Distribution Of Heavy Metal Pollution Research Articles

Spatial Distribution and Migration of Heavy Metals in Dry and Windy Area Polluted by Their Production in the North China

We explored the migration and distribution of heavy metal pollution in a dry and windy area in northern China. We collected soil, atmospheric deposition, and water samples, and measured heavy metal concentrations. Cu, Zn, As, and Pb in the 0–10 cm soil layer had a fan-shaped distribution, consistent with their atmospheric deposition fluxes. This indicates that the distribution of these heavy metals was driven by strong winds. The concentration of Cd in the river increased from 0.257 mg/L upstream to 0.460 mg/L downstream, resulting in the same distribution trends as soil near the river. Surface runoff may therefore drive Cd migration. The concentration of Pb in the river exceeded the pollution threshold, resulting in accumulation in the 5–10 cm soil layer. Atmospheric deposition fluxes were consistent with the soil distribution results, and principal component analysis showed that the contribution of surface runoff was high. This suggests that the migration of Pb and Cr is driven by both wind and surface runoff. Six heavy metals showed different migration behaviors, suggesting specific control strategies should be implemented for individual heavy metals.

Characteristics of Distribution of Heavy Metals in Rivers Around Laterite Nickel Mining Sites in the Tanggetada Area, Kolaka Regency, Southeast Sulawesi Province

The research location is located in Tanggetada sub-district, Kolaka district, which is an area very close to laterite nickel mining sites. The determination of the research location was deliberately chosen at the nickel mining location, with the consideration that at that location the river was brownish red, and at that location there were many miners who did not carry out according to mining regulations. The method used is observational which is carried out at nickel laterite mining sites. by using a cross sectional approach that is both qualitative and quantitative. Based on the results of the data analysis that has been carried out, it can be explained that the distribution of heavy metal pollution in river water is the largest in the heavy metal Copper (Cu), namely 0.0108 mg/l, which is found at station 3, heavy metal lead (Pb), namely 0.0070 mg/l l found at station 4, heavy metal chromium (Cr) is 0.0038 found at station 6 downstream, heavy metal Cadmium (Cd) is 0.0028 mg/l found at station 3, heavy metal Hexavalent Chromium (Cr6+) is 0.0026 mg/l found at station 2. From the results of the analysis there are no heavy metals that exceed the quality standard (PP No. 82 of 2001). Meanwhile, the river sediment material produced the greatest amount of heavy metal Copper (Cu), namely 0.0229 mg/kg found at station 2, Heavy metal Cadmium (Cd), namely 0.0128 mg/kg found at station 5, Heavy metal Lead (Pb) namely 0.0177 mg /kg is found at station 1 upstream, heavy metal Chromium (Cr) is 0.0118 mg/kg found at station 6 downstream, heavy metal Hexavalent Chromium (Cr6+) is 0.0116 mg/kg found at station 6 downstream. From the results of this analysis there are no heavy metals that exceed the quality standards (USEPA, 2003).

Spatiotemporal records of major historical events and human activities in river sediments: A coupled study of heavy metals distribution and lead isotopic dating

