再生水补水条件下宁夏星海湖重金属赋存特征及风险评估OA

To reveal the heavy metal pollution characteristics and potential risks after the reclaimed water reuse in landscape lakes,the central basin of Xinghai Lake in Shizuishan City of Ningxia province was selected as the research objective.Based on the historical and supplementary monitoring data,the heavy metal distribution characteristics of water and sediment in the central basin of Xinghai Lake were compared under the conditions of Yellow River water supplement and reclaimed water supplement.The risk quotient(RQ),geo-accumulation index(Igeo),and the U.S.Environmental Protection Agency health risk assessment methods were used to evaluate the heavy metals risk status in the central area of Xinghai Lake before and after the reclaimed water supplement.The results were shown as follows.The reclaimed water replenishment during 2022–2024 did not cause pollution in the central zone of Xinghai Lake,and the annual average concentrations of As,Pb,Cd,Zn,and Cu increased in some years and decreased in others compared with those of Yellow River water replenishment in 2021,but all could meet the Class I limits of China'Surface Water Environmental Quality Standards(GB 3 838-2002).D uring the Yellow River water replenishment period,the risk quotient(RQ)ranking for heavy metals was determined as Cd>Pb>Cu≈A>Zn.In contrast,the RQ order shifted to Pb>As>Zn>Cd>Cu after the reclaimed water replenishment.Although the risk levels of these five heavy metals increased slightly in certain seasons,they consistently remained within the range of no risk,low risk,or moderate risk.Both the non-carcinogenic health risks(Hazard Index,HI)and carcinogenic risks(Rc)remained within the safe level in the water body before and after the reclaimed water supplement.HI was consistently dominated by arsenic(As>Cd>Pb>Cu>Zn),and the Rc attributed to arsenic slightly increased after the reclaimed water supplement in 2024.The sediment heavy metals exhibited some degree of enrichment after the reclaimed water supplement in 2024,however their concentrations were consistently lower than the risk screening values of Soil Environmental Quality Risk Control Standard for Soil Contamination of Agricultural Land(GB 15 618–2018)under alkaline conditions(pH>7.5).The order of Igeo indices were as follow:Se>Zn>Cu>Pb>As>Cd>Hg,and all heavy metals exhibited no contamination except for Se,which was in light pollution level.All above-mentioned heavy metals posed no environmental risk.Overall,although the reclaimed water supplementation resulted in slight increases of heavy metals concentrations in the waterbody of the central zone of Xinghai Lake in certain years and seasons,all heavy metals consistently met the Class I criteria of the Surface Water Environmental Quality Standards(GB 3 838-2002).Heavy metals in the water body presented no,low,or medium risk level,and their HI and Rc values were staying within safe limitation.The heavy metals concentrations of sediment remained below the risk screening values for agricultural soils(GB 15 618–2018,pH>7.5),while sediment contamination ranged from unpolluted to slightly polluted level.