Heavy Metal Polluted Soil
Distribution of Urban Soil Heavy Metal and Pollution Evaluation in Different Functional Zones of Yinchuan City
Environmental Science,2016,Vol 37,No. 02
【Abstract】 Surface soil samples (0–20 cm) from eight different functional areas in Yinchuan city were collected. There were 10 samples respectively in each functional area. The urban soil heavy metals (Zn, Cd, Pb, Mn, Cu and Cr) pollution characteristics and sources in eight different functional areas were evaluated by mathematical statistics and geostatistical analysis method. Meanwhile, the spatial distributions of heavy metals based on the geography information system (GIS) were plotted. The average values of total Zn, Cd, Pb, Mn, Cu and Cr were 74.87, 0.15, 29.02, 553.55, 40.37 and 80.79 mg·kg−1, respectively. The results showed that the average value of soil heavy metals was higher than the soil background value of Ningxia, which indicated accumulation of the heavy metals in urban soil. The single factor pollution index of soil heavy metals was in the sequence of Cu > Pb > Zn > Cr > Cd > Mn. The average values of total Zn, Cd, Pb and Cr were higher in northeastern, southwestern and central city, while the average values of Mn and Cu were higher in northeastern and central city. There was moderate pollution in road and industrial area of Yinchuan, while the other functional areas showed slight pollution according to Nemoro synthesis index. The pollution degree of different functional areas was as follows: road > industrial area > business district > medical treatment area > residential area > public park > development zone > science and education area. The results indicated that the soil heavy metal pollution condition in Yinchuan City has been affected by human activities with the development of economy.
Transactions of the Chinese Society of Agricultural Engineering,2015,Vol 31,No. 07
【Abstract】 According to the bulletin of the national soil pollution reported by Ministry of Environmental Protection and Ministry of Land and Resources of the Peoples Republic of China,the total above standard rate is 16.1%in national soil,and above standard soils of Cd,Zn,Pb and Cu are 7.0%,0.9%,1.5% and 2.1%,respectively. Soil washing with chelating agents and phytoextraction by chelator-enhanced is potentially useful technique for remediating the heavy metal-contaminated soils. EDTA is the most frequently cited chelating agent in these techniques because of its strong chelating ability for different heavy metals. However,the slow degradation rate and persistence of residual EDTA in soil potentially increases the metal leaching risk which may cause groundwater contamination. But the environmental risk of EDTA reported in literature is from pot and column leaching experiments in laboratory scale. In order to understand the environmental risk of residual EDTA in the remediation of metal-contaminated soil,the field investigation and the incubation experiments were conducted to investigate the residue and degradation of EDTA in soil. The results of Lechang field investigation revealed that EDTA residue was not detected in the topsoil and deep soil after EDTA applied for 6 years. In Fogang field,the concentration of EDTA in soil was 0.039–0.056 mmol/kg soil,which was 2%to5%of the applied amount in the 4th month after application. However,the EDTA was not detected in soil after 1 year. In Wengyuan field,the concentration of EDTA in topsoil was approximately 50%of added amount(3.3 mmol/kg soil) after 45 d of EDTA application,while it was only 2.6%of added amount after application in one year. EDTA residue was detected in the deep soil. However,the EDTA was not detected in groundwater. In addition,the concentration of heavy metals in groundwater was not increased after EDTA application. The deep soils have considerable fixation capacity for the heavy metal-chelator complexes,which help preventing the metal-chelator complexes from leaching down to groundwater. Incubation experiments were carried out to evaluate the degradation of EDTA in different soils. The air-dried soil(2 kg with < 5 mm particle size) was placed in plastic pots with the rate of 10 mmol/kg soil EDTA addition. Soils were incubated at room temperature and about 60%–70%soil water-holding capacity. Then soil samples were taken in 0, 3, 10, 20, 30, 50 and 72 d after incubation. The results indicated that degradation of EDTA in soils followed the first-order kinetic equation. Degradation rate constant of EDTA in latosolic red soil,cinnamon soil and metal-contaminated soil was 4.6×10~(−3),1.4×10~(−2) and 5.8×10~(−3),and the half-life was 71, 25 and 53 d for each soil,respectively. The half-life of EDTA had a good correlation with the organic matter content and CEC in soil. Microorganisms had a marked influence on the degradation of EDTA in soils. The finding suggested that EDTA-enhanced remediation technology can be used on remediating heavy metals-contaminated soil,but the added amount should be controlled. As such,the environmental risk of EDTA is minimum.
China Environmental Science,2015,Vol 35,No. 04
【Abstract】 An extensive survey was conducted to evaluate the health risk of potentially toxic heavy metals in near-surface urban dust environment of Changchun, P.R. China. 232 samples were collected, using a systematic sampling strategy with a sampling density 3–5 composite dust samples (about 1.5m above the ground surface) per km2 in urban sit. X-ray fluorescence spectroscopy (XRF), atomic fluorescence spectrophotometry (AFS) and graphite furnace atomic absorption spectrometry (GF-AAS) were employed to analyze the Cu, Pb, Zn, Cr, As, Hg and Cd concentration of urban dust, respectively. The results indicated that the mean concentration of As, Cd, Cr, Cu, Hg, Pb and Zn in the near-surface urban dusts of Changchun was 23.26, 0.62, 94.53, 68.41, 0.24, 93.63 and 416.71 mg/kg, respectively, which are significant higher than the value of Changchun topsoils, meanwhile, which also shows that the urban dust in Changchun was polluted. The results of health risk assessment showed that children has had greater health risks than adults, the exposure doses for children were 7.3 times higher than those for adults, except for As which is 7.9 times higher. The exposure pathway which resulted in the highest level of risk for human exposed to near-surface dust was ingestion of this material, which was followed by dermal contact. As for the aggregate non-carcinogenic health risk (HI), As was of most concern regarding the potential occurrence of health impact, which was followed by Cr, Pb, Cu, Zn, Cd and Hg. The average non-carcinogenic health risk index for children and adults were 1.11 and 0.14, respectively. Of the three carcinogenic metals concerned in present study As, Cr and Cd, As was of most concerned. The average aggregate carcinogenic health risk index (RISKt) was 6.35 × 10−5, which was higher than the EPA advised values. However, except for some locations, risk values of both cancer and non-cancer health risk obtained in present study were in the acceptable range on the whole.
