Determining Soil Enzyme Activities for the Assessment of Fungus and Citric Acid Inducing Phytoremediation in Heavy Metals Polluted Soil Based on DCCA Method

摘要

A greenhouse pot experiment was conducted to evaluate the effect of fungus, of citric acid, or of acombination of both, in the phytoremediation of a heavy metal contaminated soil, affected by Cd and Pb. Sixenzyme activities (namely dehydrogenase, phosphatase, urease, catalase, sucrase and amylase) in soil weredetermined in this study. Detrended Canonical Correspondence Analysis (DCCA) was taken to express therelationship between all remediation methods and soil enzyme activities in the ordination diagram to assessthe remediation effect in soil health degree. Results showed that soil enzyme activities were graduallyinhibited with increasing heavy metal concentration. In the samples without any remediation, single Pbpollution showed smaller influence on inhibition of soil enzyme activity than single Cd pollution, while Cdand Pb combined pollution showed similar changing tendency with single Cd pollution. As shown in theordination graph by DCCA, All soil enzymes variables showed big change at first axis. In a certain extent, Cdand Pb complex variables could reflect the soil enzymes activities change law at first axis due to their biggerprojections at first axis. The ordination diagrams also expressed the relationship between all remediationmethod variables and soil enzyme activity variables by their distance and position. Most of remediationmethods had positive effects on enhancing soil enzyme activities, except on sucrase activity. The soil enzymeactivities of hyperaccumulator treated with fungus were similar to that of treated with citric acid. Allremediation methods had significant positive effects on enhancing dehydrogenase, urease and catalaseactivities, whereas phosphatase and amylase activities were reduced at low heavy metal concentration andincreased at high concentration as a result of remediation in soil. All remediation methods showed negativeeffects on sucrase activity.