Water quality change of Nanliu River in Guangxi Beibu Gulf Economic Zone

The single factor index assessment method is used to evaluate the water quality of Changle monitoring section and Zongjiangkou monitoring section in Nanliu River during 2003–2009. It showed that the water quality of Changle section became serious during 2006–2008, but the water quality of lower Zongjiangkou section was stable. The main pollution factors of Nanliu River were permanganate index (COD Mn ), ammonia nitrogen (NH 3 -N), dissolved oxygen (DO), five-day biochemical oxygen demand (BOD 5 ), volatile phenol, total phosphorus (T p ) and fecal colon bacterial colony. The Spearman's rank correlation coefficient method showed that BOD 5 and T p went with an upward tendency during 2003–2009. The results indicated that water quality of Nanliu River became serious due to the industrial wastewater, urban domestic sewage and livestock waste discharge directly into river without treatment, and agricultural fertilizers and pesticide.