Influences of the suspended matter on the water quality parameters including COD, Potassium Permanganate Index and BOD5 in the Yellow River, China
泥沙对黄河水质参数COD、高锰酸钾指数和BOD5的影响——三论黄河的COD值与高锰酸钾指数不能真实反映其污染状况

The paper studied the relationships between the content of suspended matter in the Yellow River and water quality parameters including COD, Potassium Permanganate Index and BOD_5. The results show that there are shortcomings in monitoring and evaluating water quality in the Yellow River using theses parameters. It indicates that, among the three above-mentioned parameters for reflecting the pollution of the oxygen-demanding organic matters, the BOD_5 can factually reflect the status of organic pollution. However, the COD and Potassium Permanganate Index obtained either from the turbid water which contains the sediment or from filtered water exaggerate the pollution of the Yellow River. The exaggeration is especially notable in the unpolluted or lightly-polluted reaches of the River. Therefore, the author deems that when using the COD or Potassium Permanganate Index to evaluate the water quality in the Yellow River, it is not suitable to use the measured raw value, but the value which has been calibrated by the "background content of the organic matters in the sediment".