Thirty sediment samples (11 on the surface and 19 from a 55 cm core) collected in the Dadu River, upstream of the Yangtze River, China, were analyzed by ICP-MS and Laser diffraction particle size techniques to determine heavy metal spatial-temporal distribution and particle size characteristics, respectively. The intent was to clarify the impact of human activities such as Pb-Zn mining and exploration on the distribution of potentially toxic elements (As, Cd, Cr, Cu, Pb and Zn) in adjacent fluvial deposits. Moreover, 210Pb isotope dating was applied to study the historical variation and distribution of heavy metal pollution in a sedimentary profile in the middle section of the Dadu River. Results suggest that Cd concentration is notably high, exceeding by 16.3 times the soil background value in Sichuan Province, China, which can be intensified by Pb-Zn ore smelting. Surface sediments are mainly composed of silt, accounting for 79% on average, and relatively minor amounts of clay and sand. The fraction of clay in the downstream segments of the Dadu River is significantly higher than that upstream, indicating that the hydrodynamic force in the downstream region is relatively low compared with the upstream flow. Samples in the sedimentary profile, collected at 3 cm intervals, are mainly composed of silty sand, accounting for 75.6%, which comprehensively reflects the strong hydrodynamic force in this area. The results of 210Pb dating of these samples indicate three intervals of historical fluctuation in heavy metal concentrations: 1950–1966, 1988–1991 and 1996–2006, respectively, which coincide to significant historical events (the Cultural Revolution, the construction of Pubugou reservoir and local smelting activities, and the implementation of environmental protection policies). Enrichment factor (EF) values of all heavy metals in the profile began to increase after 1994, and relatively high EF values of Cr and Cd indicated a significant enrichment due to increasing anthropogenic activities during this period. Our study demonstrates that anthropogenic activities can be well recorded in sedimentary profiles and provide new insights to retrieving the history of human developments.

Comprehensive Quality Assessment of Soil-Maize Heavy Metals in High Geological Background Area

The aim of this study was to analyze the pollution degree and causes of soil and agricultural products in high geological background areas and to provide a basis for the safe production of agricultural products and the risk control of soil heavy metals. A total of 36 sets of soil-corn collaborative samples were collected in the farming area of Baolong Town, Wushan County, Chongqing City; the contents of heavy metals (Cd, Hg, Pb, As, and Cr) and soil pH in the soil-maize were analyzed, the pollution degree of heavy metals in the soil-maize was evaluated using the Nemerow comprehensive pollution index method (PN) and comprehensive quality impact index (IICQ). The sources of heavy metals in the soil and the influencing factors of heavy metal excess in corn were also analyzed. The results showed that the average value of soil heavy metal content in the study area was higher than the national and Chongqing soil background values, and the soil heavy metal enrichment effect was obvious. Cd was the main factor of soil-maize exceeding the standard, and the overall exceeding rates of soil and corn Cd were 91.67% and 30.55%, respectively. The evaluation results of the Nemerow comprehensive pollution index showed that the soil was dominated by heavy pollution, accounting for 63.89%. The soil-maize comprehensive quality impact index was dominated by moderate and severe pollution, accounting for 44.44% and 47.22%, respectively. From the perspective of the spatial distribution of heavy metal pollution, corn and soil pollution areas were inconsistent. Soil heavy metal pollution was mainly affected by the Permian and Triassic strata and was related to the secondary enrichment of black rock series and limestone areas. The Cd content of maize was mainly affected by soil pH, and maize was relatively safe under alkaline conditions. It is suggested that the soil in the study area should be divided into risk zones according to the stratum distribution, and the planting structure should be adjusted in the high-risk areas. For the low- and medium-risk areas, it is recommended to strengthen the monitoring of agricultural inputs and reduce the input of heavy metals in the soil. Additionally, we recommend carrying out agronomic regulation in acidic soil areas to improve soil acidification, plant corn varieties with low accumulation of heavy metals, and reduce the risk of agricultural products exceeding the standard.

GIS-based approach and multivariate statistical analysis for identifying sources of heavy metals in marine sediments from the coast of Hong Kong.

