北运河流域典型河流水体耗氧污染特征分析

Analysis of the oxygen-consuming features of pollutants in the North Canal Watershed,northern China

以COD和NH+4-N为研究对象,阐述了北运河流域典型河流水体中耗氧污染物的时空变化规律,并结合COD组分特征分析,给出了河流水体主要耗氧因子。结果表明,河流水体中COD平均值为47.73 mg/L,接近地表水Ⅴ类标准,而NH+4-N质量浓度为9.08 mg/L,远超Ⅴ类水标准;流域河流水体中COD空间分布差异性不明显(CV=8.79%),而从上游至下游,NH+4-N质量浓度呈现降低趋势;从2005年至2011年,河流水体中COD和NH+4-N质量浓度分别从251.92 mg/L和11.15 mg/L降至44.77 mg/L和4.12 mg/L。河流水体中COD组分分析共检出31种有机化合物,其中上游包括难降解和易降解有机化合物,涉及生活源和农业源;下游多为难降解有机化合物,主要涉及农业源。NH+4-N已取代COD成为北运河流域河流水体主要耗氧因子。

The present paper intends to introduce our study findings of the characteristic features of the water pollutant oxygen-consumption in the North Canal Watershed, northern China. As is known, the government departments concerned have given a great priority to the study of the pollutants in the rivers from the point of view of chemical oxygen demand （COD） and of ammonia nitrogen （NH4＋ - N） in the period of the 11st and 12nd Five-Year Plan periods for the water pollution control. However, for the time being, the water resource for the canal watershed is mainly originated from the sewage-treating plants and farm irrigation left-over sewage, and in turn a great need for increasing the water quality of many rivers, for the pollutant concentration of the river at present fails to come up to the 5-th state- stipulated standard of surface water quality in China （that is, GB 3838--2002）. Therefore, we have chosen COD and NH4 - N for our study focus on the spatial-temporal features of oxygen-consuming pollutants in the water of the said watershed. Analyzing the COD components and the main oxygen-consuming factors in the paper by using the investigation samples, we have concluded that the average concentration of COD in the said watershed is equal to 47.713 mg/L, which is close to the 5-th standard of the surface water of the country （40.00 rag/L） ; and NH4＋ - N should be 9.08 mg/L, which is far more serious than the said 5-th standard （2.00 mg/L）. Though the spatial variation of COD concentration in the watershed under discussion doesn＇ t seem very pure （ CV = 8.79 % ）, the concentration of NH4＋ - N has been found being decreased gradually from the upstream to the downstream. From 2005 to 2011, the concentrations of COD and NH4＋ - N were found decreased from 251.92 mg/L and 11.15 mg/L to 44.77 mg/L and 4.12 mg/L, respectively, which seem to be caused by the water pollution control of the watershed under study in recent years, especially, due to the setting up of more sewage treating plants. Moreover, the COD components, including 31 organic compounds in the given part of the canal, can hardly be found easily degradable and melt in the upstream, mainly due to the left-over wastes and farming pollutants, Moreover, they were found difficult to get degraded in the downstream, mainly due to the agricultural wastes. In addition, the 12 organic compounds （38.71% of the total） involve agricultural sources （such as pesticides, herbicides, etc ）, which should be considered as the key to solving the problem of COD pollution control in the canal watershed. In accordance with the current pollution situation in comparison with the 5-th standard demands of GB 3838--2002, the COD concentration in the water of that part of the canal proves to range from 1.05 to 1.38, with an average concentration of NH2 - N being 1.19 ; and the range from 1.89 to 6.45, with an average concentration of 4.54. With the COD controlled by the sewage treatment plants, the oxygen-consumption of NH4＋- N has become the chief problem to be solved, for it has far exceeded the 5-th state standard of the surface water. Therefore, NH4＋ - N, the main oxygen-consuming factor should be taken as the focus of oxygen-consuming pollution control in the said part of the canal watershed, rather than that of COD.