Environmental Quality Standards Of China Research Articles

Assessment of Soil Heavy Metal Pollution and Health Risks in Different Functional Areas on the Northern Slope of the Eastern Tianshan Mountains in Xinjiang, NW China.

In typical semi-arid areas, the timely and effective monitoring and evaluation of soil heavy metal pollution are of critical importance to prevent soil deterioration and achieve the sustainable use of soil resources. To further understand the degree of soil heavy metal pollution in different functional areas, we studied the soil heavy metal pollution on the northern slope of the eastern Tianshan Mountains in Xinjiang. We collected 104 surface soil samples from typical commercial (A), industrial (B), and agricultural (C) areas with different land-use patterns. The contents of Zn, Cu, Cr, Pb, As, and Hg in the soil of different functional areas were evaluated using the geo-accumulation index, the single-factor pollution index, and potential ecological risk. The results showed that the contents of Pb, As, and Hg in soils of different functional areas exceeded 4.47, 8.03, and 1.5 times the background values of Xinjiang soil, respectively. The average contents of Zn, Cu, and Cr were lower than the background values of Xinjiang soil. Except for As in different functional areas, the contents of the other elements in the different functional areas reached the level of soil environmental quality standards in China (GB15618-2018). The geo-accumulation index of heavy metals in different functional areas was in the order of Area C > Area A > Area B, indicating that Area C was the most polluted. The results of the single-factor pollution index showed that the pollution levels of Pb, As, and Hg were higher, and the pollution levels of Cr, Cu, and Zn were lower. The results of the potential ecological risk index showed that the northwest of Area A was higher, the southeast of Area B was more polluted, and the central and eastern parts of Area C were more polluted. From the perspective of spatial distribution, the spatial distribution characteristics of Zn and Cr elements in different functional areas are consistent, but the spatial distribution characteristics of Cu, Pb, As, and Hg in different functional areas are quite different. The high values of these four elements are mainly distributed in residential areas, factories, and metal smelters. It is necessary to divide the functional areas based on different land-use patterns, and the prevention of soil single-element and heavy metal pollution in different functional areas is reasonable for land resources and provides a scientific basis for the effective planning of quality assurance.

Probabilistic risk assessment of heavy metals in urban farmland soils of a typical oasis city in northwest China

Previous studies lacked quantitative evaluation studies of the probability of ecology and human health risks from soil heavy metals. This study assessed heavy metal risk level by collecting topsoil samples from a typical oasis city (Wuwei) in northwest China and then quantitatively evaluating the ecological risk from heavy metals by incorporating the uncertainty of health risk model parameters into the risk assessment. This study found that anthropogenic activities have influenced the accumulation of heavy metals in the study area and that the risk of contamination of soil heavy metals was characterized as light to moderate contamination and low ecological risk. On this basis, the species sensitivity distribution curves of heavy metals were constructed using species acute toxicity data, the predicted no effect concentrations of heavy metals were derived, and a probabilistic ecological risk evaluation was conducted. The results show that the current soil environmental quality standards in China are not effective in protecting species diversity. In addition, the probability of ecological risk for Cr, Ni and As in the study area was 63.3%, 23.8% and 7.1%, however, traditional pollution assessment methods underestimate the hazard of Cr. Monte Carlo simulations have shown that the probability of the carcinogenic risk of Cr (adults: 79.4%; children: 94.5%) and As (adults: 78.9%; children: 94.0%) is high, the probability of the total carcinogenic risk exceeding 1E-06 is 99.0%, the probability of the non-carcinogenic risk is low, and the slope factor and reference dose can significantly affect the evaluation of human health risks.

Effectiveness of Exogenous Fe2+ on Nutrient Removal in Gravel-Based Constructed Wetlands.