Transactions of the Chinese Society of Agricultural Engineering,2015,Vol 31,No. 04
【Abstract】 Biochar is a solid material that is produced from biomass pyrolysis in oxygen-limited atmosphere at relatively low temperatures. Therefore, the conversion of biosolids (e.g., agricultural waste, invasive species, municipal sewage sludge, etc.) into biochar could provide a useful way to achieve resource reuse and environmental management. In China, decreased land resources and soil fertility is of increasing concern presently, which may threat national food security. Therefore, a range of biochars have been tested for their potential in improving farming soil quality considering the high fertility sustained by biochar in Amazonian Dark Earths locally known as Terra Preta de Indio. Some studies have proved that biochar can play a positive role in improving the fertility of agricultural soils and thus increasing crops yield. Moreover, biochar has also been shown to be effective in control and remediation of a range of soil contamination and hence improve soil environmental quality, leading to increased food output and quality. In the present review, the most recent advances in the effect of biochar on agricultural soil fertility and soil environment quality with the underlying mechniasms are reviewed and discussed here in detail. Firstly, most biochars, particularly those produced from wetland plant residues tend to improve water retention capacity of agricultural soil, especially for those with sandy texture. This phenomenon could be caused by the porous structure of biochar, which can increase the water-holding porosity of soils. Secondly, substantial evidence has shown that the bioavailability of key mineral nutrients increase remarkably in response to biochar application, which could be attributed to the sufficient mineral ash in biochar and relatively high caiton exchange capacity (CEC) originated from the rich surface functional groups of biochar. Thirdly, the alkalinity of biochar, which is most likely resulted from the high mineral content, has exhibited potential in mitigation of soil acidity. As a result, the leaching of essential minerals and associated water eutrophication could be controlled to different degrees. However, the long-lasting buffering performance of biochar in the areas of acid rain is still unknown, which needs long-term monitoring with locating tests. Fourthly, with high CEC and mineral content, biochar could be used as fixing agent to sequester heavy metals in agriculture soils through complexation and precipitation, resulting in decreased transfer and accumulation of heavy metals in food chain. On the other hand, a series of negative impacts of biochar on farmland are also highlighted in this review. First of all, biochar may reduce the aggregation of soil particles, and bring ammonia gas gathered in soils which is detrimental to the soil organisms. Simultaneously, the application of biochar into soil could induce the enrichment of polycyclic aromatic hydrocarbon and heavy metals in uncontaminated farmland as well as decreased nitrogen uptake by crops, All of these potential risks can not be ignored. Full realization and systematic investigation on these hazardous effects of biochar is essential to ensure the safe and efficient application of biochar for the improvement of soil fertility and environmental quality. At last, a range of research gaps and future challenges have been characterized and discussed in detail. To achieve better understanding of the effect of biochar on sustainable agriculture with associated mechanisms, long-term experiments in field scales are needed to investigate the persistent output and biogeochemical behaviors of different kinds of biochar. Besides, more field experiments should be carried out to explore the applicability of biochars in differing regions with specific soil types, which could provide more realistic information to improve the local soils. In parallel, ecological and toxicological effects of biochar should be addressed to identify the potential risks. Finally, more efforts should be paid to establish the regulation framework and reference criterion to ensure biochar quality and evaluate its effect on soil fertility and environmental quality.
Journal of China Coal Society,2016,Vol 41,No. 08
【Abstract】 In the present paper, the authors conducted some experiments on the samples of the soils of Daquanhu coal fire for analyzing the characteristics of heavy metals distribution in this fire zone, such as Hg, As, Cu, Pb, Cr and Zn, which is relevant to the soil properties of the sampling sites. Results show that the temperature increases with the depth increase of the sampling site in both normal and abnormal area, and the variation of temperature increase in the normal area is less than that of the abnormal area. The content of organic matter of soils decreases with the depth increase of the sampling site in both the normal area and the abnormal area. And the layer one, the layer two, the layer three and the layer four of the normal area soil contains more organic matter than that of the abnormal area soils. The contents of some heavy metals in the layer one of normal area soil, such as Cu, Pb, Cr, Zn and Ni, are less than those of the layer one of the abnormal soil. In the layer two of the abnormal area soil, the content of these heavy metals shows a trend of increase. In both the normal area and the abnormal area soils, the contents of Hg, As, Cu and Ni fluctuate little along the increase of the depth of sampling site. But the contents of Pb, Cr and Zn in abnormal area soil fluctuate more than those of the normal area soil. Results also show that the heat effect of the coal fire, the topography of the fire zone, the properties of the soil and the local climate parameters are the main factors to impact the spatial distribution of the heavy metals in the soil of underground coal fires. An analysis of the As speciation shows that the content of the residual As speciation is the highest, and that of the water soluble As speciation is the lowest. Contents contour maps show that the accumulating characteristics of the water soluble As speciation within the soil of the layer one to layer four consequently has the same trend of the accumulation of CaCO3 in this area. In the normal area of the fire zone, the contents of the residual As speciation and the iron As speciation have the same trend of change as the change of CaCO3 following the sampling depth increase. However, in the abnormal area of the fire zone, the content of the residual As fluctuates with a similar trend of the content of the organic matter following the increase of sampling depth. The mean contents of the water soluble As in both the normal area and the abnormal area stay stable, which indicates that no close relationship exists between the As content and the soil temperature as well as the soil properties.