Hong Kong is an urbanized coastal city which experiences substantially different metal loads from anthropogenic activities. This study was aimed at analyzing the spatial distribution and pollution evaluation of ten selected heavy metals (As, Cd, Cr, Cu, Pb, Hg, Ni, Zn, Fe, V) in the coastal sediments of Hong Kong. The distribution of heavy metal pollution in sediments has been analyzed using the geographic information system (GIS) technique, and their pollution degrees, corresponding potential ecological risks and source identifications, have been studied by applying the enrichment factor (EF) analysis, contamination factor (CF) analysis, potential ecological risk index (PEI), and integrated multivariate statistical methods, respectively. Firstly, the GIS technique was used to access the spatial distribution of the heavy metals; the result revealed that pollution trend of these metals was decreased from the inner to the outer coast sites of the studied area. Secondly, combining the EF analysis and CF analysis, we found that the pollution degree of heavy metals followed the order of Cu > Cr > Cd > Zn > Pb > Hg > Ni > Fe > As > V. Thirdly, the PERI calculations showed that Cd, Hg, and Cu were the most potential ecological risk factors compared to other metals. Finally, cluster analysis combined with principal component analysis showed that Cr, Cu, Hg, and Ni might originate from the industrial discharges and shipping activities. V, As, and Fe were mainly derived from the natural origin, whereas Cd, Pb, and Zn were identified from the municipal discharges and industrial wastewater. In conclusion, this work should be helpful in the establishment of strategies for contamination control and optimization of industrial structures in Hong Kong.

Evaluation of heavy metal pollution with uneven spatial sampling distribution based on Voronoi area density.

Ecological risk index and Voronoi diagram have been extensively used as a diagnostic guide for heavy metal pollution to support people in-depth analysis of the possibility of various contamination sources causing damage to social production, life, and the ecological environment. However, under the condition of uneven distribution of detection points, there are often situations where the Voronoi polygon area corresponding to a large degree of pollution is small or the area of the Voronoi polygon is great with a low level of pollution, and using the Voronoi area weighting or the Voronoi area density may ignore heavily polluted local areas. This study proposes the Voronoi density-weighted summation to accurately measure the concentration and diffusion of heavy metal pollution in the target area for the above issues. Then, we propose a contribution value method based on k-means to determine the number of divisions to ensure the prediction accuracy and computational cost at the same time. Moreover, applying local entropy deepens the understanding of local regional and overall system situations. Through four representative regions, the results show that the proposed whole scheme based on Voronoi diagram can effectively predict and evaluate the spatial distribution of heavy metal pollution, which provides a theoretical basis for comprehending and exploring the complex pollution environment.

Spatial Distribution and Ecological Risk Assessment of Heavy Metals in the Sediment of a Tropical Mangrove Wetland on Hainan Island, China

Mangroves have a high ecological service value and play an important role in achieving carbon neutrality. However, mangrove wetland soil quality is constantly being affected, and the ecological services provided are gradually declining due to the threat of various pollutants, especially heavy metal pollution. Exploring the sources and ecological risks of heavy metals in mangrove sediments will be helpful in improving mangrove protection. In 2020, sediments were collected from terrestrial and aquatic areas of Dongzhai Harbor mangrove wetland in Hainan, China, and were analyzed for the concentrations of nine heavy metals (As, Cd, Cr, Cu, Hg, Pb, Ni, Zn, Co). The results showed that there were obvious spatial distributions of heavy metals in sediments. The high concentrations of heavy metals occurred largely in terrestrial areas and in 0–20 cm of the sediment surface layer. Correlation analysis and cluster analysis indicated that As mainly originated from ships and aquaculture in the harbor waters, Cd and Hg from agriculture, Cr, Cu, Ni, Zn and Co from the weathering of parent rocks, and Pb from soot emitted from metal smelters and automobile exhaust. The individual potential ecological risk index (Eir) indicated that contaminating elements were mainly Cd and Hg. The potential ecological risk index (RI) and multiple probable effect concentrations quality (mPECQs) indicated that the areas with high heavy metal concentration and the 0–20 cm range of sediment surface layer were more susceptible to heavy metal contamination. Although there were no obvious ecological risks in the area, these results could facilitate the understanding of the distribution of heavy metal pollution in mangroves and provide information to achieve sustainable development of mangroves.

Sustainability of Cocoa (Theobroma cacao) Cultivation in the Mining District of Ponce Enríquez: A Trace Metal Approach.

