Heavy metals in agricultural soils from a typical township in Guangdong Province, China: Occurrences and spatial distribution

An integrated approach to quantifying ecological and human health risks from different sources of soil heavy metals

Heavy metals (HMs) in soil cause adverse effects on ecosystem and human health. Quantifying ecological risk and human health risk (HHR) from sources can determine priority sources and help to mitigate the risks. In this research, geostatistics and positive matrix factorization (PMF) were used to identify and quantify the sources of soil HMs; and then ecological risk and HHR from different sources under woodland, construction land and farmland were quantitatively calculated by combining the potential ecological risk index (RI) and HHR assessment models with PMF model. Taking Jiedong District as an example, four sources were quantitatively apportioned, which were agricultural practices (23.08%), industrial activities (29.10%), natural source (22.87%) and traffic emissions (24.95%). For ecological risk, industrial activities were the greatest contributor, accounting for about 49.71%, 48.11% and 47.15% under construction land, woodland and farmland, respectively. For non-carcinogenic risk, agricultural practices were the largest source under woodland and farmland, while industrial activities were the largest source under construction land. As for carcinogenic risk, no matter which kind of land use, agricultural practices were the largest source. In addition, the health risks of children, including non-carcinogenic and carcinogenic risks, were higher than those of adults, and the trends in health risks for children and adults were similar. The integrated approach was useful to evaluate ecological risk and HHR quantification from sources under different land use, thereby providing valuable suggestions for reducing pollution and protecting human health from the sources.

A multi-criteria evaluation system for arable land resource assessment

This study proposed a multi-criteria evaluation system for arable land resources by combining the soil integrated fertility index (IFI) with a soil cleanliness index (based on heavy metals and metalloid content). A total of 16 typical arable land units in Chongming District, China, were evaluated using the proposed evaluation system based on 104 collected soil samples in 16 towns. The comprehensive soil evaluation scores of arable lands in 16 towns were in the range of 90.7 to 99.2 with a mean of 96.2, indicating that the arable land in all 16 towns was at the level of excellent (≥ 90.0). Lower cleanliness indices had a significant impact on the final evaluation score. In comparison with single-index evaluation systems (i.e., the IFI or soil cleanliness index), the proposed multi-criteria system better reflects the quality of the soil. In the practice of arable land requisition and subsidy policy, the proposed multi-criteria evaluation system not only encourages farmers to preserve arable lands during farming but also helps agricultural authorities make effective and reliable management decisions.

Geochemical Fractions of the Agricultural Soils of Southern Poland and the Assessment of the Potentially Harmful Element Mobility

Surface samples (0–25 cm each) of agricultural soils were investigated in five Regions (voivodeships) of southern Poland. The mean Potentially Harmful Element (PHE) pseudototal content ranges were as follows (mg/kg): As 5.19–10.9, Cd 0.34–1.56, Co 1.92–6.70, Cr 9.05–25.7, Cu 8.74–69.4, Hg 0.001–0.08, Ni 3.93–19.9, Pb 20.3–183, Sb 0.80–1.42, Tl 0.04–0.17, and Zn 61.3–422. The PHE availability depended on pH, the organic carbon (Corg) content, and the pseudototal PHE content in soils. Exchangeable and acid soluble PHE contents (BCRF1) determined in the Community Bureau of Reference (BCR) three-step sequential extraction procedure decreased in this order: Cd > Zn > Co > Ni = Sb > Cu > Tl > As > Cr = Pb. Actually available PHE contents in pore water (0.01 mol/dm3 CaCl2) ranged as follows: Cd 0.81–17%, Cr 0–0.25%, Cu 0.01–2.31%, Ni 0.16–2%, Pb 0.2–0.49%, and Zn 0.25–2.12%. The potential soluble total content of PHEs in pore water (0.05 mol/dm3 Na2EDTA) ranged as follows: Cd 27–91%, Cr 0.7–7.1%, Cu 6.7–98%, Ni 3.6–41%, Pb 15–41%, and Zn 3–34%. The mobility factor (MF) values indicated Cd (31.6%) and Zn (21.0%) as the most mobile elements in soil. Other PHEs followed the order of Co > Ni > Tl > As > Sb > Cu > Cr > Pb, with the MF values <10%. The risk assessment code (RAC) values revealed a very high ecological risk of Cd and Zn in the Podkarpackie Region and a high ecological risk of Cd in the Regions of Opolskie, Śląskie, Małopolskie, and Podkarpackie, and the same of Zn in the Opolskie and Śląskie. The modified risk assessment code (mRAC) index pointed a very high potential of adverse effects in soils in the Podkarpackie and a medium potential in the Opolskie, Śląskie, Małopolskie, and Świętokrzyskie. The potential adverse effect risk, described by the individual contamination factor (ICF) factor, was the following in the Regions, in the decreasing order: Cd > Pb > Sb > Zn > Co > Cu > Ni > Tl > As > Cr, and the same as described by the global contamination factor (GCF) values: Opolskie > Podkarpackie > Świętokrzyskie > Śląskie > Małopolskie.

