Purification Effect of Constructed Wetland with Spartina alterniflora Litter on Atrazine and Heavy Metals
In order to investigate the impact of Spartina alterniflora litter on the purification efficiency of a constructed wetland in treating combined pollution of atrazine and heavy metals,a simulated wetland device was constructed.The study analyzed the removal efficiency of atrazine and the distribution of heavy metals when Spartina alterniflora litter was either buried in the soil or placed on the soil surface.The research also examined changes in soil physical and chemical properties and explored the factors influencing the removal of atrazine and heavy metals in the wetland with Spartina alterniflora litter.Results indicated that the removal rate of atrazine increased from 65.7％to 88.7％under single atrazine pollution and from 64.6％to 89.6％under combined pollution of atrazine and heavy metals.The degradation half-life of atrazine was 54.2 days for the buried treatment group and 60.8 days for the surface treatment group,suggesting that burying the litter in soil enhanced the wetland's atrazine removal capacity.Furthermore,the conversion of Cu from an exchangeable to an oxidizable state in the wetland soil was promoted by both burial and surface litter treatment,with about 10％increase in oxidizable Cu.The concentration of oxidizable Cu was approximately 14 mg/kg under single heavy metal pollution and 16 mg/kg under combined pollution,indicating more Cu transformed into a stable state under combined pollution.However,the changes of heavy metals Fe and Pb were less pronounced.Addition of Spartina alterniflora litter reduced salt content in the wetland soil,maintained a pH level between 6 and 7,and facilitated atrazine degradation and Cu conversion to a stable state.
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