Kev ntws los ntawm cov tshuaj chiv feem ntau suav nrog cov thee, cov roj nkev, cov pob zeb phosphate, cov leej faj thiab cov poov hlau. Tus nqi ntawm upstream raw khoom muaj qhov cuam tshuam ncaj qha rau tus nqi tsim tawm ntawm cov khoom siv tshuaj chiv. Tom qab kev hloov kho tus nqi ntawm cov tshuaj lom neeg, kev sib tw kev lag luam yuav qhia tus nqi thiab ua lag luam ntau.
