Soil Quality Standards Research Articles

Health risk assessment of heavy metals in soils and maize (Zea mays L.) from Yushu, Northeast China

ABSTRACTTo investigate heavy metal accumulation in soils and evaluate health risk through maize consumption, a total of 196 soils and 55 maize samples were collected from Yushu, China, one of the most important maize production bases. The mean contents of Cd, Cr, Cu, Zn and Pb were 0.119, 56.51, 19.21, 70.58, and 34.42 mg kg−1 for soils and were 0.014, 0.68, 1.33, 17.15 and 0.02 mg kg−1 for maize, respectively. The contents of Cr, Cu, Zn and Pb in all soil and maize samples did not exceed safety thresholds, but the percentages of Cd content above guideline values of Chinese Environmental Quality Standards for Soil and maximum permissible limits for maize were 6.6% and 1.8%, respectively. The spatial distribution and correlation analysis suggested that Cr and Cu in soil were of lithogenic origin, while Zn and Pb were associated with coal combustion exhausts and chemical fertilizer application. The main source of Cd may be phosphate fertilizer application. The average target hazard quotients were all less than 1 and the average hazard index for adults was 0.065, indicating that there was not a potential health risk through maize.

Coupling biological assays with diffusive gradients in thin-films technique to study the biological responses of Eisenia fetida to cadmium in soil

This work sets out to investigate biological responses of Eisenia fetida to Cd, based on the bioavailable rather than total concentration of Cd, in soils. E. fetida was cultured for 14d in three selected Chinese soils amended with 0.1–40mgkg−1 Cd. Potentially bioavailable concentrations of Cd were measured in soil solution, in extractions using CaCl2 and HAc solutions, and using the technique of diffusive gradients in thin-films (DGT). Antioxidant system responses in E. fetida to Cd were measured as biological endpoints. Biological responses were more highly correlated with Cd concentrations evaluated using bioavailable methods than with total concentrations. Cd concentration measured using DGT and CaCl2 extraction provided the narrowest ranges of lowest observed effect concentration (LOEC) values based on biological responses, indicating the potential use of these measurements in management of soil quality and setting soil remediation standards. The LOEC values obtained from 15 field soils contaminated by Cd were similar to those from the three Cd-amended soils and suggested that DGT in particular can be a good tool to predict stress responses of E. fetida to Cd in soils. The study shows the potential of combining biological response and DGT measurements in risk assessment.

Heavy metal accumulation in rice (Oryza sativa) near electronic waste dumps and related human health risk assessment

ABSTRACTThis research was conducted to assess heavy metal contamination in the environment and within Oryza sativa. The translocation factors (TFs) and bioaccumulation factors (BAFs) for heavy metals in O. sativa and estimated daily intake (EDI) and health risk index (HRI) were measured. The samples were analyzed for heavy metals using inductively coupled plasma optical emission spectrometry (ICP-OES). Pb and Cr concentrations in water samples within and near the electronic-waste dumping area exceeded water quality standards for surface water sources from the Pollution Control Department in the Ministry of Natural Resources and Environment of Thailand (PCD). The Pb concentration in soil samples within the area also exceeded soil quality standards for habitat and agriculture from PCD. Most of the metals were highly concentrated in roots, except for Mn which has the highest concentration in leaves. Pb concentrations in rice grains exceeded the FAO/WHO standard (0.2 mg/kg). The average TF values for heavy metals from the soil to roots, roots to stems, stems to leaves, and stems to grains were Mn > Pb > Ni > Cr, Mn > Cr > Ni > Pb, Ni > Pb > Mn > Cr, and Pb > Ni > Cr > Mn, respectively. The average BAF values in O. sativa were Mn > Ni > Pb > Cr. The EDI for Cr, Pb, Mn, and Ni via O. sativa consumption were 6.19, 6.02, 370.57, and 3.80 µg/kg/day, respectively. The HRI for Cr, Pb, Mn, and Ni via O. sativa consumption were 0.30, 1.50, 2.60, and 0.002, respectively.

