西北黄土高原干旱半干旱条件下城市污染特点——以西北某城市为例

Characteristics of urban pollution under arid and semi-arid condition on the Loess Plateau in northwestern China:examples form a city in northwestern China

该市地处西北黄土高原西部,是黄河河谷盆地型城市,其城市污染代表了黄土高原干旱、半干旱条件下污染特征。城市污染因子主要是大气降尘(烟尘)、沙尘、二次扬尘(地尘)以及固体垃圾物弥撒和污水灌溉。污染元素主要是Hg、Sb、Pb、Be、As、Cd、F等。以重金属为主的元素污染规律是(1)污染程度与人口密度、人群流通量密切相关;(2)人口集中商业发达的城区污染大于人口密度较小、工业较集中的城区;(3)工业污染中,重工业大于轻工业;(4)农业污染中,污水灌溉区大于非污水灌溉区;(5)污染物中重金属含量随颗粒细化而富集,其危害程度也愈来愈大。在评序污染程度时,除采取污染指数外,引入了勘查地球化学中的面金属量、衬度指数,使评价工作更具区域化、综合效应化。

Lanzhou is located in the western part of the Loess Plateau in northwestern China. The factors of urban pollution are mainly amog (smoke and dust in air), fine sand flying up in air and secondary dust (ground dust), as well as dispersion of solid waste and sewage irrigation. The main polluting elements are Hg, Sb, Pb, Be, As, Cd and F. The characteristics of pollution of elements dominated by heavy metals are as follows:(1) the pollution degree is closely related to the population density and flux of people; (2) the pollution degree in the city district where the population is concentrated and the commerce is well developed is higher than that where the population is less dense and industries are more concentrated; (3) for industrial pollution the pollution degree of the heavy industry is higher than that of the light industry; (4) for agricultural pollution the pollution degree in sewage irrigation areas is higher than that in non-sewage irrigation areas; and (5) heavy metals in pollutants increase with fining granulation of grains and then their harming degree also increases. In the evaluation of the pollution degree, in addition to the pollution index, the areal metal quantity and background index of exploration geochemistry are also introduced, which makes the evaluation have more regionalized and comprehensive effects.