Soil Background Values Research Articles

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.

Pollution Characteristics and Risk Assessments of Mercury in Jiutai, a County Region Thriving on Coal Mining in Northeastern China

Among human activities, coal mining and the combustion of fossil fuels are important sources of mercury in the environment. Research on mercury pollution in coal mining areas and surrounding cities, especially in densely populated areas, has always been at the forefront of this research field. In order to study the characteristics of environmental mercury pollution in small and medium-sized coal mining areas and surrounding towns in China, this study selected the main urban area of Jiutai District, a typical mining town in the Changchun City circle industrial base in northeast China, as the research object. In this study, the geo-accumulation index (Igeo) was used to study the soil mercury pollution degree in Jiutai District, the potential ecological risk index (Er) was used to evaluate the potential ecological risk of soil mercury in the study area, and the human exposure risk assessment model was used to evaluate the non-carcinogenic risk of soil mercury to the human body. The results showed that 32% of the soil samples in the study area had a higher mercury content than the regional soil background value of Jilin Province (0.04 mg·kg−1). According to the Igeo, 19% of the sample sites in the study area were polluted (index > 0). In general, the soil mercury pollution level in Jiutai District is low, and the polluted areas are mainly concentrated in the northeast of the study area. The Er of the soil mercury in the study area ranged from 7.2 to 522.0, with 32% of the sampling sites having a moderate or above potential ecological risk (Er > 40), and the potential ecological risk level of the soil mercury was higher in the northeast of the study area. The non-carcinogenic risk index (HQ) and total non-carcinogenic risk value (HI) of the soil mercury were all far less than 1, indicating that soil mercury pollution in the study area did not harm the health of local adults. The oral ingestion of soil mercury is the main form of human exposure to mercury.

Distribution Characteristics and Risk Assessment of Heavy Metals in Soils of the Typical Karst and Non-Karst Areas

To investigate the distribution characteristics and hazard levels of eight heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) in karst soil with a high geological background of heavy metals, 32 and 40 surface soil samples were collected from limestone and clastic rock areas, respectively, in the northern part of Mashan County, Guangxi Province, a typical mountainous county dominated by primary industries in China. Geostatistical methods, Pearson’s correlation analysis, the geo-accumulation index, and the potential ecological hazard index were applied to explore the influencing factors of those heavy metals and evaluate their potential contamination risks. The results show that (1) the levels of the eight heavy metal elements in the surface soils of karst areas exceeded the background values of soil for Mashan County, the background value of soil (layer A) in China, and abundance value of upper crust. According to the soil pollution risk screening values specified in the Soil Environmental Quality: Risk Control Standard for Contamination of Agricultural Land, the proportions of heavy metals in the soils of karst areas were ranked as Cd (100%) > As (90.6%) > Cr (84.4%) > Zn (68.8%) > Ni (37.5%). Meanwhile, the heavy metals in the soils of non-karst areas did not exceed the overall values for Mashan County, and Ni, Pb, and Zn did not exceed the overall national soil values. One-quarter of Cd in non-karst samples exceeded the risk-threshold screening value. There was a high degree of variation and a significant difference in the contents of heavy metal elements between karst and non-karst areas. (2) The element combinations of As-Cd-Cu-Hg-Ni-Pb-Zn and Cr in karst areas were characterized by the influence of carbonate rock parent material. The non-karst areas were characterized by Ni-Cu-Pb-Zn, As-Cr-Hg, and Cd assemblages, which were mainly influenced by the mixture of laterite parent materials, sand shale parent materials, and basic-rock residual materials, and that may be affected by element migration caused by soil erosion and anthropogenic activities. (3) Analysis of the geo-accumulation index showed that karst areas were generally found to be at the clean to light pollution level, except for in the areas whose samples exhibited medium/high pollution levels for Cd and Cr, with the Cd pollution being the more serious of the two. Small amounts of Cd and Cu were present in the non-karst areas at a light contamination level, while other elements were at the level of no pollution. (4) The results of the potential ecological risk index showed that Cd and Hg were the main ecologically hazardous heavy metal elements in the soils of the study areas. The potential ecological risk level in karst areas was much higher than in non-karst areas, especially for Cd, and was mainly influenced by the carbonate rock parent material.

