4、低于背景值及其判别条件。结合中国公路交通的实际情况，论证了在不考虑非公路污染源时，公路交通引起土壤中铅累积量在营运近期将低于土壤背景值。认为合理确定非公路污染源强度、铅沉降面积及铅残留系数是影响预测评价土壤铅污染的主要因素。关键词：土壤 铅 预测 模式 公路交通Abstract The pollution prediction models of Pb in soil dueto highway transportation are deduced．The available three diffe
5、rent results，i．e．greater than or less than or equal to the background value，and theirdiscriminantes are discussed while the models are used to predict theamount of Pb in soil．On the basis of the situation of highway transportation in China，it is proved
6、 that the amount of Pb in soil is less than the background value during the short operation phase of highway，if the other pollution sources are not considered．It is believed that rationally taking the non-highway pollution source，the precipition area a
7、nd the remaining fraction of Pb into account incalculation are the major factors that affect the accuracy of 中国农村医疗保险必须有商业保险公司进入，才能形成完整的医疗保障体系。面对巨大的农村医疗保险市场，保险公司却驻足不前，究其原因主要是缺乏政府政策支持，现有农村医疗卫生环境及其卫生管理体制与商业健康保险配套需求差距较大，风险较高。针对农村医疗保险市场，保险公司应积极主动地争取改善外部环境，