Historically, cocoa (Theobroma cacao) has been one of Ecuador's most important export crops. In the Ponce Enriquez district, artisanal and small gold mining (ASGM), and quarrying account for 42% of economic activities, while agriculture and livestock farming account for 30%, making the analysis of their synergy and interaction key to understanding the long term viability of the different activities. In this study, we evaluated the concentration of potentially toxic metals in different parts of the cocoa plant and fruit, in relation to mining activities within the area. Gold extraction generates pollution, including potentially toxic metals such as mercury (Hg), cadmium (Cd), arsenic (As), copper (Cu), lead (Pb) and zinc (Zn). In order to understand the mobility of these metals within the cocoa plant and fruit, the analysis was conducted separately for leaves, pod, husk and cocoa bean. Concentrations of the target metals in the different plant parts and soil were measured using ICP-MS, and the mobility and risk factors were calculated using the transfer factor (TF) and the risk ratio (HQ). The results suggest that Zn, Cd and Cu are indeed moving from the soil to cocoa leaves and beans. Furthermore, the results show that the concentrations of toxic metals in the different parts of the cocoa fruit and plant, particularly in the cocoa bean, which is used for chocolate manufacture, are not higher than those regulated by FAO food standards, as is the case of Cd, which is limited to 0.2 mg Cd/kg and in the samples analyzed does not exceed this limit. Even though the concentration of these metals does not exceed the safety standard, the presence of these potentially hazardous metals, and the fact they are absorbed by this important local crop, are worrying for the long-term sustainability of cocoa cultivation in the area. Therefore, it is fundamental to monitor the local environment, understanding the distribution of heavy metal pollution, and work with the local authorities in landscape management to minimize the exposure of crops to ASGM pollution.

Pollution Characteristics, Sources, and Health Risk Assessments of Potentially Toxic Elements in Community Garden Soil of Lin’an, Zhejiang, China

The characteristics, sources and risk assessment of heavy metal pollution in community garden soil of Lin'an District were evaluated. The 28 soil samples from community garden were collected for determination of 7 heavy metal elements. The Geostatistical analysis, Spearman correlation coefficient, Principal component analysis and PMF model have explored sources of heavy metal pollution. The health risk assessment model has assessed ecological risk of heavy metals. The results revealed that average concentration of As, Cd, Cr, Cu, Ni, Pb and Zn were 16.0, 0.158, 76.1, 34.6, 45.8, 20.9 and 166mgkg-1, respectively. Whereas As, Cd, Cr, Cu, Ni and Zn were higher than background values. The spatial distribution of heavy metal pollution in the southwest of the study area was higher than northeast. The pollution sources of Cd, Cu, Ni and Zn in the study area were due to agricultural activities (42.9%), Cr and Pb were from traffic sources (36.2%), and As was domestic pollution (20.9%) according to Spearman correlation coefficient, Principal component analysis and PMF model. The non-carcinogenic risks of As (5.39), Cr (3.53) and Ni (2.07) have a value of 1, which indicated significant risk. The potentially toxic elements have not exceeded maximum threshold of USEPA, with regard to carcinogenic risk, while As (3.37E-05) and Cr (5.74E-05) have exceeded the safety range. It is concluded that soils of community gardens are facing pollution problem due to potentially toxic elements which require environmental monitoring of the soil to reduce risk of human health.

Heavy metal pollution and risk assessment of farmland soil around abandoned domestic waste dump in Kaifeng City

In order to understand the heavy metal pollution and potential ecological risk of farmland soil around the waste dump in the eastern suburb of Kaifeng clearly and provide a scientific basis for the remediation of heavy metals in farmland soil, the single factor pollution index method, Nemero comprehensive pollution index method and Hakanson potential ecological risk method were used to evaluate the heavy metal pollution status and potential ecological risk degree of farmland in this area at the same time. The ArcGIS software was employed to map the spatial distribution of heavy metal pollution and potential ecological risks. The results show that the average values of heavy metals in this area are higher than the soil Background Value of Kaifeng City, and the problem of excessive heavy metals in the soil is significant. Of the 41 surface soil samples, Cd’s heavy and moderate pollution rates were up to 15% and 38%, respectively, and the potential ecological risk caused by Cd element was quite serious, and more than 35% of the soil samples were at higher potential ecological risk. The comprehensive review results showed that 38% of the samples were heavy pollution, and 23% of the sample soils were at higher potential ecological risk. The spatial distribution characterized by the levels of most heavy metals and the extent of potential ecological risk showed high levels in the center of the dump, with a gradual decrease towards the outward radiation zone. This means dust and leachate from waste dump are major causes of heavy metal contamination and potential ecological risks. In addition, the retrieval of the waste mound soil from landfills by villagers as soil fertilizer for rapeseed also caused, to some extent, the transfer of the waste mound contaminants.

