The Effects Of EDFA And Lime On Soil Enzymatic Activities In Heavy Metal Contaminated Soil

With the development of the industry, agriculture, mining and metallurgy in ourcountry, the status of heavy metal contamination is increasingly severies, it becomesa major environmental problems of the world. At present, treatments of heavy metals whichhave been studied most are chemical remediation methods, bioleaching andphyto-remediation. With rapid and efficient characteristics, chemical methods are widelyused in the repair of heavy metal contaminated soils. But chemicals may have some effectson soil and affect soil environmental quality. Therefore, base on the research ago, adding thechemical remediation agent EDTA and lime which have been studied much to the heavymetal contaminated soil(from Changsha landfill), we investigated the changes of soilenzyme activities in the repairing process. And the aim of this study is to provide a usefulreference of the impact of chemical agents on soil environmental quality.The results showed that: The applying of EDTA could effectively increase the facilitiesof the migration of heavy metals, and released residual state heavy metals in soil. It wasgood for combining with phytoremediation to completely remove heavy metals in the soil.Percentage of acid extractable state increases in the range Cu＞Pb＞Zn, the percentage ofresidual state declined as following: Pb＞Zn＞Cu. Applying of lime had certain effect to theactivation of soil heavy metal Pb. And that increased effective percentage state of Pb in soil,while it showd a certain degree of inactivation in Cu and Zn.Both EDTA and lime activated the activity of catalase. The effect of EDTA was betterthan that of lime. The impact of EDTA to soil urease was small. The activity of ureaseincreased a little during the early7days, whereas it began to come back7days later.Applying of lime inhibited activity of urease in percentage of95.In order to find out the best dosage of EDTA on soil enzyme’s activities, we added0.56g/kg,1.40g/kg,2.23g/kg,2.79g/kg,4.19g/kg EDTA to the soil and investigated thechanges of four soil enzyme’s activities (calatase, urease, protease and invertase).The results showed that: the applying of EDTA could improve activities of calatase,urease and invertase, the increasing range of three enzymes’ activities were calatase>invertase> urease; EDTA can not activate the activity of protease. Both The activityprotease of the compared group and treatment groups increased a lot. And the activity ofcompared group is higher than that of the treatment group.EDTA of different dosages had different effects on soil enzyme activities. EDTA of 2.23g/kg and2.79g/kg showed the best effect on of soil enzyme’s activities. Theincreasing rates of the enzymatic activities followed the order ofD(2.79g/kg)≥C(2.23g/kg)＞E(4.19g/kg)＞B(1.40g/kg)＞A(0.56g/kg). Synthesizingthe influences of different concentrations of EDTA on four kinds of soil enzymes andconsidering reducing the cost, we should choose2.23g/kg EDTA in technical design.