Contents and spatio-temporal variability of soil heavy metals in the coastal mud-flat area of north Jiangsu Province
China Environmental Science,2016,Vol 36,No. 06
【Abstract】 The study was carried out in a representative coastal mudflat area in northern Jiangsu Province, China. Classical statistical and geostatistical methods were employed to summarize the concentrations of the four types of elements (Pb, Cr, Cd, As) in surface soil in 2009 and 2014, to analyze the effect of land use types on heavy metal content, and to determine spatial patterns and spatio-temporal variability of soil heavy metals in these two periods. Results indicated that the content was generally below the widely accepted environmental quality standard (first class) for the four types of soil elements. During the five years from 2009 to 2014, soil Cd accumulated significantly across the study area, soil Pb content in the residential area also increased remarkably, and significant accumulation of soil Pb and Cd was also observed in the industrial area, whereas the change of soil Cr and As contents was not significant in each type of land use. Under the control of large-scale tide deposits and small-range human activities, soil Pb and Cr contents exhibited similar spatial patterns during these two periods, whereas the spatial patterns of soil Cd and As showed great difference in the two periods. The enrichment of soil heavy metals across the different land use types in the study area exhibited spatial variability and directional trends. Atmospheric deposition was another important factor that influenced the spatio-temporal variability of soil heavy metals. The coastal mudflat area presently faces the problem of soil heavy metal enrichment. We should take preventive countermeasures, such as strengthening in situ monitoring and source reduction, optimizing industrial layout, and prompting process blocking and biological remediation, to prevent and minimize heavy metal hazards.
China Environmental Science,2016,Vol 36,No. 05
【Abstract】 Chitosan and activated carbon, with different quality ratio, were added into the tested soil, then toxicity characteristic leaching procedure (TCLP) was conducted to study the stabilization effect of adsorption materials on V and Cr from the tested soil. Besides, Fourier Transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were performed to explore the stabilization mechanisms of the adsorption materials. The results show that chitosan could effectively stablize V and Cr in the tested soil. The stabilization effect of activated carbon on Cr is better than that on V in the tested soil, while the stabilization effect is not affected significantly by the dosage of adsorption materials. The stabilization rate of V and Cr in the tested soil 74.04% and 46.77%, respectively,by chitosan with the dosage of 0.5% after 30 d stabilization; while 1.86% of V and 87.75% of Cr could be stabilized, respectively, when 0.5% of active carbon was applied. FTIR and XPS results on the adsorption materials show that there are numerous of amino and hydroxyl groups in the chitosan, while amino and oxygen-containing groups are limited in activated carbon. Thuerefore, chitosan and activated carbon can be promising stabilizers available to remediate the vanadium mining contaminated soil.
Spatial Characteristics and Environmental Risk of Heavy Metals in Typical Gold Mining Area of Shandong Province
Environmental Science,2016,Vol 37,No. 08
【Abstract】 In order to reveal the influence of anthropogenic factors on soil environment quality, a total of 77 samples in topsoils were collected from Jiaojia gold mining area in Shandong province and were determined for Cu, Pb, Zn, Cr contents. Spatial variation structure, spatial distributions of concentrations and potential contamination risk of heavy metals were analyzed using spatial statistic analysis. The average concentrations of Cu, Pb, Zn and Cr were 19.41 mg·kg−1, 27.32 mg·kg−1, 49.81 mg·kg−1 and 39.27 mg·kg−1, respectively. Pb, Zn and Cr were distributed normally and Cu was distributed normally after logarithm transformation. Semi-variance analysis demonstrated that Pb could be fitted for exponential model, and Cu, Zn and Cr were fitted for spherical model. Nugget coefficents of Cu and Pb were between 0.25 and 0.75, which illustrated middle spatial autocorrelation; Zn and Cr showed the structural variation with Nugget values below 0.25. Cu and Pb in the topsoils were distributed dispersedly due to effects of some human factors, whereas contents of Zn and Cr indicated relatively regular distributions and were mainly affected by natural factors. Spatial distributions of the four heavy metals were approximately consisitent and the high value areas appeared in the gold mines band. The result of hot spot analysis and indicator kriging interpolation revealed that the relatively high risk areas were located in the boundary zone of Jincheng town, Xinzhuang town and Canzhuang town, while the safe zone was situated in south part of the study area. Pb had the highest probability exceeding the threshold and distributed widely in middle or high environmental risk areas. The results of the study offered reference and foundation for the evaluation and control of soil pollution in the study area.
bTracing Sources of Heavy Metals in the Soil Profiles of Drylands by Multivariate Statistical Analysis and Lead Isotope
Environmental Science,2016,Vol 37,No. 06
【Abstract】 Contents of 26 heavy metals from two soil profiles in drylands in Xiamen City were determined by inductively coupled plasma source mass spectrometer (ICP-MS). The distribution characteristics, environmental risk and pollution sources of heavy metals in soil profiles were studied. Combining the assessment results of Nemero comprehensive pollution index method, the geological accumulation index method and potential ecological hazard index method, which indicated that Cd was the main pollution factor in soil of drylands in Xiamen City; the soil pollution was serious in the depth of 50–60 cm. Multivariate statistical analysis showed that the main sources of heavy metals were agricultural production activities and natural resources, and the main pollution factor Cd was from agricultural production. Composition of acid-extractable Pb isotope in soil profiles and potential pollution sources were compared and analyzed. The results showed that Pb in soil of drylands in Xiamen City was mainly from sludge and parent material. According to the distribution characteristics of soil profiles in the 206Pb/207Pb–206 Pb/204 Pb diagram, applying Bivariate Mixture Model of Pb isotope, the contribution rate of parent material in P180 and P181 profiles was calculated, i.e., 54.36% and 42.88%, respectively, that of sludge was45.64% and 57.12%, respectively. The results show that the main sources of lead in soil of drylands in Xiamen City were parent material and sludge, which was consistent with the results of the multivariate statistical analysis.
Rock and Soil Mechanics,2016,Vol 37,No. 09
【Abstract】 Permeability is the key control factor representing anti-seepage ability and anti-fouling property of clay layer, and the proper choice of permeability coefficient of clay liner is crucial to ensure anti-fouling effect of the liner. The purpose of this investigation is to characterize the variation of the permeability of saturated clay with mixed heavy metal ions solution as permeant fluid. The permeability tests are performed with flexible-wall permeameters. It is shown that the permeability of saturated clay is enhanced with the increase in proportion of ions concentration for the permeant fluid with soluble Cu2+ and Cr3+, Cu2+ and Mn2+. In addition, under the same experiment conditions, the permeability coefficient of clay liner permeated with Cu2+ and Cr3+ mixed solution is larger than that with Cu2+ and Mn2+ mixed solution; the existence of mixed heavy metal ions weakens the ability of clay liner, and deteriorates the hydraulic conductivity of clay layer. The scanning electron microscope reveals that the permeant fluid plays an important role in changing the soil microstructure. The effective transport pore fluid passage increases with increasing mass ratio of mixed ions in permeant fluid, and aggregates are found in the soil samples, which is in good agreement with variation of macroscopic permeability. The results can provide a reference for evaluating anti-fouling ability of clay as valid barrier.
