The economical,environmentalfriendlyandefficient materialstoremediatethepollutionwithmultiple
heavymetalsandmetalloidsarescarce.Silkwormexcrement(SE)andmushroomdregs(MD)aretwo
types ofagriculturalwastes,andtheyarewidelyusedtoimprovethesoilfertilityinmanyregionsof
China. ApotexperimentwithsixteentreatmentswassetuptoassessthepossibilityofusingSEandMD
to stabilizeheavymetalsandmetalloidsandreducetheiruptakeinpakchoicultivatedinslightlycon-
taminated soilswitharsenic(As),cadmium(Cd),lead(Pb)andzinc(Zn).Theresultsshowedthatthe
single additionofSEobviouslystimulatedthegrowthofpakchoi,reducedthecontentsofalltestedheavy
metals andmetalloidsintheediblepartofpakchoiandavailabilityofZnandCdinsoil.ThesingleMD
treatment showedaninferiorabilitytoenhancethegrowthandreducethecontentsofheavymetalsand
metalloids intheediblepartofpakchoi.ThecombinedutilizationofSEandMDappearednottoshow
better effectsthantheirindividualtreatmentwhenusingthemtoremediatethiscontaminatedsoil.
Some potentialmechanismsonthestimulationonpakchoigrowthanddecreasingtheaccumulationof
heavymetalsandmetalloidsinpakchoisubjectedtoSEweresuggested,including:(1)enhancingsoilpH
to impacttheavailabilityofheavymetalsandmetalloids;(2)improvethefertilityofsoil;(3)sulfhydryl
groups oforganicmaterialsinSEplayaroleinconjugatingheavymetalsandmetalloidstoaffecttheir
availabilityinsoil;and(4)stimulatingthegrowthofpakchoisoastoshowa “dilution effect” of heavy
metals andmetalloids.