A group of microcosm-scale unplanted constructed wetlands (CWs) were established to evaluate the effectiveness of exogenous Fe2+ addition on ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3−-N), and total phosphorus (TP) removal. The addition of Fe2+ concentrations were 5 mg/L (CW-Fe5), 10 mg/L (CW-Fe10), 20 mg/L (CW-Fe20), 30 mg/L (CW-Fe30), and 0 mg/L (CW-CK). The microbial community in CWs was also analyzed to reveal the enhancement mechanism of pollutant removal. The results showed that the addition of Fe2+ could significantly (p < 0.05) reduce the NO3−-N concentration in the CWs. When 10 mg/L Fe2+ was added and the hydraulic retention time (HRT) was 8 h, the highest removal rate of NO3−-N was 88.66%. For NH4+-N, when the HRT was 8–24 h, the removal rate of CW-Fe5 was the highest (35.23% at 8 h and 59.24% at 24 h). When the HRT was 48–72 h, the removal rate of NH4+-N in CWs with 10 mg/L Fe2+ addition was the highest (85.19% at 48 h and 88.66% and 72 h). The removal rate of TP in all CWs was higher than 57.06%, compared with CW-CK, it increased 0.63–31.62% in CWs with Fe2+ addition; the final effluent TP concentration in CW-Fe5 (0.13 mg/L) and CW-Fe10 (0.16 mg/L) met the class III water standards in Surface Water Environmental Quality Standards of China (GB3838-2002). Microbical diversity indexes, including Shannon and Chao1, were significantly lower (p < 0.05) in Fe2+ amended treatment than that in CW-CK treatment. Furthermore, phylum Firmicutes, family Carnobacteriaceae, and genus Trichococcus in Fe2+ amended treatments was significantly (p < 0.05) higher than that in CW-CK treatment. Fe3+ reducing bacteria, such as Trichococcus genus, belonging to the Carnobacteriaceae in family-level, and Lactobacillales order affiliated to Firmicutes in the phylum-level, can reduce the oxidized Fe3+ to Fe2+ and continue to provide electrons for nitrate. It is recommended to consider adding an appropriate amount of iron into the water to strengthen its purifying capacity effect for constructed artificial wetlands in the future.

Ecological risk assessment of toxic metal pollution in the industrial zone on the northern slope of the East Tianshan Mountains in Xinjiang, NW China

Abstract The ecological risks of six toxic metals (Zn, Cu, Cr, Pb, Hg, and As) in the industrial zone on the northern slope of the East Tianshan Mountains in Xinjiang, northwest (NW) China, were assessed. The results showed that the soil toxic metal contents of Zn, Pb, Hg, and As exceeded the regional background values, and concentrations of Zn, Cu, Pb, and As exceeded the national soil environmental quality standards of China (GB15618-1995). The Cu and Cr contamination levels were lower than the limits of both soil standards and mainly originated from the parent material, Pb mainly originated from agricultural activity and traffic emissions, and Hg mainly originated from the coal burning and chemical industries. As contamination originated from automobile exhaust emissions, and Zn contamination was influenced by a combination of natural factors and human activities. The mean geo-accumulation index (I geo) values of As, Hg, and Pb ranged from unpolluted to moderately polluted. There was an area not polluted by Zn, Cu, and Cr. The pollution index (PI) value of the six heavy metals showed that the mean PI values of Zn, Cr, and Cu showed no pollution, As and Pb presented medium pollution, and Hg presented heavy pollution. The results of the potential ecological risk analysis in this region showed that Zn, Cu, Cr, and Pb in all sample sites presented a low risk, while Hg presented a high ecological risk. Therefore, it is necessary to prevent further Hg contamination in this region.

