Assessment of Heavy Metals in Grain Fields with Long-term Treatment of Agrochemicals and Organic Manure in Hailun City of Northeast China

Heavy metals were evaluated in the soils of grain fields in Hailun City Experimental Research Station–Chinese Academy of Sciences (CAS). Four categories of the soil samples were chosen from the fields after 19 years of treatment with chemicals, no fertilizer, organic manure, and organic manure combined with chemical fertilizer. The study revealed a prevalence of significantly high concentrations of Cu, Zn and Pb in organic manure combined with chemical fertilizer in the grain fields of black soils. The concentrations of Cu and Zn in no fertilizer treatment, chemical treatment, and organic treatment also exceeded the permissible limits. However, the concentrations of Hg and As were found to be within the safe limits in all treatments.