Temporal and spatial distribution of total nitrogen, total phosphorus and COD in the largest shallow lake of the upper Yellow River

Concentrations of total nitrogen (TN), total phosphorus (TP) and Chemical Oxygen Demand (COD) were studied by using the geostatistical analysis module of ArcGIS in Wuliangsuhai Lake which was based on the monitoring data collected from 2006 to 2010. The results indicated that the contamination of TN, TP and COD were very serious, and the water quality was beyond the limition of the fifth category national lake water quality standard. Wuliangsuhai Lake is in a serious eutrophication and the contamination is obviously deeper than other lakes. Changes of the concentrations of TN, TP and COD are very little from 2006 to 2010. But all the minimum value of TN, TP and COD arised in 2008. Then the concentration distribution of TN and TP showed gradually decreasing trend from north to south in last 5 years. The minimum value of COD appears at the middle of Wuliangsuhai Lake and is higher then the both sides of the lake. In a word, the status of Wuliangsuhai Lake eutrophication is very serious.