Heavy metal-contaminated soil is one of the major environmental pollution problems of agricultural production and human health in the world.Remediation of heavy metals in soil is one of the most popular research subje...Heavy metal-contaminated soil is one of the major environmental pollution problems of agricultural production and human health in the world.Remediation of heavy metals in soil is one of the most popular research subjects.Different remediation strategies have been reported to remove heavy metals from contaminated soil,among which phytoremediation is the most important one.Compared with other major crops,cotton shows the strongest and most widespread resistance to abiotic stresses,such as heavy metals.Although heavy metal stress adversely affects the growth and development of cotton,cotton possesses a set of sophisticated stress-resistance strategies.As the main product of cotton is nonedible fibers,which have a large biomass and strong heavy metal absorption and enrichment capacities,cotton is an ideal crop to restore heavy metal-contaminated soils and has unique advantages in terms of both ecological and economic benefits,with great application prospects.In this review,based on domestic and foreign research results in recent years,the effects of heavy metals on cotton growth and product quality were analyzed,the heavy metal absorption,accumulation,translocation and enrichment characteristics of cotton plants were summarized,and the adaptation and tolerance mechanisms of cotton to heavy metals were explored.Furthermore,the view that cotton is an effective crop to remediate heavy metal pollution in farmland soil has been proposed,and popularization and application suggestions for planting cotton to repair heavy metal pollution have been put forward to provide a reference for the comprehensive evaluation of the economic feasibility of cotton to repair heavy metal pollution in farmland soil.展开更多
In line with the author’s long-time experience on soil reconnaissance, monitoring and scientific probes, this article expounds the vital significance in systematic build-up of pedological data, protection of arable l...In line with the author’s long-time experience on soil reconnaissance, monitoring and scientific probes, this article expounds the vital significance in systematic build-up of pedological data, protection of arable land, employment and renovation of the farmland soil in accordance with the local edaphic setting in a bid to increase the grain yield.展开更多
With the rapid development of mining,the soil heavy metal contamination is increasingly serious in Shaoguan,directly affecting the production of crops. This paper analyzes the farmland soil heavy metal contamination i...With the rapid development of mining,the soil heavy metal contamination is increasingly serious in Shaoguan,directly affecting the production of crops. This paper analyzes the farmland soil heavy metal contamination in the mining area of Shaoguan and the causes of heavy metal contamination in recent years,brings forward the bioremediation measures to control soil heavy metal contamination,and points out the development direction of bioremediation in farmland soil heavy metal contamination in the mining area.展开更多
The three-pool and first-order model separates the mineralizable organic carbon into active,slow,and passive carbon pools.This paper used the model and decomposition curves of the soil organic carbon to fit the active...The three-pool and first-order model separates the mineralizable organic carbon into active,slow,and passive carbon pools.This paper used the model and decomposition curves of the soil organic carbon to fit the active pool and its decomposition rate,slow pool and its decomposition rate.The results showed that the size of the active pool from different profiles accounted for 2.09%-3.08% of the total soil organic carbon and the mean residue time was 3.57-17.21 days.And the size of the slow pool accounted for 3.19%-43.55% and the mean residue time was 1.12-4.94 years.Acid hydrolysis(6M HCl) was used to fractionate the passive organic carbon,which accounted for 50.83%-94.44% of the total soil organic carbon.展开更多
Soil pollution significantly reduces environmental quality.In this study,farmland soil samples were collected from 25 sites in Baghrash County,Northwest China;and the concentrations of eight heavy-metal elements(arsen...Soil pollution significantly reduces environmental quality.In this study,farmland soil samples were collected from 25 sites in Baghrash County,Northwest China;and the concentrations of eight heavy-metal elements(arsenic,As;cadmium,Cd;chromium,Cr;copper,Cu;manganese,Mn;nickel,Ni;lead,Pb;zinc,Zn)were determined by standard methods.The spatial distribution,contamination level,and ecological risk stature of heavy metals were analyzed based on GIS technology,the Geo-accumulation Index(Igeo),the Pollution Load Index(PLI),and the Potential Ecological Risk Index(RI).Results indicated that(1)The average concentrations of Cd exceeded 12.12 times the allowed national standard for soil environmental quality of China.The average concentrations of Cd,Cr,Ni,Pb,and Zn exceeded the background values of irrigation soils in Xinjiang by 60.58,1.25,1.50,4.95,and 5.10 times,respectively.(2)The pollution order of the average value of Igeo for heavy metals was ranked as Cd>Zn>Pb>Ni>Cr>Cu>As>Mn.The individual potential ecological risk index for heavy metals was ranked in the order of Cd>As>Ni>Cu>Pb>Cr>Zn.The average PLI for the study area showed a heavy pollution level,while the average RI showed a considerable ecological risk stature,as compared to the classification standard.(3)The spatial distribution patterns of eight heavy metal elements were substantially heterogeneous.The moderately polluted areas with moderate potential ecological risks were distributed in the southern parts of the study area,whereas the heavily polluted areas with considerable potential ecological risks were distributed in the northern parts.Overall,it was observed that Cd contributed most to the PLI and RI of the farmland soils in Baghrash County.The pollution risk of Cd should be a major concern,and human activities in the region should be cautious.展开更多
The heavy metal content of the farmland soil at two sides of Cheng-Guan Expressway is measured to make a preliminary evaluation on its heavy metal pollution status.After digestion and volume fixation of the soil sampl...The heavy metal content of the farmland soil at two sides of Cheng-Guan Expressway is measured to make a preliminary evaluation on its heavy metal pollution status.After digestion and volume fixation of the soil samples collected,measure the Cu,Zn,Cd,Pb and Cr content with atomic absorption spectrophotometry and evaluate the measured data according to Level Two of National Soil Environmental Quality Standard to obtain the contamination status.Cu,Zn and Cd content of the farmland soil for sections of Cheng-Guan Expressway goes beyond Level Two of National Soil Environmental Quality Standard,while the Pb and Cr content meets Level Two of National Soil Environmental Quality Standard.Pb and Cr content of the farmland soil at two sides of Cheng-Guan Expressway is in safe state,while the Cu,Zn and Cd content is in a mild contamination state.Cu,Zn and Cd are the main pollution elements.展开更多
