Characteristics of Particulate Organic Matter Mineralization in Polluted Soils

Particulate organic matter (POM) is a key component of soil organic matter (SOM), which is easily biodegradable and rich in organic carbon (OC) and heavy metals. However, the characteristics of C mineralization and the releases of cadmium (Cd) and zinc (Zn) during POM mineralization are still poorly understood. In the present study, a 90-day incubation experiment was conducted to study the releases of CO2-C and of Cd/Zn during POM mineralization with and without organic acids amendment. The results showed that 16.6%-26.6% OC, 17.0%-29.1% of Cd and 5.09%-14.3% Zn were stored in 2000-53 mu m POM size fractions. Comparing with one-time amendment, frequent organic acids amendment caused 76.4%-83.7% decreases in C priming effects. The total amounts of CO2-C emissions in POM size fractions were lower in soil with high pollution level than with low pollution level, and lower in 250-53 mu m POM size fractions than in 2000-250 mu m POM size fractions, respectively. The two-compartment first-order kinetic model can better fit the CO2-C mineralization process, and organic acids amendment resulting in increase in mean residence time of labile C. After 90-day incubation, 8.58%-26.5% Cd and 10.38%-38.1% Zn in 2000-53 mu m POM size fractions discharged into other phrases, and frequent organic acids amendment resulted more Cd/Zn release than that by one-time amendment in soil with high pollution level. Overall, frequent organic acids amendment facilitated C mineralization and Cd/Zn release of POM in comparison with one-time organic acids amendment in soil with high pollution level.