 12,800-11,500 cal yr B.P.) revealed by multi-proxies was characterized by relatively colder and drier climate. A warmer and wetter climate, occurred in ca. 10,000-6000 cal yr B.P., was consistent with the Holocene Optimum, which coincided with the maximum Northern Hemisphere insolation. The "8.2kyr cool event" and even the "8.8kyr cool event" were indicated as well from our sediment core. A dry mid-Holocene period (ca. 6000- 3000 cal yr B.P.) indicated by multi-proxies does not follow the traditional concept of the wet mid-Holocene conditions observed in other regions in China.展开更多
The TMS5e sequence from the Tumen section,at the southern edge of Tengger Desert in the northwestern China,is synchronous with Marine Isotope Stage 5e(MIS5e).It consists of 16 layers of aeolian dune sands,11 layers of...The TMS5e sequence from the Tumen section,at the southern edge of Tengger Desert in the northwestern China,is synchronous with Marine Isotope Stage 5e(MIS5e).It consists of 16 layers of aeolian dune sands,11 layers of lacustrine loess-like facies,and 5 layers of lacustrine facies.The results of grain-size analysis shows that the palaeo-mobile dune sands,palaeo-fixed to semi-fixed dune sands and loess-like sandy loams are mainly composed of sands,ranging from 70% to 96%;their silt contents ranged from 4% to 20%,and their clay contents ranged from 1% to 5%;the climate under which the aeolian dune sands were deposited is similar to that under which modern mobile dune sands form,which is caused by the dominance of the cold,dry East Asian winter monsoon.In contrast,the lacustrine loess-like facies and lacustrine facies had a lower sand contents than those of the three aeolian dune sands,but have higher silt and clay contents,most of their sand content ranged from 30% to 60%,their silt contents ranged from 35% to 55%,and their clay contents ranged from 6% to 20%.The lacustrine loess-like facies and lacustrine facies formed under the influence of the warm,humid East Asian summer monsoon based on their similarity with modern sediments.The grain-size indicator Mz(mean grain diameter) and the SC/D value in the TMS5e sequence indicate climatic insta-bility at the southern edge of the Tengger Desert during MIS5e,with at least 14 fluctuations between a warm,humid climate and a cold,dry climate,divided into five stages:TMS5e5(139 kyr to 129.3 kyr B.P.),TMS5e4(129.3 kyr to 124 kyr B.P.),TMS5e3(124 kyr to 119.5 kyr B.P.),TMS5e2(119.5 kyr to 116.5 kyr B.P.),and TMS5e1(116.5 kyr to 113.7 kyr B.P.).These correspond roughly to MIS5e5,MIS5e4,MIS5e3,MIS5e2,and MIS5e1,respectively,in the GRIP ice core data.展开更多
The Mushroom Stone Forest, which consists of granite boulders looking like mushrooms with flared sidewalls, is located in eastern Guangdong China, and is a famous scenic spot that draws many tourists each year. The Mu...The Mushroom Stone Forest, which consists of granite boulders looking like mushrooms with flared sidewalls, is located in eastern Guangdong China, and is a famous scenic spot that draws many tourists each year. The Mushroom Stone Forest has been traditionally recognized as a collection of wave erosion landforms and used for the reconstruction of palaeo-sea-level changes along the coastal areas of eastern Guangdong in previous coastal researches. By combining in situ measurements of the aspect,vertical profile and height of boulder sidewalls,palaeo-coastal wave direction estimation, rock density determination, major elemental analysis, and petrographic thin section analysis, this paper presents an alternative origin for the Mushroom Stone Forest.Our results suggest that wave or wind erosion cannot offer a satisfactory explanation for the formation of the Mushroom Stone Forest; The boulders that make up the Mushroom Stone Forest originated from the corestones in the granite weathering crusts of the Little Sangpu Mountain; When the debris of the weathering crust was removed, the corestones are perched on rocky outcrops or half-buried by weathering debris beneath the natural land surface;The flared sidewall (concave vertical profile) of the boulders is a particular form developed in the foot zone of a half-buried boulder through increased chemical weathering beneath the land surface. A recent exposed half-buried boulder found in the study area provides convincing evidence to support this argument. Sea water reached the foot of the Sangpu Mountain during the Holocene transgression, but it merely provided a mechanism to erode the weathering debris from the bottom of the mushroom rocks and enhanced salt weathering that created tafoni on the boulders. These findings demonstrate that the boulders of the Mushroom Stone Forest are not sea stacks and cannot be served as a palaeo-sea-level indicator.展开更多
Based on investigation of sediments in the Yutian-Hotan Oasis at the southern margin of the Tarim basin, 14C ages and grain-size and chemical element analyses, the following views are put forward in this paper.(1) Sed...Based on investigation of sediments in the Yutian-Hotan Oasis at the southern margin of the Tarim basin, 14C ages and grain-size and chemical element analyses, the following views are put forward in this paper.(1) Sediments in the Yutian-Hotan Oasis are composed chiefly of 'oasis soil', similar to the recent oasis soil, i.e. brown desert soil, which was formed due to pedogenesis after aeolian sand (sandy loam) and dust (loess) of 3.32-6.64 j were deposited.(2) The ancient Yutian-Hotan Oasis represented by oasis soil was formed at 13000 a B.P. During the cold period of the past 13000 years, this region is characterized mainly by accumulation of sand and dust storms, and sandy oasis soil was developed in this region due to pedogenesis in an oasis environment; during the warm period, dust falls predominated along with certain current concomitants (lacustrine facies), and silty oasis soil was formed by pedogenesis. Owing to fluctuations of cold and warm climates since 13000 a B.P., sandy oasis soil was deposited alternately with silty oasis soil and lacustrine soils. Nevertheless, the Yutian-Hotan Oasis has been preserved and developing continuously towards the contemporary time.(3) At the latest, the oasis became an important site of human inhabitancy at 10000 a B.P., and since then it has been an important base for the propagation and activity of local people in the Tarim Basin.展开更多