Pb in the farmland surface soil of Changchun suburb was taken as the main research object. The field research and laboratory analysis were used to investigate Pb content,spatial distribution characteristics and its ec...Pb in the farmland surface soil of Changchun suburb was taken as the main research object. The field research and laboratory analysis were used to investigate Pb content,spatial distribution characteristics and its ecological risk in different farmland soils. The results showed that Pb content was during 18. 85- 41. 34 mg /kg in farmland soil of Changchun suburb,and was higher than the background value of Jilin Province at 90%of the sampling sites. The spatial distribution of Pb content in farmland soil had obvious geographical features,and Pb content in southwest and northeast soils was higher. The high-content areas were relatively concentrated,and Pb content gradually reduced from the high-content islandshape center to its surrounding. The soil Pb contents in paddy field,dry field and vegetable field had insignificant difference with the background value,indicating that Pb accumulations in dry field,paddy field and vegetable field were not significant. The order of Pb content in different land use types was showed as follows: vegetable field > dry field > paddy field. Pb pollution of all samples belonged to light pollution. The average potential ecological risk of soil Pb in different land use types presented the following order: vegetable field > dry field > paddy field.展开更多
Cd contamination range of farmland soil in China is wide,which has constituted a major threat for food safety and residents' health. Via multi-year development,there are more remediation methods suitable for soil ...Cd contamination range of farmland soil in China is wide,which has constituted a major threat for food safety and residents' health. Via multi-year development,there are more remediation methods suitable for soil contaminated by Cd among the world,but some methods are only suitable for the contaminated sites and indoor research,and can not be applied in large-range contaminated farmland. We analyze the source of Cd in farmland soil. By combining farmland's characteristics,three remediation techniques( low-absorption crops plantation,soil solidification and phytoremediation) and their effects are analyzed,and the existing problems and research prospects of the above techniques are explored. The research could provide reference for restoring farmland soil contaminated by Cd in China,recovering its production function and enhancing food safety standards.展开更多
Finite-Difference Time-Domain(FDTD)is the most popular time-domain approach in computational electromagnetics.Due to the Courant-Friedrich-Levy(CFL)condition and the perfect match layer(PML)boundary precision,FDTD can...Finite-Difference Time-Domain(FDTD)is the most popular time-domain approach in computational electromagnetics.Due to the Courant-Friedrich-Levy(CFL)condition and the perfect match layer(PML)boundary precision,FDTD cannot simulate soil medium whose surface is connected by multiple straight lines or curves(multi-scale)accurately and efficiently,which greatly limits the application of FDTD method to simulate buried objects in soils.Firstly,this study proposed the absorption boundary and adopted two typical perfect matching layers(UPML and CPML)to compare their absorption effects,and then using the three forms of improved Yee-FDTD algorithm,alternating-direction implicit(ADI-FDTD),unconditionally stable(US-FDTD)and hybrid implicit explicit finite time-domain(HIE-FDTD)to divide and contrast the boundary model effects.It showed that the HIE-FDTD was suitable for inversion of multi-scale structure object modeling,while ADI-FDTD and US-FDTD were ideal for single-boundary objects in both uniaxial perfectly matched layer(UMPL)and convolution perfectly matched layer(CPML)finite element space.After that,all the models were tested by computer performance for their simulated efficiency.When simulating single boundary objects,UPML-US-FDTD and ADI-FDTD could achieve the ideal results,and in the boundary inversion of multi-scale objects,HIE-FDTD modeling results and efficiency were the best.Test modeling speeds of CPML-HIE-FDTD were compared with three kinds of waveform sources,Ricker,Blackman-Harris and Gaussian.Finally,under the computer condition in which the CPU was i5-8250,the HIE-FDTD model still had better performance than the traditional Yee-FDTD forward modeling algorithm.For modeling multi-scale objects in farmland soils,the methods used CPML combined with the HIE-FDTD were the most efficient and accurate ways.This study can solve the problem that the traditional FDTD algorithm cannot construct non-mesh objects by utilizing the diversity characteristics of Yee cell elements.展开更多
The characteristics of eight heavy metals(lead,zinc,copper,nickel,chromium,cadmium,mercury and arsenic)in the surface soil of the historical slag area of the Au ore dressing plant in the South-West of Luoyang City wer...The characteristics of eight heavy metals(lead,zinc,copper,nickel,chromium,cadmium,mercury and arsenic)in the surface soil of the historical slag area of the Au ore dressing plant in the South-West of Luoyang City were investigated and evaluated in terms of a pollution index,potential ecological hazards and health risks.The results showed that the average amounts of the heavy metals Pb,Zn and As in the soils of plots S3,S5,S7,S12 and S18 exceeded the soil pollution risk screening values.The Mero comprehensive pollution index in plots S7,S12 and S18 was greater than 3,indicating severe pollution.The severe pollution plot integrated the potential ecological risk index(RI)of each sampling point,which was in the order of RI_(S12)>RI_(S18)>RI_(S7)>RI_(S5)>RI_(S3).Among the heavy metals,Cd poses the greatest threat to ecological and human health.The effects of heavy metals in soil on the single non-carcinogenic health risk index(HQ)and the non-carcinogenic total risk index through three exposure pathways were in the order of HQ_(Hg)<HQ_(Cu)<HQ_(Ni)<HQ_(Zn)<HQ_(Cd)<HQ_(Cr)<HQ_(Pb)<HQ_(As)<1,which meant that the adult and child total carcinogenic risk(TCR)and individual carcinogenic health risk indices CRAs and CRCd were above the maximum acceptable human health level recommended by the USEPA(10^(-6)).TCRAs and TCRCd accounted for 75.65%and 23.94%of the adult TCR,respectively.TCR^(As) and TCR^(Cd) accounted for 75.93%and 23.97%of the child TCR,respectively.Overall,the TCR of children was greater than that of adults.In summary,the soil in the historical slag area of the Au ore dressing plant constitutes a serious threat to the surrounding ecological environment and to residents.展开更多