Co-Effects of Hydrological Conditions and Industrial Activities on the Distribution of Heavy Metal Pollution in Taipu River, China.

In Taipu River, after being transformed from a drainage channel to a drinking water supply river in 1995, heavy metals that have accumulated in sediments have become an environmental issue. Herein, we collected sediments of Taipu River in 2018, 2020, and 2021 and analyzed the distribution of Sb, As, Cd, Cu, Pb, Cr, and Zn to identify their sources. The results revealed that the mean concentrations of heavy metals were above the background values, except for Cr and As. During the non-flood season, the midstream of Taipu River becomes a heavy metal hotspot, with their concentrations 2–5 times higher than those in upstream sediment. There were significant correlations (r = 0.79–0.99) among drainage, precipitation and flow rate, which indicated that drainage caused by both the opening of Taipu Gate and precipitation control the flow rate and, then, possibly influenced the distribution of heavy metals. Moreover, three sources (industrial sources, particle deposition sources, and natural sources) were characterized as the determinants for the accumulation of heavy metal by the Positive Matrix Factorization model, with the contribution rates of 41.7%, 32.9%, and 25.4%, respectively. It is recommended that the influence of hydrological conditions and industrial activities should be a key consideration when developing regulations for the management of heavy metals in rivers.

Distribution feature of heavy metals in the system of sediment-submerged plant-water in Xuanwu Lake

Abstract In view of the distribution of heavy metal pollutants in Xuanwu Lake after the comprehensive dredging, contents of Cr, Mn, Ni, Cu, Zn, Cd and Pb in 4 dominant submerged plants and their corresponding sediments in the lake and in surface water were determined, so as to reveal the pollution and distribution of the heavy metals in the system of sediments-submerged plants-water in Xuanwu Lake. Results showed that the average mass concentration of Cr and Ni in the surface water of Xuanwu Lake exceeded the national standard Grade II of the quality of surface water which were 1.79 and 1.56 times, respectively; The content of Cd and Pd in sediments was respectively 3.31 and 1.17 times of the background value of Nanjing soil, and the North Lake, the contents of Mn, Ni, Zn, Cd and Pd in surface water and Cr, Ni, Zn, Cd and Pd in sediments were higher than other lake areas. The average value Igeo of each element was ranked by size as Cd > Pb > Zn > Cr > Cu > Mn > Ni, except that Cd was slight pollution (Igeo value is 0.20–0.47), the other heavy metal elements were at a clean level. In the four submerged plants, Mn was significantly positively correlated with Ni, Cu, Zn and Cd (p < 0.01). Ni was significantly positively correlated with Cu, Zn and Cd. Cr in the submerged plants was significantly positively correlated with Cr and Ni in the surface water; The contents of Cd and Pd were significantly positively correlated with Pd and Cu in the surface water (p < 0.05).

Spatial Distribution and Migration Characteristics of Heavy Metals in Grassland Open-Pit Coal Mine Dump Soil Interface.