The fuzzy comprehensive evaluation (FCE) and the principal component analysis (PCA) model simulation and its applications in water quality assessment of Nansi Lake Basin, China

The Fuzzy Comprehensive Evaluation (FCE) and the Principal Component Analysis (PCA) were simulated to assess water quality of the Nansi Lake Basin, China. The membership functions were established via the Nor-Half Sinusoidal Distribution Method, and the weight was calculated via the Exceeding Standard Multiple Method. To enhance the efficiency of extracting principal pollutant, the eigenequation was solved through the Jacobi Method, and the principal components were extracted based on eigenvalue, contribution ratio, accumulating contribution ratio, principal component loading and score. Water quality classification based on “National Surface Water Environmental Quality Standards of China (GB3838-2002) was used to assess the water quality. Considering the difference of the temporal and spatial distribution in average, water quality of Level I was 28.9%, 28.1%, 25.1%, 25.6%, respectively in spring, summer, autumn, and winter, which suggested that water quality in spring and summer was better than in autumn and winter. The order of water quality was Zhaoyang Lake (Level I) &gt; Nanyang Lake (Level I) &gt; Dushan Lake (Level III) &gt; Weishan Lake (Level III and IV). There were four extracted principal components that can replace the fourteen pollutant indexes for assessing water quality. According to the annual mean data of the 1st principal components, the most important pollutions were heavy metals, including As (0.933), Hg (0.931), Cd (0.929), Cr(VI) (0.926), Pb (0.925), and Cu (0.534). It is proved that the combined FCE-PCA model could provide valuable information in the water quality assessment for the Nansi Lake Basin.

Cd accumulation and transfer in pepper (Capsicum annuum L.) grown in typical soils of China: pot experiments.

Food chain contamination by soil cadmium (Cd) through vegetable consumption poses a threat to human health. It is imperative to understand the Cd uptake and transfer in different soil-vegetable systems. The aims of this study were to understand the effect of soil characteristics on Cd accumulation and transfer in pepper and to derive regression models to predict Cd concentrations in the vegetable grown on a wide range of soils with different properties. The accumulation and transfer of Cd in the root, stem, and fruit of pepper (Capsicum annuum L.) grown in 18 typical soils of China were investigated through pot experiments. The bioavailability of Cd in soil was evaluated by using EDTA and HNO3 extraction methods. The pot experiments included a control and two concentration levels of Cd salt added to soils according to Soil Environmental Quality Standards of China. The results showed that the Cd content in pepper fruits ranged from 0.007 to 0.049 for the control, 0.045 to 0.260 for the low Cd treatment, and 0.076 to 0.345 mg/kg for the high Cd treatment, respectively. The concentrations of Cd in the different parts of pepper decreased in the order of root > stem > fruit, and there were significant correlations among the Cd concentrations in pepper root, stem, and fruit tissues. Bioaccumulation factor (BCF) and transfer factor (TF) of Cd in pepper fruits exhibited a low accumulation of Cd in the fruit of pepper. The Cd accumulation in pepper fruit could be quantitatively predicted by EDTA-extractable Cd content in soils. Multiple linear regression models proved functional in predicting Cd accumulation in different parts of pepper. The Cd content in pepper tissues was well predicted using EDTA-extractable Cd and soil variables, such as pH, EC, CEC, total phosphorus, and CaCO3 content. Soil pH and EC were major soil factors influencing Cd transfer from soil to pepper fruits, whereas total phosphorus content presented a negative effect on Cd accumulation in stem and root parts of pepper.

Health Assessment of Trace Metal Concentrations in Organic Fertilizer in Northern China.

The application of organic fertilizer could be accompanied by potential hazards to soil and humans caused by trace metals. A wide survey of organic fertilizers was carried out in northern China. A total of 117 organic fertilizer samples were collected to analyze the concentrations of seven trace metals. Simulation models were used to estimate the trace metal accumulation risk in soil and non-carcinogenic and carcinogenic risks to the human body. The concentrations of trace metals varied widely (Cr: 2.74–151.15; Ni: 2.94–49.35; Cu: 0.76–378.32; Zn: 0.50–1748.01; As: 1.54–23.96; Cd: 2.74–151.15; and Pb: 1.60–151.09 mg·kg−1). Chinese organic fertilizer standard limits were exceeded by0.85% for Cr, 5.98% for As, 1.71% for Cd, and 4.27% for Pb. Monte Carlo simulations showed that repeated application of organic fertilizer likely significantly increased the concentrations of Zn, Cd, and As in soil compared with the soil background levels according to the Soil Environmental Quality Standards of China. As and Cr pose high risks to human health, especially as carcinogenic risk factors with a skin exposure pathway. Reducing the content of Cr, Cu, Zn, As, and Cd in organic fertilizer would be of great significance for minimizing the damage caused by trace metals.