The aim of this study was to determine the nitrate pollution status of soil, groundwater, and vegetable from three typical farmlands (croplands, vegetable fields, and orchards) in Beijing region. During the investigat...The aim of this study was to determine the nitrate pollution status of soil, groundwater, and vegetable from three typical farmlands (croplands, vegetable fields, and orchards) in Beijing region. During the investigation, hundreds of the soil, groundwater, and vegetable samples from three typical farmlands were collected and analyzed. In addition, attributes of all samples were recorded for data analysis. The results showed that nitrate was substantially accumulated in soil profiles, while the soil nitrate concentrations of vegetable fields and orchards were higher than those of croplands. Nitrate concentration in 0-30 cm soil of vegetable field and orchard were 3.8 and 1.2 times of that of cropland, respectively. Nitrate content of groundwater in vegetable field was 13.8 mg L-1 (with the over-standard ratio 44.8%), which was 2.8 folds of that in cropland. Nitrate concentration of groundwater under orchard was 9.3 mg L-1 (with the over-standard ratio 23.5%), which was 1.9 folds of that in cropland. High concentrations of the nitrate in vegetables were detected, particularly green leafy vegetables ranked first with 2 685.5 mg kg-1, followed by rhizome vegetables, cabbages, and fruit vegetables. The nitrate over-standard ratios of rhizome vegetables, green leafy vegetables, fruit vegetables, and cabbages were 80.9, 37.9, 29.7, and 2.2%, respectively. The results revealed that the high nitrate concentrations of soil, vegetable, and groundwater might result from the high fertilization dose.展开更多
The soil surface roughness and hydraulic roughness coefficient are important hydraulic resistance characteristic parameters. Precisely estimating the hydraulic roughness coefficient is important to understanding mecha...The soil surface roughness and hydraulic roughness coefficient are important hydraulic resistance characteristic parameters. Precisely estimating the hydraulic roughness coefficient is important to understanding mechanisms of overland flow. Four tillage practices, including cropland raking, artificial hoeing, artificial digging, and straight slopes, were considered based on the local agricultural conditions to simulate different values of soil surface roughness in the Loess Plateau. The objective of this study was to investigate the relationship between the soil surface roughness and hydraulic roughness coefficient on sloping farmland using artificial rainfall simulation. On a slope with a gradient of 10°, a significant logarithmic function was developed between the soil surface roughness and Manning's roughness coefficient, and an exponential function was derived to describe the relationship between the soil surface roughness and Reynolds number. On the slope with a gradient of 15°, a significant power function was developed to reflect the relationship between the soil surface roughness and Manning's roughness coefficient, and a linear function was derived to relate the soil surface roughness to the Reynolds number. These findings can provide alternative ways to estimate the hydraulic roughness coefficient for different types of soil surface roughness.展开更多
Soil organic carbon (SOC) and total nitrogen (N) concentrations from bulk soils and soil particle size fractions in the different extent of desertified farmlands (potential, light, medium, severe, and most severe dese...Soil organic carbon (SOC) and total nitrogen (N) concentrations from bulk soils and soil particle size fractions in the different extent of desertified farmlands (potential, light, medium, severe, and most severe desertified farmlands) were examined to quantitatively elucidate losses of carbon and nitrogen and its mechanisms in the desertification process. Particle size fractions (2-0.1 mm, 0.1-0.05 mm, <0.05 mm) were obtained by granulometric wet sieving from 30 sandy soils (0-15cm depth) of different desertified extent. It was shown that soil physical stability index (St) in most severe desertified farmlands was 5-7% and St in other farmlands was less than 5%, which contributed to very low soil organic matter content. This was the intrinsic cause that sandy farmlands in Horqin sandy land was subject to risk of desertification. Desertification resulted in considerable losses of SOC and N. Regression analysis indicated that SOC and N content reduced 0.169 g kg-1 and 0.0215 g kg-1 respectively with one percent loss of soil silt and clay content. Losses of SOC and N were mostly the removal of fine particle size fractions (silt and clay, and a less extent very fine sand) from the farmlands by wind erosion, which were rich in organic matter and nutrients, as well as the depletion of organic C and N associated with coarse particles (>0.05 mm) in desertification process. The concentrations of C and N associated with sand (2-0.1 mm and 0.1-0.05 mm) significantly decreased with increase of desertified extent. Silt and clay associated C and N concentrations, however, were less changed, and in contrast, were higher in soils under most severe desertified extent than in soils under potential and severe desertified extent. The percentage of distribution in sand (>0.05 mm) associated C and N significantly increased with increase of desertified extent, suggesting that stability of SOC decreased in the desertification process.展开更多
Increased food demand from the rapidly growing human population has caused intensive land transition from desert to farmland in arid regions of northwest China. In this developing ecosystem, the optimized fertilizatio...Increased food demand from the rapidly growing human population has caused intensive land transition from desert to farmland in arid regions of northwest China. In this developing ecosystem, the optimized fertilization strategies are becoming an urgent need for sustainable crop productivity, efficient resources use, together with the delivery of ecosystems services including soil carbon(C) and nitrogen(N) accumulation. Through a 7-year field experiment with 9 fertilization treatments in a newly cultivated farmland, we tested whether different fertilizations had significant influences on soil C and N accumulation in this developing ecosystem, and also investigated possible mechanisms for this influence. The results showed that applying organic manure in cultivated farmland significantly increased the soil C and N accumulation rates; this influence was greater when it was combined with chemical fertilizer, accumulating 2.01 t C and 0.11 t N ha^(–1) yr^(–1) in the most successful fertilization treatment. These high rates of C and N accumulation were found associated with increased input of C and N, although the relationship between the N accumulation rate and N input was not significant. The improved soil physical properties was observed under only organic manure and integrated fertilization treatments, and the significant relationship between soil C or N and soil physical properties were also found in this study. The results suggest that in newly cultivated farmland, long term organic manure and integrated fertilization can yield significant benefits for soil C and N accumulation, and deliver additional influence on physical properties.展开更多
