Study On Source Apportionment And Pollution Assessment Of Heavy Metals In Contaminated Site Soils

With the rapid development of industrialization and urbanization,there have been a large number of abandoned contaminated sites in various regions.And the problem of soil pollution has become increasingly serious.The polluting enterprises relocate the abandoned sites in a complex situation.The problem of heavy metal pollution is particularly acute and seriously endangers the ecological safety and human health of the soil environment.It is imperative to carry out the evaluation of heavy metal pollution in soils.Based on the existing problems in the evaluation of heavy metal pollution in soils,the paper constructed a system for apportioning and assessing the risk of heavy metal pollution in soils from the aspects of source apportionment,ecological risk assessment and prediction,and human health risk assessment.In the analysis of the pollution sources,pollution characteristics of heavy metals in soils were analyzed by the analysis of the total quantity.Correlation analysis and positive matrix factorization?PMF?model were used to identify the pollution sources,and the accuracy and uncertainty were analyzed through principal component analysis?PCA?and error estimation.In the ecological risk assessment,the individual ecological risk,comprehensive ecological risk and potential ecological hazards were evaluated using the index of geoaccumulation(I_geo),index of Nemerow and potential ecological hazard index model respectively.The situational accumulation was estimated using the scenario prediction method.In the human health risk assessment,combined with the Monte Carlo method and health risk assessment model,a human health risk assessment method based on uncertainty analysis was established.A typical contaminated site in Dalian was selected as a case area,the assessment of heavy metal pollution in soil was conducted.The results indicated that the mean contents of heavy metals in topsoils exceeded respective soil background values,followed the order:Zn>Pb>V>Cr>Cu>Ni>Co>As>Sb>Cd>Hg.Correlation analysis and PMF identified three main sources of pollution and their contribution rates:industrial activities?49.1%?,soil parent materials?33.8%?,traffic and burning dust?17.0%?.Bootstrap test,Displacement test and PCA verified results valid.I_geo results showed that Cd and Zn were heavily contaminated,Pb was ranked as moderately to heavily contaminated level,Sb and Hg were moderately contaminated,Cu,Co,Ni and Cr were ranked as uncontaminated to moderately contaminated level,V and As were uncontaminated.Nemero pollution index descripted that the comprehensive pollution was serious.Potential ecological risk assessment showed that the degree of ecological risk of Cd was very high,Hg was at high risk,Pb was at moderate risk and others were at low risk.The comprehensive potential ecological risk of heavy metals in soil was very high.The forecast indicated that by 2030,under the optimistic scenario,the heavy metal contents in soils would be significantly reduced,and under the non-mutation scenario,the contents would increase with Hg and Ni exceeding the secondary standard value.The actual situation would be between them.The human health risk assessment results based on Monte Carlo uncertainty analysis showed that the carcinogenic risks?CR?and non-carcinogenic hazard indexes?HI?of Cd,Zn and Sb were far below the maximum acceptable risk level.Under high exposure,HI of Pb was unacceptable.Under moderate exposure,HI of V were unacceptable,and the contribution of inhalation of soil particulate matter was significant;CR and HI of Co to children were both unacceptable,among which harm caused by orally ingesting soil contributed significantly.Under low exposure,CRs of V were unacceptable to all populations;CRs of As were unacceptable to all populations,of which the contribution of oral intake and skin contact routes was significant;CR of Co to adults was unacceptable.The study enriched the theoretical research of source apportionment and pollution assessment of heavy metal in site soils.It provided a basis for scientific decision-making and management for managers to carry out control and remediation.