Spatial distribution, source, and risk assessment of soil toxic metals in the coal-mining region of northwestern China

Soil toxic metal pollution is one of the most prominent environmental problems in the rapid industrialization of societies because of the considerable harm caused to human existence and the surrounding environments. Soil samples from 80 sampling sites around the coal-mining region of northwestern China were collected, and the geo-accumulation index (Igeo), pollution index (PI), and potential ecological risk index (PRI) were calculated, with the objective of assessing the soil toxic metal pollution level. The results showed that the average concentrations of Cr, Hg, and As exceeded the regional background values and the national soil environmental quality standards of China, while those of Zn, Cu, and Pb were below both soil-quality standards. The Igeo of toxic metals was ranked as Hg > As > Cr > Pb > Cu > Zn. The Igeo of Zn, Cu, and Pb indicated low pollution; the soils were moderately polluted by Hg and slightly moderately polluted by As, while other elements presented low pollution levels. The PI values of both As and Hg were higher than 3, indicating heavy pollution of these two metals. Zn and Cu originated from parent material, while Cr, As, and Hg originated from human activities such as coal burning, chemical industry, and traffic. Pb was influenced by both natural factors and human activities. The results of ecological risk assessment in the region showed that Zn, Cu, Cr, and Pb in all sample sites presented a low ecological risk, while Hg presented a high ecological risk. Therefore, Hg is the most hazardous toxic metals in the region. The spatial distribution trends revealed that the high-risk regions were found to be the industrial region of the study area. The research results provide a scientific basis and technical support for monitoring and early warning of soil pollution in arid regions.

Accumulation and bioavailability of heavy metals in a soil-wheat/maize system with long-term sewage sludge amendments

A long-term field experiment was carried out with a wheat-maize rotation system to investigate the accumulation and bioavailability of heavy metals in a calcareous soil at different rates of sewage sludge amendment. There are significant linear correlations between the contents of Hg, Zn, Cu, Pb, and Cd in soil and sewage sludge amendment rates. By increasing 1 ton of applied sludge per hectare per year in soil, the contents of Hg, Zn, Cu, Pb, and Cd in soil increased by 6.20, 619, 92.9, 49.2, and 0.500 µg kg–1, respectively. For Hg, sewage sludge could be safely applied to the soil for 18 years at an application rate of 7.5 t ha–1 before content exceeded the soil environmental quality standards in China (1 mg kg–1). The safe application period for Zn is 51 years and is even longer for other heavy metals (112 years for Cu, 224 years for Cd, and 902 years for Pb) at an application rate of 7.5 t ha–1 sewage sludge. The contents of Zn and Ni in wheat grains and Zn, Cu, and Cr in maize grains increased linearly with increasing sewage sludge amendment rates. The contents of Zn, Cr, and Ni in wheat straws and Zn, Cu, and As in maize straws were positively correlated with sewage sludge amendment rates, while the content of Cu in wheat straws and Cr in maize straws showed the opposite trend. The bioconcentration factors of the heavy metals in wheat and maize grains were found to be in the order of Zn>Cu>Cd>Hg>Cr=Ni>Pb>As. Furthermore, the bioconcentration factors of heavy metals in wheat were greater than those in maize, indicating that wheat is more sensitive than maize as an indicator plant. These results will be helpful in developing the critical loads for sewage sludge amendment in calcareous soils.