Marine benthic dinoflagellates in the genus Coolia were reported in both tropical and temperate regions.We conducted a morphological and phylogenetic characterization of Coolia species from Hainan Island,South China S...Marine benthic dinoflagellates in the genus Coolia were reported in both tropical and temperate regions.We conducted a morphological and phylogenetic characterization of Coolia species from Hainan Island,South China Sea.The morphologies of three Coolia species were similar to those of the original descriptions of Coolia canariensis,C.tropicalis,and C.malayensis.In phylogenetic analyses based on the LSU rDNA and ITS regions(ITS1-5.8 S-ITS2),the Hainan strains of C.canariensis,C.tropicalis,and C.malayensis clustered within the clades of these species with other isolates from different areas.No differences(p-distance)in LSU rDNA sequences were found between the Hainan C.malayensis strains and the strains from New Zealand,Florida of USA,Malaysia,Japan,Dominican Republic and Guangxi and Hong Kong of China.For C.canariensis and C.tropicalis,no differences(p-distance)in the LSU rDNA sequences were found between the Hainan strains(D1 C2 and DS5 F4,respectively)and the Australian strains(NQAIF252 and NQAIF90,respectively).Our study reveals the morphological and genetic diversity of Coolia species from Hainan Island,South China Sea,which provides a detailed understanding of Coolia species of this area.展开更多
Although the taxonomy of oligotrich ciliates has been widely investigated,yet the species diversity remains poorly known.We newly designed a pair of oligotrich-specific LSU rDNA primers covering the 600-bp D1/D2 regio...Although the taxonomy of oligotrich ciliates has been widely investigated,yet the species diversity remains poorly known.We newly designed a pair of oligotrich-specific LSU rDNA primers covering the 600-bp D1/D2 region,and it was effective for detecting oligotrich species.Using the primers,we constructed the cloning libraries to investigate the species diversity of oligotrichs in the northern coastal waters of the South China Sea.In total,165 oligotrich sequences were obtained from five widely separated sampling sites.Sixty operational taxonomic units(OTUs)were obtained at 99%similarity threshold,and low-abundance OTUs with no more than two sequences contributed most of these(about 78%).Our findings are consistent with previous morphological studies,Strombidium was found the most abundant and widely distributed genus in this area.In addition,the BLAST search in the NCBI database resulted in 95%OTUs matching with named oligotrich species in similarity below 99%.Therefore,oligotrich morphospecies diversity has been underestimated as low-abundance species,and the LSU rDNA oligotrich sequence database needs to be better promoted.展开更多
Invasive predators have been widely regarded as one of the principle drivers of the global decline of amphibians, which are among the most threatened vertebrate taxon on Earth. The American bullfrog(Lithobates catesbe...Invasive predators have been widely regarded as one of the principle drivers of the global decline of amphibians, which are among the most threatened vertebrate taxon on Earth. The American bullfrog(Lithobates catesbeianus) is identified as one of the most successful vertebrate invaders and has caused the decline or extinction of some native amphibians in many regions and countries including China. Based on field surveys and stomach content analyses, we examined the diet composition of the invasive bullfrog for the first time in two invaded populations in Yunnan Province, southwestern China, a region of global conservation priority, during the breeding season from 2008 to 2014. Additionally, we conducted the first quantitative study on the prey selection of this global invader among their invaded ranges after controlling for the local anuran assemblage and other aquatic preys in the environment. Our results showed that the range of food items in the stomachs of bullfrogs spanned more than 30 species belonging to ten taxonomic classes. Both of post-metamorphosis individuals and juveniles preyed upon native frogs, independent of the bullfrog's body size and mouth width. Importantly, Jacobs' selection index showed a bullfrog preference for the Yunnan pond frog(Babina pleuraden), one native endemic anuran with population decline, in terms of both food volume and occurrence. We therefore provided direct evidence on the predation impact of the invasive bullfrog on an endemic anuran and urged further efforts to prevent the dispersal of this invader into more fragile habitats to reduce their negative impacts on native amphibians.展开更多
The morphology,microstructure and demographic parameters of statolith of Sthenoteuthis oualaniensis were studied from 90 individuals captured in the central South China Sea in September and October,2012. The morpholog...The morphology,microstructure and demographic parameters of statolith of Sthenoteuthis oualaniensis were studied from 90 individuals captured in the central South China Sea in September and October,2012. The morphologic results showed that the statolith has great lateral dome and wing dome,small dorsal dome,and long narrow rostrum dome. S. Oualaniensis could be divided into three populations by statolith morphology in the central South China Sea. Five most important featured parameters including total statolith length( TSL),wing length( WL),maximum width( MW) were described by logarithmic functions with mental length( ML)( P < 0. 05); rostrum length( RSL),dorsolateral length( DLL) were described by linear functions with ML( P < 0. 05). With the squid growth,the size of statolith gradually develops,while the ratio of each featured parameter to ML slowly decreases,the ratio of DLL,LDL,RSL and WL to TSL almost remain the same level,corresponding to 48. 05%,60. 05%,35. 44%,67. 59%,and the ratio of LDL and WL to SL show little higher.展开更多
The distribution patterns of rare earth elements(REEs)in fine-grained materials in various depositions were often found to be similar to those of the aeolian sediments deposited in the Loess Plateau in North China and...The distribution patterns of rare earth elements(REEs)in fine-grained materials in various depositions were often found to be similar to those of the aeolian sediments deposited in the Loess Plateau in North China and the fine-grained materials were suggested to be derived from wind-blown dust.However,increasing evidence indicated that the REEs in the water-soluble portion of atmospheric depositions also displayed similar patterns to those of aeolian sediments.In this study,water-soluble REEs in three atmospheric depositions collected from different climatic zones in China were adsorbed with two adsorbents with distinct adsorption capacity,glass powder,and co-precipitated iron hydroxide.The results showed that the REEs adsorbed by the two adsorbents displayed patterns similar to those of the original atmospheric depositions.The typical characteristics of the REE patterns of atmospheric deposition can be well reproduced in the adsorbed REEs.The higher the REE concentrations in the atmospheric depositions,or the higher adsorption efficiency of the adsorbents,the better reproducibility of the REEs patterns.The results suggest that the REEs of the fine-grained materials in various sediments,which have a high adsorption capacity,especially those deposited in South China,may come from the water-soluble REEs in atmospheric deposition,and may not be appropriate tracers of wind-blown dust from North China.展开更多
