Trend Analysis and Assessment of Surface Water Quality in the Yangzhou Reach of Jinghang Canal

Eight organic and chemical variables were analyzed in surface water samples collected every season over a period of twenty two years. They were determined from seven sampling stations located along the Yangzhou reach of JingHang Canal. The assessment was performed using membership function of twice-slope classification. The results illustrated that: in the past twenty-two years, the water quality of Yangzhou reach of JiangHang Canal stayed mainly between Class III and Class IV. Among the main pollutants, the concentrations of both COD
_Mn
and BOD
₅
were decreasing. They were below Class III after 2000. The concentrations of volatile hydroxybenzene and petroleum were remarkably high during 1998 to 2000. In the whole period, they fluctuated in a large degree; the trend of ammonia nitrogen(NH
₃
-N) was relatively smooth, oscillating between Class III and Class IV; other variables were in low concentration and did not fluctuate significantly.