A human health risk assessment of heavy metals in agricultural soils of Yanqi Basin, Silk Road Economic Belt, China

ABSTRACTA total of 195 farmland soil samples were collected in Yanqi Basin, Xinjiang, northwest China, and the concentrations of As, Cd, Cr, Cu, Ni, Pb, and Zn were analyzed for their concentrations and pollution levels using the Nemerow comprehensive index. The health risk assessment model introduced by USEPA was utilized to evaluate the human health risks of heavy metals. Results indicated that the average concentrations of these seven metals were lower than the allowed soil environmental quality standards of China, while the average concentrations of Cd, Cr, Ni, Pb and Zn exceeded the background values of irrigation soils in Xinjiang. The average contamination factor (CF) for Pb indicated the heavy pollution, whereas the CF for Cd, Zn, Ni, Cu and Cr indicated the moderate pollution. The average PLI of heavy metals indicated the low pollution. The non-carcinogenic hazard index were below the threshold values, and the total carcinogenic risks due to As and Cr were within the acceptable range for both children and adults. As and Pb were the main non-carcinogenic factors, while As was the main carcinogenic factor in the study area. Special attentions should be paid to these priority control metals in order to target the lowest threats to human health.

A review of heavy metal pollution levels and health risk assessment of urban soils in Chinese cities.

This study assessed literature-based data for the period 2006-2016 regarding heavy metal (As, Cd, Cr, Cu, Pb, Ni, Zn, and Hg) concentrations in soils from 32 Chinese cities and the associated human health risks. The mean concentrations of the eight metals were lower than the soil environmental quality standards in China, but were much higher than the background values for most cities. The enrichment factor (EF) and geoaccumulation index (I geo) values showed moderate pollution levels, possibly influenced by anthropogenic activity for Cd, Hg, Pb, and Zn. The pollution levels in eastern cities were much higher than those in western cities, and heavy metals concentrations in different types of cities followed the order: industrial based cities > more developed cities > metropoles > underdeveloped cities. The human health risk assessment for heavy metals in most cities indicated that non-carcinogenic risks were within threshold values (HI <1). The total carcinogenic risk due to As, Cr, and Ni in most urban areas was in excess of 1×10-5, but was lower than 1×10-4. However, in some cities (e.g., Baoji City, Tiyuan City, and Xuzhou City), Ni and Cr have potential cancer risks for both adults and children. Compared to adults, children could be more seriously threatened by heavy metal contamination in soils. In general, we recommend that Cd, Hg, and Pb are selected as priority heavy metals pollutants that require control in Chinese cities.

Polycyclic aromatic hydrocarbons and organochlorine pesticides in surface water from the Yongding River basin, China: Seasonal distribution, source apportionment, and potential risk assessment

The presence of 17 polycyclic aromatic hydrocarbons (PAHs) and 15 persistent organochlorine pesticides (OCPs) in surface water of the Yongding River Basin was analyzed through GC/MS/MS during the spring and summer at 46 sampling sites. The goal was to investigate their seasonal distribution, possible sources, and potential risk. Our results showed that the total PAH concentration in surface water of Yongding River Basin ranged from 41.60 to 1482.60ng/L with a mean value of 137.85ng/L in the spring, and from 53.53 to 506.53ng/L with a mean value of 124.43ng/L in the summer. The total OCP concentration ranged from <0.08 to 197.71ng/L with a mean value of 7.69ng/L in the spring, and from <0.08 to 93.58ng/L with a mean value of 7.92ng/L in the summer. Moreover, the total PAH concentration was slightly lower in the spring than in the summer, whereas the total OCP concentration was similar between seasons. Source analysis indicated that combustion sources and petroleum sources both contributed to the presence of PAHs. Historical environmental residues and long range atmospheric transport were the major sources of HCH and DDT contamination. The concentrations of total PAHs and single PAHs including benz(a)anthracene, benzo(a)pyrene, benz(b)fluoranthene, and benz(k)fluoranthene in surface water at some sampling sites exceeded the water environmental quality standards of China and several other countries or organizations. This indicated a potential threat to human health from the consumption of aquatic organisms due to PAH bioaccumulation. The concentrations of α-HCH, p,p’-DDE, and p,p’-DDD at several sampling sites exceeded the limit for human health specified in the ambient water quality criteria developed by the US Environmental Protection Agency, which indicated that these pollutants provide potential hazards to the residents around the sampling sites.

