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.

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.