The current status of heavy metal in lake sediments from China: Pollution and ecological risk assessment.

Heavy metal contamination in lake sediments is a serious problem, particularly in developing countries such as China. To evaluate heavy metal pollution and risk of contamination in lake sediments on a national scale in China, we collated available data in the literature of the last 10 years on lake sediments polluted with heavy metals from 24 provinces in China. Based on these data, we used sediment quality guidelines, geoaccumulation index, and potential ecological risk index to assess potential ecological risk levels. The results showed that approximately 20.6% of the lakes studied exceeded grade II level in Chinese soil quality standards for As, 31.3% for Cd, 4.6% for Cu, 20.8% for Ni, 2.8% for Zn, and 11.1% for Hg, respectively. Besides, the mean concentrations for As in 10.3% of lakes, Hg in 11.9% of lakes, and Ni in 31.3% of lakes surpassed the probable effect level. The potential ecological risk for toxic metals decreased in the order of Cd > Hg > As > Cu > Pb > Ni > Cr > Zn, and there were 21.8% of the lakes studied in the state of moderate risk, 10.9% in high risk, and 12.7% in very high risk. It can be concluded that Chinese lake sediments are polluted by heavy metals to varying degrees. In order to provide key management targets for relevant administrative agencies, based on the results of the pollution and ecological risk assessments, Cd, Hg, As, Cu, and Ni were selected as the priority control heavy metals, and the eastern coastal provinces and Hunan province were selected as the priority control provinces. This article, therefore, provides a comprehensive assessment of heavy metal pollution in lake sediments in China, while providing a reference for the development of lake sediment quality standards.

Environmental risk assessment as a new basis for evaluation of soil contamination in Polish law

Abstract This paper discusses new regulations on the assessment of soil contamination and the principle rules for remediation of contaminated sites included in the Environmental Protection Act, amended in 2014., as well as in related implementing legislation of 2016. In place of soil quality standards and the requirement to bring soil to the state that meets the standards, the new rules of contamination assessment and new remediation criteria have been introduced, based on environmental risk assessment. Similar rules are becoming increasingly common in many countries. This article provides general knowledge on the principles for the assessment of environmental risks associated with soil contamination, taking into account its two fundamental aspects: human health risk and environmental risk. On this background, the paper presents the principles of the assessment on soil contamination contained in the Regulation 1395 (2016) of the Minister of the Environment, as well as the rules for the choice of remediation method and design of remedial actions that should be basically aimed to eliminate the risk to human health and the environment.

Spatial distribution of organochlorine and organophosphorus pesticides in soil-groundwater systems and their associated risks in the middle reaches of the Yangtze River Basin.

Soil and groundwater samples were collected from paddy fields in the middle reaches of the Yangtze River Basin to study the occurrence and the risks associated with organochlorine pesticides (OCPs) and organophosphorus pesticides (OPPs) in soil and groundwater. Results showed that OCPs and OPPs were widely distributed throughout the study area. The levels of OCPs and OPPs in the soil were much lower than those specified by soil quality standards. However, the levels of four OCPs (heptachlors, aldrin, dieldrin, and γ-hexachlorocyclohexane) in groundwater were higher than those permitted by drinking water standards. The health risk assessment method suggested by the US Environment Protection Agency was used to evaluate the regional risks from selected pesticides. Results showed that there were low health risks from OCPs and OPPs in soil at the regional scale, but high risks from heptachlor, aldrin, and endrin in groundwater, suggesting an urgent need for groundwater protection. There are widespread concerns on dichlorodiphenyltrichloroethane and hexachlorocyclohexane, but little focus on other pesticides in China. However, our results suggest that the presence of, and risks from, other pesticides in groundwater should be a focus from the region aspect.