黑岱沟露天煤矿复垦区土壤重金属变化及评价

为了揭示煤矿复垦区土壤重金属含量随复垦年限的分布变化情况，并进行土壤环境污染的评价，本文以黄土高原区的黑岱沟露天煤矿的排土场复垦区为研究对象，采取不同复垦年限0~40 cm土层土样，对不同复垦年限下土壤重金属含量变化情况进行了分析和评价。结果表明：随着复垦年限的延长，复垦区土壤Pb、Cr、Cd和As含量整体均表现为逐年较少，表层含量高于下层，复垦15 a后含量均低于中国环境质量标准的一级标准。然而土壤Hg含量却整体表现为升高的变化趋势，0~20 cm土层含量增加，含量高于中国环境质量标准的一级标准，但低于中国环境质量标准的二级标，但20~40 cm土层含量减少，含量低于中国环境质量标准的一级标准。矿区复垦时间越长，重金属含量越低，对环境污染越小，而对于Hg含量不降反升的原因建议进一步的深入探究。 To reveal the changes of heavy metals distribution in different reclaimed years in coal mine re-claimed areas, and evaluate the environmental pollution, in this study we chose the reclaimed areas of Heidaigou mining opencast coal mine in loess plateau region as our research object. We sampled from 0 - 40 cm soil depth in different reclaimed areas, analyzed and evaluated the changes of soil heavy metals under different years after reclamation. The results showed that: As the years increased after reclamation, the content of Pb, Cr, Cd and As reduced gradually from a whole respect, and the contents in topsoil were higher than subsoil. After reclamation of 15 years, its contents were lower than the primary standard of the soil environmental quality standards in China. However, the content of Hg followed an increasing trend. It increased in 0 - 20 cm, and the value was higher than the secondary standard of the soil environmental quality standards in China, but lower than the primary standard. But it decreased in 20 - 40 cm soil layer, its value was lower than the primary standard of the soil environmental quality standards in China. The longer of reclamation, the lower contents of heavy metals, and smaller pollution to the environment. As to the phenomenon of Hg content increasing rather than reducing, it needs further study.

Assessments of levels, potential ecological risk, and human health risk of heavy metals in the soils from a typical county in Shanxi Province, China

A total of 128 surface soil samples were collected, and eight heavy metals, including As, Cd, Cr, Cu, Pb, Ni, Zn, and Hg, were analyzed for their concentrations, potential ecological risks, and human health risks. The mean concentrations of these eight metals were lower than the soil environmental quality standards in China, while they were slightly higher than the background values in Shanxi Province. The enrichment factor, coefficient variation, and potential ecological risk index were used to assess the pollution and eco-risk level of heavy metals, among which, Cd and Hg showed higher pollution levels and potential risks than the others in the studied area. Moreover, multivariate geostatistical analysis suggested that Hg originated mainly from point sources such as industrial emissions, while agricultural activity is the predominant factor for Cd. The human health risk assessment indicated that non-carcinogenic values were below the threshold values. The total carcinogenic risks due to As, Cr, and Ni were within the acceptable range for adults, while for children, they were higher than the threshold value (1.0E-04), indicating that children are facing higher threat to heavy metals in soils. These results provide basic information on heavy metal pollution control and human health risk assessment management in the study regions.

Accumulation, transfer, and potential sources of mercury in the soil-wheat system under field conditions over the Loess Plateau, northwest China