Evaluation and Source Analysis of Heavy Metal Pollution in Sediments of the Yellow River Basin Based on Monte Carlo Simulation and PMF Model

As sediment is an essential component of rivers, the enrichment of heavy metals in sediment presents a serious threat to the aquatic environment. Many industrial cities are located along the Yellow River, and heavy metal pollution is a prominent problem in these areas. Thus, the study of heavy metal pollution in sediments of the Yellow River basin is of vital significance to the safety of the Yellow River basin ecosystem. In this study, we collected data on the concentrations of heavy metals (Pb, Cd, Cr, As, Zn, Cu, Ni, and Hg) in the sediments of the Yellow River basin from 2000 to 2020. We first analyzed the spatial distribution characteristics of heavy metals based on descriptive statistics and geostatistics and then used the Monte Carlo method to evaluate the probability of the ground accumulation index(Igeo), potential ecological risk, and toxicity units. Finally, the number of pollution sources and their contribution rates were determined by combining the positive definite matrix factor (PMF) decomposition model and Pearson correlation analysis. It was found that the mean values of ω(Pb), ω(As), ω(Zn), ω(Ni), ω(Cu), ω(Hg), ω(Cr), and ω(Cd) in the Yellow River basin sediments were 26.92, 11.78, 87.17, 31.13, 24.96, 0.07, 73.36, and 0.58 mg·kg-1, which exceeded the mean soil background values in the Yellow River basin provinces by 1.27, 1.08, 1.26, 1.05, 1.09, 2.32, 1.14, and 5.95 times, respectively, among which Cd exceeded the standard by the largest factor and should be taken seriously. The Igeo was ranked as Cd>Hg>Cr>Cu>Pb>Zn>As>Ni, and Cd and Hg showed medium-severe pollution. The proportions of heavy ecological risk in sediments in the upper, middle, and lower reaches of the Yellow River basin were 18.6%, 15.7%, and 7.1%, respectively, with a decreasing trend. Heavy metals in the sediments of the Yellow River basin were in a low-toxicity state. The PMF-Pearson correlation analysis showed that the four sources of heavy metals in the Yellow River basin sediments were mining sources (42.2%), natural activities (38.3%), agricultural activities (11.6%), and electroplating wastewater (7.9%). The results of this study can provide a basis for developing relevant pollution prevention and control measures in the Yellow River basin.

Pollution Characteristics and Risk Assessment of Heavy Metals in the Bioretention Systems of Sponge Cities

As an important water purification and seepage measure for sponge cities, biofiltration systems have been widely used in their construction in China. In order to identify the heavy metal accumulation, pollution, and its potential environmental risk in the biofiltration systems, this study examined the heavy metal contents and spatial distribution characteristics by taking the biofiltration systems of Yuelai new town, Chongqing, the first demonstration area of sponge city construction in China, as the research object, and conducted a risk evaluation of the pollution level and ecological environment in this new town using the contamination factor (CF), geo-accumulation Index (Igeo), and potential ecological risk coefficient (PERC). The results showed that, except for Mn, the average contents of Cu, Zn, Pb, Ni, and Cd in the biofiltration systems of Yuelai new town were 4.14, 1.77, 4.98, 1.23, and 6.51 times higher than the soil background values of Chongqing. In terms of spatial distribution, the contents of heavy metals in biofiltration systems along the roads in different functional areas showed great differences. The contents of Cu, Zn, Mn, Pb, Ni, and Cd in the industrial area were significantly higher than those of the same types of heavy metals in the biofiltration systems in other areas (P<0.05). The CF and Igeo showed that the pollution level of heavy metals was ranked as follows:Mn<Zn<Ni<Cu<Pb<Cd. Among them, Cu and Pb were highly polluted, Cd was severely polluted, and the PERC of Cd was 194.13, which indicated a high risk; the remaining heavy metals were at a minor risk. The pollution contribution of Cd to the composite PERC of all heavy metals was 78.73%, which was the major source of heavy metal potential risk. After the long-term operation of the biofiltration systems in a sponge city, certain environmental and ecological risks may exist later due to the accumulation of filler heavy metals. Hence, it is necessary to strengthen the operation management and carry out research on the non-polluted management of the filler of biofiltration facilities, to prevent them from becoming a new source of urban heavy metal pollution.