Soil enzymes activities and microbial biomass have an important influence on nutrient cycling. The spatial distribution of soil enzymes activities and microbial biomass were examined along a latitudinal gradient in fa...Soil enzymes activities and microbial biomass have an important influence on nutrient cycling. The spatial distribution of soil enzymes activities and microbial biomass were examined along a latitudinal gradient in farmlands of Songliao Plain, Northeast China to assess the impact of climatic changes along the latitudinal transect on nutrient cycling in agroecosystems. Top soils (0-20 cm depth) were sampled in fields at 7 locations from north (Hailun) to south (Dashiqiao) in the end of October 2005 after maize harvest. The contents of total C, N, and P, C/N, available N, and available P increased with the latitude. The activities of invertase and acid phosphatase, microbial biomass (MB) C and N, and MBC/MBN were significantly correlated with latitude (P < 0.05, r2 = 0.198, 0.635, 0.558, 0.211 and 0.317, respectively), that is, increasing with the latitude. Significant positive correlations (P < 0.05) were observed between invertase activity and the total N and available P, and between acid phosphatase activity and the total C, C/N, available N, total P and available P. The urease, acid phosphatase, and dehydrogenase activities were significantly correlated with the soil pH and electrical conductivity (EC) (P < 0.05). MBC and MBN were positively correlated with the total C, C/N, and available P (P < 0.05). The MBC/MBN ratio was positively correlated with the total C, total N, C/N, and available N (P < 0.05). The spatial distribution of soil enzyme activities and microbial biomass resulted from the changes in soil properties such as soil organic matter, soil pH, and EC, partially owing to variations in temperature and rainfall along the latitudinal gradient.展开更多
The black soil region of northeast China is one of the most important grain-producing areas in China.Increasingly severe gully erosion in this region has destroyed much farmland and reduced grain production.We analyze...The black soil region of northeast China is one of the most important grain-producing areas in China.Increasingly severe gully erosion in this region has destroyed much farmland and reduced grain production.We analyzed SPOT5 imagery from 2007 and TM imagery from 2008 to describe the distributions of gullies and farmland shelterbelts in Kedong County and to assess the effect of farmland shelterbelts on gully erosion. The imagery revealed 2311 gullies with average density of 418.51 m km-2, indicating very serious gully erosion.With increasing slope gradient there was an inverse trend between gully density and shelterbelt density, indicating that farmland shelterbelts can prevent gully erosion. The defense effect of farmland shelterbelts against gullyerosion varied with distance: for distances<120 m, the defense effect was consistent and very strong; for distances of 120–240 m, a weak linear decrease was found in the defense effect; and for distances>240 m, the defense effect of the shelterbelts was significantly weaker. We recommend an optimal planting density of farmland shelterbelts for the prevention of gully erosion at1100–1300 m km-2.展开更多
This paper studied soil erodibility of slope farmland in Guizhou mountain areas by the plot runoff method,analysis and test. Results show that the variation coefficient of erodibility K value calculated according to f...This paper studied soil erodibility of slope farmland in Guizhou mountain areas by the plot runoff method,analysis and test. Results show that the variation coefficient of erodibility K value calculated according to formula introduced by Sharply is low and relatively stable and accurate,so it is a suitable method for calculating erodibility K value of slope farmland in Guizhou mountain areas. K value of layer A slope farmland decreases with increase of years. The erodibility of entire soil layer is high,and the erosion resistance is weak. From the influence of different planting system and use types in 4 years,K values of different soil layers decrease,average reduction of A,B and C layers reaches 3. 17%- 11. 64%( 1. 26%- 12. 34% for layer A,1. 29%- 13. 80% for layer B,and 1. 26%- 10. 80% for layer C). Except engineering terraced treatment,the decline of K value of grassland,zoning crop rotation,economic fruit forest,grain and grass intercropping,plant hedge, and mixed forest treatment is higher than farmers' treatment,and the decline level is grassland > zoning crop rotation > economic fruit forest > grain and grass intercropping > plant hedge > and mixed forest treatment. Planting grass and trees is favorable for lowering erodibility of slope farmland and improving farmland quality. Interplanting of corns with other plants can increase plant coverage and species,so it is favorable for improving erodibility of slope farmland.展开更多
There have been few in-depth quantitative studies on soil erosion control and the ecological effects of land use changes.Soil erosion is the first eco-environmental problem particularly in mountainous areas.A major pr...There have been few in-depth quantitative studies on soil erosion control and the ecological effects of land use changes.Soil erosion is the first eco-environmental problem particularly in mountainous areas.A major problem in the conversion of farmland to forest is to control soil erosion and improve ecological environment and thus to improve land use sustainability.We report results of calculation and analysis on soil erosion from converted farmland parcels in city of Mangshi (near the SW frontier of China) and the surrounding areas before and after the nine-year (2000-2009) project of converting farmland to forest.There was increased water conservation effect,as a result of decreased soil erosion.The average erosion modulus of the farmland returning to eco-friendly uses decreased by 5,535.59 t/km2?a and the control degree of soil erosion modulus reached 71.00%.The increased soil erosion after the returning in the typical sample area "did not drop,but increased" as the terraced fields decreased but sloping farmland increased and yet woodland decreased.展开更多
An environmental investigation of soil, water and vegetable around Asphalt production plant for heavy metals;Zinc (Zn), Manganese (Mn), Cadmium (Cd), Lead (Pb), Cobalt (Co), Nickel (Ni) and Chromium (Cr) was carried o...An environmental investigation of soil, water and vegetable around Asphalt production plant for heavy metals;Zinc (Zn), Manganese (Mn), Cadmium (Cd), Lead (Pb), Cobalt (Co), Nickel (Ni) and Chromium (Cr) was carried out. Their mean concentrations in soil, water and vegetable were Zn (13.84 mg/Kg, 12.949 mg/L and 11.177 mg/Kg), Mg (3.728 mg/Kg, 0.125 mg/L and 21.837 mg/Kg), Cd (0.012 mg/Kg, 0.018 mg/L and 0.028 mg/Kg) and Pb (0.011 mg/Kg). Co, Ni and Cr were not detected. The results of physiocochemical parameters (pH, moisture content (%), conductivity (μS/cm), organic matter (%), organic carbon (%), CEC (cmol/Kg) and soil composition (%)) were all within the permissible limits by NAFDAC and NDWQS. Results of mineral composition of soil include (N (%) of 0.42, K (cmol/kg) 0.32, Na (cmol/kg) 0.28, Mg (cmol/kg) 3.40, Ca (cmol/kg) 3.80, ?(cmol/kg) 0.46 and (cmol/kg) 0.49);analytical results were within the acceptable range. The chemical parameters investigated for water samples are (Cl- (mg/L) = 1871.20, ?(mg/L) = 12.60, ?(mg/L) = 10.20, NH3 (mg/L) = 8.20, DO (mg/L) = 9.40, BOD (mg/L) = 6.40 and COD (mg/L) = 12.80) within agricultural farmlands around the Asphalt production plant. From the analytical results, conductivity (μS/cm), N (%), ?(mg/L) were significantly different (p which are also the predominant mineral composition in the soil.展开更多
基金The work supported by the funding from the National Natural Science Foundation of China(31960414)High-level Talent Fund of Scientific Research for Intrduction and Training in Yan'an,Shaanxi Province of China(2019-06)+3 种基金Specialized Research Fund for the Doctoral Program of Yan’an University(YDBK2017-35)Research Project of Yan’an University(YDZ2019-07,YDQ2019-26)Scientific Research Program Funded by Shaanxi Provincial Education Department(18JS116)Innovation and Entrepreneurship Training Program of Shaanxi Province(S201910719069,S202010719118).
