| Lots of municipal sludge becomes more and more with the progress of urbanization.It was the hot topics about sewage sludge reclamation.The land utilization of sewage sludge had most of advantages,such as the higher organic matter,the more nutrient element.However,it was insufficient for sewage sludge reclamation to bring in a lot of toxic and harmful substance,for example bacteria and heavy metal.For this study,the tested soil was sewage sludge amended soil that applied low concentration municipal sewage sludge into loess,radish as the selected plants,finally through pot experiment and laboratory analysis,this study explored systematically the migration characteristics and bioavailability of cadmium,copper and zinc in municipal sludge amended soil and radish.The main results were as follows:1.The basic physical and chemical properties of loess amended with compost of 0.5% content changed.Amended with compost of 0.5% content,the pH of soils reduced to 7.82 from 8.05.The EC of soils increased 781 ?s/cm to 848 ?s/cm.The soil organic matter increased from 4.34 g/kg to 6.17 g/kg.The soil carbonate content showed a trend of decline as municipal sludge applied.Although municipal sludge could take heavy metal into soils,found in the study,application of municipal sludge were 0.5%,the content of heavy metals in soil improvement basically was lower than the national standards.2.Soil cadmium form changed when added 0.5% content municipal sewage sludge into loess.After added municipal sewage sludge,the content of the acid extractable was depressed;other forms were increased.With added 0.5% content municipal sewage sludge,the percentage of the acid extractable reduced 0.02%-14.74%,other forms were integrally increasing tendency,the variation range of the reducible was 1.01%-9.81%,the variation range of the oxidizable was 1.05%-4.08%,the variation range of the residual was 0.25%-3.46%,.Exogenous Cd and sewage sludge had given rise to Cd distribution;the tendency becomes more stable with time.3.It was effect for soil enzyme activity to add 0.5% content municipal sewage sludge into loess.Soil enzyme activity was improved after added municipal sewage sludge.All kinds of soil enzyme activity(urease,alkaline phosphatase,sucrase,catalase)were rising 0.41 mg/g?0.56 mg/g?0.10 mg/g ? 0.10 ml/g respectively.It was different for soil enzyme to add exogenous Cd,soil enzyme activity increased,as well as decreased.The exchangeable and the oxidizable were the main factor which had an effect in the soil enzyme activity.4.It was effect for other heavy metal forms(Cu and Zn)to add 0.5% content municipal sewage sludge into loess.The exchangeable form was decreased tendency,other forms were increased tendency.For Cu,the variation range of the exchangeable was 0.26-0.94 mg/kg,the variation range of the reducible was 0.21-0.98 mg/kg,and the variation range of the oxidizable was 0.11-2.26 mg/kg.For Zn,the variation range of the exchangeable was 0.02-0.42 mg/kg,the variation range of the reducible was 0.68-1.81 mg/kg,and the variation range of the oxidizable was 0.54-3.68 mg/kg.The activity of Cu and Zn were decreased when added municipal sludge.5.The radish grew better after added municipal sewage sludge.The radish dry weight including overground part and belowground part were increased 0.12-0.73 g and 0.07-0.45 g.The tendency of radish growth was firstly increased,and then decreased.The dry weight was the best value when the content of Cd was 2.4 mg/kg.6.the content of Cd was decreased which the radish absorbed when added municipal sewage sludge.After added 0.5% municipal sewage sludge,the content of overground part and belowground part were decreased0.01-0.56 mg/kg and 0.04-0.17 mg/kg respectively,the BCF had the decreased tendency when added 0.5% municipal sewage sludge.It that added municipal sewage sludge was declined radish to heavy metal enrichment.High content heavy metal could cause the inhibition of radish absorption.7.the content of Cd present a very significant positive correlation between radish and soil,namely the broad radish cadmium content in organs had a direct relationship between the degree of soil pollution.Municipal sludge not only make effect on the correlation between cadmium in broad radish and soil cadmium forms,also have an impact on the major contribution form in the form of soil cadmium.In general,municipal sludge can affect bioavailability of soil cadmium.8.It that added municipal sludge was an effect Radish absorbed other heavy metal(Cu,Zn).The tendency firstly increased,and then decreased when the content of Cd increased.However,it facilitated the absorption of other heavy metal(Cu,Zn)after added 0.5% municipal sludge. |
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