Although diesel exhaust may be a source of secondary aerosols, paint and solvents, outdoor barbecues, and vegetation also contribute significantly, he says.
他说虽然柴油燃烧的排放可能是次生气溶胶的来源之一，涂料和溶剂，室外烧烤和植物也是重要的来源。
2
Wasteland caused by rats is the secondary bare land of grassland on which vegetation is damaged by rodent movement and overgrazing.
鼠荒地主要是因鼠类活动和超载过牧等原因引起草原严重退化的次生裸地。
3
Vegetation is Laiyuan County of North China flora, the majority of existing vegetation for irrigation in the bushes, followed by natural secondary forest and plantation, forest coverage is 18.24%.