文摘Heavy metal-contaminated soil is one of the major environmental pollution problems of agricultural production and human health in the world.Remediation of heavy metals in soil is one of the most popular research subjects.Different remediation strategies have been reported to remove heavy metals from contaminated soil,among which phytoremediation is the most important one.Compared with other major crops,cotton shows the strongest and most widespread resistance to abiotic stresses,such as heavy metals.Although heavy metal stress adversely affects the growth and development of cotton,cotton possesses a set of sophisticated stress-resistance strategies.As the main product of cotton is nonedible fibers,which have a large biomass and strong heavy metal absorption and enrichment capacities,cotton is an ideal crop to restore heavy metal-contaminated soils and has unique advantages in terms of both ecological and economic benefits,with great application prospects.In this review,based on domestic and foreign research results in recent years,the effects of heavy metals on cotton growth and product quality were analyzed,the heavy metal absorption,accumulation,translocation and enrichment characteristics of cotton plants were summarized,and the adaptation and tolerance mechanisms of cotton to heavy metals were explored.Furthermore,the view that cotton is an effective crop to remediate heavy metal pollution in farmland soil has been proposed,and popularization and application suggestions for planting cotton to repair heavy metal pollution have been put forward to provide a reference for the comprehensive evaluation of the economic feasibility of cotton to repair heavy metal pollution in farmland soil.
文摘In line with the author’s long-time experience on soil reconnaissance, monitoring and scientific probes, this article expounds the vital significance in systematic build-up of pedological data, protection of arable land, employment and renovation of the farmland soil in accordance with the local edaphic setting in a bid to increase the grain yield.
基金Supported by National Natural Science Foundation of China(U1033004-06)Guangxi Key Agricultural Science Planning Project(201528)
文摘With the rapid development of mining,the soil heavy metal contamination is increasingly serious in Shaoguan,directly affecting the production of crops. This paper analyzes the farmland soil heavy metal contamination in the mining area of Shaoguan and the causes of heavy metal contamination in recent years,brings forward the bioremediation measures to control soil heavy metal contamination,and points out the development direction of bioremediation in farmland soil heavy metal contamination in the mining area.
基金Supported by the Work Project of China Geological Survey (1212010911062)Guangxi Zhuang Autonomous Region Innovation Project (0842008)National Natural Science Foundation (40872213)
文摘The three-pool and first-order model separates the mineralizable organic carbon into active,slow,and passive carbon pools.This paper used the model and decomposition curves of the soil organic carbon to fit the active pool and its decomposition rate,slow pool and its decomposition rate.The results showed that the size of the active pool from different profiles accounted for 2.09%-3.08% of the total soil organic carbon and the mean residue time was 3.57-17.21 days.And the size of the slow pool accounted for 3.19%-43.55% and the mean residue time was 1.12-4.94 years.Acid hydrolysis(6M HCl) was used to fractionate the passive organic carbon,which accounted for 50.83%-94.44% of the total soil organic carbon.
基金supported by the Fund for Training Program of Distinguished Young Scientists of Xinjiang (No. qn2015jq003)the National Natural Science Foundation of China (No. 41561073 and No. 41361002)
文摘Soil pollution significantly reduces environmental quality.In this study,farmland soil samples were collected from 25 sites in Baghrash County,Northwest China;and the concentrations of eight heavy-metal elements(arsenic,As;cadmium,Cd;chromium,Cr;copper,Cu;manganese,Mn;nickel,Ni;lead,Pb;zinc,Zn)were determined by standard methods.The spatial distribution,contamination level,and ecological risk stature of heavy metals were analyzed based on GIS technology,the Geo-accumulation Index(Igeo),the Pollution Load Index(PLI),and the Potential Ecological Risk Index(RI).Results indicated that(1)The average concentrations of Cd exceeded 12.12 times the allowed national standard for soil environmental quality of China.The average concentrations of Cd,Cr,Ni,Pb,and Zn exceeded the background values of irrigation soils in Xinjiang by 60.58,1.25,1.50,4.95,and 5.10 times,respectively.(2)The pollution order of the average value of Igeo for heavy metals was ranked as Cd>Zn>Pb>Ni>Cr>Cu>As>Mn.The individual potential ecological risk index for heavy metals was ranked in the order of Cd>As>Ni>Cu>Pb>Cr>Zn.The average PLI for the study area showed a heavy pollution level,while the average RI showed a considerable ecological risk stature,as compared to the classification standard.(3)The spatial distribution patterns of eight heavy metal elements were substantially heterogeneous.The moderately polluted areas with moderate potential ecological risks were distributed in the southern parts of the study area,whereas the heavily polluted areas with considerable potential ecological risks were distributed in the northern parts.Overall,it was observed that Cd contributed most to the PLI and RI of the farmland soils in Baghrash County.The pollution risk of Cd should be a major concern,and human activities in the region should be cautious.
文摘The heavy metal content of the farmland soil at two sides of Cheng-Guan Expressway is measured to make a preliminary evaluation on its heavy metal pollution status.After digestion and volume fixation of the soil samples collected,measure the Cu,Zn,Cd,Pb and Cr content with atomic absorption spectrophotometry and evaluate the measured data according to Level Two of National Soil Environmental Quality Standard to obtain the contamination status.Cu,Zn and Cd content of the farmland soil for sections of Cheng-Guan Expressway goes beyond Level Two of National Soil Environmental Quality Standard,while the Pb and Cr content meets Level Two of National Soil Environmental Quality Standard.Pb and Cr content of the farmland soil at two sides of Cheng-Guan Expressway is in safe state,while the Cu,Zn and Cd content is in a mild contamination state.Cu,Zn and Cd are the main pollution elements.