In the present work,15400 yr old geochemical records of a core from the subalpine Daping swamp are presented with the aim to examine the relationship between the chemical weathering and the climatic changes in the reg...In the present work,15400 yr old geochemical records of a core from the subalpine Daping swamp are presented with the aim to examine the relationship between the chemical weathering and the climatic changes in the region of the western Nanling Mountains,China.The climate of the study region was deeply controlled by the East Asian summer monsoon.The results indicate that,in the past 15400 yrs,the values of chemical index of alteration(CIA)ranged from 73.9%to 88.2%(mean:85.3%),suggested a medium and high intensity of chemical weathering.The local exogenous clastic materials,which were derived from the weathered residues,played a key role in contributing towards the sediments.Since the climate-induced chemical weathering exerted strong influences on the geochemical features of weathered residues,the geochemical characteristics of the sediments were deeply impacted by climatic conditions.Wetter and warmer conditions would favor increased chemical weathering,resulting in more leaching of soluble and mobile elements(e.g.,Ba and Sr)and leaving the resistant and immobile elements(e.g.,Al and Ti)enriched in the weathered residues.These materials were then eroded and transported into the lake,and led to the sediments characterized by the characteristic of having depleted soluble elements.In contrast,dry and cold conditions would result in an opposite trend.In this sense,the geochemical records can serve as proxies to indicate changes of chemical weathering intensity,which were closely related to the evolution of summer monsoon.展开更多
The genus Woodwardia,which together with the genera Anchistea and Lorinseria comprise the subfamily Woodwardioideae of Blechnaceae,has a disjunct distribution across Central and North America,Europe and the temperate ...The genus Woodwardia,which together with the genera Anchistea and Lorinseria comprise the subfamily Woodwardioideae of Blechnaceae,has a disjunct distribution across Central and North America,Europe and the temperate to tropical areas of Asia.Fossil records of Woodwardia occur throughout the Paleogene and Neogene of North America,Europe and Asia.However,well-preserved fertile pinna fossils of this genus have not yet been reported in South China.In this paper,a new species,W.changchangensis Naugolnykh et Song,sp.nov.is described from the middle Eocene of the Changchang Basin,Hainan Island,South China.Macromorphological and micromorphological features of the fertile pinna show a straight pinna rachis,alternate,subtriangular pinnules,acute pinnule apices,almost entire or slightly undulate pinnule margins,long-ovoid sori,stalked sporangia and spores with wing-like folds on the surface,which are characterised in detail.Overall,the present fossil is most similar to the extant species Woodwardia japonica,which mostly grows in warm and moist environments.The discovery of this new species from the Changchang Basin of Hainan Island indicates that this genus has been distributed in the low-latitude tropical regions of South China from as early as the middle Eocene.Based on this find,and previous studies of other ferns from the same site,we infer that the climate of the Palaeo-Hainan landscape during deposition of the Changchang Formation was warm and humid,similar to conditions prevailing today across this region.展开更多
The Old Red Sand is composed of brown-red, red, or orange-yellow semi-cemented and medium-fine sand sediment, mainly distributed along the southeast coast of China. Based on previous studies, this paper summarizes the...The Old Red Sand is composed of brown-red, red, or orange-yellow semi-cemented and medium-fine sand sediment, mainly distributed along the southeast coast of China. Based on previous studies, this paper summarizes the distribution and forms, sedimentary characteristics, formation mechanism, developing age, reddening process and the paleo-environment, suggesting that the Old Red Sand is mainly aeolian sediment of Late Pleistocene Age. The reddening process is mainly the result of decomposition and oxidation of iron-containing minerals caused by hot and humid tropical and sub-tropical climate. In this study, existing problems are discussed and the prospect of further research is presented as well.展开更多
The term“pragmatics borrowing”refers to a conscious use of foreign pragmatic marker within or between utterances.Distinctive pragmatics functions of using the“cross-linguistic”pragmatic markers in online conversat...The term“pragmatics borrowing”refers to a conscious use of foreign pragmatic marker within or between utterances.Distinctive pragmatics functions of using the“cross-linguistic”pragmatic markers in online conversations have become a research focus.In a sample of Wechat communication among university students,the English pragmatics marker“em”and its variations occurred frequently.By analyzing its spelling variations,placement,pragmatic meanings and functions,the study indicates that,besides using it as a hesitator,chat participants consciously use this foreign pragmatic marker as a buffer for later utterance,which is usually an apology or a request,to soften the intonation and give the addressee an impression of politeness.展开更多
基金Under the auspices of the National Natural Science Foundation of China(No.42071108,41671194)。
文摘The toxic heavy metal mercury(Hg)has significantly enhanced the global Hg cycle influenced by human activities over the last century.In this study,we presented a high-resolution Hg deposition history between∼1780 and 2015 AD in a sediment core from Xincun Lagoon,located in the southeastern Hainan Island,South China,and analyzed it in conjunction with geochemical elements,grain-size distribution,organic matter,and HYSPLIT backward trajectory simulation.The objective was to investigate the influencing factors affecting historical Hg deposition in relatively remote regions and assess the extent of the effects of natural background and human activities.The results showed that the Hg in the sediment was deposited primarily through atmospheric deposition,which was closely related to regional and even global human activities.Anthropogenic Hg contamination increased gradually from the 1830s to 1850s,possibly due to Hg emissions from Opium Wars I and II occurring in southeastern China.High broad peaks of anthropogenic Hg were observed during the 1910s to 1950s and in the 1980s,likely associated with the two world wars and modern Chinese wars.In addition,a further sharp increase in anthropogenic Hg from the mid-1970s to the present occurred,likely originating from the intense industrial activities in China triggered by the reform and opening-up policy of China in 1978 and some countries in Southeast Asia.
