乌鲁木齐市表层土壤Pb的化学形态分布及潜在生态危害评价

Chemical Speciation of Pb and Its Potential Ecological Risk in Urban Superficial Soils of Urumqi City

研究了乌鲁木齐市不同功能区表层土壤Pb的含量及其化学形态分布,并采用Hakanson的潜在生态危害指数法对土壤中Pb的潜在生态危害进行评价.结果表明：土壤中w（Pb）的平均值为50.9 mg/kg,变幅为27.9-113.7 mg/kg.w（Pb）在各功能区表现为商业区（65.5 mg/kg）〉交通密集区（61.0 mg/kg）〉工业区（55.6 mg/kg）〉居民区（45.9 mg/kg）〉文教区（41.2 mg/kg）〉绿化风景区（35.9 mg/kg）;不同功能区表层土壤Pb化学形态存在差异,Pb元素的化学形态总的分布趋势是残渣态〉铁锰氧化物结合态〉有机结合态〉碳酸盐结合态〉可交换态.其中,工业区和交通密集区是以铁锰氧化物结合态和残渣态为主,分别占52.33%,28.59%和42.96%,38.69%;居民区、商业区、文教区和绿化风景区主要以残渣态和铁锰氧化物结合态为主.各功能区土壤中Pb的金属活性表现为工业区〉交通密集区〉文教区〉商业区〉绿化风景区〉居民区.乌鲁木齐市土壤的Pb污染处于中等到强污染之间,达到轻微生态危害水平.

The content and chemical speciation distribution of Pb in superficial soils in different functional areas of Urumqi was studied, and Hakanson＇ s Potential Ecological Risk Index was used to assess the Potential Ecological Risk of Pb in soil. The results showed that the average content of Pb in urban soil was 50.9 mg/kg, ranging from 27.9 to 113.7 mg/kg, where the order of average content of Pb was business area （65.5 mg/kg） 〉 traffic area （61.0 mg/kg） 〉 industrial area （55.6 mg/kg） 〉 living area （45.9 mg/kg） 〉 culture and education area （41.2 mg/kg） 〉 scenic spots （35.9 mg/kg）. The chemical speciation of Pb in superficial soils of different functional areas was different. The general distribution trend of the chemical speciation of Pb was residual fraction 〉 Fe - Mn oxides 〉 organic phase 〉 carbonates 〉 exchangeable form. Among them, Pb existed mainly in Fe - Mn oxides and residual fraction in industrial area and traffic area, accounting for 52.33%, 28.59% and 42.96%, 38.69%, respectively; residual fraction and Fe - Mn oxides were the main speciation of living area, business area, culture and education area and scenic spots. In the soils of different functional areas, the metal activities were industrial area 〉 traffic area 〉 culture and education area 〉 business area 〉 scenic spots 〉 living area. The content of Pb in Urumqi urban soil had already reached the level of slightly ecological harm.