Effects of Continuous Application of Sewage Sludge Compost on Heavy Metals Accumulation and Migration Characteristics in Soil Profile and on Heavy Metals Uptake of Wheat
Environmental Science,2017,Vol 38,No. 02
【Abstract】 The use of sewage sludge compost (SSC) as fertilizer may cause increased leaching due to its high concentration of heavy metals and thus pose a threat to groundwater quality. The effect of SSC application on heavy metals leaching in calcareous soils has been studied in field trials, which provides basis for determining heavy metals environmental capacity and preventing metal pollution in farmland soil scientifically. The results indicated that the concentrations of Cu, Zn elevated obviously with the increase of the age and the dosage of SSC utilization in the surface soil (0–15 cm) under 4-year continuous application of SSC. Under higher levels of the compost treatment, the heavy metals Cu and Zn were found to migrate into the 15–30 cm soil and 60–90 cm soil under the experimental condition. Nevertheless, the majority of Cu and Zn from SSC accumulated in surface soil and the highest accumulation rates could reach 75.3% for Cu and 85.9% for Zn. The concentrations of Cd, Pb increased significantly in surface soil after 4-year continuous application of SSC, and their increases could reach 57.2%–165.2% for Cd and 13%–34% for Pb compared with CK. At 60–90 cm soil, the concentrations of Cr, As and Pb were also significantly higher than those in CK treatment. Application of SSC not only caused accumulation of some heavy metals in surface soil but also leached heavy metals located in the subsurface soil down in this experiment. Continuous utilization of SSC increased Zn concentration of wheat grain, and the increase could reach 13.3%–47.9%. For the concentrations of Cr and Pb in wheat grain, the values exceeded the limit refer to Food and Healthy Standards (GB2762-2012) in part of compost treatments. The cumulative ratio of heavy metals carried out by wheat was all below 10% after 4-year experiment, wheat grain carried much more Cu, Zn out than wheat straw, but it was opposite for Cr, As, Cd, Pb. The cumulative ratio of heavy metals carried by wheat decreased with the increasing level of SSC utilization. The amounts of heavy metals migrated to deeper soil should be considered when determining the environmental capacity of heavy metals in farmland soil.
Risk Assessment of Heavy Metal Contamination in Farmland Soil in Du'an Autonomous County of Guangxi Zhuang Autonomous Region, China
Environmental Science,2015,Vol 36,No. 08
【Abstract】 For a comprehensive understanding of the pollution characteristics and ecological risk of heavy metals of farmland soil in Du’an Autonomous County of Guangxi Zhuang Autonomous Region, China, this study evaluated the cadmium (Cd), arsenic (As), nickel (Ni), zinc (Zn), chromium (Cr), antimony (Sb), copper (Cu) and lead (Pb) pollution situation using the single factor index, the Nemerow pollution index and the Hakanson ecological risk index. The results showed that heavy metal pollution of farmland soil in Du’an County was serious. 74.6% of the soil samples had heavy metals concentrations higher than the Grade II of Environmental quality standard for soils (GB 15618-1995). The standard-exceeding rates of Cd, As, Ni, Zn, Cr, Sb, Cu, Pb were 70.6%, 42.9%, 34.9%, 19.8%, 19.6%, 2.94%, 1.59%, 0.79%, respectively. Cd and As were the main contaminants in Du’an County, the pollution was far more serious than those of the national and Guangxi Zhuang Autonomous Region. In terms of the ecological risk, heavy metals of farmland soil in Du’an County showed a “moderate”ecological risk, with Cd accounting for 88% of the total ecological risk. The north-east of Jiudu Town and the zone between Bao’an Town and Dongmiao Town were two areas with high ecological risk in Du’an County. The contamination of farmland soils in Du’an County was caused by two main sources. The As and Sb pollution in the farmland soil irrigated with polluted water near Diaojiang River may be caused mainly by the mining activities in the upper reaches of Diaojiang River.
Assessment of Heavy Metal Pollution and Tracing Sources by Pb & Sr Isotope in the Soil Profile of Woodland in Quanzhou
Environmental Science,2017,Vol 38,No. 04
【Abstract】 The contents of 8 heavy metal elements (Sr, Ni, Fe, Cr, Cu, Mn, Pb, Zn) and the lead & strontium isotope composition of soil profile of woodland in Quanzhou city were analyzed by AAS and ICP-MS, respectively. A modified BCR four-step sequential extraction procedure was carried out to obtain the speciation fractionation of heavy metals in the soil profile from 4 stations. The results of the heavy metal elements and the speciation fractionation of heavy metals in the soil profile showed that the heavy metal pollution in the woodland in Quanzhou was relatively light, and the main pollution factor was Sr. The non-residue state of Pb was the highest, leading to the highest activity. The result of Nemero comprehensive pollution index showed that Sr in the depth of 0–60 cm was at heavy pollution level. The results of the RSP showed that the activity of Pb was the highest. The results of EF showed that Pb, Sr, Mn and Zn had exogenous sources. Factor analysis showed that the main sources of heavy metals were the compound pollution of agricultural activities, natural resources, and the vehicle exhaust. Composition of Pb isotopic ratios showed that, Pb in soil profile of woodland in Quanzhou was from vehicle exhaust and parent material. The contribution rates of the two sources in the soil profile were calculated by using the two-mixed model. The contribution rates of parent material and vehicle exhaust were 85.14% (62.53%–98.36%) and 14.86% (1.640%–37.47%) on average, respectively. Strontium isotope tracing results showed that the main sources of strontium were also vehicle exhaust and parent material. Coupling both Pb and Sr isotope ratios agreed with the above mentioned results.