基金Shenzhen Dapeng Peninsula National Geopark Project of China under contract No.340775the Natural Science Foundation of Guangdong Province of China unde contract No.S2012010008610the National Natural Science Foundation of China under contract No.40871020
文摘The coast of the Dapeng Peninsula has been honored as one of "the eight most beautiful coasts in China". The most precious tourism resource for the peninsula is headland bay beaches, among which the beach at Xichong on the southern coast of the peninsula is the longest and the most important one. The information of the stability, sedimentary source and shape change of the beach is very important for maintaining the beach in terms of sustainable development of the peninsula. Heavy minerals in the sand of the beach and the inland stream at Xichong are compared with those of a nearby beach on the same coast to determine the beach sand source; with help of a computer software, MEPBAY, the equilibrium planforms of the beaches on the peninsula are compared with those of an island without rivers to evaluate the stream's effects on the beach stability; cross shore profiles along the Xichong beach are also surveyed in different seasons of a year to assess the annual shore normal beach changes affected by the stream input, and the relation between the equilibrium planform state and cross shore changes of the beach. It is shown that(1) stream is the main sedimentary source of the beach and the weathering materials of the rocky headlands on both sides of the bay transported by waves are the second source for the beach but it is limited, sand from an inner shelf is not the sedimentary source for the beach at present and was not even during the Holocene transgression;(2) the Xichong beach cannot reach static equilibrium around the entire bay shoreline, the segment of the shoreline where a stream outlet is located is in dynamic equilibrium, and the unstable section occurs in the wave shadow region in the lee of an offshore island;(3) no matter whether the section of the beach shoreline at Xichong is in an equilibrium state or not, it is eroded in the typhoon season and recovered after the season, the maximum change in erosion and accretion occurs in the unstable segment;(4) the Xichong beach can only have small sand body since it is supplied with sand mainly form inland streams, resulting in a possible danger in which sand loss induced by human activities or huge storms cannot be replenished naturally.
基金This study was supported by the National Natural Science Foundation of China(Nos.41872015,31770241,41820104002,and 41661134049)the grant of the Natural Environment Research Council of Research Councils UK(No.NE/P013805/1).
文摘Quercus is the largest genus within the Fagaceae and has a rich fossil record.Most of the fossil material is attributed to the subgenus Quercus based on leaves,pollen or rarely acorns and nuts.Fossil records of Q.section Cyclobalanopsis characterized by ring-cupped acorns are relatively few and especially those described based on nuts are scant.In this study,we described four new species of Quercus section Cyclobalanopsis based on mummified acorns and nuts:Q.paleodisciformis X.Y.Liu et J.H.Jin sp.nov.,Q.paleohui X.Y.Liu et J.H.Jin sp.nov.,Q.nanningensis X.Y.Liu et J.H.Jin sp.nov.and Q.yongningensis X.Y.Liu et J.H.Jin sp.nov.These species closely resemble the extant species Q.disciformis,Q.hui,Q.kerrii,and Q.dinghuensis.The occurrence of Q.section Cyclobalanopsis in the Oligocene stratum of Guangxi,South China,suggests that the section has diversified within its extant distribution center since the Oligocene.By combining records from other areas,we propose that the section first appeared in the middle Eocene of East Asia(Sino-Japan),has diversified in situ with a few elements scattering into West Asia and southern Europe since the Oligocene and Pliocene,respectively,and finally became restricted in East Asia since the Pleistocene.This indicates that the section originated and diversified in East Asia,before spreading into West Asia no later than the Oligocene and into southern Europe by the Pliocene.Subsequently it disappeared from South Europe and West Asia due to the appearance of the(summer dry)Mediterranean climate and widespread cooling during the Pleistocene.
