THE LONG-TERM VARIATIONS OF WATER QUALITY IN THE HAIHE RIVER, CHINA

Water samples collected from the Haihe River in China between 2001 and 2010, were analyzed for pH, chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen (TN), and total phosphorus (TP). The water pollution index was preferred to assess the water quality according to water quality parameters. The concentrations of pH, COD, BOD, TN and TP in the water samples were 7.67-8.54, 33-142 mg/L, 0.9-73.4 mg/L, 4.98-18 mg/L and 0.17-0.81 mg/L, respectively. These results exceeded Grade-III surface water quality standards in China. TN and TP have been one of most important pollutants the Haihe River, which have been exceeded Grade-V surface water quality standards in China. The concentration of TN decreased from 2001 to 2004 and then increased, while TP increased from 2001 to 2006 and then decreased. The annual mean ratio of TN/TP ranged between 16.63 and 49.45, with a decreasing trend between 2001 and 2004, while an increasing trend between 2004 and 2010, probably indicating that P-limit in the Haihe River. The temporal variations of the pollution indexes showed a decreasing trend between 2001 and 2004, while an increasing trend between 2004 and 2010. However, the spatial variations of water pollution index were higher than one in the upstream sections while lower than one in the downstream sections, suggesting that the upstream sections did not meet the standards for water quality in China while the downstream sections were met. These results indicate that the pollutants in the Raffle River came from different sources.