Science of Surveying and Mapping,2017,Vol 42,No. 05
【Abstract】 Space sampling cannot accurately estimate the comprehensive pollution of heavy metals in the soil and the variation of migration laws, so this paper puts forward grey comprehensive evaluation model based on GIS and combination empowerment in multiple attribute decision making. Firstly, we use the GIS technology analysis method to reveal the soil polluted by heavy metal spatial variation and distribution pattern; the maximum entropy theory which integrates subjective and objective factors is introduced to construct the optimization performance of grey comprehensive evaluation system of heavy metal pollution in soil, finally we use experimental comprehensive pollution status of heavy metals as the case which contains eight kinds of heavy metals (Cu, Zn, Pb, Cd, As, Cr, Hg, Ni) in the soil to inspect application effect of this method. The results show that the gray comprehensive analysis method using the optimal combination takes subjective preference and objective attributes into consideration, obtaining the evaluation results with higher reliability and risk identification. This method improves the rationality and effectiveness of comprehensive evaluation, which can provide basis for monitoring soil heavy metal pollution.
Contamination Assessment and Sources Analysis of Soil Heavy Metals in Opencast Mine of East Junggar Basin in Xinjiang
Environmental Science,2016,Vol 37,No. 05
【Abstract】 The opencast mine of East Junggar Basin in Xinjiang is the largest self-contained coalfield in China, and the ecological environment of the opencast is very fragile because of its arid climate and poor soil. In this study, 50 soil samples (from 0 to 30 cm depth soil at intervals of 10 cm) in opencast Mine of East Junggar Basin in Xinjiang were collected in order to explore the heavy metals contamination of the coal mining. The contents of zinc (Zn), copper (Cu), cadmium (Cr), lead (Pb), mercury (Hg) and arsenic (As) were measured and the degree of pollution was assessed by Nemerow index, geo-accumulation (Igeo) index and potential ecological risk index. In addition, the layered comparison, dust fall and the distance between coal mine and samples location were used to analyze the source of heavy metals contamination. The results showed that value of As surpassed the Grade I of Environmental quality standard for soils (GB 15618-1995) mostly severely, followed by Cr, a relatively lower surpass was obtained by Hg and Cu, while Zn and Pb did not surpass the standard. According to the standard, the soil heavy metals content of research region was in light pollution status and the pollution index for each heavy metal followed the order of As (2.07) > Cr (0.95) > Cu (0.55) > Zn (0.48) > Hg (0.45) > Pb (0.38), which demonstrated a heavy pollution of As and clean status of others. Additionally, an Igeo value of 1.14 for Hg reflected a moderated pollution. The major contribution factor was Hg with a risk index of 251.40. The source analysis showed that the content of Pb in the surface soil (10–20 cm) was different from that in the deep layer (20–30 cm), which may be caused by coal combustion and other human activities. The sources of Hg and As were similar and may come from coal combustion. The distance to the mining area was not the major factor affecting the diffusion of heavy metals, other candidate factors included terrain, aspect and wind direction, etc.
China Environmental Science,2017,Vol 37,No. 06
【Abstract】 In order to study the pollution characteristics and potential ecological risk of heavy metals in topsoil of Beijing, topsoil samples were collected in different functional areas of Beijing during November 2013 to December 2013. Totally 49 groups of topsoil samples with different particle sizes were obtained using precipitation method after the settlement and classification from the initial samples. Then the concentrations of 8 heavy metals (Cr, Ni, Cu, Zn, Mo, Cd, Ba and Pb) were measured by ICP-MS. The results showed that the average concentrations of Cd, Cu, Zn and Pb were1.4 mg/kg, 85 mg/kg, 333 mg/kg and 69 mg/kg in topsoil of Beijing, respectively, and the pollution of those heavy metals in traffic areas was significantly heavier than that in other functional areas. Geo-accumulation indexes (Igeo) of Cd, Cu, Mo, Ni, Pb and Zn were negatively correlated with the particle size. That is to say, the smaller the particle size was, the higher the corresponding value of Igeo would be, and the higher the pollution level would be. The total potential ecological risks of heavy metals in traffic areas were much higher than those in other functional areas. And the total potential ecological risks of heavy metals in industrial zones and urban-rural fringe areas were the second highest. The smaller the particle size was, the higher the potential ecological risk indexes (RIs) would be. In addition, the potential ecological risk of Cd accounted for the major part of the total potential ecological risks.
China Environmental Science,2018,Vol 38,No. 01
【Abstract】 Increasing attention has been paid to soil heavy metal pollution. A method that rapid detection of soil heavy metal concentrations was provided for the field screening and monitoring of soil heavy metal pollution. Aiming to understand the research status and trend of soil heavy metal rapid monitoring, X-ray fluorescence (XRF) was used as an example for visualized analysis by software CiteSpace based on the Web of Science database. The results showed that: (1) For the term of agent, the largest amount of literature around rapid monitoring of heavy metals was reported by the Chinese Academy of Sciences and the National Scientific Research Council of Spain. For the term of country, the reports were dominated by the United States, followed by China and Germany. (2) The instrument development, practical application and the factors influencing quantitative monitoring were the research concern. (3) The future research possibly focused on the instrument miniaturization and intelligence, rapid monitoring of farmland soil heavy metal and the monitoring of spatial distribution of soil heavy metal. The review on soil heavy metal rapid monitoring could provide reference for related research in China.
Comparision of Ecological Risk Assessment Based on the Total Amount and Speciation Distribution of Heavy Metals in Soil: A Case Study for Longyan City, Fujian Province
Environmental Science,2017,Vol 38,No. 10
【Abstract】 A total of 110 topsoil samples and 61 crop samples along the Lantian–Yangdong Villages were collected in Shizhong, Longyan City. The total amount and speciation of heavy metals (Pb, Cd, and As) in soil and crops were determined. The characteristics of the absorption of heavy metals by specific crops in the study area were analyzed, and a new method of risk assessment based on the heavy metal speciation and its bioavailability was established by statistical analysis. This new method was used to evaluate the soil ecological risk and to compare it with the traditional method of potential ecological risk index (RI). The results indicated that the Lantian-Yangdong Villages were located in an area where Pb, Cd, and As mainly originated from the natural soil parent material with weak human disturbance. There was no significant Pb or As pollution in the whole region. Cd was the main pollutant with low pollution intensity. Four types of biological components except for the residual form followed the order of Cd (53. 28%) > Pb (43. 28%) > As (30. 71%). Correlation and regression analyses of total metal concentrations, heavy metal speciation, and crop uptake in the study area showed that the correlations between the total amount of heavy metals and the ion exchange state, carbonate state, and other active forms were low; the results even showed nonlinear relationships between those variables. The ion exchange state had the greatest effect on the absorption of Pb, Cd, and As by coix seeds and rice. From the perspective of bioavailability, the new method based on the heavy metal speciation was more accurate than the traditional method based on the total amount of heavy metals.