Mercury background values in soils and saprolites in the gold-rich greenstone belt of Suriname, Guiana Shield: The role of parent rock and residual enrichment

In order to develop criteria to distinguish polluted from unpolluted materials in areas subjected to artisanal small-scale gold mining, background mercury values were established in 62 natural soil and saprolite profiles on 16 different parent rock types in the greenstone belt of Suriname. Hg values in pristine topsoils often amount to up to 200 μg/kg, about 100 times higher than Hg in common parent rocks. Additional analyses of 40 major and trace elements in two pilot profiles show that Hg values are strongly correlated to Fe, Cr and V values, which suggests that just as those elements Hg is residually enriched in topsoils by laterisation processes. In the deeper pallid zones of the profiles, Hg has often been leached almost completely together with iron by reducing groundwater action. In this way the range of Hg values within a single profile can be greater than between profiles. Maximum and average Hg values of 196 samples from the 16 different parent rock types fall apart into two main groups. Felsic parent rocks with predominance of quartz and feldspar have maximum Hg values around 100 μg/kg and averages around 50 μg/kg, mafic ones with less silica and higher Fe, Mg and Ca have maximum values around 250–300 μg/kg and averages around 150 μg/kg. In general the natural soil and saprolite Hg values are in the same order of magnitude as many published mine tailings and stream sediments, and therefore cannot be used to separate polluted from unpolluted materials.

Soil health and ecological risk assessment in the typical coal mines on the Mongolian Plateau

Mining activities always lead to severe soil pollution and vegetation degradation. However, the assessment of soil pollution and ecological risk due to mining has not been applied on the Mongolian Plateau, which has plenty of typical coalmines with environmental heterogeneity. Soil samples were collected from the Shengli Mine and the Baorixile Mine in Inner Mongolia to compare soil physicochemical properties and concentrations of metals/metalloids in locations with climate and precipitation differences. The single-factor pollution, Nemerow composite, geo-accumulation and potential ecological risk indices were used to investigate the environmental risks from two mines. The results show that the soils of these two mining areas have the characteristics of high pH (close to 8.5), high sand ratio and low nutrient content, and the soil texture was classified as sandy soil. Cu, Pb, Zn, Mn, Ni, As and Hg in the two mines all exceeded the average soil background values. Furthermore, the two mining areas have differences in the soil environment, including a higher C/N ratio and sand content in the Shengli Mine while having significantly higher As and Pb contents in the Baorixile Mine. In addition, pollution indices indicated that the soil of the Baorixile Mine poses a higher ecological risk even though it has higher nutrients and better soil structure than Shengli Mine does. In summary, coal mining is the key driver that leads to the ecological risk of the two mines, and the environment with relatively higher vegetation abundance and more suitable climatic conditions could have a higher ecological risk due to the comprehensive factors of climate and human interference. This study helps to clarify the ecological risks of soil metals, determine the priority control components of contaminated soil and prioritise appropriate protection measures and monitoring plans for the Inner Mongolian Plateau.

Impact of tourism activities on the distribution and pollution of soil heavy metals in natural scenic spots on the northern slope of Tianshan Mountain

Human activities can significantly impact the natural ecosystem. As an important part of terrestrial ecosystems, soil participates in energy and material cycle. With the continuous intensification of human activities, soil undergoes increasingly serious disturbance. Under the influence of global change and human activities, the variability of heavy metals in soil is worthy of further discussion. Taking Lujiaowan and Juhuatai Scenic Spot on the northern slope of Tianshan Mountain as the research area, this study investigated the concentrations of Pb, As, Zn, Cu and Mn in the soil and analyzed their distribution and pollution levels. Meanwhile, the main sources of soil heavy metals were explored using autocorrelation analysis and principal component analysis. Results showed that the order of the average concentration of heavy metals in the study area was as follows: Mn> Zn> Cu> Pb> As. None of them exceeded the national soil environmental quality level II standard, and the average concentrations of Zn, Cu, and As exceeded the background value of Xinjiang soil, reaching a light pollution level. In addition, the distribution of heavy metals in soil displayed a regular trend, and a positive correlation was found between disturbance intensity and heavy metal concentration. The geoaccumulation index also showed that the five heavy metals in the study area had lower pollution degree compared with the background value in Xinjiang. The order of potential ecological risk was As > Cu > Pb > Zn > Mn.