Soil heavy metal contamination and health risk assessment associated with development zones in Shandong, China

Heavy metal pollution in soils of development zones has attracted wide attention. In this study, soil heavy metal pollution levels and health risks in 15 selected development zones in Shandong Province were investigated for the first time. Geo-accumulation and potential ecological risk indexes were used to assess pollution levels, and health risk was assessed using the US Environmental Protection Agency model. The soil was contaminated by various heavy metals, among which Hg was dominant. A total of 19% of the monitoring sites showed moderate ecological risk level, and low risk level was observed in general. Pollution control of Hg and Cd in each development zone must be strengthened. Health risk analysis showed that noncarcinogenic and carcinogenic risk levels for adults and children were acceptable or nearly acceptable. Positive matrix factorization model was used to identify three possible sources of heavy metal pollution, namely, industrial sources, atmospheric deposition, and transportation. Some specific measures should be taken to prioritize the control of Hg, As, and Cr for protecting the soil environment and human health, especially vulnerable groups, such as children.

Eight Elements in Soils from a Typical Light Industrial City, China: Spatial Distribution, Ecological Assessment, and the Source Apportionment

Contamination with the eight elements, Hg, As, Cr, Cu, Ni, Pb, Zn, and Cd, is a serious concern in Zhongshan, which is a typical light industrial city, China. 60 surface soil samples were collected to investigate the concentrations, spatial distribution, human health risk, and sources of these elements in the soils in Zhongshan. The concentrations of the eight elements were analyzed while using ordinary kriging analysis, pollution load index (PLI), potential ecological risk index (RI), human health risk, correlation analysis, and factor analysis. The mean concentrations of the tested elements, excluding Pb and As, were higher than the soil background values in the Pearl River Delta. The spatial distribution of the tested elements revealed a zonal distribution pattern and high values in several areas. The mean PLI and RI indicated slight and moderate risk levels. Health risk assessment demonstrates that both children and adults were more exposed to Cu than to Cr, As, and Cd. However, the associated carcinogenic risk is acceptable. Hg that originated from human activities; As, Cr, Cu, Ni, and Cd originated from industrial activities; and, Pb and Zn originated from transportation activities. Cd was the main pollutant in the study area and it was present at higher concentrations when compared with those of the other elements. Therefore, Zhongshan should encourage enterprises to conduct industrial transformation to control the ecological risk.

Metals in soils from a typical rapidly developing county, Southern China: levels, distribution, and source apportionment

A total of 321 surface soil samples were collected from Huilai County, Guangdong Province, Southern China. Concentrations of 12 metals (Cr, Hg, As, Pb, Ni, Cd, Cu, Zn, Sb, Sn, Ti, and V) were measured. The mean concentrations of As, Pb, Cd, Zn, Sn, and Ti were higher than their corresponding soil background values, especially for As, Cd, and Sn, which were 1.36, 2.50, and 2.77 times of the background values, respectively. And the results of enrichment factor and pollution load index suggested that soil metals in the study area were moderately contaminated, but pollution of As, Cd, and Sn was relatively serious. According to one-way analysis of variance, there were significant differences in concentrations of Hg, As, Pb, Cd, Zn, and Sn between different land use types, indicating that they were associated with the anthropogenic inputs. The potential sources of metals were quantitatively apportioned by positive matrix factorization, and combined with correlation analysis and geostatistical. The results showed that Cr, Ni, Ti, and V mainly originated from natural sources. Lead, Zn, and partially, Cd mainly came from traffic emissions. Arsenic, Cu, and partially, Sb were ascribed to agricultural practices. Mercury, Sn, partially, Cd, and Sb were derived from industrial activities. Their corresponding contributions were 36.88%, 22.14%, 20.87%, and 20.11%, respectively.

Spatial distribution and source apportionment of heavy metals in soil from a typical county-level city of Guangdong Province, China

The contents of ten heavy metals (Cr, Hg, As, Pb, Ni, Cd, Ti, Cu, Zn and V) in 413 topsoil samples from Puning City, Guangdong Province, China were investigated. Obvious enrichment of Hg, As, Pb, Cd and Zn were presented, and the contents of Hg and As in 5.8% and 3.4% samples respectively were higher than the guideline values recommended by the Chinese Environmental Quality Standard for Soils. Chromium and V were presented no enrichment and no pollution. According to one-way analysis of variance, the mean contents of Hg, Pb, Cu and Zn in land for construction were significantly higher than farmland and natural vegetation, but the land use had no obvious effect on other heavy metals. Furthermore, the potential sources of ten heavy metals were identified and apportioned in combination with geostatistics, correlation analysis and positive matrix factorization model. The results were following as: a) Pb, Zn and Cu mainly origin from vehicle emission and atmosphere deposition, and the hotspots approximately distributed in the areas of intensive traffic and near main roads; b) Hg and Cd were derived to industrial activities related to pharmaceutical industries, the textile and dyeing industries and e-waste recycling industries, and high-value areas were mainly concentrated in the northeast of the urban area where the industrial parks have been distributed; c) Soil parent material (Jurassic shale) was the main source of Cr, Ni, V and Ti; d) As mainly came from agricultural inputs such as pesticides or herbicides, livestock and fertilizers. Meanwhile, the contributions of four sources were 33.08%, 24.04%, 27.11% and 15.77% of the total contribution, respectively.