Analysis of Characteristics and Sources of Heavy Metals in Farmland Soils in the Xijiang River Draining of Guangxi
Environmental Science,2018,Vol 39,No. 09
【Abstract】 In order to determine the distribution characteristics of heavy metal pollution in farmland soils and related influencing factors in the Xijiang River basin, 2 187 farmland soil samples were collected and their heavy metal content was tested. The spatial structure and distribution characteristics of heavy metal elements were studied using a combination of geostatistical theory and GIS spatial interpolation. The potential ecological risk index was employed for risk assessment. Multivariate statistical methods, such as correlation analysis and principal component analysis, were used to analyze heavy metal sources. Results showed that farmland soils in the basin were enriched with seven kinds of heavy metal to some extent, with Cd accumulation being the most evident. The independent sample t-test results showed significant differences in heavy metal content between dry and field paddy soils ( P < 0.05). Cd content in paddy soils was significantly higher than in corresponding dry land soils. Cd in farmland soils in Xijiang River exhibited higher potential ecological risk. Correlation analysis and principal component analysis showed that enrichment of Pb, Zn, As, Cd, and Cu in soil was due to anthropogenic factors such as mining activities, traffic, and sewage irrigation, while Ni and Cr were influenced by natural factors, such as soil parent material. High-content areas of As, Cd, Pb, Zn, and Cu in the upper reaches of the basin are all distributed in the Diaojiang River basin and the Dahuan River basin. Cd was most widely distributed. The most intensive sampling sites indicated that mining activities have caused some degree of heavy metal pollution in local farmland soils.
Occurrence and source identification of heavy metals in the alluvial soils of Pearl River Delta region, south China
China Environmental Science,2018,Vol 38,No. 09
【Abstract】 Forty-four alluvial samples were collected at 22 sites in the Pearl River Delta to study the distribution and sources of eight heavy metals with factor analysis, enrichment factor and lead isotopic tracing methods. The study showed that the concentrations of all heavy metals were enriched relative to the background value of soil of China and Guangdong Province. The concentrations of Cr and Ni were similar in top soil and deep soil, while the concentrations of As, Cu, Zn, Cd, and Pb in top soils were slightly elevated to deep soils. And the concentration of Hg was significantly enriched in the top soils. Factor analysis indicated that the concentrations of Cu, Cr, Ni were mainly controlled by the natural conditions, and the anomalies of As, Pb, Hg were caused by anthropogenic contamination. In some cases, the high concentrations of Cd and Zn were controlled by both geological background and anthropogenic contamination. The results of enrichment factor analysis indicated that the pollution levels of eight heavy metals were Hg > As > Cd > Cu > Pb > Zn > Cr > Ni. The enrichment factor values would be low if the elements were enriched in deep soils. The scatter plot showed there was significantly negative correlation between Pb concentration and 206Pb/ 207Pb ratio. A binary comprehensive model showed that at least 30% Pb in the top soils were derived from anthropogenic contamination. In conclusion, the study found that the enhanced levels of Hg, Cd, As, Pb were due to contamination.
Comparative research on spatio-temporal variability of heavy metal pollution in cultivated soils—A case study of Huang-Huai-Hai Plain and middle reaches of the Yangtze River and Jianghuai Region
China Environmental Science,2018,Vol 38,No. 09
【Abstract】 Taking the Huang-Huai-Hai Plain (HHHP) and middle reaches of the Yangtze River and Jianghuai Region (MYJR) as the study area, the data of heavy metals in the cultivated soil were collected from published literatures. The single factor index method and Nemerow synthesis index method were used to evaluate the pollution degree of heavy metals. Combined with the soil survey data in the 1980s, the spatio-temporal variation characteristics during the period of the 1980s and 2000s were analyzed. Results showed that: (1) the heavy metals in cultivated soils in the study area were at a safe level, and more than 80% of the HHHP and more than 60% of the MYJR were at the clean level. (2) Heavy metal pollution in the MYJR was more serious than that of the HHHP. The single factor index evaluation results showed that the exceedance percentage of soil heavy metals pollution was 35.02% in MYJR, which is twice that of 15.97% in the HHHP. The Nemerow synthesis index method found that there were 20.29% and 13.17% in the pollution levels, where the proportion of light and serious pollution in the MYJR was larger than that in the HHHP, and the proportion of serious pollution in the MYJR was three times that in the HHHP. (3) The order of proportions of pollution at the different locations is as follows: the cultivated soils near the industrial and mining area, the cultivated soils in the sewage irrigation area, the cultivated soils in the main agricultural production area, and the suburban cultivated soils. (4) The heavy metal pollution proportion increased during the 1980s and 2000s. The increased exceedance percentages of Cd, Zn, Hg, and As in the HHHP were 6.34%, 1.98%, 12.78%, and 0.91%, respectively. And those of Cd, Ni, Zn, Cu, Hg, and As in the MYJR were 14.02%, 11.36%, 7.28%, 5.49%, 1.93%, and 0.72%, respectively. Areas of worsening pollution were mainly located in Tianjin, Cangzhou in Hebei, Ji’nan in Shandong and Yueyang in Hunan. In the process of urbanization, industrialization and agricultural development, the cultivated soils are threatened by the heavy metal pollution in the study area, which calls for the effective measures to prevent and remedy heavy metals pollution.