Spatial heterogeneity analysis and source identification of heavy metals in soil: a case study of Chongqing, Southwest China

BackgroundHeavy metal pollution in urban soil is an important indicator of environmental pollution. Selecting the best interpolation method can accurately reflect the distribution characteristics of heavy metals in soil. In addition, source analysis can reveal heavy metal pollution of soil and help manage and protect the soil environment. This study used a uniform sampling method and obtained a total of 342 sampling points. After acid reduction, the concentration of As, Cu, and Mn in each sample was determined by ICP-MS (Agilent VISTA, USA). The accuracy and results of different spatial interpolation methods were compared and the CATREG model was used to identify the sources of heavy metal pollution.ResultsThe average concentration of As, Cu, and Mn were 5.802 mg kg −1, 23.992 mg kg−1, and 573.316 mg kg−1, respectively, lower than the soil background value of Chongqing. Compared to other Chinese cities and countries in the world, the concentration of As and Cu was lower in Chongqing, while the concentration of only Mn was higher. The interpolation results of inverse distance weighting (IDW) and radial basis function (RBF) largely retained the maximum information of element concentration. Soil source identification found that population density mainly affected Cu (0.539), slope Mn (0.206), and water quality As (0.453). The highest hotspot value (99% confidence interval), high hotspot value (95% confidence interval), and high hotspot value (90% confidence interval) of As were adjacent to the secondary water environment. Furthermore, the highest hotspot value of Cu was mainly located in the surrounding areas with population density > 3000/km2 and 1000–3000/km2. Mn was distributed along the slope direction and diffused from center to periphery.ConclusionsDifferent spatial interpolation methods are significant for the analysis of soil properties. Heavy metals have a high degree of coincidence with environmental factors such as slope and population. The results of this research provide a reference for formulating effective control and management strategies for heavy metal pollution of soil.Graphical

Comprehensive assessment of heavy metals in soil-crop system based on PMF and evolutionary game theory

The traditional assessment of farmland environmental quality usually focuses on soil heavy metals, but ignores agricultural produce safety. It is urgent to comprehensively assess the effects of farmland environmental quality based on soil quality and produce safety. To fill this gap, the comprehensive assessment method was improved based on previous studies, which was used to assess the pollution level of heavy metals in soil-crop system of Shenyang, Liaoning Province, Northeast China. In addition, this study also made a comprehensive analysis of pollution sources based on positive matrix factorization (PMF) model, and discussed soil-crop system income stability by evolutionary game theory. The mean concentrations of As, Cd, Cr, Hg, Pb, Cu, Zn, and Ni in soil exceeded the corresponding Shenyang soil background values (5.68 %, 14.36 %, 57.61 %, 7.86 %, 30.32 %, 5.21 %, 211.72 %, 171.88 %). The results showed that about 28.28 % of paired soil-crop points were polluted by heavy metals, especially rice-soil points. Furthermore, heavy metals in crops may be transmitted less from soil and more from other environmental media. The PMF analysis results showed that there were six pollution sources in study area, and the major contributor of pollution were agricultural activities, traffic-related activities, and industrial activities. In farmland environment protection, the only stable strategy is soil-crop system, and soil-crop system is better than the benefits of single soil or crop from the perspective of benefits. This study provides a scientific and reliable method to combine soil quality with produce safety to assess the risk of heavy metals in farmland.

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 &amp;gt; Pb &amp;gt; Zn &amp;gt; Cr &amp;gt; Cu &amp;gt; Mn &amp;gt; 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 &amp;lt; 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 &amp;lt; 0.05).

Distribution Characteristics and Risk Assessment of Accumulated Heavy Metals in Bioretention Systems

