Removal of agricultural non-point source pollutants by ditch wetlands of the Maixi River, Guizhou Province, China

摘要

A natural ditch wetland grown with nature annual bluegrass {Poa annua L.), alligator weed {Alternanthera philoxeroides {Mart.) Griseb.), common duckweed {Lemna minor L.) and curly pondweed (Potamogeton crispus L.) etc. were selected to study the removal capacity of agricultural non-point source pollutants in the Maixi River in Guiyang City, the capital of Guizhou Province, China. The removal characteristics and seasonal variation of chemical oxygen demand (COD), total phosphorus (TP), ammonia-nitrogen (NH~+4-N), and suspended solids (SS) in the ditch water was studied. The results showed that there existed a certain seasonal diversity in the removal characteristics of nitrogen, phosphorus and organic pollutants by the ditch. The removal efficiency of TP, COD and SS demonstrated an increasing tendency with their increasing concentration at the ditch inlet, whereas that of the NH/-N displayed contrary tendency as the concentration of NH/-N increased.