The effect of urban biochar on urban soil DOM characteristics and heavy metal availability

In order to solve the two problem of increasing urban waste and generally high content of heavy metals in urban soil, three kinds of urban source waste (garden pruned branches, domestic waste and rice husk) were prepared into biochar, and the effects of different application of urban source biochar on the availability of heavy metals and soil dissolved organic matter in two kinds of urban soil (riverside soil and industrial soil) were discussed. The results showed that the organic matter content of industrial soil was significantly higher than that of riverside soil, but the content, aromaticity/hydrophobicity and molecular weight of dissolved organic matter were significantly lower than those of riverside soil. Rice husk biochar treatment significantly reduced the contents of protein-like substance C2 and humus-like substance C3 in riverside soil. Three kinds of biochar increased the percentage of humus-like substance C1 and decreased the percentage of C2, among which, rice husk biochar was the most obvious. The total and available concentrations of Cu and Pb in industrial soil were significantly higher than those in riverside soil. However, the total concentration of Zn in industrial soil was significantly higher than that in riverside soil, but there was no difference in available concentration. Domestic waste biochar reduced the available Zn concentration in riverside soil, which is expected to be used to reduce the environmental risk of Zn in urban soil.