Study on the effects of several amendments on the antioxidant defense system of Chinese cabbage in heavy metal contaminated soil

Abstract

In this paper, the effects of applying straw biochar, attapulgite, phosphate rock powder, diatomite, humic acid and other passivation materials on the physical and chemical properties of heavy metal contaminated soil and the antioxidant enzyme activity of Chinese cabbage were studied.The results showed:Soil pH increased by 0.26–1.15 units, and organic matter (OM) content increased by 1.23% -48.77%. The application of passivation agent effectively reduced the available content of heavy metals in soil, and the activities of catalase, acid phosphatase, urease and sucrase in soil were improved to varying degrees, especially in T4(biochar1.5% + humic acid1.5%) treatment; Compared with CK, the contents of heavy metals in the aboveground and underground parts of Chinese cabbage were significantly decreased ( p < 0.05 ), while the transport coefficients of Chinese cabbage under each treatment were different. Under different treatments, the activities of catalase(CAT), superoxide dismutase(SOD) and peroxidase ( POD ) in the leaves of Chinese cabbage were significantly increased, the contents of malondialdehyde ( MDA ) and non-protein thiol(NPT) were significantly lower than those in the control, and the activity of glutathione reductase(GR) was significantly decreased, especially in T4 ( biochar1.5% + humic acid1.5% ) treatment; Under each treatment, soil pH and OM were significantly negatively correlated with soil heavy metal content ( p < 0.05 ), positively correlated with soil enzyme activity, significantly positively correlated with CAT, SOD and POD of Chinese cabbage ( p < 0.05 ), and negatively correlated with MDA, GR and NPT content of Chinese cabbage.In summary, the combination of several passivation agents can effectively improve soil heavy metal pollution and reduce the effective state of soil heavy metals, thereby reducing the toxicity of heavy metals to Chinese cabbage.