Distribution Characteristics of Heavy Metal Pollution in Soil Under Recycling Mode of Direct Straw Manuring

摘要

A large number of straw resources are inefficiently used in China. Direct straw manuring is the mostcommon method for efficiently utilizing these resources. The migration of nutrients and the transfer ofhazardous elements such as heavy metals during the cycle, endanger the growth of crops, therebydecreasing food production and adversely affecting human health through the food chains. Themechanism of heavy metal-polluted soil under the recycling mode of direct straw manuring is analysedto determine its distribution characteristics. The concentration distribution characteristics of heavymetals such as Pb, Cr, Cd and As in the soil are identified through experiments. Empirical study showsthat the contents of the four heavy metals in the soil of the wheat-maize rotating farmland under directstraw manuring mode do not exceed the values listed in the Environmental Quality Standards for Soils(GB15618-1995). The contents of Cr and Cd in the roots of wheat and maize are significantly higherthan those in the soil, suggesting the accumulation of these metals in the roots, while those of Pb andAs do not have this phenomenon. The contents of the heavy metals in the roots, stems, leaves andseeds of the crops decrease in order. The pollution of the heavy metals including Pb, Cr, Cd, As underthe direct straw manuring is explored, and their migration rules in the farmland ecosystem aresystematically explored. The results provide a basis for regulating and blocking heavy metals, preventingheavy metal pollution and safeguarding food safety.