大宁河菜子坝汇流口网箱养鱼对周围水质的影响

以大宁河菜子坝汇流口网箱养鱼水质现场监测结果为基础，采用综合营养状态指数法对网箱养鱼水域的现状进行了营养状态评价，并用污染物浓度等值线法进行了网箱养鱼对周围水质的影响分析。结果表明：①养鱼网箱及其影响区水体综合营养状态均为轻度富营养，水质污染程度为轻度污染，其综合营养状态变化总趋势为网箱养鱼区大于网箱影响区；②养鱼网箱附近水域的Chla浓度明显高于网箱核心区域，其余污染物浓度的平面分布总趋势是由网箱核心区向网箱影响区由高向低变化；③若以超河流背景断面浓度5%作为划定超背景污染带的标准，大宁河菜子坝汇流口网箱养鱼引起CODMn、NH3-N、TN、TP和Chla超背景的污染面积分别为8 670、9 000、9 500、12 000和800m^2，分别是网箱养鱼区面积（1 375 m^2）的6.3、6.5、6.9、8.7和5.8倍。

The Effect of Fish Cage Culture on Environmental Water Quality of Caiziba Infall in Daning River

Based on autoptic monitoring results of water quality in caiziba infall of Daning River,the study used a comprehensive nutrition state index method to evaluate nourishment of fish cage culture water and analyzed the effect of fish cage culture on environmental water quality by using pollutant concentration isoline method.The results showed that:(1) The comprehensive nutrition state of fish cage culture and its effect area is low-level eutrophication as a whole and water quality is low-grade contamination.The change tendency of comprehensive nutrition state in fish cage culture area is bigger than in effective area.(2) Chla concentration of water near fish cage culture is higher than cage core area,the total tendency of plane distribution of other pollutant concentration is gradually decreasing from core area to effective area.(3) If taking the river background section concentration is over 5% as the standard of exceeding background pollution belt,fish cage culture induced CODMn,NH3-N,TN,TP and Chla exceeding background pollution area is 8 670,9 000,9 500,12 000,and 800 m2,respectively.CODMn,NH3-N,TN,TP and Chla exceeding background pollution area is 6.3,6.5,6.9,8.7,and 5.8 multiple of fish cage culture.