Remediation of Cd-contaminated soils by GWC application, evaluated in terms of Cd immobilization, enzyme activities, and pakchoi cabbage uptake

Compost (mainly composed of cow manure, horse manure, chicken manure, and straw) has turned out to be effective in remediation of heavy metal-contaminated soil. However, in recent years, the effects of green waste compost (GWC) on plant growth and the immobilization of heavy metal cadmium (Cd) in the soil have not been clearly studied. We considered the effects of different GWC ratios on the growth of pakchoi cabbage, soil physical and chemical properties, total and availability of Cd content, and soil enzyme activity. The results showed that organic matter, total nitrogen, available phosphorus, and available potassium in the soil gradually put in place over the increase of compost proportion and showed a significant difference. Dehydrogenase, urease, and catalase activities grew by 380, 35, and 32% under the treatment of T10, respectively. The increase of enzyme activity indirectly reflects the enhancement of self-purification ability of contaminated soil. The addition of GWC improved soil quality, leading to a significant increase in soil nutrients, and in biomass and chlorophyll content of pakchoi cabbage. The decrease of Cd availability led to a significant reduction of Cd content in pakchoi cabbage, with a 30-36% reduction of Cd content in roots and a 43-69% reduction in leaf. The BCF of leaves decreased from 0.62 to 0.22, and the TF decreased from 0.94 to 0.46, indicating that the addition of GWC reduced the mobility of Cd to pakchoi cabbage leaves. The result is decreased in Cd content in edible parts of pakchoi cabbage.