Comparisons of heavy metal input inventory in agricultural soils in North and South China: A review.

A national-scale inventory of heavy metal inputs is essential to understand the current situation of contribution and spatial heterogeneity of heavy metal sources in China. Published literatures from 2008 to 2018 about heavy metal inputs from various pollution sources (atmospheric deposition, livestock manures, fertilizers, and sewage irrigation) to agricultural soils were collected. In the past ten years, atmospheric deposition was the main pollution source which was responsible for 50-93% of the total As, Cd, Cr, Hg, Ni, and Pb inputs, with livestock manures contributed to approximately 76% of total Cu inputs. However, due to industrial structure, geographical condition and the characteristics of economic development, the contribution of different sources to heavy metal pollution varies in different regions. For example, atmospheric deposition was the most important contributor in North China with its highly developed heavy industry and more coal combustion, while the contribution of livestock manures was obviously higher in South China due to its flourishing agricultural production and animal husbandry. Based on the analysis for clarifying the major pollution sources of five typical heavy metals (namely Cd, As, Hg, Cu and Pb), the controlling measures are suggested to make more effective and targeted strategies to protect agricultural soils in the future.