유류/중금속 복합오염토양 정화를 위한 다단 토양세척 효율평가

In typical remediation practices, separate washing systems have to be applied to clean up the soils contaminated with both oil and heavy metals. In this study, we evaluated the efficiency of successive two-stage soil washing in removal of mixed-contaminants from soil matrix. Two-stage soil washing experiments were conducted using different combinations of chemical agent: 1) persulfate oxidation, followed by organic acid washing, and 2) Fenton oxidation, followed by inorganic acid washing. Persulfate oxidation-organic acid washing efficiently removed both organic and inorganic contaminants to meet the regulatory soil quality standard. The average removal rates of total petroleum hydrocarbons (TPH), Cu, Pb, and Zn were 88.9%, 82.2%, 77.5%, and 66.3% respectively, (S/L 1:10, reaction time 1 h, persulfate 0.5 M, persulfate:activator 3:1, citric acid 2 M). Fenton oxidation-inorganic acid washing also gave satisfactory performances to give 89%, 80.9%, 87.1%, and 67.7% removal of TPH, Cu, Pb, and Zn, respectively (S/L 1:10, reaction time 1 hr, hydrogen peroxide 0.3 M, hydrogen peroxide:activator 5:1, inorganic acid 1 M).

Evaluation of heavy metal pollution and its ecological risk in one river reach of a gold mine in Inner Mongolia, Northern China

The spatial distribution characteristics of As, Cu, Hg, Pb, Zn and pH were analyzed by measuring the contents of several heavy metals in surface and profile sediment, in one river reach of a gold mine, Inner Mongolia. The results indicated that heavy metal pollution had less and less effect on river reach with the distance from the gold mine, and the effect nearly disappeared when falling into the Zhaosu River. In vertical profile, there was a trend that the contents of heavy metals gradually decreased with the depth increasing. The river reach in the gold mine was contaminated more seriously by As and Hg, for which As contents exceeded the national soil quality standard of grade III, and the contents of Cu, Pb and Zn all didn't exceed it. The evaluation results by Hakanaon risk index method indicated that the ecological risk for Hg and As were higher, reaching up to grade C, while the risk for Cu, Pb and Zn were low. The comprehensive ecological risk of heavy metals reached up to grade III in the junction of river and valley and near the mining site, while the grades were A and B in two sampling sites of Zhaosu River. It was believed that mining activities and adsorption by clay minerals were primary controls for ecological impact of As and Hg.

Heavy metals and nutrients (carbon, nitrogen, and phosphorus) in sediments: relationships to land uses, environmental risks, and management.

Management of sediments in polluted rivers requires an inventory of sediment quantities as well as their nutrient and metal contents and the chemical forms of pollutants. We investigated the influence of three major land uses (i.e., orange plantation-OP, OP + residential + industrial-OPRI, and residential + industrial-RI) on the quality of surface sediments (0-20cm below water/sediment interface) at the Sanyang Wetland (China). The total contents of metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) and nutrients (C, N, and P) as well as metal speciation in sediments were examined. GIS technology was used to estimate the volume of sediments needed to calculate the amounts of stored nutrients and metals in sediments. The surface sediments in the 3.2-km2 study area contain more than 2800Mg C, 200Mg N, and 100Mg P. OPRI and RI land uses contribute more total C, N, P, Zn, and Cd to sediments than OP land use. High contents of C, N, and P may provide options to recycle the sediments as fertilizer but must be used with caution due to high levels of metals. Total Cd in sediments is at an order of magnitude (up to 59mgkg-1) higher than the Level III criterion in the Chinese Environmental Quality Standards for Soil. Sediments in all land uses have very high risks due to >50% exchangeable + carbonate-bound Zn, Ni, and Cd. It is suggested that toxicity tests be conducted to better assess the environmental risks associated with any potential use of sediments.

