活化土壤重金属天然植物螯合剂的筛选

Selection of appropriate natural botanic chelators for mobilization of heavy metals in soils

目前常用的化学合成的土壤重金属活化剂EDTA(乙二胺四乙酸)存在难降解、成本高等问题。选用3种天然植物叶子汁液[马尾松(Pinus massonianaLamb.)、湿地松(Pinus elliottiiEngelm)、酸藤果(Embelia LaetaL.Mez)],并与3种浓度(1.25、2.50、5.00mmol.L-1)的EDTA作对比,对采自广东清远市和乐昌市的二种铅锌矿废水污染水稻土(分别为酸性土壤和中性土壤)进行重金属活化试验,比较不同天然植物螯合剂对土壤重金属Cd、Pb、Zn的活化效率。结果表明,不同种类的植物汁液对土壤Cd、Pb和Zn的活化能力为:酸藤果>湿地松>马尾松。1∶1(鲜叶重∶蒸馏水重)提取的酸藤果汁液的活化能力显著高于其1∶2提取的汁液。天然植物螯合剂对Pb、Cd的活化能力明显低于EDTA,但对Zn的活化能力强,酸藤果1∶1汁液和湿地松1∶2汁液对酸性的酸性土壤活化量显著高于5.00mmol.L-1EDTA,其它天然植物螯合剂对Zn的活化量显著高于2.50mmol.L-1EDTA。植物汁液对中性土壤重金属的活化率通常较低。结果表明,酸藤果汁液是一种较有前途的天然植物螯合剂。

The common used chemically-synthetic chelator EDTA（ethylene diamine tetraacetate）is hardly degradable and expensive in mobilizing soil heavy metals for enhancing phytoextarction.Using three botanic leaf juices including Masson pine（Pinus massoniana Lamb）,Slash pine（Pinus elliottii Engelm）and Embelia（Embelia Laeta L.Mez）,the mobilization of Cd,Pb and Zn in two agricultural soils contaminated by lead-zinc mining wastewater and different in soil pH from Qingyuan and Lechang District,Guangdong Province of China,was studied in batch experiments in comparison with EDTA in 1.25,2.50 and 5.00 mmol·L-1.Results showed that the studied botanic juices had different mobilization ability to Cd,Pb and Zn of the soils,and decreased in the order：Embelia Slash pine Masson pine.The concentrated Embelia 1∶1 juice（fresh leaf weight：water weight）were significantly higher than that of 1∶2 juice in mobilizing soil heavy metals.The mobilization ability for Pb and Cd of the studied botanic chelators was significantly lower than EDTA,but they exhibited a strong mobility for soil Zn.The mobilized amount of Zn by Embelia 1∶1 and Slash pine1∶2 from acid Qingyuan soil were significantly higher than that by 5.00 mmol·L-1EDTA and the other natural botanic chelators were higher than 2.50 mmol·L-1 EDTA.For neutral Lechang soil,the mobilization rate of heavy metals were generally lower than that for the acid soil.Based on these results,Embelia leaf extract can be a promising natural botanic chelator.