Evaluating the release risk of potentially toxic elements from sediments in the New Zhuzhao River Estuary of Nansi Lake, using high-resolution technology and sequential extraction.

Potentially toxic elements (PTEs) re-release from sediment is an essential process in the sediment-water interface (SWI), especially for the influent river estuary as an important accumulation site. In this study, the diffusive gradient in thin films (DGT), high-resolution dialysis (HR-peeper) technique, and BCR sequential extraction were employed to evaluate the release risk of PTEs (As, Cu, Pb, Zn, Cd) in the New Zhuzhao River Estuary of Nansi Lake. Results showed that Cd existed primarily in the non-residual fraction (accounting for 59.87%), and the residual fractions of As, Cu, Pb, and Zn accounted for a greater proportion (12.65 to 33.07%). The mobility of Cd was the highest with a risk assessment code of 33.53% reaching the medium risk category. The resupply capacity calculated by CDGT/CDis showed that As was the largest, with an average value of 0.43, indicating the strongest release capacity of As from the sediment to pore water. Furthermore, the diffusive fluxes using DGT and HR-peeper showed that As possesses a much higher potential to release upward overlying water than other elements.

Distribution characteristics of heavy metals in surface soils from the western area of Nansi Lake, China.

Surface soil samples collected from the western area of Nansi Lake, China, were analyzed for selected heavy metals including As, Cd, Pb, and Zn, to determine their spatial distributions and environmental effects. The average concentrations of As, Cd, Pb, and Zn in soil were 13.21 mg/kg, 0.20 mg/kg, 23.94 mg/kg, and 79.95 mg/kg, respectively. The concentration of As, Cd, and Zn was approximately 1.44-, 2.33-, and 1.25-fold higher than its background values in study area, respectively. Meanwhile, the concentrations of heavy metals progressively decreased from east to west within the study area, in a step-function distribution. The differences in the heavy metal distribution characteristics might be caused by the lake water irrigation and agricultural activities such as fertilizer and pesticide use. There were significant positive correlations between the values of OrgC, Al2O3, and Fe2O3 and concentrations of heavy metals. According to the Geo-accumulation index (Igeo) and the potential ecological risk index (PERI), Cd posed higher potential ecological risk in surface soil when compared with As, Pb, and Zn. These results could provide the scientific basis on which to evaluate the distribution of heavy metals under natural and anthropogenic influences in the surface soil near Nansi Lake, China.

Bacterial community shaped by heavy metals and contributing to health risks in cornfields.

Scientists are increasingly aware that heavy metal contamination in soils, especially in farmland ecosystems, can negatively affect human health and alter the bacterial community that plays a critical role in plant growth and heavy metal accumulation. The goal of the present paper was to uncover how various heavy metals and non-metallic elements affect human health and bacterial diversity in cornfields and to explore the contribution of soil bacteria to heavy metal accumulation in crops. Soil samples were collected from five counties in Shandong Province, China, where abnormally high levels of heavy metals and metalloids were caused by mining and heavy industry. We calculated a hazard quotient (HQ) to evaluate the health risk these heavy metals cause and analyzed the soil bacterial community using 16S rRNA gene sequencing. The HQ results showed that As posed the greatest threat to human health followed by Pb although concentrations of all metals did not reach the health risk threshold. Meanwhile, principal component analysis (PCA) and redundancy analysis (RDA) revealed soil bacterial richness was significantly influenced by As, Ni, and Cr as well as pH and phosphorus, but not by the species diversity of aboveground weeds. The most abundant bacteria in our study region were heavy metal tolerant groups, specifically Actinobacteria and Proteobacteria. Moreover, correlation analysis suggested that Actinobacteria might reduce the phytoaccumulation of Cr, Cu, Zn, and Hg in corn, while Proteobacteria might weaken phytoaccumulation of Pb, Ni, As, and Cd. Our results verified that heavy metals play an important role in shaping the soil bacterial community. Using native bacteria in farmland provides a potential biological strategy for reducing the health risk posed by heavy metals related to food consumption.

Distribution, fractionation and risk assessment of mercury in surficial sediments of Nansi Lake, China.