Spatial differentiation of ecosystem risks of soil pollution in floodplain areas of the Czech Republic

Extensive soil sampling and screening assessment of ecosystem risks combined with a multidimensional statistical analysis were used to estimate and spatially characterize the ecosystem risks stemming from the contamination of floodplain soils in the Czech Republic. We proved structural differences in regional pollution patterns where different regional/local pollution sources led to various nature and extent of the environmental load of floodplain soils. The established spatial patterns helped reveal the areas where soils do not meet soil quality standards and where the ecosystem risks were elevated. Furthermore, the results allowed to establish priority contaminants of flood affected areas in various catchments in the Czech Republic. Combining both the magnitudes of estimated ecosystem risks and structural characteristics of pollution profiles, the highest estimated risks showed the localities with high contents of organochlorine pesticides, several samples connected to geochemical anomalies of metallogenic zones (deposits), and localities with a long history of industrial load. Since extreme weather events have recently become more frequent, our results highlight the importance of a continual monitoring of pollutant turnover in floodplain soils with a high flood frequency.

Characteristics and Environmental Assessment of Facing Bricks Produced from Dredged Sediments and Waste Glasses

The laboratory-scale study was conducted to assess the feasibility of using dredged sediments with waste glasses to produce facing bricks. This study was investigated into three different proportions of waste glasses ranging from 0, 20, and 40% by weight mixed with dredged sediments as raw materials in producing facing bricks. The characteristics of the dredged sediments, waste glasses, and fired facing bricks were analyzed using X-ray fluorescence (XRF) and X-ray diffraction (XRD. The physical-mechanical properties of fired bricks were compliant with the criteria for facing bricks (Thai Industrial Standards 168-2546). The results showed that major chemical compositions of dredged sediments and waste glasses were silica (SiO2) with the value of 43.50% and 70.70%, respectively. Heavy metal contents including Cr, Cu, Zn, As, Cd, Hg, Pb, Mn, Sr, and Ni were lower than the soil quality standard. Results of this study indicated that dredged sediments and waste glasses are suitable as primary raw materials in the production of facing bricks and could be considered to represent an environmental friendly product.

Using microbiological leaching method to remove heavy metals from sludge

Microbial leaching is one of the most effective methods to remove heavy metals from sludge. In the conducted researches, the sludge samples were processed with Thiobacillus ferrooxidans and Thiobacillus thiooxidans obtained via cultivation, extraction and purification processes. Heavy metals such as Pb, Cd, Cu and Ni were leached from sludge by Thiobacillus ferrooxidans and Thiobacillus thiooxidans within different substrate concentration and pH value conditions. It is defined that from the point of view of economy and efficiency the optimal concentration of FeSO4.7H2O and sulfur for bio-leaching process was 0.2 g. The leaching rates of heavy metals such as Pb, Cd, Cu and Ni of the same concentration were 74.72%, 81.54%, 70.46% and 77.35% respectively. However, no significant differences depending on the pH value among the leaching rates were defined, even for the pH value of 1.5. Along with the removal of heavy metals from sludge, the organic matter, N, P, K were also leached to some extent. The losing rate of phosphorus was the highest and reached 38.44%. However, the content of organic matter, N, P, K in the processed sludge were higher in comparison with level I of the National Soil Quality Standards of China. Ecological risk of heavy metals in sludge before and after leaching was assessed by Index of Geo-accumulation (Igeo) and comprehensive potential risk (RI). The results of research defined that the content of heavy metals in sludge meets the level of low ecological risk after leaching and their contents is lower in comparison with the National Agricultural Sludge Standard of China. Sludge leached by biological methods is possible to use for treatment for increasing soil fertility.