Topsoil samples (0-10 cm) from four bioretention systems with different land-use types were collected, including parking lot, roadside, residential area, and industrial park systems. The accumulation contents of As, Hg, Cd, Cr, Pb, Cu, Ni, and Zn were analyzed and evaluated, as were the influencing factors, pollution level, potential ecological risk, and human health risk. The results showed that there were significant differences in the accumulated contents of eight heavy metals. The average ω(As), ω(Hg), ω(Cd), ω(Cr), ω(Pb), ω(Cu), ω(Ni), and ω(Zn) were 8.92, 0.25, 0.10, 31.56, 14.81, 21.27, 23.69, and 62.75 mg·kg-1, respectively, and the average contents of As and Hg were 1.26 and 5.21 times the soil background values, respectively. Correlation analysis showed that the contents of the eight heavy metals were positively correlated with soil organic matter, pH value (except Hg), and phosphorus content (except As). The results of the Nemerow Comprehensive Pollution Index and Hakanson Potential Ecological Index showed that the pollution level and ecological risk of the other seven heavy metals were relatively low, whereas the pollution level and ecological risk of Hg reached the level of severe pollution and strong ecological risk, respectively. Affected by Hg, the comprehensive pollution level and ecological risk were relatively high; thus, Hg was a potential threat to the soil environment. The non-carcinogenic risks of heavy metals in the four systems were acceptable, but the carcinogenic risks were all beyond 10-6 though lower than 10-4, which indicated that these four systems had a certain carcinogenic risk, in which As was the main risk factor. Among these four land-use types, the accumulated pollutant contents, pollution levels, ecological risk, and human health risk of parking lots and roadside bioretention systems were much higher than those of residential areas and industrial parks.

Concentrations, sources and ecological–health risks of potentially toxic elements in finer road dust from a megacity in north China

Finer road dust has attracted considerable attention due to its more serious environmental detriment and ecological–health risk than coarser road dust. In this study, the concentrations of nine potentially toxic elements (PTEs, i.e. As, Co, Cr, Cu, Hg, Mn, Ni, Pb, and Zn) were analyzed in finer road dust with particle size <63 μm (FRD) collected from Shijiazhuang, a typical megacity in north China. Based on this investigation, the contamination levels, ecological–health risks, and sources of PTEs in FRD were comprehensively analyzed and the main pollution factors and areas of the high risks were identified. The results revealed that the average contents of As, Co, Cu, Hg, Pb, and Zn were significantly greater than the local soil background values. As a whole, the PTEs analyzed in Shijiazhuang FRD exhibited different contamination levels, viz. Hg was moderate to strong contamination; Zn was moderate contamination; Co, Cu and Pb were no-contamination to moderate contamination; As was no–contamination and no–contamination to moderate contamination; Cr, Mn and Ni were uncontaminated. The comprehensive ecological risks of PTEs in most sites were very high. The health risks of PTEs to the local inhabitants fell within safety limits. The pollution source analysis of PTEs showed that As and Hg were primarily derived from coal–related industrial source, which accounted for 27.5% of the total PTEs contents. Cu, Co, Pb, and Zn were mainly associated with traffic sources, which accounted for 26.5%. Mn, Ni, and Cr were principally generated by natural source, which accounted for 46.0%. It is worth noting that the coal–related industrial discharges and traffic emissions are the focus of anthropogenic sources control, which should be concerned.

Copper isotope ratios allowed for quantifying the contribution of coal mining and combustion to total soil copper concentrations in China

The most prominent source of Cu contamination in soils is metal mining and processing, partly since the Middle Age. However, coal mining and combustion can also cause (some) Cu contamination. We studied the distribution of Cu concentrations and isotope ratios in soils of the Huaibei coal mining area. The contribution of the coal mining and combustion to total Cu concentrations in soil was determined with a two-end-member mixing model based on the distinct δ65Cu values of the Cu emitted from coal mining and combustion and in native soil. The mean Cu concentration of 75 mg kg−1 exceeded the local soil background value (round to 22.13 mg kg−1). The similar δ65Cu value of grass near the coal mining and combustion operation as in gangue and flying ash indicated a superficial Cu contamination. Mining input was the dominant source of Cu in the contaminated soils, contributing up to 95% and on average 72% of the total Cu in the topsoils. The mining-derived Cu was leached to a depth of 65 cm, where still 29% of the Cu could be attributed to the mining emissions. Grasses showed lower δ65Cu values than the topsoils, because of the preferential uptake of light Cu isotopes. However, the Δ65Cugrass-soil was lower in the contaminated than the uncontaminated area because of superficial adsorption of isotopically heavy Cu from the mining emissions. Overall, in this study the distinct δ65Cu values of the mining-derived Cu emissions and the native soil allowed for the quantification of the mining-derived Cu and had already reached the subsoil and contaminated the grass by superficial adsorption in only 60 years of mining operation.