There is limited information on accumulation, transfer, and source of mercury in wheats under field conditions over the Loess Plateau, northwest China. The present study collected 26 pairs of topsoil and whole wheat samples (roots, stems, leaves, shells, and grains) from Dongdagou stream watershed and upper Xidagou stream watershed, Baiyin City, northwest China. Hg concentrations from these samples were used to identify their relationships with soil properties, interactions with other metals, localization of Hg in the different wheat tissues, bio-concentration and transfer of Hg, and major sources of Hg in wheat. Results show that Hg levels in 11 out of 26 sampled soils (42.3% of soil samples) exceeded Hg limit of grade II soil environmental quality standards in China (1.0mg·kg−1). Likewise, it was also found that Hg in over 50% of wheat grain samples reached or exceeded the maximum permissible food safety levels (0.02mg·kg−1) according to the General Standard of Contaminants in Food in China (GB 2762-2012). The spatial distribution pattern of Hg in wheats grains was different from that in the sampled soils. Hg concentrations in different wheat tissues were highest in roots, followed by leaves, stalks, shells, and grains, respectively. Bio-concentration factors (BCF) of Hg in almost all grains samples were one or two orders of magnitude lower than that in roots, except for two wheat samples. The translocation factors (TF) of Hg in wheat tissues on average were leaves>stems>shells>grains. The spatial distribution of Hg and its correlation with other heavy metal detected simultaneously in the soil samples suggested that the Hg soil contamination was probably caused by past sewage irrigation practices and atmospheric deposition. Correlation analysis revealed that the principle source of Hg in wheat roots was very likely from Hg contaminated soils.

Effects of Composted Sewage Sludge on Soil Properties and Vegetable Quality from Abandoned Quarries

The effects of composted sewage sludge on soil properties and vegetable quality were investigated in a field experiment for two years. The soil was amended with 3, 15 or 30 t/ha of compost. The results indicated that the vegetable net production increased with the amendment dosage of 3 and 15 t/ha, while the net production decreased in the application amount of 30 t/ha. However, the Vitamin C (Vc) content of the three vegetables was reverse. The heavy metals concentrations in vegetables and soils could meet the national food and soil environmental quality standards of China (II). The accumulation concentrations of Cd, As and Hg in the three vegetables increased with the increasing amendment dosage, while the concentrations of Cr and Pb changed significantly with different types of vegetable. Heavy metal accumulation ability was in the order of celery > lettuce > cabbage, except for Cr. The accumulation of different heavy metals in soil was related to the migration characteristic of heavy metals, plant absorption capacities and the amendment dosage. The concentration of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in the soils increased with addition of 15 t/ha and 30 t/ha, while the change was not statistically significant between the amendment of 3 t/ha and the control. The concentration of PCBs and PAHs in vegetables was positively correlated with compost addition amounts. The dissipation rate of PCBs and PAHs followed the principle of first-order kinetics, and vegetables could improve the dissipation rate. Therefore, the application of compost as soil amendment to abandoned quarries is a feasible strategy for sludge disposal because appropriate amount of compost could enhance the soil fertility, while the long-term application should be considered seriously.

Spatial distribution of water quality parameters of rivers around Erhai Lake during the dry and rainy seasons

Surface water from 18 rivers (including the buffer zone and lakeside area) around Erhai Lake was sampled in the dry and rainy seasons of 2013. The water quality was measured and the spatial variations of selected water quality parameters were determined. The results indicated that the following five parameters, ρ(TN), ρ(NO3 −-N), ρ(NH3-N), ρ(TP), and ρ(CODMn), in the surface water of the 18 rivers changed seasonally. The average value of ρ(TN), ρ(NO3 −-N), ρ(NH3-N), ρ(TP), and ρ(CODMn) in the rainy reason was higher than that in the dry season, respectively. The average value of ρ(TN) in three rivers (Mijuhe, Yonganjiang, and Luoshijiang rivers) flowing into the lake from the north was clearly higher than that in rivers flowing into the lake from the west. In contrast, the average value of ρ(TP) in the three northern rivers was lower than that in the western rivers. In the dry season, the distribution of ρ(TP) had a significant positive correlation with the distribution of ρ(TN), but this was not significant in the rainy season. The average value of ρ(CODMn) was within the Class I of “Surface Water Environmental Quality Standards of China”.

