三峡库区不同土地利用土壤重金属分布特征与污染评价

摘要

为揭示不同土地利用方式土壤重金属的含量、分布及污染特征,选取三峡库区典型小流域不同土地利用方式:柑橘果园(C0)、林地(FL)、旱坡麦地(WD)、旱坡菜地(VD)、温室大棚蔬菜地(VG)、水稻田(PL)作为研究对象,研究了不同土地利用方式土壤重金属的含量变化、分布规律,并进行污染评价.研究结果表明,6种土地利用类型土壤重金属元素Pb含量由大到小表现为:VG、CO、PL、VD、FL、WD,土壤重金属元素Cr含量由大到小表现为:CO、VG、PL、VD、FL、WD,土壤重金属元素Cu含量由大到小表现为:VG、VD、CO、PL、FL、WD,土壤重金属元素Zn含量由大到小表现为:CO、VG、PL、WD、VD、FL,土壤重金属元素Cd含量由大到小表现为:VG、CO、WD、PL、VD、FL.土壤重金属Pb含量与Cr、Cu、Zn、Cd含量均存在极显著正相关关系(p＜0.01),Cr含量与Cu和Cd含量呈极显著正相关(p＜0.01),与Zn含量呈显著正相关(P＜0.05).6种土地利用类型土壤重金属Pb、Cr、Cu、Zn、Cd的单项污染指数变化分别为0.06、0.14、0.15、0.14和1.70,综合污染指数为0.91,污染等级为警戒线,污染水平属于Ⅱ级,尚清洁,6种土地利用类型土壤重金属的综合污染指数由大到小表现为:VG、CO、VD、PL、WD、FL.潜在生态风险评价表明,6种土地利用类型土壤的重金属Pb、Cr、Cu和Zn均属于轻度生态危害.土壤重金属元素Cd在林地、旱坡麦地和水稻田土壤中属于中度生态危害,而在柑橘果园、旱坡菜地和温室大棚蔬菜地土壤中属于较强生态危害.5种土壤重金属潜在生态危害系数从大到小分别为:Cd、Pb、Cu、Cr、Zn.%Aimed to reveal the distribution characteristics of different land use types,six land use types were chosen,including citrus orchard (CO),forest land (FL),wheat dry land (WD),vegetable dry land (VD),vegetable greenhouse land (VG) and paddy land (PL) as the research objectives in the typical watershed in Three Gorges Reservoir region.The contents and distribution characteristics and pollution evaluation were all analyzed,the results showed that the order of Pb contents changed from high to low were VG,CO,PL,VD,FL and WD,the Cr contents changed from high to low were CO,VG,PL,VD,FL and WD,the Cu contents changed from high to low were VG,VD,CO,PL,FL and WD,the Zn contents changed from high to low were CO,VG,PL,WD,VD and FL and the Cd contents changed from high to low were VG,CO,WD,PL,VD and FL.Meanwhile,there existed obviously positive correlation between Pb content and Cr,Cu,Zn and Cd contents(p ＜0.01),there also existed obviously positive correlation between Cr content and Cu,Cd contents (p ＜ 0.01) and there existed positive correlation between Cr content and Zn content (p ＜ 0.05).The estimation of single pollution index of these five soil heavy metals,i.e.,Pb,Cr,Cu,Zn,Cd contents of the six land use types changed from high to low were 0.06,0.14,U.15,U.14 and 1.70.And the comprehenve polluuo n index was O.91,the pollution degree belonged to guard line and the pollution level was the Ⅱ level—relative clean.Meanwhile,the order of the six land use type of soil heavy metals changed from high to low were VG,CO,VD,PL,WD and FL.The results of the potential ecological risk index indicated that the soil heavy metals Pb,Cr,Cu and Zn belonged to light ecological risk.However,the soil heavy metal of Cd belonged to middle ecological risk in the forest land,dry land of wheat and paddy land,Cd belonged to a bit strong ecological risk in the citrus orchard,vegetable dry land and vegetable greenhouse land.And the potential ecological risk index of these five soil heavy metals changed from high to low were Cd,Pb,Cu,Cr and Zn.