沈阳市土壤铅的空间分布及风险评价研究

经测定,沈阳市土壤铅含量范围为22～2910.600mg/kg,平均值是270.297mg/kg。铅污染比较严重且空间变化大,局地污染非常严重。利用地统计方法研究了沈阳市土壤铅的空间结构和分布特征。结果显示,沈阳市土壤铅具有较好的空间结构性,利用半方差函数的结果进行克里格插值得到土壤铅含量的分布图。沈阳市有6个土壤铅污染中心,其中以铁西区和太原街的污染比较突出。工业排放、汽车尾气和污灌是沈阳市铅污染的三大污染源。风险评价结果表明,铁西区属于极高风险区,儿童铅中毒的潜在风险非常大。

Spatial distribution of Pb in soils and its risk assessment in Shenyang city

The range of Pb in soils in Shenyang city was 22-2910.600mg/kg, with the average value of 270.297mg/kg, which was 7.72 times of reference value (35.001mg/kg). It was evident that Pb accumulated in soils. In addition difference distribution of Pb was obvious, and Pb pollution was serious in some areas in Shenyang city. Statistical analysis of lead contents in soils showed only the distribution characteristics in whole, not picturing the spatial correlation of lead in contaminated soils, and semivariogram is a helpful tool to determine the spatial structure. The analysis result indicated that the semivariogram of lead contents increased rapidly with increasing of interval, but at the interval of 1165m, there was a quantitative change, after that, the semivariogram of lead contents are similar to each other, and the lead contents are independent of spatial structure. The nugget (464056) was likely to be caused by experiment error, furthermore it indicated that the lead contents in soils were affected by other factors, especially anthropic disturbance. The spatial change of soil Pb was studied using the Kriging interpolation method. There were six high contaminated areas, including Tiexi district, Taiyuan Street, crossroad of Chang'an road and Xiaoheyan Road, Aeroplane-Plant, farmland in economic developing area and southwest suburban area. There are many factories in Tiexi district, which led the "pollution league" in Shenyang city, and the degree of pollution was extremely high there. There are strong indications that the Pb pollution was initiated in 1936 with smelting operation in Shenyang Smeltery, which was located in Tiexi District. Taiyuan Street and Crossroad of Chang'an road and Xiaoheyan Road were "blacklisted" because high Pb concentration in soils. It should be noted that Taiyuan Street and Crossroad of Chang'an road and Xianheyan Road had a lower Pb-contaminatin than Tiexi District, where the dominant pollution source is automobile exhaust emission. Southwest suburban area should be regard as a clean area because this area doesnt directly receive any industrial or automobile waste gas. But due to activities inherent to metallurgy, and particular Pb were carried by the wind to the areas next to Tiexi district, so Pb pollution can not be neglected in the southwest suburban area which is situated leeward of the high-intensity discharge. The farmland in the economic developing area was also contaminated by the particulate Pb, which was caused by irrigation using sewage, whereas the Pb input in soils of north suburb was mainly from Aeroplane Plant. In general, smelting and gasoline are the main sources of Pb pollution, which is serious in industrial area and business area in Shenyang city. According to the results of risk assessment, the high potential risk areas included Tiexi district based Smeltery as center.