Synergistic remediation of heavy metal Cd and Pb contaminated clay by freeze-thaw and chemical washing
Transactions of the Chinese Society of Agricultural Engineering,2018,Vol 34,No. 23
【Abstract】 Contamination of heavy metals in agricultural soil has been a worldwide challenge for the food security and people’s health. Especially, cadmium (Cd) and lead (Pb) contamination in soil is a serious problem in China. Therefore, it is imperative to develop remediation techniques able to remove contaminants in a highly efficient and cost effective way. The traditional washing method is widely used for soil remediation on account of its high efficiency and simple operation. However, the efficiency of traditional washing method is limited by soil permeability, so this method can only remediate a small range of heavy metal-contaminated soil, which cannot be popularized at a large scale, and the removal effect for the clayey soil is generally poor. In order to solve the problem of low washing efficiency resulted from the heavy texture and low permeability of clayey soil, a cooperative remediation by freeze-thaw and chemical washing method was proposed. Taking the Cd and Pb contaminated soil in a smelter as the research object, we conducted the empirical tests of freeze-thaw and washing (FTW) for soil columns with 0.1 mol/L ethylene diaminetetraacetic acid disodium salt (EDTA). The results showed that repeated freezing and thawing (frost heave–water absorption, thaw settlement–drainage) of soil destroyed the original cohesive force and soil skeleton structure between the soil particles, so that the soil particles were rearranged, which contributed to the fully contact with the eluent and contaminants. The washing effect was significantly improved by this method. The removal rates of Cd in FTW3 (FTW treatment with three freeze-thaw cycles; adding EDTA at 1st and 3rd cycle), FTW5 (FTW treatment with five freeze-thaw cycles; adding EDTA at 1st and 2nd cycle), and FTW7 (FTW treatment with seven freeze-thaw cycles; adding EDTA at 1st to 3rd cycle) groups were 9.05%, 64.90%, and 77.24%, respectively; and the removal rates of Pb in FTW3, FTW5, and FTW7 groups were 2.06%, 14.42%, and 37.78%, respectively. The forms of heavy metals at different depths in the soil column after washing were analyzed by the three-stage continuous extraction method (BCR method) proposed by the European Community Bureau of Reference. The weak acid extractable Cd increased by 20.76%, the average reducible Cd decreased by 41.58%, and the residual Cd increased by 193.45% in FTW3. The weak acid extractable Cd decreased by 0.39%, the average reducible Cd decreased by 45.75%, and the residual Cd increased by 43.73% in FTW5. The weak acid extractable Cd decreased by 41.46%, the average reducible Cd decreased by 63.02%, and the residual Cd decreased by 26.33% in FTW7. The average reducible Pb increased by 11.23%, the average oxidizable Pb decreased by 63.12%, and the residual Pb increased by 53.97% in FTW3. The average reducible Pb decreased by 0.12%, the averageoxidizable Pb decreased by 64.13%, and the residual Pb increased by 30.68% in FTW5. The average reducible Pb decreased by 32.32%, the average oxidizable Pb decreased by 62.05%, and the residual Pb decreased by 67.36% in FTW7. Moreover, the freeze-thaw and washing method had a lower ratio of liquid to soil, which were 0.32, 0.47, and 0.62, respectively, so that the amount of eluent was much smaller than that of the traditional washing method. Besides, this study provides a method for the ex-situ remediation of heavy metal-contaminated soil in seasonally frozen areas by using the phenomenon of freeze-thaw alternation in cold regions in the future.
Spatiotemporal Variability and Source Apportionment of Soil Heavy Metals in an Industrially Developed City
Environmental Science,2019,Vol 40,No. 02
【Abstract】 In the present study, a total of 1 130 soil samples were collected in 2003 and 2013 in Ningbo City, and the content of eight typical heavy metals was measured. The degree of heavy metal pollution in the soil in the study area was evaluated using the pollution index evaluation method. The spatiotemporal variation in the pollution were analyzed by the geostatistical method, and the principal component analysis (PCA) and the UNMIX model were adopted to analyze the heavy metal pollution sources. The results showed that (1) apart from As, the mean values of the other seven heavy metals in both periods exceeded the soil background values in Zhejiang Province and national background values of China, which indicated that heavy metal pollution was common in the soil from the study area. From 2003 to 2013, the mean content of all elements increased to some degree, indicating that the heavy metals pollution was generally aggravated in ten years; the increase in the mean Hg content was the greatest; (2) the evaluation results based on the single-factor pollution index showed that the pollution degree was high for Hg, moderate for Cd, Cu, and Pb, slight for Zn, Cr, and Ni, and unpolluted for As. The evaluation results based on NCPI showed that the pollution index for all samples exceeded the warning value, and the number of soil samples that were characterized as heavily polluted with a comprehensive pollution index over 3 had increased significantly; (3) the spatial distribution of the same heavy metal in different periods presented similar characteristics. Generally speaking, the spatial distribution of Pb was similar to that of Hg, and the spatial distributions of Cr, As, Cu, Zn, and Ni were similar to each other; high value areas were mainly concentrated in the four areas of Haishu, Jiangbei, Jiangdong, and Zhenhai districts, where the polluted enterprises were densely distributed and human activities were frequent; (4) based on PCA and the UNMIX receptor model, the source analysis results of soil heavy metals in 2013 were essentially the same, i.e., the source of heavy metal pollution in the study area included the industrial sources and living sources. Industrial sources of heavy metal pollution had the highest contribution rate and derived from industrial wastewater, waste gas, and waste residue discharged by plasticizing, mining, and metallurgical enterprises, chemical and mechanical manufacturing enterprises, etc., causing the accumulation of Cr, As, Cu, Zn, and Ni in the soil. The living sources had the second highest contribution rate originated from the pollution of particulates and dust caused by domestic waste, automobile exhaust, and road friction. Additionally, natural factors had small contribution rates, mainly due to the spread of pollutants by prevailing winds and atmospheric settlement.