Effect of Land Use/Land Cover Change on the Concentration of Se and Heavy Metals in Soils from a "Return Cropland to Forest" Area, Southwest China

Human activities (land use) and environmental change (land cover change) affect the concentration of Se and heavy metals in soils. The implementation of the "Return Cropland to Forest (RCF)" ecological project has changed the land use and cover, which has provided an ideal experimental area for studying the effects of land use and cover change on selenium (Se) and heavy metals in the soil. In this study, 91 top soil samples from different land use and land cover types, including dry land, paddy land, natural forest land, and secondary forest land, were collected, and the contents of Se, heavy metals, and soil organic matter (SOM) and pH were analyzed. The results showed that:① the average values of ω(Se) (0.42×10-6), ω(As) (13.0×10-6), and ω(Sb) (1.03×10-6) were higher than the soil background values of western Chongqing. ② The concentrations of Se, Cd, Cr, Ni, Pb, and Zn in soils from secondary forest land were significantly higher than those from dry land soils, suggesting that the Se and heavy metals might have significantly increased in the surface soil after the implementation of the RCF ecological project. ③ The SOM was the key controlling factor for the enrichment and distribution of Se and heavy metals in the top soils. Our results indicated that the land use and land cover change would deeply impact the concentrations of Se and heavy metals in the top soils via influencing the soil properties, especially the SOM.

Spatial distribution, source identification, and risk assessment of heavy metals in the cultivated soil of the Qinghai–Tibet Plateau region: Case study on Huzhu County

Assessing the risk and sources of heavy metals in cultivated soil is important for the agricultural development of the Qinghai–Tibet Plateau. A survey was conducted in this study to determine the spatial distribution and possible sources of heavy metals in the agricultural soils in Huzhu county, a representative agricultural suburb in Qinghai-Tibet Plateau. A total of 120 surface soil samples were collected, soil pH and concentrations of chromium(Cr), cadmium(Cd), plumbum(Pb), arsenic(As), and hydrargyrum(Hg) were analyzed. The pollution risk degree of heavy metal pollution was also evaluated. The mean concentrations of the heavy metals were 70.8, 0.24, 23.7, 12.2, and 0.08 mg/kg for Cr, Cd, Pb, As, and Hg, respectively, higher than the soil background values of Qinghai Province with the exception of As, but lower than the guideline values of Chinese standard for soil contamination of agricultural land. The sampling point contamination risk of the heavy metals showed a site feature, and most sampling points of Cd and Hg was exhibit polluted. The potential ecological risk index indicated that most of the cultivated soils have low and moderate ecological risks. Multivariate and geostatistical analysis suggested that Cr, As, and Pb were due mainly to soil parent materials, Cd contamination was caused by agricultural and transportation activities, and Hg contamination was caused by coal combustion and industrial activities. The results of this study is a basis for undertaking more effective and accurate heavy metal control strategies to protect the safety of agricultural ecosystems. • Concentrations of heavy metals were measured in cultivated soils of Huzhu County in the Qinghai-Tibet Plateau. • The cultivated soils were mainly polluted by Cd and Hg. • Spatial heterogeneity of heavy metals was closely related with human activities.

Characteristics and Assessment of Soil Heavy Metals Pollution in the Xiaohe River Irrigation Area of the Loess Plateau, China

Heavy metals in soil are a potential threat to ecosystems and human well−being. Understanding the characteristics of soil heavy metal pollution and the prediction of ecological risk are crucial for regional eco−environment and agricultural development, especially for irrigation areas. In this study, the Xiaohe River Irrigation Area in the Loess Plateau was taken as the study area, and the concentration, as well as their accumulation degree and ecological risk and distribution of soil heavy metals, were explored based on the geo−accumulation index (Igeo) and Hakanson potential ecological risk index methods. The results showed that the concentrations of soil heavy metals were all lower than the second grade Environmental Quality Standard for Soils of China. However, the average concentrations of Cu, Hg, Cd, Pb, Zn, Ni and As were higher than the above−mentioned standard. Compared with the soil background values of Shanxi Province, eight heavy metals of all samples presented different accumulation degrees, with the highest accumulation degree in Hg, followed by Cd, and the values were 11.3 and 4.0 times more than the background value, respectively. Spatially, the distribution of soil heavy metals in the Xiaohe River irrigation area was quite different, generating diverse pollution patterns with significant regional differences and complex transportation routes. The content of soil heavy metals in the Xiaohe River irrigation area was highly affected by land use types. The pollution degree varied with the distance to an urban area, declining from the urban area to suburban farmland, and the outer suburban farmland. Among these heavy metals, Hg and Cd were the principal contamination elements, and transportation, service industry and agricultural activities were the main potential contamination sources. The potential ecological risk of soil heavy metal positioned as follows: Hg &gt; Cd &gt; Pb &gt; Zn &gt; Cu &gt; As &gt; Ni &gt; Cr. As indicated by the Hakanson potential ecological risk index strategies, except for the Wangwu examining site, the other six sampling sites experienced extremely strong risks, and as a whole, the entire study region was in a condition of incredibly impressive perils. Consequently, these results suggest that improving soil environmental investigation and assessment, setting up soil heavy metal contamination prevention and control innovation framework and reinforcing contamination source control are effective approaches for soil heavy metal contamination anticipation and control in irrigated areas of the Loess Plateau.

