The investigations on heavy metal contamination that have been conducted over the past ten years in several Chinese cities are reviewed in this study. In this study, heavy metal concentrations, sources, contamination levels, sample collecting methods, and analytical instruments were compared and discussed in great detail for urban soils, urban road dusts, and agricultural soils. According to the findings, practically every concentration of Cr, Ni, Cu, Pb, Zn, As, Hg, and Cd is greater than background soil levels in China. The levels of heavy metal contamination throughout the cities differ widely. According to the geoaccumulation index, urban soils and road dusts in cities are heavily contaminated with Cr, Ni, Cu, Pb, Zn, and Cd. In general, Cu, Pb, Zn, and Cd contamination levels are higher than those of Ni and Cr. Additionally, anthropogenic sources of Cd, Hg, and Pb have a substantial impact on agricultural soils. According to the integrated pollution index (IPI), heavy metal contamination levels are higher in the urban soil and road dust of industrial and developed cities. The levels of metal pollution in urban road dusts are higher than those in urban soils in the cities of Shanghai, Hangzhou, Guangzhou, and Hong Kong, according to a study of the IPIs of heavy metals in urban soils and urban road dusts from these cities. Additionally, the primary sources of the metals in agricultural soils, urban traffic dusts, and urban soils vary.( Whitehorn PR et al.,2012)
The soil is home to a large portion of an agroecosystem's biodiversity. The functions of soil biota have significant direct and indirect effects on crop growth and quality, soil- and residue-borne pests, disease incidence, the efficiency of nutrient cycling, water transfer, and, ultimately, crop management systems' ability to persist. Whether on purpose or accidentally, farmers control soil biodiversity through tillage. Given the significance of soil biota, one of the major challenges in tillage research is understanding and predicting the effects of tillage on soil ecology. This is important for both assessing the impact of tillage on soil organisms and functions as well as designing tillage systems that make the best use of soil biodiversity, particularly for crop protection. In this essay, we begin by discussing (Ding W et al., 2016).
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