基金Supported by Science Technology Development Plan Item in Jilin,China(20110403)Key Item of Water Pollution Control and Treatment,China(2012ZX07201-001)
文摘Pb in the farmland surface soil of Changchun suburb was taken as the main research object. The field research and laboratory analysis were used to investigate Pb content,spatial distribution characteristics and its ecological risk in different farmland soils. The results showed that Pb content was during 18. 85- 41. 34 mg /kg in farmland soil of Changchun suburb,and was higher than the background value of Jilin Province at 90%of the sampling sites. The spatial distribution of Pb content in farmland soil had obvious geographical features,and Pb content in southwest and northeast soils was higher. The high-content areas were relatively concentrated,and Pb content gradually reduced from the high-content islandshape center to its surrounding. The soil Pb contents in paddy field,dry field and vegetable field had insignificant difference with the background value,indicating that Pb accumulations in dry field,paddy field and vegetable field were not significant. The order of Pb content in different land use types was showed as follows: vegetable field > dry field > paddy field. Pb pollution of all samples belonged to light pollution. The average potential ecological risk of soil Pb in different land use types presented the following order: vegetable field > dry field > paddy field.
基金Supported by Special Project of National Environmental Protection Public Interest Research,China(201109020)
文摘Cd contamination range of farmland soil in China is wide,which has constituted a major threat for food safety and residents' health. Via multi-year development,there are more remediation methods suitable for soil contaminated by Cd among the world,but some methods are only suitable for the contaminated sites and indoor research,and can not be applied in large-range contaminated farmland. We analyze the source of Cd in farmland soil. By combining farmland's characteristics,three remediation techniques( low-absorption crops plantation,soil solidification and phytoremediation) and their effects are analyzed,and the existing problems and research prospects of the above techniques are explored. The research could provide reference for restoring farmland soil contaminated by Cd in China,recovering its production function and enhancing food safety standards.
基金This work was financially supported by the State Key Research Program of China(Grant No.2016YFD0700101)the State Key Research Program of China(Grant No.2017YFD0700404)+1 种基金the Guangdong Provincial Department of Agriculture’s Specialized Program for Rural Area Rejuvenation(Grant No.2019KJ129)and the Guangdong Provincial Department of Agriculture’s Modern Agricultural Innovation Team Program for Animal Husbandry Robotics(Grant No.200-2018-XMZC-0001-107-0130).
文摘Finite-Difference Time-Domain(FDTD)is the most popular time-domain approach in computational electromagnetics.Due to the Courant-Friedrich-Levy(CFL)condition and the perfect match layer(PML)boundary precision,FDTD cannot simulate soil medium whose surface is connected by multiple straight lines or curves(multi-scale)accurately and efficiently,which greatly limits the application of FDTD method to simulate buried objects in soils.Firstly,this study proposed the absorption boundary and adopted two typical perfect matching layers(UPML and CPML)to compare their absorption effects,and then using the three forms of improved Yee-FDTD algorithm,alternating-direction implicit(ADI-FDTD),unconditionally stable(US-FDTD)and hybrid implicit explicit finite time-domain(HIE-FDTD)to divide and contrast the boundary model effects.It showed that the HIE-FDTD was suitable for inversion of multi-scale structure object modeling,while ADI-FDTD and US-FDTD were ideal for single-boundary objects in both uniaxial perfectly matched layer(UMPL)and convolution perfectly matched layer(CPML)finite element space.After that,all the models were tested by computer performance for their simulated efficiency.When simulating single boundary objects,UPML-US-FDTD and ADI-FDTD could achieve the ideal results,and in the boundary inversion of multi-scale objects,HIE-FDTD modeling results and efficiency were the best.Test modeling speeds of CPML-HIE-FDTD were compared with three kinds of waveform sources,Ricker,Blackman-Harris and Gaussian.Finally,under the computer condition in which the CPU was i5-8250,the HIE-FDTD model still had better performance than the traditional Yee-FDTD forward modeling algorithm.For modeling multi-scale objects in farmland soils,the methods used CPML combined with the HIE-FDTD were the most efficient and accurate ways.This study can solve the problem that the traditional FDTD algorithm cannot construct non-mesh objects by utilizing the diversity characteristics of Yee cell elements.
基金supported by the National Natural Science Foundation of China(41201224)Henan Province Science and Technology Research Project(192102110050)Project for the Training of Young Backbone Teachers of Higher Education Institutions in Henan Province(2018GGJS047).
文摘The characteristics of eight heavy metals(lead,zinc,copper,nickel,chromium,cadmium,mercury and arsenic)in the surface soil of the historical slag area of the Au ore dressing plant in the South-West of Luoyang City were investigated and evaluated in terms of a pollution index,potential ecological hazards and health risks.The results showed that the average amounts of the heavy metals Pb,Zn and As in the soils of plots S3,S5,S7,S12 and S18 exceeded the soil pollution risk screening values.The Mero comprehensive pollution index in plots S7,S12 and S18 was greater than 3,indicating severe pollution.The severe pollution plot integrated the potential ecological risk index(RI)of each sampling point,which was in the order of RI_(S12)>RI_(S18)>RI_(S7)>RI_(S5)>RI_(S3).Among the heavy metals,Cd poses the greatest threat to ecological and human health.The effects of heavy metals in soil on the single non-carcinogenic health risk index(HQ)and the non-carcinogenic total risk index through three exposure pathways were in the order of HQ_(Hg)<HQ_(Cu)<HQ_(Ni)<HQ_(Zn)<HQ_(Cd)<HQ_(Cr)<HQ_(Pb)<HQ_(As)<1,which meant that the adult and child total carcinogenic risk(TCR)and individual carcinogenic health risk indices CRAs and CRCd were above the maximum acceptable human health level recommended by the USEPA(10^(-6)).TCRAs and TCRCd accounted for 75.65%and 23.94%of the adult TCR,respectively.TCR^(As) and TCR^(Cd) accounted for 75.93%and 23.97%of the child TCR,respectively.Overall,the TCR of children was greater than that of adults.In summary,the soil in the historical slag area of the Au ore dressing plant constitutes a serious threat to the surrounding ecological environment and to residents.
