通过对两个地点多组样品的系统分析，揭示了北京良乡两采样点的APM特征、元素富集程度以及两地污染源类型。
Through the system analysis, it announced APM's character, elements enrichment degree and style of pollutant source of the two sampling sites in Liangxiang of Beijng.
总结和评价了我国大气铅浓度水平、大气铅污染源的主要类型和排放特征，对今后我国大气铅污染发展趋势进行了说明。
The concentration of lead in atmosphere and the main types and emission characteristics of pollution sources in China are summarized and estimated.
水体环境污染源按其发生类型分为点源、非点源。
Sources of water pollution can be classified broadly into two categories: point sources and nonpoint sources.
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