基金Under the auspices of the Fund of Social Sciences Research,Ministry of Education of China(No.17YJA840011)。
文摘Since China’s reform and opening-up,the growing disparity between urban and rural areas and regions has led to massive migration.With China’s Rural Revitalization Strategy and the industrial transfer from the eastern coastal areas to the inland,the migration direction and pattern of the floating population have undergone certain changes.Using the 2017 China Migrants Dynamic Survey(CMDS),excluding Hong Kong,Macao,and Taiwan regions of China,organized by China’s National Health Commission,the relationship matrix of the floating population is constructed according to the inflow place of the interviewees and their outflow place(the location of the registered residence)in the questionnaire survey.We then apply the complex network model to analyze the migration direction and network pattern of China’s floating population from the city scale.The migration network shows an obvious hierarchical agglomeration.The first-,second-,third-and fourth-tier distribution cities are municipalities directly under the central government,provincial capital cities,major cities in the central and western regions and ordinary cities in all provinces,respectively.The migration trend is from the central and western regions to the eastern coastal areas.The migration network has‘small world’characteristics,forming nine communities.It shows that most node cities in the same community are closely linked and geographically close,indicating that the migration network of floating population is still affected by geographical proximity.Narrowing the urban-rural and regional differences will promote the rational distribution this population.It is necessary to strengthen the reform of the registered residence system,so that the floating population can enjoy urban public services comparable to other populations,and allow migrants to live and work in peace.
基金The Science and Technology Project of Guangdong under contract No.2009B030600006the National Science and Technology Support Program sub-topics under contract No.2009BADB2B0401-02+2 种基金the Appropriative Researching Fund for Professors and Doctors,Guangdong University of Education under contract No.10ARF01the National Spark Plan of China under contract No.2013GA780019the Scientific Research Project of Guangdong University of Education under contract No.2013yjxm03
文摘The Sonneratia apetala artificial mangroves in the intertidal zone of Da Wei Bay at Qi'ao Island of Zhuhai, South China were chosen as the macrofauna succession plots while bare tidal flats of the same size were established as control plots in surrounding interference-free areas. Conventional change indicators of community structure, such as biomass and biodiversity, and indicators, such as exergy and specific exergy, which reflect the information change of overall communities, were used to analyze the succession of macrofauna communities in S. apetala artificial mangroves. The similarities and differences in variation tendency of the different ecological indicators and their reflected ecological principles were compared. The results showed that from D-1 to D-1275 after planting S. apetala, the biomass of the macrofauna communities first increased, which was then followed by an increase in the network relationship between the macrofauna communities(analysis of the Pielou evenness index and Shannon-Wiener diversity index). The system information(specific exergy) increased the slowest. Between D-1460 and D-2370 after planting S. apetala, there was a decrease in biomass, network structure, and system information in the succession plots. After the decrease in the system information(the specific exergy), there was a decline in the network relationships(Pielou evenness index and Shannon-Wiener diversity index). Biomass was the last indicator to decrease. The similarities and differences among the different ecological indicators varied during the succession process, which reflected the relativity and differences among the indicators. This study suggested that, although the species diversity index can be an effective indicator of two types of changes(network structure and system information), it was quite clear that species diversity measurement was not suitable for expressing the changes in biomass during the succession process. While exergy and specific exergy can provide useful information about the structural development of communities, they cannot identify the information state of the system. Therefore, when evaluating macrofaunal succession in S. apetala artificial mangrove wetlands, it would be better to apply a number of different ecological indicators, rather than just one single indicator.
基金Zhang Hongda Science Research Fund of Sun Yat-sen Universitythe Young and Middle-aged Excellet Reacher's Research Fund of Guangdong Education Institute in China.
文摘Contents of heavy metals,polycyclic aromatic hydrocarbons (PAHs),dichlorodiphenyltrichloroethanes (DDTs) and hexachlorcyclohexanes (HCHs) in surface sediments from mangrove areas of the Leizhou Peninsula were analyzed in July and November 2005. Risk assessment criteria applied by Long E R et al. (1995) and Long E D et al. (1998) (effects range low,ERL; effects range mean,ERM) of chemicals in sediments from the gulf or estuary were used to assess the potential ecological risks of heavy metals,PAHs,DDTs and HCHs to aquatic organisms in the studied area. The results indicated that the average contents of zinc,nickel,chromium,lead,copper,arsenic and mercury were (61.97 ± 55.87),(59.99 ± 39.01),(47.93 ± 28.37),(26.64 ± 13.00),(23.45 ± 41.96),(9.32 ± 3.62),(0.14 ± 0.18) mg/kg in dry weight in the sediment samples collected from five studied sites in the Leizhou Peninsula,respectively. Cadmium was not calculated due to its content being below the detection limit (< 0.3 mg/kg). The average levels of Cr,Cu,Ni,Pb,Zn and Hg exceed their background values. The average contents of Ni were higher than ERM. The contents of PAHs in the sediments from the five studied sites were (79.78 ± 43.70) ng/g in dry weight,far lower than ERL(4 022 ng/g). The contents of DDE,DDD and DDTs in the sediments from five studied sites were (2.60 ± 4.68),(17.52 ± 27.25),(27.78 ± 46.64) ng/g in dry weight respectively,clearly higher than ERL,and the average contents of DDT were (7.66 ± 15.93) ng/g in dry weight,much higher than ERM. HCHs could be detected in the sediments only from Gaoqiao sampling site,with the average contents (0.07 ± 0.08) ng/g in dry weight.
基金Under the auspices of National Natural Science Foundation of China (No. 40671189)Natural Science Foundation of Guangdong Province (No. 8151063101000044, 06025042)the Fok Ying Tung Education Foundation (No. 91021)
文摘A 350-cm-long sediment core sequence from Dahu Swamp situated in the eastern Nanling Mountains was selected for high-resolution paleoclimatic reconstruction since the Late Glacial period. The multi-proxy records of this paper reveal several evidently dry and cold events that may coincide with the Oldest Dryas, the Older Dryas, the Younger Dryas in the late deglacial period. Two relatively wetter and warmer phases occurred in ca. 15,000-14,400 cal yr B.P. and 13,500-12,800 cal yr B.P. respectively may correspond to the Blling and Allerd warming events. The Younger Dryas event (ca. 12,800-11,500 cal yr B.P.) revealed by multi-proxies was characterized by relatively colder and drier climate. A warmer and wetter climate, occurred in ca. 10,000-6000 cal yr B.P., was consistent with the Holocene Optimum, which coincided with the maximum Northern Hemisphere insolation. The "8.2kyr cool event" and even the "8.8kyr cool event" were indicated as well from our sediment core. A dry mid-Holocene period (ca. 6000- 3000 cal yr B.P.) indicated by multi-proxies does not follow the traditional concept of the wet mid-Holocene conditions observed in other regions in China.