基金the Special Fund for Agro-Scientific Research in the Public Interest, China (20100314)the Major Projects of Water Pollution Control and Treatment, China (2008ZX07425)+1 种基金the Agriculture Resources and Environment Protection Fiscal Project of Ministry of Agriculture, China, the SciTech New Star Plan of Beijing City, China (2007B045)the China Project of IPNI
文摘The aim of this study was to determine the nitrate pollution status of soil, groundwater, and vegetable from three typical farmlands (croplands, vegetable fields, and orchards) in Beijing region. During the investigation, hundreds of the soil, groundwater, and vegetable samples from three typical farmlands were collected and analyzed. In addition, attributes of all samples were recorded for data analysis. The results showed that nitrate was substantially accumulated in soil profiles, while the soil nitrate concentrations of vegetable fields and orchards were higher than those of croplands. Nitrate concentration in 0-30 cm soil of vegetable field and orchard were 3.8 and 1.2 times of that of cropland, respectively. Nitrate content of groundwater in vegetable field was 13.8 mg L-1 (with the over-standard ratio 44.8%), which was 2.8 folds of that in cropland. Nitrate concentration of groundwater under orchard was 9.3 mg L-1 (with the over-standard ratio 23.5%), which was 1.9 folds of that in cropland. High concentrations of the nitrate in vegetables were detected, particularly green leafy vegetables ranked first with 2 685.5 mg kg-1, followed by rhizome vegetables, cabbages, and fruit vegetables. The nitrate over-standard ratios of rhizome vegetables, green leafy vegetables, fruit vegetables, and cabbages were 80.9, 37.9, 29.7, and 2.2%, respectively. The results revealed that the high nitrate concentrations of soil, vegetable, and groundwater might result from the high fertilization dose.
基金supported by the National Natural Science Foundation of China(Grant No40901138)the Project of the State Key Laboratory of Earth Surface Processes and Resource Ecology(Grant No 2008-KF-05)the Project of the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau(Grant No10501-283)
文摘The soil surface roughness and hydraulic roughness coefficient are important hydraulic resistance characteristic parameters. Precisely estimating the hydraulic roughness coefficient is important to understanding mechanisms of overland flow. Four tillage practices, including cropland raking, artificial hoeing, artificial digging, and straight slopes, were considered based on the local agricultural conditions to simulate different values of soil surface roughness in the Loess Plateau. The objective of this study was to investigate the relationship between the soil surface roughness and hydraulic roughness coefficient on sloping farmland using artificial rainfall simulation. On a slope with a gradient of 10°, a significant logarithmic function was developed between the soil surface roughness and Manning's roughness coefficient, and an exponential function was derived to describe the relationship between the soil surface roughness and Reynolds number. On the slope with a gradient of 15°, a significant power function was developed to reflect the relationship between the soil surface roughness and Manning's roughness coefficient, and a linear function was derived to relate the soil surface roughness to the Reynolds number. These findings can provide alternative ways to estimate the hydraulic roughness coefficient for different types of soil surface roughness.
文摘Soil organic carbon (SOC) and total nitrogen (N) concentrations from bulk soils and soil particle size fractions in the different extent of desertified farmlands (potential, light, medium, severe, and most severe desertified farmlands) were examined to quantitatively elucidate losses of carbon and nitrogen and its mechanisms in the desertification process. Particle size fractions (2-0.1 mm, 0.1-0.05 mm, <0.05 mm) were obtained by granulometric wet sieving from 30 sandy soils (0-15cm depth) of different desertified extent. It was shown that soil physical stability index (St) in most severe desertified farmlands was 5-7% and St in other farmlands was less than 5%, which contributed to very low soil organic matter content. This was the intrinsic cause that sandy farmlands in Horqin sandy land was subject to risk of desertification. Desertification resulted in considerable losses of SOC and N. Regression analysis indicated that SOC and N content reduced 0.169 g kg-1 and 0.0215 g kg-1 respectively with one percent loss of soil silt and clay content. Losses of SOC and N were mostly the removal of fine particle size fractions (silt and clay, and a less extent very fine sand) from the farmlands by wind erosion, which were rich in organic matter and nutrients, as well as the depletion of organic C and N associated with coarse particles (>0.05 mm) in desertification process. The concentrations of C and N associated with sand (2-0.1 mm and 0.1-0.05 mm) significantly decreased with increase of desertified extent. Silt and clay associated C and N concentrations, however, were less changed, and in contrast, were higher in soils under most severe desertified extent than in soils under potential and severe desertified extent. The percentage of distribution in sand (>0.05 mm) associated C and N significantly increased with increase of desertified extent, suggesting that stability of SOC decreased in the desertification process.
基金funded by the National Natural Science Foundation of China (41201284, 41401337)the China Postdoctoral Science Foundation (2013M542406)
文摘Increased food demand from the rapidly growing human population has caused intensive land transition from desert to farmland in arid regions of northwest China. In this developing ecosystem, the optimized fertilization strategies are becoming an urgent need for sustainable crop productivity, efficient resources use, together with the delivery of ecosystems services including soil carbon(C) and nitrogen(N) accumulation. Through a 7-year field experiment with 9 fertilization treatments in a newly cultivated farmland, we tested whether different fertilizations had significant influences on soil C and N accumulation in this developing ecosystem, and also investigated possible mechanisms for this influence. The results showed that applying organic manure in cultivated farmland significantly increased the soil C and N accumulation rates; this influence was greater when it was combined with chemical fertilizer, accumulating 2.01 t C and 0.11 t N ha^(–1) yr^(–1) in the most successful fertilization treatment. These high rates of C and N accumulation were found associated with increased input of C and N, although the relationship between the N accumulation rate and N input was not significant. The improved soil physical properties was observed under only organic manure and integrated fertilization treatments, and the significant relationship between soil C or N and soil physical properties were also found in this study. The results suggest that in newly cultivated farmland, long term organic manure and integrated fertilization can yield significant benefits for soil C and N accumulation, and deliver additional influence on physical properties.
基金the National Key Basic Research Support Foundation of China (No.2005CB121105)theNational Natural Science Foundation of China (No.30670379).
