基于多元场景下的滇池环保清淤底泥重金属污染特征风险评价OA

In the in-situ scenario of river and lake sediment,the potential receptor is the aquatic ecological environment,while in the ex-situ comprehensive utilization scenario,the potential receptors for construction land and agricultural land are human and crops/fruits,respectively.Currently,risk assessment of river and lake sediment lacks a multi-scenario evaluation covering both in-situ and ex-situ utilization scenarios.This study proposed and constructed a risk assessment model under the multi-scenario framework of"in-situ and ex-situ":the in-situ scenario using dual background values(national/Yunnan soil background values)potential ecological risk assessment model,while the ex-situ scenario established pollution risk assessment models based on agricultural land(paddy fields/orchards/others)and construction land(the first category land).Taking the dredging project of Dianchi Lake in Kunming as an example,a grid-based sampling method was used to collect and test six typical heavy metals in the polluted layer and transition layer of the dredging area.By combining background values and relevant standard values,the risk levels were quantified.The results showed that:1)Within the dredging area,under different soil background values,97.83％or more of the sediment samples had medium or higher ecological risks,with Hg and Cd being the main contributing factors(Hg posing a higher risk),indicating a potential ecological risk that cannot be ignored;2)Under the scenarios of the two types of agricultural lands(paddy field/orchard,others),the proportion of sediment sampling points with unacceptable risks was 95.65％for both,with the comprehensive pollution risk intensity of heavy metals in descending order as Cd>Cu>Zn>As>Cr.In the scenario of second-category construction land,the pollution risks of the six heavy metals were all within acceptable limits.Under the scenario of first-category construction land,As was the target pollutant for sediment comprehensive treatment,with 93.48％of sampling points being within the unacceptable range;3)Spatially,there were obvious differences.Horizontally,the risk at the estuary of the lake was significantly higher than that at the inlet of Cixiang River.Vertically,the risk in the polluted layer was significantly higher than that in the transition layer.In the Dianchi dredging area,the values of Hg and Cd in the polluted layer sediment were 11.58％and 24.19％higher than those in the transition layer,respectively,and the potential ecological hazard index of pollutants in the polluted layer sediment was 43.27％higher than that in the transition layer.Under the agricultural land scenario,the pollution coefficient of Cd,Zn,and Cu in the polluted layer increased by 123.02％,6.3％,and 4.1％,respectively,compared to the transition layer.Under the first-category construction land scenario,the pollution risk of As increased by 41.02％;4)There were significant differences in the results obtained using different assessment methods(e.g.,background value selection,differences in receptor protection targets).Some heavy metals that did not exhibit potential ecological pollution risks might still pose pollution risks under comprehensive utilization scenarios and should not be ignored during the treatment process.