基于稻虾共作系统水稻收割后水体水质及沉积物重金属风险评估

Assessment of water quality and heavy metal contamination of sediments after rice harvesting in a rice-shrimp co-cropping system

为探究稻虾共作系统中水稻收割后水体营养盐和沉积物重金属的分布特征,评估其水生态风险,通过监测4块稻虾田的种养后期水体中的理化指标,评价了稻虾田中分子氨和沉积物重金属的毒性,系统分析了种养体系中水体营养盐、重金属的生态毒性风险.结果表明,稻虾种养模式的水稻收割后,水体pH值高,达到9.25;总氮、氨氮和COD浓度分别达到14.15、11.49和92.01 mg/L.常年的稻虾共作系统中,沉积物中的重金属wAs(16.21 mg·kg^(-1))和wCd(0.20 mg·kg^(-1))水平较高,分别超背景值2.35倍和1.72倍,其他重金属含量较低.综合潜在生态风险指数和潜在生物毒性评价结果均表明,稻虾共作系统中沉积物重金属的生态风险低,这与克氏原螯虾(Procambarus clarkii)养殖需要矿物质元素有关.综上所述,稻虾共作系统具有潜在修复土壤重金属污染的能力.

We explored nutrient distribution in water and heavy metal contamination in sediments after rice harvest in a rice-shrimp co-cropping system.Additionally,we assessed aquatic ecological risks by evaluating molecular ammonia toxicity and heavy metal levels in rice-shrimp fields and systematically analyzed the ecotoxicity of nutrients and heavy metals in water in the co-cropping system by monitoring physicochemical indices in water during the late cultivation period in four rice and shrimp co-cultivation fields.After rice harvesting,the water showed high pH(9.25)and the total nitrogen concentration,ammonia nitrogen,and COD reached 14.15,11.49,and 92.01 mg/L,respectively.In perennial rice-shrimp co-cropping systems,elevated levels of wAs(16.21 mg·kg^(-1))and wCd(0.20 mg·kg^(-1))were found in sediments,exceeding natural baseline levels by 2.35 and 1.72 fold,respectively.Levels of other heavy metals were lower,in addition,the concentration of heavy metal was lower than the baseline levels of the sediments.The potential ecological risk index and our potential biological toxicity evaluation revealed low ecological risks posed by heavy metals in rice-shrimp co-cropping system sediments,which can be attributed to mineral elements required for Procambarus clarkii culture.In conclusion,co-cultivating rice with shrimp can potentially mitigate soil heavy metal pollution.