The open-pit coal mine dump in the study area contains many low-concentration heavy metal pollutants, which may cause pollution to the soil interface. Firstly, statistical analysis and geostatistical spatial interpolation methods described heavy metal pollution’s spatial distribution. The mine dump heavy metal pollution distribution is strongly random due to disorderly piles, but it is closely related to slope soil erosion. Furthermore, the soil deposition area is where pollutants accumulate. For example, all heavy metal elements converge at the bottom of the dump. Usually, the pollution in the lower part is higher than that in the upper part; the pollution in the lower step is higher than the upper step; the pollution in the soil deposition locations such as flat plate and slope bottom is higher than the soil erosion locations such as slope tip and middle slope. Finally, the hyperspectral remote sensing method described heavy metals pollution’s migration characteristics, that the pollutants could affect the soil interface by at least 1 km. This study provides a basis for preventing and controlling critical parts of mine dump heavy metal pollution and pollution path control.

Integrated Approach of Heavy Metal Evaluation Using Geostatistical and Pollution Assessment Index in Soil of Bauxite Mining Area

Heavy metals contamination in soil is one of the global issues, posing a threat not just to the environment but also to human health. Identifying the source and distribution of heavy metal pollutants around mining areas can provide a scientific basis for future environmental control. Distributions of the heavy metals (Cd, Cr, As, and Ni) in this study were evaluated using descriptive and multivariate statistics and further described using a geostatistical approach and pollution indices. The total content of Cr, Cd, and Ni in surface soil was observed with a higher concentration level according to the Dutch target values and the 95% Investigation Levels determined for Malaysia soil. Statistical analyses, geostatistics, and GIS mapping suggested that Cd, Cr, and Ni were derived mainly from anthropogenic sources, including mining and agricultural activities, while As could be derived from lithogenic and anthropogenic sources. Geoaccumulation index analysis demonstrated that the contamination that occurred with Cd posed the greatest risk of contamination, followed by Cr, Ni, and As. A spatial interpolated map showed a higher concentration of heavy metals in the vicinity of the mining area. These findings highlight the effectiveness of principal component analysis, geostatistics, and geospatial analyses in evaluating heavy metal contents in the study area. The obtained results could be used by authorities to identify areas requiring remediation management and establish scientific baseline data related to soil quality.

Spatiotemporal distribution patterns and risk characteristics of heavy metal pollutants in the soil of lead\u2013zinc mines

BackgroundThe current soil environmental assessment system is inadequate in terms of the spatiotemporal distribution of heavy metal pollutants. This study employed the numerical simulation technique to predict spatiotemporal distribution patterns of heavy metals within 50 days and to assess the soil risk characteristics of heavy metal pollution near a lead–zinc mine in Hunan Province, China.ResultsThe spatiotemporal distribution results indicate that the soil in the sewage plant and mining areas served as the pollution center, exhibiting a ladder-shaped pollution diffusion trend outward. When the pollution migration time reached 20 days, pollutant migration and changes tended to remain stable, high-pollution areas exhibited no drastic changes within 10 m, and low-pollution and medium-pollution areas revealed obvious changes. Moreover, the low-pollution area width approached 2 m, the depth reached 2 m, the medium-pollution area width was close to 2.5 m, and the depth approached 4 m. The percentage of areas containing lead–zinc mine soil with high to extremely high risks reached 82.88%, and extremely high-risk farmland, mining and residential areas accounted for up to 100%, 95% and 90%, respectively, of the total area. Among the pollution sources, high-risk and extremely high-risk areas in regard to heavy metal Cd accounted for 13.51 and 49.55%, respectively, of the total area.ConclusionThis study provides new insights into the migration patterns and risk characteristics of pollutants to address soil environmental assessment system problems.

Spatial and Seasonal Distribution of Heavy Metal Pollution in Tropical Lagoon off the Gulf Of Guinea

