APPLICATION OF WATER QUALITY IDENTIFICATION INDEX TO ENVIRONMENTAL QUALITY ASSESSMENT OF NANSI LAKE

This study was carried out to evaluate the water quality of Nansi Lake with the method of single factor and comprehensive water quality identification index,based on the data collected from six sampling sites from May 2005 to August 2011. The results indicated that the average comprehensive water quality identification index of Nansi Lake in seven years was 4. 431,3. 980,3. 630,3. 470,4. 081,3. 570,4. 081,respectively; the comprehensive water quality grade of Nansi Lake was between III ~ IV,which has been improved,but not stable to water quality III standard. The lake was mainly polluted by total nitrogen(TN),total phosphorus(TP),chemical oxygen demand(COD Mn),and the corresponding single factor water quality identification index average range were 3. 58 ~ 6. 88,2. 23 ~ 8. 42 and 3. 47 ~ 4. 73. The water quality identification index average range of the Chla was 3. 24 ~ 5. 03. The range of dissolved oxygen(DO)and ammonia-nitrogen(NH 3-N)were 1. 00 ~ 2. 95 and 1. 00 ~ 3. 69,which could meet the standard of functional objectives of water. During the seven years, the comprehensive water quality identification index showed seasonal fluctuations,which was low in May,but high in August. The present study carried out evaluating on Nansi Lake by water quality identification index, which provided support for the improvement and rehabilitation of Nansi Lake water quality.