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| DOI： |
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| The Background Values of Ammonia-nitrogen, Total Phosphorus and COD of the Mainstream of Yellow River within Ningxia Province |
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HOU Kai, YANG Mi, QIAN Hui, LIN Tao, XU Panpan
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Environmental Science and Engineering, Chang’an University College, Xi’an 710054, China; Key Laboratory of Subsurface Hydrology and Ecology in Arid Areas, Ministry of Education, Xi’an 710054, China
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| Abstract: |
| 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; ②The concentration of ammonia-nitrogen, total phosphorus and COD decreased and the river water was only slightly contaminated; ③The 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. |
| Key words: water quality analysis; environmental background value; relative cumulative frequency; ammonia-nitrogen; total phosphorus; COD |
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