基金Foundation item:Under the auspices of State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,Chinese Academy of Sciences (No.SKLLQG0901,SKLLQG1013)Research Fund for the Doctoral Program of Higher Education of China (No.20094407120004)
文摘The TMS5e sequence from the Tumen section,at the southern edge of Tengger Desert in the northwestern China,is synchronous with Marine Isotope Stage 5e(MIS5e).It consists of 16 layers of aeolian dune sands,11 layers of lacustrine loess-like facies,and 5 layers of lacustrine facies.The results of grain-size analysis shows that the palaeo-mobile dune sands,palaeo-fixed to semi-fixed dune sands and loess-like sandy loams are mainly composed of sands,ranging from 70% to 96%;their silt contents ranged from 4% to 20%,and their clay contents ranged from 1% to 5%;the climate under which the aeolian dune sands were deposited is similar to that under which modern mobile dune sands form,which is caused by the dominance of the cold,dry East Asian winter monsoon.In contrast,the lacustrine loess-like facies and lacustrine facies had a lower sand contents than those of the three aeolian dune sands,but have higher silt and clay contents,most of their sand content ranged from 30% to 60%,their silt contents ranged from 35% to 55%,and their clay contents ranged from 6% to 20%.The lacustrine loess-like facies and lacustrine facies formed under the influence of the warm,humid East Asian summer monsoon based on their similarity with modern sediments.The grain-size indicator Mz(mean grain diameter) and the SC/D value in the TMS5e sequence indicate climatic insta-bility at the southern edge of the Tengger Desert during MIS5e,with at least 14 fluctuations between a warm,humid climate and a cold,dry climate,divided into five stages:TMS5e5(139 kyr to 129.3 kyr B.P.),TMS5e4(129.3 kyr to 124 kyr B.P.),TMS5e3(124 kyr to 119.5 kyr B.P.),TMS5e2(119.5 kyr to 116.5 kyr B.P.),and TMS5e1(116.5 kyr to 113.7 kyr B.P.).These correspond roughly to MIS5e5,MIS5e4,MIS5e3,MIS5e2,and MIS5e1,respectively,in the GRIP ice core data.
基金jointly funded by National Natural Science Foundation of China (41571002)Natural Science Foundation of Guangdong, China (2015A030313385)Foundation for the Young Creative Talent Foundation in Higher Education of Guangdong, China (2014KQNCX193)
文摘The Mushroom Stone Forest, which consists of granite boulders looking like mushrooms with flared sidewalls, is located in eastern Guangdong China, and is a famous scenic spot that draws many tourists each year. The Mushroom Stone Forest has been traditionally recognized as a collection of wave erosion landforms and used for the reconstruction of palaeo-sea-level changes along the coastal areas of eastern Guangdong in previous coastal researches. By combining in situ measurements of the aspect,vertical profile and height of boulder sidewalls,palaeo-coastal wave direction estimation, rock density determination, major elemental analysis, and petrographic thin section analysis, this paper presents an alternative origin for the Mushroom Stone Forest.Our results suggest that wave or wind erosion cannot offer a satisfactory explanation for the formation of the Mushroom Stone Forest; The boulders that make up the Mushroom Stone Forest originated from the corestones in the granite weathering crusts of the Little Sangpu Mountain; When the debris of the weathering crust was removed, the corestones are perched on rocky outcrops or half-buried by weathering debris beneath the natural land surface;The flared sidewall (concave vertical profile) of the boulders is a particular form developed in the foot zone of a half-buried boulder through increased chemical weathering beneath the land surface. A recent exposed half-buried boulder found in the study area provides convincing evidence to support this argument. Sea water reached the foot of the Sangpu Mountain during the Holocene transgression, but it merely provided a mechanism to erode the weathering debris from the bottom of the mushroom rocks and enhanced salt weathering that created tafoni on the boulders. These findings demonstrate that the boulders of the Mushroom Stone Forest are not sea stacks and cannot be served as a palaeo-sea-level indicator.
基金the National Key Project for Basic Research(Nos.G1999043502,G2000048701) the project of State Key Labor ator yof Loess and Quatemary Geology,Institte of Earth Environm ent,Chinese Academy of Sciences(No.SKLLQG0008).
文摘Based on investigation of sediments in the Yutian-Hotan Oasis at the southern margin of the Tarim basin, 14C ages and grain-size and chemical element analyses, the following views are put forward in this paper.(1) Sediments in the Yutian-Hotan Oasis are composed chiefly of 'oasis soil', similar to the recent oasis soil, i.e. brown desert soil, which was formed due to pedogenesis after aeolian sand (sandy loam) and dust (loess) of 3.32-6.64 j were deposited.(2) The ancient Yutian-Hotan Oasis represented by oasis soil was formed at 13000 a B.P. During the cold period of the past 13000 years, this region is characterized mainly by accumulation of sand and dust storms, and sandy oasis soil was developed in this region due to pedogenesis in an oasis environment; during the warm period, dust falls predominated along with certain current concomitants (lacustrine facies), and silty oasis soil was formed by pedogenesis. Owing to fluctuations of cold and warm climates since 13000 a B.P., sandy oasis soil was deposited alternately with silty oasis soil and lacustrine soils. Nevertheless, the Yutian-Hotan Oasis has been preserved and developing continuously towards the contemporary time.(3) At the latest, the oasis became an important site of human inhabitancy at 10000 a B.P., and since then it has been an important base for the propagation and activity of local people in the Tarim Basin.