Zinc in soil reflecting the intensive coal mining activities: Evidence from stable zinc isotopes analysis

In the mining area affected by coal mining activities for a long time, heavy metal Zn pollution poses a serious threat to soil quality and human health, and direct evidence showing the relationship between Zn accumulation mechanism in soils and mining activities is lacking. In this study, the Zn content and isotopes composition (δ66Zn) from soil and environmental samples around mining area were determined and analyzed to clarify the Zn characteristics in soil. Moreover, the distribution and source of Zn content in soil of mining area were analyzed by mathematical statistics, correlation analysis and isotope mass mixing model. The results showed that: (1) the Zn content in soil ranged from 95 to 327 mg·kg−1 (mean: 233 mg·kg−1), exceeding the control point and the soil background value of Anhui Province; (2) the results of Zn isotope analysis showed that Zn in soil mainly derived from the wind dispersion input of fine particles in gangue and fly ash, followed by the natural weathering of parent material; (3) isotopic mass mixing model can be used to distinguish the contribution of anthropogenic and natural Zn sources. Mining input was the main contribution source of Zn in soil (mean: 67%), followed by natural background (mean: 33%). The employment of Zn isotopes can effectively evaluate the impact of anthropogenic and natural long-term processes on Zn in the soil of the mining area, and provide important information for the formulation of soil metal pollution control measures.

Feasibility study on using excavated soil and rock to sintering utilization

Urban construction, especially the ongoing large-scale expansion and utilization of underground space, has resulted in massive excavated soil and rock (ESR) from buildings and subways. Therefore, this study aims to explore the technical ways of ESR sintering utilization from the perspective of technology, environment, and policy through qualitative and quantitative methods. The study analyzes the soil properties and distribution of different depths, and the annual production of clay-rich ESR accounts for about 30 million m³ in Shenzhen. More importantly, the comparison between various pollutant concentrations of ESR in Shenzhen and local soil background values showed that the ESR in Shenzhen had no environmental risks. This study can not only provide a scientific basis for ESR as the raw material of sintering but also provide a theoretical basis for the promotion of the pilot of “Zero waste city”.

Research on the geochemical background values and evolution rules of lake sediments for heavy metals and nutrients in the Eastern China Plain from 1937 to 2017

For the first time, background quality guidelines have been developed for lake sediments along the Yangtze River. Evolution Rules of watershed environment in Eastern China were analyzed in 1937–2017. These methods of 137Cs and 210Pb radionuclide, 75% cumulative frequency, and background method were applied to calculate the sediment geochemical backgrounds (GB). The average GB values of Cu, Zn, Cd, Pb, Cr, total carbon (TC), total nitrogen (TN) and total phosphorus (TP) are 45.14 mg/kg, 86.99 mg/kg, 0.29 mg/kg, 33.71 mg/kg, 110.90 mg/kg, 17.20 mg/g, 1.60 mg/g, and 665.78 mg/kg, respectively. The radionuclide methods indicated that the sediment rate of 34 cm corresponding to 1963 is 0.63 cm yr−1. The risk and accumulation of the sediment metals and nutrients in Yangtze Plain were uncontaminated levels before 1960, raised since 1980, and increased significantly in 2000. The Cd, TC, and TN in lake sediment were at low to moderate pollution, and few lakes are at high pollution. Sediment background values of the plain are different from soil background values in China and Consensus-Based Sediment Quality Guidelines in Europe/America. Results of sediment quality guidelines provide an important guidance for pollution prevention, environmental management, and risk assessment, especially the formulation of environmental laws.