黄河宁夏段氨氮、总磷及化学需氧量环境背景值研究

了解黄河干流宁夏段氨氮、总磷以及化学需氧量(COD)的环境背景值,可为评价其水质提供科学依据。基于2013年宁夏环境监测站统计的水质监测资料,运用正态分布法、相对累积频率法和迭代标准差法对黄河宁夏段的环境背景值进行了研究。结果表明,(1)人类活动对黄河水质有一定的影响,特别是氨氮、总磷及化学需氧量质量浓度变化特征显著,即黄河环境背景值的时间差异性;(2)氨氮、总磷及化学需氧量年内整体呈下降趋势,水质污染较轻;(3)水质的污染来源主要为工业排污、农业灌溉退水及生活污水,其中氨氮、总磷和化学需氧量的污染源分别有3个、3个和4个;(4)利用迭代标准差法对正态分布法和相对累积频率法得到的结果进行检验,其结果通过置信度为95%的Lilliefors检验,即利用迭代标准差法估算不受明显污染水体的环境背景值是有效的。综合3种方法的计算结果及《地表水环境质量标准》,得出黄河宁夏段氨氮、总磷和化学需氧量的环境背景值范围分别为0.11~0.31、0.03~0.10、7.00~10.10 mg/L。

The Background Values of Ammonia-nitrogen,Total Phosphorus and COD of the Mainstream of Yellow River within Ningxia Province

Under standing the background values of ammonia-nitrogen,total phosphorus and COD in the mainstream of Yellow River within Ningxia province is essential to evaluate water contamination in the river basin.Using normal distribution method,relative cumulative frequency and the iterative 2-σ technique,we calculated the background values of the above chemicals based on the data measured from this region in 2013.The results indicated that:①Human activity had the most profound impact on water quality of the river,especially the concentration of ammonia-nitrogen,total phosphorus and COD;② The concentration of ammonia-nitrogen,total phosphorus and COD decreased and the river water was only slightly contaminated;③ The water quality was mainly affected by industrial wastewater,domestic sewage,and drainage from agricultural fields,which are the main pollution sources of the ammonia-nitrogen,phosphorus,and COD;④The normal distribution method and the relative cumulative frequency were tested iteratively using the 2-σ technique,and the result passed the Lilliefors tests of 95％ confidence coefficient.The iterative 2-σ technique is an effective method to calculatethe background values of rivers without noticeable pollution.The results calculated by the three methods and the Environmental Quality Standards for Surface Water found that the background values of ammonia-nitrogen,total phosphorus and COD of the Yellow River mainstream within Ningxia were 0.11～0.31 mg/L,0.03～0.10 mg/L and 7.00～10.10 mg/L respectively.