Evaluation Of Heavy Metal Pollution In Agricultural Soil Based On Improved AHP-TOPSIS Comprehensive Analysis Method

J city is regared as a significantgrain production base of Hubei Province,which is rich in agriculture resources.And its agriculturalland accounts for a large proportion of land resources.However,the monitoring,treatment andremediation of agricultural soil did not have an early beginning.Also,its foundation is relativelyweak.Therefore,in this thesis,agricultural soil of J city was taken as study object.And the contentcharacteristics of eight evaluation factors(Hg,As,Ni,Cu,Zn,Cd,Pb,Cr)were analyzed.Meanwhlie,thepollution status and ecological risk of heavy metals in agricultural soil of J city were estimated bysingle factor pollution index method,Nemerow comprehensive pollution index method,improved AHP-TOPSIS comprehensive pollution analysis method and potential ecological riskmethod.According to the research conducted,the conclusions are as follows:(1)The results showed that Hg,As,Ni,Cu,Zn,Cd and Pb were enriched to some extent in 0-20 cm topsoil.Amongthem,Hg is the most abundant,which is more than 90 of the whole.From the coefficient of variation,Hg,Pb and Cr are relatively larger than the others,and their distribution is uneven,which may beaffected by external factors.As,Ni,Cu,Zn and Cd are relatively small,with relatively uniformdistribution in elements.(2)By improved AHP-TOPSIS comprehensive pollution analysis methodand reasonable weight calculation,itmakes the outstanding influence of the comparison of thepollution situation between soil samples more objectively reflected.The results showed that thecomprehensive pollution of 55.36 samples in J city was better than that in Hubei backgrand.The mostpolluted areas are mainly concentrated in the south of J city,and a small number are distributed inthe north and east of J city.(3)The results of single index showed that the average index of heavymetals in agricultural land of J city did not exceed the relevant limits in the classification standard.Butthere were partial enrichment of Cd and Hg,in which the enrichment of Cd was light,and theenrichment of Hg was slightly serious.The results of Nemerow index showed that the overallcomprehensive pollution level of agricultural land in J city belonged to ”clean” state.The area ispartially slightly polluted,in which the ”clean”samples,” warning limit ” samples and ”slightlypolluted” samples accounted for 76.8,17.8 and 5.4 respectively.According to the evaluation ofpotential ecological hazard index,the average of single factor ecological hazard index in agriculturalsoil of J city was less than 40 except for Hg,belonging to mild ecological hazard.Meanwhile,theaverage value of Hg was the largest,which was in a serious ecological hazard state.From thecomposite ecological risk index,the ecological risk of J city was in the moderate level.The proportionsof mild,moderate and severe ecological hazards were57.14,28.57 and 14.29 respectively.