Spatial Distribution Characteristics and Source Apportionment of Soil Heavy Metals in Chinese Wolfberry Land Based on GIS and the Receptor Model
Environmental Science,2019,Vol 40,No. 06
【Abstract】 A total of 119 surface soil samples (depth of 0–20 cm) were collected from a Chinese wolfberry demonstration garden in Zhongning of Ningxia, and the samples were analyzed for seven heavy metals (Pb, Ni, Zn, Mn, Cu, Cr, and Cd). The single factor index, comprehensive index, and potential ecological risk were used to assess the soil heavy metal contamination with the soil background values of Ningxia as the evaluation standards. The absolute principal component scores and multivariate linear regression (APCS-MLR) model as well as geostatistical analysis were combined to identify and apportion the pollution sources of soil heavy metals. The results showed that the average concentrations of Pb, Ni, Zn, Mn, Cu, Cr, and Cd in soils were 34.78, 52.376, 83.692, 641.114, 38.130, 87.257, and 0.149 mg·kg −1, respectively. The mean concentrations of heavy metals were higher than the local soil background values but lower than the risk screening values for soil contamination of agricultural land. The comprehensive index results showed that the pollution degree of soil heavy metals was at the slight pollution level in 81.51% of the samples, at the moderate pollution level in 16.81% of the samples, and at the zero pollution level in 1.68% of the samples. The comprehensive index values for potential ecological hazards were less than 60 in 13.45% of the samples, and these values were associated with a slight potential for ecological risks. The comprehensive index values for potential ecological hazards were less than 120 and more than 60 in 86.55% of the samples, and these values were associated with a moderate potential for ecological risks. The four main pollution sources of soil heavy metals in the study area included natural sources, industrial activity, traffic, and agricultural activity. Natural sources were the main source of Ni and Cr with average contribution rates of 55.49% and 64.66%, respectively. Industrial activity was the main source of Pb and Mn with average contribution rates of 46.93% and 42.53%, respectively. Traffic was the main source of Zn and Cu with average contribution rates of 43.51% and 53.71%, respectively. Agricultural activity was the main source of Cd with an average contribution rate of 76.79%. The study results indicated that the soil heavy metals tended to concentrate in the Chinese wolfberry demonstration garden, and the sources of heavy metals were complex and were obviously influenced by human activities. Controls should be strengthened for the sources that contribute to soil heavy metals to ensure the sustainable utilization of soil resources in the Chinese wolfberry land.
Heavy Metal Accumulation in Irrigated Desert Soils and Their Crop Effect After Applying Different Organic Materials
Scientia Agricultura Sinica,2019,Vol 52,No. 19
【Abstract】 [Objective] This study aimed to explore the effects of long-term application of organic materials on the heavy metal content, fractionation, crop uptake in irrigated desert soil and further to provide a theoretical basis and technical support to control the soil heavy metal accumulation during fertilization with organic materials. [Method] A long-term (7 years) positioning experiment was conducted through the application of six types of organic materials, including chicken manure, cattle manure, pig manure, sludge, biogas residue and mushroom residue, in irrigated desert soil. Subsequently, the soil heavy metal content, fractionation and crop uptake were analyzed. [Result] Application with chicken manure, pig manure or sludge significantly increased the soil contents of Cu and Zn, which were in the order of pig manure treatment > chicken manure treatment > sludge treatment. No significant effect on soil heavy metals was observed for the other organic materials. After application with pig manure, chicken manure and sludge, the soil Cu content was increased by 62.20%, 20.10%, and 10.26%, respectively, while the soil Zn content was increased by 79.98%, 39.24%, and 18.31%, respectively, showing an increasing trend with application year. The average annual cumulative rates of Cu were 4.16, 1.25, and 0.97 mg·kg −1·a −1, while those for Zn were 11.04, 4.86, and 2.59 mg·kg −1·a −1, respectively. No significant effect on the soil Cd, Cr, Pb and Ni was observed. The application of cattle manure, mushroom residue and biogas residue had no significant effect on the total contents of Cu and Zn in soil. Application with pig manure, chicken manure, cattle manure and sludge significantly affected the forms of Cu and Zn in soil, and significantly increased the proportion of the available forms and total contents of Cu and Zn in soil. [Conclusion] Long-term application of pig manure, chicken manure and sludge could lead to the rapid accumulation of Cu and Zn and the increase in Cu and Zn bioavailability in irrigated desert soil, especially for pig manure. In the future, the heavy metals in organic fertilizers should be emphasized during the soil fertility improvement, so as to reduce the heavy metal accumulation in soil and sustain the soil healthy and agricultural use.
Migration and Source Analysis of Heavy Metals in Vertical Soil Profiles of the Drylands of Xiamen City
Environmental Science,2019,Vol 40,No. 08
【Abstract】 The concentrations of eight heavy metal elements (V, Cr, Co, Ni, Cu, Zn, Sr, and Pb) and the isotopic compositions of Pb and Sr were determined in vertical soil profiles of the drylands of Xiamen City using ICP-MS and TIMS. The vertical distributions and leaching migration patterns of the heavy metals were also analyzed. The results showed that most of the heavy metals (except for Sr) were not enriched relative to background values at most profile depths, which indicated that the heavy metal contents were less affected by exogenous sources. The migration coefficients of Sr were greater than 0 throughout the entire soil profile; Zn and Co were enriched in the surface soil; Cr, Ni, and Cu were depleted throughout the profile. V and Pb were less influenced by external activities. Sr and Pb showed clear vertical migration characteristics, and the migration depth of Sr was greater than that of Pb. The factor analysis showed that the heavy metals mainly originated from natural sources, followed by agricultural activities, transportation, and other complex anthropogenic activities. The enrichment factor analysis showed that Sr was affected by exogenous sources to varying extents. The isotopic composition analysis of Pb and Sr showed that Pb was mainly derived from the parent material, whereas Sr was interpreted as deriving from both the parent material and anthropogenic activities, and tended to migrate to the subsurface soil horizons (30–70 cm).
China Environmental Science,2019,Vol 39,No. 07
【Abstract】 To explore the impacts of variables on receptor model results in source apportionment for soil pollutants, we used the sampling data set of soil heavy metals in the middle and upper reaches of Le’an River as the input data set for the typical receptor model (PMF model). After the results of basic scenarios were obtained by PMF model, local sensitivity analysis method was introduced to study the sensitivity of variables to PMF diagnosis and source identification. The six-factor scenario was the best result for the simulation of PMF based model, and Cu, Mo, Na 2O, As, Mn, and Cd in the soil were the sensitive variables and also the main loading elements in each factor profile (i.e., the typical pollutants of each source). There was a significant difference in the sensitivity for these variables: the total sensitivity of Cu and Mo is much higher than that of the other variables, reaching 12.1 and 8.2, respectively. Therefore, it revealed that the sensitive variables should be the specific pollutants when the receptor model was applied in source apportionment, and the data quality was an important factor affecting the reliability of source apportionment.