青岛市农用地土壤重金属背景值研究与土壤环境容量的计算

Research on background concentrations of agricultural land soil heavy metals and heavy metal environmental capacity in Qingdao City

以青岛市农用地表层土壤为研究对象,利用内梅罗综合污染指数和《土壤环境质量标准》(GB 15618—1995)确定As、Cd、Cr、Cu、Hg、Ni、Pb、Zn的背景值分别为5.770、0.088、35.900、15.700、0.027、20.900、21.400、46.600 mg/kg。以此背景值为基础,结合GB 15618—2018风险筛选值,对农用地表层土壤重金属环境容量进行计算,8种重金属的现存环境容量均值分别为74.37、0.42、227.12、69.16、3.95、99.14、151.33、327.65 kg/hm^(2)。8种重金属的环境容量均处于中容量水平,容量较大,但受轻微污染。土壤环境综合容量以中容量区为主,面积比例达到78.75%,全市农用地无超载区和警戒区,低容量面积比例仅为2.02%,主要分布在即墨区丰城镇、店集镇和龙泉镇以及莱西市南墅镇。内梅罗污染指数结果显示,土壤环境质量状况较好,以清洁状态为主,面积比例达到96.61%,污染空间分布情况与低环境容量区域基本一致。

Based on Nemerow comprehensive pollution index and Soil Environmental Quality(GB 15618—1995),8 kinds of background concentrations(mass ratio)of heavy metals(As、Cd、Cr、Cu、Hg、Ni、Pb and Zn)in the agricultural topsoil of Qingdao City were determined as 5.770,0.088,35.900,15.700,0.027,20.900,21.400 and 46.600 mg/kg,respectively.Using these background concentrations,combined with the risk screening values of GB 15618—2018,the environmental capacities of heavy metals in the agricultural surface soil were calculated and evaluated.The average existing environmental capacities of the eight heavy metals were 74.37,0.42,227.12,69.16,3.95,99.14,151.33 and 327.65 kg/hm^(2),respectively.The environmental capacities of 8 heavy metals were all at the middle capacity level,but it showed that the soil of some area was slightly polluted.The comprehensive capacity of soil environment was mainly at medium capacity level,and the proportion of medium capacity area was 78.75%.There was no overload area and warning area for agricultural land in the whole city,and the proportion of low capacity area was only 2.02%which was mainly distributed in Fengcheng Town,Dianji Town,Longquan Town and Nanshu Town.The results of Nemerow pollution index showed that the soil environmental quality was good,mainly at clean level,and the area proportion reached 96.61%.The spatial distribution of pollution was basically consistent with that of low environmental capacity area.