Adsorption Of Streptomycin And Cadmium On Biochars And The Effect Of Biochars On Respiration And Enzyme Activities In The Contaminated Soil

In recent years,antibiotics and heavy metals pollution receive more and more attention.Biochars have been increasingly studied in the field of soil restoration due to special surface structure and strongly adsorption performance.In this paper,Biochars were producted from the waste corn stalk and cattle manure of pastoral areas of Inner Mongolia.The adsorption behavior of streptomycin(STR)and heavy metals on biochars was studied from the standpoint of combined pollution.The effects of biochar on enzyme activities and respiration intensity of soil were investigated by adding biochars to the soil contaminated by heavy metal.The observed results are important for applications of biochars in the restoration of soil contaminated by heavy metal and STR.(1)Biochars derived from corn stalk and cattle manure were prepared by natural burning and oxygen-limited pyrolysis.The obtained biochars were characterized.Biochars from natural burning have more surface functional groups and higher mineral content,and biochars from high temperature pyrolysis have strong aromaticity,larger specific surface area and pore structure.(2)The adsorption properties of biochars to STR and Cd were different.For STR,the biochars from high temperature pyrolysis or cattle manure had stronger adsorption,while the biochars from natural burning or corn stalk showed stronger adsorption for Cd.The environmental pH affects the adsorption of STR and Cd on biochars.Ion exchange and mineral precipitation were the important adsorption mechanism for Cd,and hole filling adsorption and π-π interaction could play important role in the adsorption of STR.(3)For STR-Cd combined pollution,the presence of Cd promoted the adsorption of STR on biochars,which may be due to ternary complexes of biochars,Cd and STR:biochar-O-Cd-STR.In the process of STR adsorption,Cd plays a key role as bridging so as to promote the adsorption of STR,but the amount of sorbed Cd on biochars decreased due to space hindrance effect.(4)During the incubation time,STR exhibited stimulated effect on the activities of invertase and inhibit the soil respiration,the activities of urease and catalase when adding STR to soil.The STR-Cu joint toxicity effect on enzyme activities and respiration intensity of soil were evaluated with the presence of heavy metals.The joint toxicity presented a correlation with their concentration.(5)The enzyme activities and respiration intensity of soil were measured during a 100-day laboratory incubation of a Cd contaminated soil amended with biochar.The positive effects of biochar amendments were presented,which were closely related to biochars concentration level,soil type and soil pH.The organic matter of soil promoted the stimulation effects of biochars on enzyme activities of soil.