Reducing The Bioavailability Of Heavy Metals In The River Sediment By Composting With The Agricultural Waste: Effects Of Physico-Chemical Parameters

Contemporarily,river pollution has been widely concerned.Sediment pollution abatement plays an important role during river pollution control,especially heavy metal pollution in sediment.It is a focus and difficulty of river pollution control in recent years.Therefore,a method to reduce the bioavailability of heavy metals(Cd,Cr,Cu,Zn,and Pb)in river sediments by co-composting with the agricultural waste was investigated in this study.First of all,sediment was analyzed in terms of physico-chemical characteristics and heavy metal content,and to study the main composition of sediment and pollution status.In order to find out the key factors that can reduce the bioavailability of heavy metals during co-composting.The multivariate analysis(Redundancy analysis,forward selections,variation partitioning)was innovatively used to evaluate the correlation between the ten physical-chemical parameters and the bioavailability of heavy metals.At the same time,humic acid(HA),fulvic acid(FA),humic index(HI),heavy metal fractions were analyzed,to study the change trend of humus composition and heavy metal fractions during co-composting.In addition,the correlation between the components of humus and heavy metal fractions was determined by correlation analysis.Through the study,the main conclusions could be drawn as follows:At the end of co-composting,heavy metals content increased in varying degrees.At the same time,co-composting can significantly reduce the bioavailability of multiple heavy metals by transforming the fractions from exchangeable fraction or reducible fraction to oxidizable fraction or residual fraction.This suggested that co-composting was a feasible method to reduce the bioavailability of heavy metals.The significant parameters statically explained up to 78.4%,83.1%,62.4%,58.7%,and 67.7%for the bioavailability of Cd,Cr,Zn,Pb,and Cu,respectively.And WSC was the most direct and closely related factor of heavy metal passivation because WSC explained the changed of the bioavailability of all heavy metals.Co-composting was more effective and easy to control for the recovery of Cd,because the three significant parameters totally explained 67.6%for the variance,following by Cr.Co-composting showed that the small molecule humus was reduced,the macromolecule structure was increased,and the structure of the humus was more complex.At the same time,Cu,Cr,Cd,and Pb were mainly combined with humic acid.Co-composting promoted the soluble heavy metals,which reduced the efficiency and mobility of heavy metals.The correlation analysis showed that the heavy metal fractions of Cr were significantly correlated with the composition and humification index of humus,and bound heavy metals of Pb were significantly correlated with HA,FA,and HI.The Cd fractions and humus components were no significantly related.