| Vermicomposting is an eco-friendly organic solid waste treatment technology,which can effectively realize the harmless and resource utilization of manure.It is an effective method for large-scale and low-cost treatment of organic waste.At present,previous studies on the use of vermicomposting to treatment heavy metals have been done,but most of them focus on sludge and soil.There are few studies on the relationship between the speciations of heavy metals and the activities of enzymes,changes of enzymes activities,heavy metals speciations and microbial indicators during the vermicomposting.In this research,pig manure was dicided unsterilized pig manure treatment group and the sterilized pig manure treatment group,8 treatments were set up according to the number of earthworms added,respectively(CK、T1、T2、T3 和 CM、M1、M2、M3).Through the analysis of the experimental data to study the effect of the heavy metal speciations,key enzyme activity and microbial indicators,the relationship between the speciations of heavy metals and key enzyme activities during vermicomposting.In addition,the changes of physical and chemical properties of sterilized pig manure were compared with those of natural decomposed pig manure without sterilization under vermicomposting to explore the effect of environmental factors on the changes of various indicators.The results of this study are expected to provide scientific basis for the utilization of solid wastes from aquaculture industry as agricultural resources.The results are as follows:(1)End of vermicomposting,the content of Cu and Zn were decreased,especially in the unsterilized treatment group.T3 was the best,and the contents of Cu and Zn decreased by 26.41% and 19.58%,respectively.The speciations of Cu and Zn tended to be stable in residual form,vermicomposting can reduce the bioavailability of heavy metal elements.(2)Vermicomposting can significantly increase the activities of six enzymes,the urease,dehydrogenase,invertase and protease activities increased and then decreased.The change trend of alkaline phosphatase was not obvious.In addition,it was found that the activities of variou s enzymes in the sterilized treatment group were lower than those in the unsterilized treatment group,indicating that the enzymatic activities of pig manure decreased after sterilization treatment.(3)In Vermicomposting,the relationship between heavy metal speciations and enzyme activity are as follows: (1)From the point of view,the sensitivity of enzymes to heavy metal speciations are as follow,invertase and protease are more sensitive to Cu,invertase,urease and catalase are more sensitive to Zn,while in the treatment group of sterilized pig manure,catalase,invertase and urease are more sensitive to Cu,catalase is sensitive to Zn.(2)The effects of Cu and Zn in vermicomposting on enzyme activity can be concluded as follows,among the unsterilized pig manure treatment groups,the enzyme activity which was inhibited by the reducible specifications of Cu and Zn,followed by the oxidizable and residual specifications,and then by the acid-soluble specifications.Additionally,the water-soluble specifications of heavy metals had little effect on enzyme activity.Among the sterilized pig manure treatment groups,the enzyme activity which was inhibited by the acid-soluble specifications of Cu and Zn,followed by the reducible and residual specifications.Additionally,the oxidizable and water-soluble specifications of heavy metals had little effect on enzyme activity.(4)The Shannon evenness and Mc Intosh index of microbial community during the vermicomposting changed significantly,while the Shannon-Weave and Simpson diversity index changed slightly.Sterilization treatment can lead to the decrease of microbial functional diversity index.After vermicomposting,the utilization of various carbon sources in the reactor is more balanced,the main type of carbon source was carbohydrate,carboxylic and polymers. |
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