Impact of salinity and Pb on enzyme activities of a saline soil from the Yellow River delta: A microcosm study

Abstracts Soil enzyme activities are sensitive to the changes of soil properties and pollutants. In this study, the influence of salinity and Pb on the soil enzyme (catalase, CAT; invertase, IA; urease, UA) activities regarding the soil aggregate size classes was investigated. We selected a saline soil from the Yellow River delta, and adopted an orthogonal experiment designed with five Pb concentration levels and five salinity levels. The soil was dry sieved into three soil aggregate size classes: >2000 μm, 250–2000 μm, and P P −1 . When Pb concentration exceeded 400 mg kg −1 , with the increase of Pb concentration, there were no significant changes of all the enzyme activities under the inhibition or promotion effects of Pb. The Pb concentration which leads to a significant reduction is between 0 and 200 mg kg −1 for IA activity and 200–400 mg kg −1 for UA activity. And the increase of soil salinity led to a higher toxicity of Pb for UA activity. The toxicity range could be a valid reference for the formulation of soil quality standards in estuarine wetlands. We concluded that the effects of Pb on soil enzyme activities depend on the Pb concentration, soil salinity and the enzyme types. IA activity showed a higher activity in the macro-aggregate (250–2000 μm), while there was no significant difference in CAT and UA activities among three particle size classes. Since the IA activity was sensitive to soil salinity, Pb concentration and soil aggregate size, it could be selected as a representative indicator for soil monitoring in the Yellow River delta.

Exoenzyme activity in contaminated soils before and after soil washing: ß-glucosidase activity as a biological indicator of soil health

It is essential to remediate or amend soils contaminated with various heavy metals or pollutants so that the soils may be used again safely. Verifying that the remediated or amended soils meet soil quality standards is an important part of the process. We estimated the activity levels of eight soil exoenzymes (acid phosphatase, arylsulfatase, catalase, dehydrogenase, fluorescein diacetate hydrolase, protease, urease, and ß-glucosidase) in contaminated and remediated soils from two sites near a non-ferrous metal smelter, using colorimetric and titrimetric determination methods. Our results provided the levels of activity of soil exoenzymes that indicate soil health. Most enzymes showed lower activity levels in remediated soils than in contaminated soils, with the exception of protease and urease, which showed higher activity after remediation in some soils, perhaps due to the limited nutrients available in remediated soils. Soil exoenzymes showed significantly higher activity in soils from one of the sites than from the other, due to improper conditions at the second site, including high pH, poor nutrient levels, and a high proportion of sand in the latter soil. Principal component analysis revealed that ß-glucosidase was the best indicator of soil ecosystem health, among the enzymes evaluated. We recommend using ß-glucosidase enzyme activity as a prior indicator in estimating soil ecosystem health.

Regional accumulation characteristics of cadmium in vegetables: Influencing factors, transfer model and indication of soil threshold content

A regional investigation in the Youxian prefecture, southern China, was conducted to analyze the impact of environmental factors including soil properties and irrigation in conjunction with the use of fertilizers on the accumulation of Cd in vegetables. The Cd transfer potential from soil to vegetable was provided by the plant uptake factor (PUF), which varied by three orders of magnitude and was described by a Gaussian distribution model. The soil pH, content of soil organic matter (SOM), concentrations of Zn in the soil, pH of irrigation water and nitrogenous fertilizers contributed significantly to the PUF variations. A path model analysis, however, revealed the principal control of the PUF values resulted from the soil pH, soil Zn concentrations and SOM. Transfer functions were developed using the total soil Cd concentrations, soil pH, and SOM. They explained 56% of the variance for all samples irrespective of the vegetable genotypes. The transfer functions predicted the probability of exceeding China food safety standard concentrations for Cd in four major consumable vegetables under different soil conditions. Poor production practices in the study area involved usage of soil with pH values ≤ 5.5, especially for the cultivation of Raphanus sativus L., even with soil Cd concentrations below the China soil quality standard. We found the soil standard Cd concentrations for cultivating vegetables was not strict enough for strongly acidic (pH ≤ 5.5) and SOM-poor (SOM ≤ 10 g kg−1) soils present in southern China. It is thus necessary to address the effect of environmental variables to generate a suitable Cd threshold for cultivated soils.