基金Supported by the National Natural Science Foundation of China(Nos.41606176,41576162,41606175)the IOC Yeosu Benthic Dinofl agellate Project。
文摘Marine benthic dinoflagellates in the genus Coolia were reported in both tropical and temperate regions.We conducted a morphological and phylogenetic characterization of Coolia species from Hainan Island,South China Sea.The morphologies of three Coolia species were similar to those of the original descriptions of Coolia canariensis,C.tropicalis,and C.malayensis.In phylogenetic analyses based on the LSU rDNA and ITS regions(ITS1-5.8 S-ITS2),the Hainan strains of C.canariensis,C.tropicalis,and C.malayensis clustered within the clades of these species with other isolates from different areas.No differences(p-distance)in LSU rDNA sequences were found between the Hainan C.malayensis strains and the strains from New Zealand,Florida of USA,Malaysia,Japan,Dominican Republic and Guangxi and Hong Kong of China.For C.canariensis and C.tropicalis,no differences(p-distance)in the LSU rDNA sequences were found between the Hainan strains(D1 C2 and DS5 F4,respectively)and the Australian strains(NQAIF252 and NQAIF90,respectively).Our study reveals the morphological and genetic diversity of Coolia species from Hainan Island,South China Sea,which provides a detailed understanding of Coolia species of this area.
基金Supported by the National Natural Science Foundation of China(Nos.31772440,31430077,41576124,31761133001)the Pearl River Science and Technology Nova Program of Guangzhou(No.201610010162) to YZ+1 种基金Guangdong MEPP Fund(No.GDOE(2019)A23)the Special Support Program of Guangdong Province to YZ
文摘Although the taxonomy of oligotrich ciliates has been widely investigated,yet the species diversity remains poorly known.We newly designed a pair of oligotrich-specific LSU rDNA primers covering the 600-bp D1/D2 region,and it was effective for detecting oligotrich species.Using the primers,we constructed the cloning libraries to investigate the species diversity of oligotrichs in the northern coastal waters of the South China Sea.In total,165 oligotrich sequences were obtained from five widely separated sampling sites.Sixty operational taxonomic units(OTUs)were obtained at 99%similarity threshold,and low-abundance OTUs with no more than two sequences contributed most of these(about 78%).Our findings are consistent with previous morphological studies,Strombidium was found the most abundant and widely distributed genus in this area.In addition,the BLAST search in the NCBI database resulted in 95%OTUs matching with named oligotrich species in similarity below 99%.Therefore,oligotrich morphospecies diversity has been underestimated as low-abundance species,and the LSU rDNA oligotrich sequence database needs to be better promoted.
基金supported by grants from National Natural Science Foundation of China (31200416 and 31370545)The collection and handling of amphibians were conducted by the Animal Care and Use Committee of Institute of Zoology, Chinese Academy of Sciences (Project No. 2008/73)
文摘Invasive predators have been widely regarded as one of the principle drivers of the global decline of amphibians, which are among the most threatened vertebrate taxon on Earth. The American bullfrog(Lithobates catesbeianus) is identified as one of the most successful vertebrate invaders and has caused the decline or extinction of some native amphibians in many regions and countries including China. Based on field surveys and stomach content analyses, we examined the diet composition of the invasive bullfrog for the first time in two invaded populations in Yunnan Province, southwestern China, a region of global conservation priority, during the breeding season from 2008 to 2014. Additionally, we conducted the first quantitative study on the prey selection of this global invader among their invaded ranges after controlling for the local anuran assemblage and other aquatic preys in the environment. Our results showed that the range of food items in the stomachs of bullfrogs spanned more than 30 species belonging to ten taxonomic classes. Both of post-metamorphosis individuals and juveniles preyed upon native frogs, independent of the bullfrog's body size and mouth width. Importantly, Jacobs' selection index showed a bullfrog preference for the Yunnan pond frog(Babina pleuraden), one native endemic anuran with population decline, in terms of both food volume and occurrence. We therefore provided direct evidence on the predation impact of the invasive bullfrog on an endemic anuran and urged further efforts to prevent the dispersal of this invader into more fragile habitats to reduce their negative impacts on native amphibians.