Nansi Lake is composed of four sub-lakes from north to south: Nanyang Lake, Dushan Lake, Zhaoyang Lake and Weishan Lake. An environmental pollution investigation was carried out to determine the fractionation, and pollution assessments of mercury (Hg) in surficial sediments from Nansi Lake. Results showed that the mean concentration of Hg was 3.1 times higher than its background value (0.015 mg kg-1), and the high concentration of Hg which even reached up to five times than the background value in the part of Dushan Lake and Weishan Lake, which indicated that there are obvious spatial differences. The content of Hg was positively correlated with that of total organic carbon, and negatively correlated with that of pH and SiO2 in surface sediments. An improved Tessier sequential extraction procedure was used to study the fractions of Hg in sediments. The results indicated that Hg existed primarily in the fraction of residual, which accounts for 58.4% of total mercury (THg), and the percentage of extractable Hg was only 1.93% of total mercury. High concentrations of mercury of non-residual phase were found in part lake area from the Nanyang Lake and the Weishan Lake, which indicating a higher potential ecological risk relative to the other lake areas. Based on the values of enrichment factor and geo-accumulation index, most part of Dushan Lake and Nanyang Lake and Weishan Lake were in a moderate pollution. And based on the fractionation of mercury, risk assessment code of Hg exhibited low risks to the environment in Nansi Lake.

Spatial trends and pollution assessment for mercury in the surface soils of the Nansi Lake catchment, China.

Surface soil samples collected from Nansi Lake catchment were analyzed for mercury (Hg) to determine its spatial trends and environmental impacts. Results showed that the average soil Hg contents were 0.043 mg kg-1. A positive correlation was shown between TOC and soil Hg contents. The main type of soil with higher TOC contents and lower pH values showed higher soil Hg contents. Soil TOC contents and CV values were both higher in the eastern catchment. The eastern part of the catchment, where the industry is developed, had relatively high soil Hg contents and a banding distribution of high Hg contents was corresponded with the southwest-northeast economic belt. Urban soils had higher Hg contents than rural soils. The urbanization pattern that soil Hg contents presented a decreasing trend from city center to suburb was shown clearly especially in the three cities. Soil Hg contents in Jining City showed a good consistency with the urban land expansion. The spatial trends of soil Hg contents in the catchment indicated that the type and the intensity of human activities have a strong influence on the distribution of Hg in soils. Calculated risk indices showed that the western part of the catchment presented moderately polluted condition and the eastern part of the catchment showed moderate to strong pollution level. The area with high ecological risk appeared mainly along the economic belt.

[Residues and Spatial Distribution Characteristics of Organochlorine Pesticides DDTs in Soil of Linyi City, Shandong Province].

Surface soil samples were collected every 36 km2 from Linyi City to study the residues, composition and origin, influencing factors, spatial distribution and environment quality characteristics of soil DDTs. Measurements were taken for DDTs, OrgC, N, etc. for all samples. The results indicated that the detectable rate of DDTs was 71. 75%, and the mean content of DDTs was 0. 035 µg.g-1. p,p'-DDT and p,p'-DDE were the predominant contaminant compounds, with mean concentrations of 0.033 µg.g-1 and 0.010 µg.g-1, and accounted for 60. 99% and 34. 62% of the detectable samples, respectively. The degradation rate of DDTs suggested that 58% surface soils were recently inputted, these newly inputted locations were especially distributed in the middle to south of the study area, meanwhile, p,p'-DDD/p,p'-DDE revealed that the degradation of DDTs was mainly under oxidizing condition, and o,p'-DDT/p,p'-DDT illustrated that 71. 37% DDTs in soils of the study area were concerned with technical DDTs sources. Besides, the correlation, analysis showed that the external factors affecting the distribution of DDTs included OrgC, N, C and pH etc. and the higher the p, p'-DDT proportion of DDTs, the greater the effect. The distribution of DDTs had an obvious point source characteristic, and significant concentration centers were located nearby the cities and counties, typically, the DDTs concentrations of middle to southern area were much higher. However, DDTs environmental quality assessment suggested that the pollution level was relatively low, and the soil was mainly classified into grade I or II, which accounted for 78. 95% and 21. 05% of the whole study area, respectively.

Factorial kriging and stepwise regression approach to identify environmental factors influencing spatial multi-scale variability of heavy metals in soils.

The knowledge about spatial variations of heavy metals in soils and their relationships with environmental factors is important for human impact assessment and soil management. Surface soils from Rizhao city, Eastern China with rapid urbanization and industrialization were analyzed for six key heavy metals and characterized by parent material and land use using GIS-based data. Factorial kriging analysis and stepwise multiple regression were applied to examine the scale-dependent relationships among heavy metals and to identify environmental factors affecting spatial variability at each spatial scale. Linear model of coregionalization fitting showed that spatial multi-scale variation of heavy metals in soils consisted of nugget effect, an exponential structure with the range of 12 km (short-range scale), as well as a spherical structure with the range of 36 km (long-range scale). The short-range variation of Cd, Pb and Zn were controlled by land use, with higher values in urban areas as well as cultivated land in mountain area, and were related to human influence; while parent material dominated the long structure variations of these elements. Spatial variations of Cr and Ni were associated with natural geochemical sources at short- and long-range scales. At both two scales, Hg dominated by land use, corresponded well to spatial distributions of urban areas, and was attributed to anthropic emissions and atmosphere deposition.