The Effects of Coal Seam Gas Infrastructure Development on Arable Land in Southern Queensland, Australia: Field Investigations and Modeling

<abstract> <b><sc>.</sc></b> The production of coal seam gas (CSG) in Australia is set to increase, driven by increasing global demand for energy and in response to the transition to a lower carbon economy through greater use of gas for electricity generation. Despite the many economic benefits delivered by the CSG industry, concerns have been raised over the potential environmental impacts associated with CSG production, particularly the long-term effects on the soil resource. Therefore, this work was conducted to: (1) assess the extent of damage to agricultural soil caused by the various elements of CSG development and (2) estimate the likely impact of soil compaction, caused during establishment of CSG infrastructure, on crop productivity. The study was undertaken using a paired-sites approach by comparing measurements conducted on selected soil properties in areas around and including well-head sites with measurements in neighboring agricultural fields. These spatial areas are referred to as “lease” and “field” areas, respectively. Measurements were used to guide parameterization and application of the Agricultural Production Systems Simulator (APSIM) model to assess the likely effects of changed soil conditions on crop productivity. To achieve this, the APSIM model was used to simulate wheat ( L.) yields for 115 years on Grey Vertosols in the Darling Downs region of Queensland. Simulations were conducted with soil properties representing: (1) field area conditions not affected by CSG activities, (2) lease area conditions in which soil had been impacted by CSG activities during the development phase, and (3) lease area conditions where soils had been rehabilitated. Results showed that soil compaction within lease areas in the top 300 mm of the profile was approximately 15% higher compared with field areas (p < 0.05). The modeling work suggested that near-surface (0 to 300 mm depth) soil compaction within affected areas can lead to significant losses in crop productivity due to adverse effects on soil hydraulic properties. The simulation analyses predicted a 53% reduction in median wheat yields compared with simulated results in neighboring agricultural fields. For the bottom and top deciles, predicted relative yields were up to 60% and 32% lower, respectively. Practical solutions for management of such compaction are presented and discussed. Soil cultivation of the top 300 to 350 mm will ensure sufficient soil water storage in most years, thereby reducing the risk of crop failure. Progressive soil loosening techniques for alleviation of deeper compaction were reviewed; however, their cost-effectiveness under Australian soil conditions requires further investigation. Limit bulk density values of 1.45 and 1.60 g cm^-3 for the 0 to 350 mm and 350 to 700 mm depth intervals, respectively, are suggested as references for CSG-rehabilitated soil. These critical values may be used as guidance until further studies are undertaken. The assessment of soil chemical properties indicated that these were affected to a lesser extent by the establishment of CSG infrastructure. However, a general requirement is careful manipulation of sodium-rich subsoil and avoidance of soil blending during reinstatement operations. The dataset acquired and the simulation approach employed in this study can be used to further develop soil management guidelines relevant to the Australian CSG industry. Cost-benefit analyses of soil management practices for reinstatement, development of soil quality standards, and industry best management practices are required.

Cytotoxic evaluation of rice field frogs (Fejervarya limnocharis) from gold mine area with arsenic contamination

The objectives of this study were to investigate chromosomal aberrations in rice field frogs (Fejervarya limnocharis) from gold mine area compared to those from non-affected area. Three frogs were collected from each site, and chromosomal aberrations were studied in their bone marrow. Arsenic (As) was also measured in water and sediment from both areas. The average As concentrations in samples from the gold mine and the non-affected areas were 0.03 ± 0.003 mg/L and not detected in water and 351.59 ± 5.73 and 1.37 ± 1.07 mg/kg in sediment, respectively. The values in the gold mine were still higher than that allowed by the water and soil quality standards; however, the As concentrations in the samples from the non-affected area were acceptable. The average concentrations of As in the frog samples from the gold mine and the non-affected areas were 0.35 ± 0.33 and 0.07 ± 0.01 mg/kg, respectively, which were both lower than the standard of As contamination in food. The diploid chromosome number of frogs in both areas was 2n = 26, and the percentage of chromosomal aberrations in rice field frogs in the gold mine area was higher than in the non-affected area. There were seven types of chromosomal aberrations observed: single chromatid gap, isochromatid gap, single chromatid breaks, deletion, fragmentation, centric fragmentation and polyploidy. The most common chromosomal aberration in the samples from the affected area was the single chromatid gap. The difference in the percentages of chromosomal aberrations in rice field frogs from each area was statistically significant (p < 0.05).