文摘The morphology,microstructure and demographic parameters of statolith of Sthenoteuthis oualaniensis were studied from 90 individuals captured in the central South China Sea in September and October,2012. The morphologic results showed that the statolith has great lateral dome and wing dome,small dorsal dome,and long narrow rostrum dome. S. Oualaniensis could be divided into three populations by statolith morphology in the central South China Sea. Five most important featured parameters including total statolith length( TSL),wing length( WL),maximum width( MW) were described by logarithmic functions with mental length( ML)( P < 0. 05); rostrum length( RSL),dorsolateral length( DLL) were described by linear functions with ML( P < 0. 05). With the squid growth,the size of statolith gradually develops,while the ratio of each featured parameter to ML slowly decreases,the ratio of DLL,LDL,RSL and WL to TSL almost remain the same level,corresponding to 48. 05%,60. 05%,35. 44%,67. 59%,and the ratio of LDL and WL to SL show little higher.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 41473093 and 41271212)。
文摘The distribution patterns of rare earth elements(REEs)in fine-grained materials in various depositions were often found to be similar to those of the aeolian sediments deposited in the Loess Plateau in North China and the fine-grained materials were suggested to be derived from wind-blown dust.However,increasing evidence indicated that the REEs in the water-soluble portion of atmospheric depositions also displayed similar patterns to those of aeolian sediments.In this study,water-soluble REEs in three atmospheric depositions collected from different climatic zones in China were adsorbed with two adsorbents with distinct adsorption capacity,glass powder,and co-precipitated iron hydroxide.The results showed that the REEs adsorbed by the two adsorbents displayed patterns similar to those of the original atmospheric depositions.The typical characteristics of the REE patterns of atmospheric deposition can be well reproduced in the adsorbed REEs.The higher the REE concentrations in the atmospheric depositions,or the higher adsorption efficiency of the adsorbents,the better reproducibility of the REEs patterns.The results suggest that the REEs of the fine-grained materials in various sediments,which have a high adsorption capacity,especially those deposited in South China,may come from the water-soluble REEs in atmospheric deposition,and may not be appropriate tracers of wind-blown dust from North China.
基金Under the auspices of the National Natural Science Foundation of China(No.41971101,41571187,41071137)。
文摘In the present work,15400 yr old geochemical records of a core from the subalpine Daping swamp are presented with the aim to examine the relationship between the chemical weathering and the climatic changes in the region of the western Nanling Mountains,China.The climate of the study region was deeply controlled by the East Asian summer monsoon.The results indicate that,in the past 15400 yrs,the values of chemical index of alteration(CIA)ranged from 73.9%to 88.2%(mean:85.3%),suggested a medium and high intensity of chemical weathering.The local exogenous clastic materials,which were derived from the weathered residues,played a key role in contributing towards the sediments.Since the climate-induced chemical weathering exerted strong influences on the geochemical features of weathered residues,the geochemical characteristics of the sediments were deeply impacted by climatic conditions.Wetter and warmer conditions would favor increased chemical weathering,resulting in more leaching of soluble and mobile elements(e.g.,Ba and Sr)and leaving the resistant and immobile elements(e.g.,Al and Ti)enriched in the weathered residues.These materials were then eroded and transported into the lake,and led to the sediments characterized by the characteristic of having depleted soluble elements.In contrast,dry and cold conditions would result in an opposite trend.In this sense,the geochemical records can serve as proxies to indicate changes of chemical weathering intensity,which were closely related to the evolution of summer monsoon.
基金the National Natural Science Foundation of China (Grant Nos.41872015,42111530024, 41820104002,41661134049 to JHJ and XYL)a grant from the UK Natural Environment Research Council (Grant No.NE/P013805/1 to XYL)+3 种基金the Fundamental Research Funds for the Central Universities (Grant No.2021qntd18 to XKW)the Scientific Research Fund, Hongda Zhang,Sun Yat-sen Universitya subsidiary of the Russian Government that supports a Program of Competitive Growth of Kazan Federal University among World’s Leading Academic Centersthe State Program of Geological Institute of RAS (Grant No.0135-2019-0044 to SVN).
文摘The genus Woodwardia,which together with the genera Anchistea and Lorinseria comprise the subfamily Woodwardioideae of Blechnaceae,has a disjunct distribution across Central and North America,Europe and the temperate to tropical areas of Asia.Fossil records of Woodwardia occur throughout the Paleogene and Neogene of North America,Europe and Asia.However,well-preserved fertile pinna fossils of this genus have not yet been reported in South China.In this paper,a new species,W.changchangensis Naugolnykh et Song,sp.nov.is described from the middle Eocene of the Changchang Basin,Hainan Island,South China.Macromorphological and micromorphological features of the fertile pinna show a straight pinna rachis,alternate,subtriangular pinnules,acute pinnule apices,almost entire or slightly undulate pinnule margins,long-ovoid sori,stalked sporangia and spores with wing-like folds on the surface,which are characterised in detail.Overall,the present fossil is most similar to the extant species Woodwardia japonica,which mostly grows in warm and moist environments.The discovery of this new species from the Changchang Basin of Hainan Island indicates that this genus has been distributed in the low-latitude tropical regions of South China from as early as the middle Eocene.Based on this find,and previous studies of other ferns from the same site,we infer that the climate of the Palaeo-Hainan landscape during deposition of the Changchang Formation was warm and humid,similar to conditions prevailing today across this region.
基金supported by National Natural Science Foundation of China (No. 40971007)
文摘The Old Red Sand is composed of brown-red, red, or orange-yellow semi-cemented and medium-fine sand sediment, mainly distributed along the southeast coast of China. Based on previous studies, this paper summarizes the distribution and forms, sedimentary characteristics, formation mechanism, developing age, reddening process and the paleo-environment, suggesting that the Old Red Sand is mainly aeolian sediment of Late Pleistocene Age. The reddening process is mainly the result of decomposition and oxidation of iron-containing minerals caused by hot and humid tropical and sub-tropical climate. In this study, existing problems are discussed and the prospect of further research is presented as well.
文摘The term“pragmatics borrowing”refers to a conscious use of foreign pragmatic marker within or between utterances.Distinctive pragmatics functions of using the“cross-linguistic”pragmatic markers in online conversations have become a research focus.In a sample of Wechat communication among university students,the English pragmatics marker“em”and its variations occurred frequently.By analyzing its spelling variations,placement,pragmatic meanings and functions,the study indicates that,besides using it as a hesitator,chat participants consciously use this foreign pragmatic marker as a buffer for later utterance,which is usually an apology or a request,to soften the intonation and give the addressee an impression of politeness.