Abstract: The consistency of the aquatic environment at any point reflects basin lithology, anthropogenic input and climatic conditions. Spatial and seasonal distribution of heavy metal pollution in tropical Lagoon off the Gulf of Guinea was investigated between November, 2018 to October, 2019. Water samples were collected bi-monthly for heavy metal analysis and physicochemical parameters were measured in-situ every month. Results for physicochemical parameters were presumed to be ideal for marine life for both seasons as prescribed by the Federal Ministry of Environment. Salinity showed a significant negative correlation with temperature and a significant positive correlation with electrical conductivity (EC) during wet season. During the dry season, temperature showed a significant positive correlation with pH. As the temperature rises, molecular vibrations increase which results in the ability of water to ionize and form hydrogen ions and resulted into pH drop. The trend of heavy metal concentrations in the entire study area during the wet and dry season were in the order: Pb>Cu>Zn=Cr>Cd and Cu>Cr>Zn=Cd>Pb respectively. Nemerow’s Pollution Index (NPI) and Contamination Index (CI) were further used to evaluate pollution status of each metal in each sample station and contamination status of the entire sample stations respectively. The CI of the study area showed a decreasing order: Apapa > Iddo > Makoko > Ibeshe > Egbin and Ibeshe > Makoko > Iddo > Apapa > Egbin for wet and dry seasons respectively. Keyword: tropical Lagoon, Gulf of Guinea, Physicochemical, heavy metal, Nemerow’s Pollution Index, Contamination Index

Analysis of Heavy Metal Pollution in Cultivated Land of Different Quality Grades in Yangtze River Delta of China

The distribution of heavy metal pollution in cultivated land is closely related to the quality of the cultivated land. In this study, 533 soil samples were collected from cultivated land in the Yangtze River delta region in China for Cd, Pb, and Hg analyses. Spatial statistical analysis was used to study the heavy metal pollution in the cultivated land, and the driving forces of heavy metal distribution in different cultivated land quality subdivisions were analyzed with GeogDetector. The conclusions are as follows: (1) Among the three heavy metals in the study area, the coefficient of variation of Cd is the largest, and that of Pb is the smallest. The proportion of Cd and Hg exceeding the standard value (the standard of level two in GB 15618—2018) is relatively large, both of which are 5%; (2) From the perspective of the spatial distribution of soil heavy metal pollution, only four counties (CX, HN, WY, and LH) were free of heavy metal pollution. Soil heavy metal pollution in AJ, SY, QJ, and DS counties is relatively serious, and the pollution may come from agricultural activities, manufacturing, and prevalent coastal shipping industries in these counties; (3) The heavy metal pollution levels of cultivated land with different quality levels are different. The high-quality cultivated land has no high contamination, while the medium and the general cultivated land both have high contamination. High contamination is related to Cd for medium and general cultivated lands, and to Hg in only general cultivated land; (4) The main driving factors of heavy metal concentration in cultivated soil were GDP, followed by soil organic matter, and pH. These results indicate that the spatial distribution of heavy metal concentration in cultivated soil was affected by the level of economic development, followed by the ecological environment, indicating that human activities had a critical impact on the ecological environment of cultivated land.

Spatial Distribution Characteristics of Heavy Metals in Surface Soil of Xilinguole Coal Mining Area Based on Semivariogram

Heavy metal pollution is a major environmental problem facing humankind. Locating the source and distribution of heavy metal pollutants around mines can provide a scientific basis for environmental control. The structure effect and random effect of a semivariogram can be used to determine the reason for spatial differences in the heavy metal content in surface soil, and the coefficient of variation and regression analysis can be used to confirm that the verification accuracy meets the geostatistical requirements. According to the maximum difference method, the content of heavy metals in the surface soil of the mining area is higher than that of the surroundings, and Cu and Zn levels are higher than the background values for Inner Mongolia. In the present case, Zn, Mn, Pb, Cr, Ni, and Cu levels exceeded the background values for the surroundings of the study area by 65.10%, 53.72%, 52.17%, 46.24%, 33.08%, and 29.49%, respectively. The results show that human activities play a decisive role in the spatial distribution of heavy metals, leading to their spatial distribution in the form of “core periphery”. This distribution pattern was significantly affected by the slope, NDVI value, and the distance from the mining area, but the spatial distribution of Pb was significantly related to high-grade roads. The research methods and conclusions have reference significance for the sources and spatial distribution characteristics of heavy metal pollution in similar mining areas and provide a target for the prevention and control of environmental pollution in the study area.

