internal pollution sources的用法和樣例：
例句
- Soil erosion and non-point source pollution are two serious environmental issues.
土壤侵蝕與非點(diǎn)源污染是兩大重要的環(huán)境問(wèn)題。 - The distribution of non-point sources of pollution from different effluents had distinct spatial characteristics.
各流域非點(diǎn)源污染的發(fā)生具有明顯的地域分異特征。
