Effect of DOM derived from composting on the changes of Pb bioactivity in black soil

Abstract

Exogenous dissolved organic matter (DOM) plays an important role in the migration and transformation of heavy metals in soil. This study investigated the effect of composting-DOM with different maturity on changes of Pb bioactivity in soil, and evaluated the soil environmental factors driving these changes. The results showed that the activating ability of DOM to Pb in chernozem and dark brown soil increased by 4.11%−22.42% and 13.22%−30.15%, respectively. And the order followed: fresh manure (FDOM) > immature compost (IDOM) > mature compost (MDOM). The pH and dissolved organic carbon (DOC) were the main factors driving the changes in diethylenetriaminepentaacetic acid extraction (DTPA) -Pb in chernozem and dark brown soil, respectively. In chernozem, the input of MDOM can reduce the proportion of easily mobile fractions of Pb. While, DOM promotes the transformation of Pb from organic bound and residual fractions to exchangeable and carbonate bound fractions under other conditions. Moreover, the input of DOM can also drive the transformation of Pb species by regulating soil pH, electrical conductivity (EC), organic matter (SOM), DOC, and enzyme activity.