Analysis of the spatial distribution of heavy metals in an area of farmland in Sichuan province, China

To accurately visualize the spatial distribution of heavy metal pollution and provide information that assists in remediating farmland soil, this study employed GIS technology and collected 0–20 cm-depth surface soil and shallow groundwater samples from farmland in Jianxin Village, Xiba Town, Wutongqiao City, Sichuan Province, China. The soil samples were decomposed using a high-temperature closed digestion method, and the contents of Cr, Cd, Pb, As, Cu and Zn were determined using ICP-MS. A geographic semi-variogram analysis was then conducted to delineate spatial variations in the heavy metal concentrations within the soil, and a spatial distribution map of heavy metals in the soil was drawn using ArcGIS10.2 software based on a GIS Kriging interpolation spatial structure analysis. The results showed that all heavy metal element concentrations exceeded the soil background values of Sichuan Province; the exceeded rates of Cr, Cd, and Zn were 100%. All Cd samples exceeded the soil baseline value, and the pollution accumulation of Cr, Cd, and Zn was determined as being serious. Through a comparison of cross-validation methods, a theoretical optimal semi-variogram model of six heavy metal elements was obtained. Indexes C0/(C0 + C) of Cd, Pb, As, Cu, and Zn were in the range of 48–75%, which showed that their contents related to structural factors, such as the soil parent material and topography, and also to non-structural factors such as human activities. The index C0/(C0 + C) of Cr was more than 75%, which indicates that its content is mainly related to non-structural factors and human activities. The spatial correlation followed the order of Cu > Cd > Pb > Zn > As > Cr. The vertical distribution of heavy metals was greatly affected by the soil physical properties: the Cu and Pb contents of sandy soil decreased at first and then increased with depth; the Cr, Zn, and As contents first increased and then decreased with depth; and the Cd contents decreased with depth. In clay soil, there was little change in the Cu content with depth; the Cd, Zn, Pb, and As contents first decreased and then increased with depth, and the Cr content increased first and then decreased with depth. These results show that visualizing the spatial distribution of heavy metal contamination using GIS technology is significant for providing information that can be used to remediate farmland soil.

The use of fractal theory to study the sources of soil Cd and Pb pollution in Youjiang River Basin

Fractal theory can be applied to study the complexity of spatial structures in nature, and operates by extracting the deterministic parameters driving complex processes. However, to date there has been little reported application of fractal theory to the analysis of the sources of soil heavy metal pollution. This study aimed to determine the sources of heavy metal accumulation in the shallow soil of the Youjiang River Basin. A total of 71 shallow soil samples were collected across an area of 1,000 km2 for the analysis of Cd and Pb to determine the spatial distribution of heavy metal pollution in the basin. The fractal characteristics of Cd and Pb for the eastern, central and western parts of the study area were analyzed using a content-frequency fractal model. The results showed that the content-frequency fractal distributions of Cd and Pb in the area were similar and multifractal. Linear models described the three different groupings of the sample points well with a scattering of several high points, indicating a chaotic distribution of high-content Cd and Pb areas. Two linear models similarly could describe the fractal distributions of these two elements in the eastern part of the study area, with a scattering of several high-value points, whereas although the fractal distributions of the central and western parts of the study area also showed linear distributions, the linear fit for the western part of the study area was slightly worse. The fractal distributions indicated that the spatial distributions of soil Cd and Pb show several trends, which indicates the influence of multiple geochemical processes. When combined with regional industrial and mining enterprises and high density population, the fractal Cd and Pb distributions infer that soil Cd and Pb in the area originate from the same sources, and four major geochemical process are responsible for the distribution of Pb and Cd: 1) the soil formation process; 2) modern agricultural production; 3) industrial sources and dense population; 4) aluminum resources development and utilization. Among these, exploitation and utilization of aluminum resources is the most complex, resulting in a chaotic distribution of Cd and Pb.