文摘Soil enzymes activities and microbial biomass have an important influence on nutrient cycling. The spatial distribution of soil enzymes activities and microbial biomass were examined along a latitudinal gradient in farmlands of Songliao Plain, Northeast China to assess the impact of climatic changes along the latitudinal transect on nutrient cycling in agroecosystems. Top soils (0-20 cm depth) were sampled in fields at 7 locations from north (Hailun) to south (Dashiqiao) in the end of October 2005 after maize harvest. The contents of total C, N, and P, C/N, available N, and available P increased with the latitude. The activities of invertase and acid phosphatase, microbial biomass (MB) C and N, and MBC/MBN were significantly correlated with latitude (P < 0.05, r2 = 0.198, 0.635, 0.558, 0.211 and 0.317, respectively), that is, increasing with the latitude. Significant positive correlations (P < 0.05) were observed between invertase activity and the total N and available P, and between acid phosphatase activity and the total C, C/N, available N, total P and available P. The urease, acid phosphatase, and dehydrogenase activities were significantly correlated with the soil pH and electrical conductivity (EC) (P < 0.05). MBC and MBN were positively correlated with the total C, C/N, and available P (P < 0.05). The MBC/MBN ratio was positively correlated with the total C, total N, C/N, and available N (P < 0.05). The spatial distribution of soil enzyme activities and microbial biomass resulted from the changes in soil properties such as soil organic matter, soil pH, and EC, partially owing to variations in temperature and rainfall along the latitudinal gradient.
基金supported by the National Natural Science Foundation of China(31400612,41271305)the Key Technologies Research and Development Program of Henan Province(142102110147)
文摘The black soil region of northeast China is one of the most important grain-producing areas in China.Increasingly severe gully erosion in this region has destroyed much farmland and reduced grain production.We analyzed SPOT5 imagery from 2007 and TM imagery from 2008 to describe the distributions of gullies and farmland shelterbelts in Kedong County and to assess the effect of farmland shelterbelts on gully erosion. The imagery revealed 2311 gullies with average density of 418.51 m km-2, indicating very serious gully erosion.With increasing slope gradient there was an inverse trend between gully density and shelterbelt density, indicating that farmland shelterbelts can prevent gully erosion. The defense effect of farmland shelterbelts against gullyerosion varied with distance: for distances<120 m, the defense effect was consistent and very strong; for distances of 120–240 m, a weak linear decrease was found in the defense effect; and for distances>240 m, the defense effect of the shelterbelts was significantly weaker. We recommend an optimal planting density of farmland shelterbelts for the prevention of gully erosion at1100–1300 m km-2.
基金Supported by Project of Guizhou Agricultural Engineering Center(G[2009]4001)Special Fund for Scientific Research of Public Welfare Industry(Agriculture)(201003059)+1 种基金Key Agricultural Project of Guizhou Province(NY[2012]3046)International Sci-tech Cooperation Program of Guizhou Province(G[2011]7031)
文摘This paper studied soil erodibility of slope farmland in Guizhou mountain areas by the plot runoff method,analysis and test. Results show that the variation coefficient of erodibility K value calculated according to formula introduced by Sharply is low and relatively stable and accurate,so it is a suitable method for calculating erodibility K value of slope farmland in Guizhou mountain areas. K value of layer A slope farmland decreases with increase of years. The erodibility of entire soil layer is high,and the erosion resistance is weak. From the influence of different planting system and use types in 4 years,K values of different soil layers decrease,average reduction of A,B and C layers reaches 3. 17%- 11. 64%( 1. 26%- 12. 34% for layer A,1. 29%- 13. 80% for layer B,and 1. 26%- 10. 80% for layer C). Except engineering terraced treatment,the decline of K value of grassland,zoning crop rotation,economic fruit forest,grain and grass intercropping,plant hedge, and mixed forest treatment is higher than farmers' treatment,and the decline level is grassland > zoning crop rotation > economic fruit forest > grain and grass intercropping > plant hedge > and mixed forest treatment. Planting grass and trees is favorable for lowering erodibility of slope farmland and improving farmland quality. Interplanting of corns with other plants can increase plant coverage and species,so it is favorable for improving erodibility of slope farmland.
基金funded by the National Natural Science Foundation of China (No.40861014)
文摘There have been few in-depth quantitative studies on soil erosion control and the ecological effects of land use changes.Soil erosion is the first eco-environmental problem particularly in mountainous areas.A major problem in the conversion of farmland to forest is to control soil erosion and improve ecological environment and thus to improve land use sustainability.We report results of calculation and analysis on soil erosion from converted farmland parcels in city of Mangshi (near the SW frontier of China) and the surrounding areas before and after the nine-year (2000-2009) project of converting farmland to forest.There was increased water conservation effect,as a result of decreased soil erosion.The average erosion modulus of the farmland returning to eco-friendly uses decreased by 5,535.59 t/km2?a and the control degree of soil erosion modulus reached 71.00%.The increased soil erosion after the returning in the typical sample area "did not drop,but increased" as the terraced fields decreased but sloping farmland increased and yet woodland decreased.
文摘An environmental investigation of soil, water and vegetable around Asphalt production plant for heavy metals;Zinc (Zn), Manganese (Mn), Cadmium (Cd), Lead (Pb), Cobalt (Co), Nickel (Ni) and Chromium (Cr) was carried out. Their mean concentrations in soil, water and vegetable were Zn (13.84 mg/Kg, 12.949 mg/L and 11.177 mg/Kg), Mg (3.728 mg/Kg, 0.125 mg/L and 21.837 mg/Kg), Cd (0.012 mg/Kg, 0.018 mg/L and 0.028 mg/Kg) and Pb (0.011 mg/Kg). Co, Ni and Cr were not detected. The results of physiocochemical parameters (pH, moisture content (%), conductivity (μS/cm), organic matter (%), organic carbon (%), CEC (cmol/Kg) and soil composition (%)) were all within the permissible limits by NAFDAC and NDWQS. Results of mineral composition of soil include (N (%) of 0.42, K (cmol/kg) 0.32, Na (cmol/kg) 0.28, Mg (cmol/kg) 3.40, Ca (cmol/kg) 3.80, ?(cmol/kg) 0.46 and (cmol/kg) 0.49);analytical results were within the acceptable range. The chemical parameters investigated for water samples are (Cl- (mg/L) = 1871.20, ?(mg/L) = 12.60, ?(mg/L) = 10.20, NH3 (mg/L) = 8.20, DO (mg/L) = 9.40, BOD (mg/L) = 6.40 and COD (mg/L) = 12.80) within agricultural farmlands around the Asphalt production plant. From the analytical results, conductivity (μS/cm), N (%), ?(mg/L) were significantly different (p which are also the predominant mineral composition in the soil.