Joint toxic action of binary metal mixtures of copper, manganese and nickel to Paronychiurus kimi (Collembola)

The joint toxic effects of binary metal mixtures of copper (Cu), manganese (Mn) and nickel (Ni) on reproduction of Paronhchiurus kimi (Lee) was evaluated using a toxic unit (TU) approach by judging additivity across a range of effect levels (10–90%). For all metal mixtures, the joint toxic effects of metal mixtures on reproduction of P. kimi decreased in a TU-dependent manner. The joint toxic effects of metal mixtures also changed from less than additive to more than additive at an effect level lower than or equal to 50%, while a more than additive toxic effects were apparent at higher effect levels. These results indicate that the joint toxicity of metal mixtures is substantially different from that of individual metals based on additivity. Moreover, the close relationship of toxicity to effect level suggests that it is necessary to encompass a whole range of effect levels rather than a specific effect level when judging mixture toxicity. In conclusion, the less than additive toxicity at low effect levels suggests that the additivity assumption is sufficiently conservative to warrant predicting joint toxicity of metal mixtures, which may give an additional margin of safety when setting soil quality standards for ecological risk assessment.

Major controlling factors and prediction models for arsenic uptake from soil to wheat plants

The application of current Chinese agriculture soil quality standards fails to evaluate the land utilization functions appropriately due to the diversity of soil properties and plant species. Therefore, the standards should be amended. A greenhouse experiment was conducted to investigate arsenic (As) enrichment in various soils from 18 Chinese provinces in parallel with As transfer to 8 wheat varieties. The goal of the study was to build and calibrate soil–wheat threshold models to forecast the As threshold of wheat soils. In Shaanxi soils, Wanmai and Jimai were the most sensitive and insensitive wheat varieties, respectively; and in Jiangxi soils, Zhengmai and Xumai were the most sensitive and insensitive wheat varieties, respectively. Relationships between soil properties and the bioconcentration factor (BCF) were built based on stepwise multiple linear regressions. Soil pH was the best predictor of BCF, and after normalizing the regression equation (Log BCF=0.2054 pH- 3.2055, R2=0.8474, n=14, p<0.001), we obtained a calibrated model. Using the calibrated model, a continuous soil–wheat threshold equation (HC5=10(−0.2054 pH+2.9935)+9.2) was obtained for the species-sensitive distribution curve, which was built on Chinese food safety standards. The threshold equation is a helpful tool that can be applied to estimate As uptake from soil to wheat.

Heavy metal concentration in soil in the tailing dam vicinity of an old gold mine in Johannesburg, South Africa

Soil contamination with heavy metals is a serious concern to food production and human health. The present study was conducted to evaluate the impact of tailings from an old mining site on heavy metal contamination of soil. Using a GPS to map out different sites around the tailing dam, soil samples were taken from under grassland at the different sites, at depths of 15 cm and 1 m, using a shovel and handheld auger. The samples were prepared, acid digested, and analyzed for a multi-element suite by inductively coupled plasma atomic emission spectrometry. Results showed heavy metal concentration in the order of Cr &gt; Zn &gt; As &gt; Mn &gt; Cu &gt; Pb &gt; Ni &gt; Sr &gt; Hg. Most of the soil samples contained high concentration of As (13.46–234.6 mg kg−1). Soil concentrations of As, Hg, Cr, and Mn also decreased with distance from the dump material. Single contamination index of each pollutant, calculated according to the South African Soil Quality Standards revealed very high and medium pollution grades for As (index = 7.39) and Cr (index = 2.16), respectively. Arsenic is a metal associated with gold ore and soil pollution by such metals can make it infertile and unsuitable for plants.