Heavy metal pollution diagnosis and ecological risk assessment of the surrounding soils of coal waste pile at Naluo Coal Mine, Liupanshui, Guizhou

In accordance with the National Soil Environmental Quality Standards of China, Grade I and Grade II (GB15618-1995), this study adopted single pollution index (SPI) and Nemeiow synthetical pollution index (NSPI) methods to analyse and assess the ecological risk of the seven heavy metals, namely Cd, Hg, As, Cu, Pb, Cr and Zn, contained in the surrounding soils of one coal waste pile at Naluo Coal Mine, Liupanshui, Guizhou, China. The results revealed that (1) Cd had higher SPI than any other heavy metal and the maximum Cd SPI, indicative of serious pollution, was found in the soil sample collected from the 150 m distant from the centre along possible coal gangue alluvial flow; (2) synthetical pollution assessment of heavy metals per Grade I found that soil sample collected from sites 150 m from the centre along possible coal gangue alluvial flow had the maximum NSPI, which suggests that the soil is seriously polluted, and that there is a link between heavy metal pollution level in the surrounding soils of the coal waste pile and the sampling direction; (3) synthetical pollution assessment of heavy metals per Grade II revealed that sampling distance had a bearing on the pollution level in the surrounding soils of the coal waste pile, and the soil samples collected from 100 or 150 m distant in all the sampling paths had minor pollution.

Levels and health risk assessments of heavy metals in urban soils in Dongguan, China

Human body may be directly exposed to heavy metals in urban soils through oral ingestion, dermal contact, and inhalation of soil particles. A total of 170 topsoil samples were collected from the urbanized area of Dongguan, China. Concentrations of As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, V, and Zn in soils were measured to calculate enrichment factors (EFs), pollution indexes (PIs), carcinogenic risks (CRs), and hazard indexes (HIs) of these elements. The mean concentrations of every element in urban soils of Dongguan are lower than both the soil environmental quality standards of China and the Canadian soil quality guidelines. However, concentrations of Cd, Cu, Ni, and Zn have increased slightly in the past 20years. Slight contamination was observed in some samples for all heavy metals according to the Chinese soil quality standards, and the element of As may be the most important contaminant. Furthermore, the element of As may pose both carcinogenic and non-carcinogenic risks to human health. Oral ingestion and inhalation of soil particles are the main exposure pathways of As to the human body. This study may provide a scientific basis for strategies to protect human health in urban areas.

Source identification and hazardous risk delineation of heavy metal contamination in Yanqi basin, northwest China

A total of 469 surface soil samples were collected from the Yanqi basin in northwest China and evaluated for levels of ten heavy metals. Multivariate statistical analyses were used to study sources of and map the spatial distribution of heavy metals, as well as determine the relationship between land use types and soil source materials. It was found that: (1) the average amounts of ten heavy metals in the Yanqi basin were all below the national soil environmental quality standards of China (GB15618-1998), but the average amount of Cd, Hg, Mn, Ni, Pb, and Zn all exceeded the heavy metal background levels of soil in Xinjiang, China and exhibited accumulation. The ten heavy metals analyzed in this study can be categorized into four principal components as follows: Principal component 1 was Co, Cr, Mn, Ni, and Zn, and principal component 3 was As and Cu. Both of these originated from a natural geological background. Principal component 2 consisted of Cd and Pb and originated from industrial, agricultural and transportation influences. Principal component 4 consisted of Hg and was due to industrial influences. Our study found that Pb and Zn were a large part in the principal components 1 and 3 and were influenced by a combination of geologic background and human activity. (2) Heavy metals Cd and Hg were at high levels in construction land and farmland, while Co, Cr, Cu, Mn, and Ni were significantly higher in lacustrine deposits than in sandy shale from weathered material, coarse crystalline rock weathered material, and diluvial material. The land use types correlated significantly with the accumulation of Cd and Hg, and the soil parent material was the major factor for the accumulation of As, Co, Cr, Cu, Mn, and Ni. (3) The single element, element integration and the corresponding principal component presented similar spatial patterns of hazardous risk. Following comprehensive assessment of all elements, the high risk regions were found to be located in densely-populated urban areas and western parts of the study area. This was attributed to the higher geological background in the western part and strong human influence in the central part. Research shows that Cd, Hg, Pb, and Zn were locally enriched in the basin and this warrants increased attention.