关键词: 氮肥利用率, 差减法, ¹⁵N标记法, 改进计算法, 综合评价体系

Abstract: To understand the influence of cage culture on the methylmercury production and distribution in water column of reservoir, water samples were collected from four cage culture sites in Wujiangdu Reservoir in September (warm season), 2010 and in March (cool season), 2011, taking the sites with a distance of 100-200 m from the culture sites and at the center of the reservoir as the reference sites. In warm season, the total mercury (THg) and methylmercury (MeHg) concentrations in cage culture sites were 2.04±0.53 ng·L^-1 and 0.146±0.231 ng·L^-1, and those in reference sites were 3.33±2.39 ng·L^-1 and 0.380±0.577 ng·L^-1, respectively; in cool season, the corresponding values were 3.04±1.53 ng·L^-1 and 0.047±0.028 ng·L^-1, and 3.24±1.23 ng·L^-1 and 0.046±0.013 ng·L^-1, respectively. No significant differences were observed in the concentrations of THg and MeHg (for THg, n=35, P=0875, andforMeHg,n=35,P=0.091) between cage culture sites and corresponding reference sites. The analysis on the water parameters total phosphorus, total nitrogen, dissolved organic carbon, temperature, and chlorophyll-a at the cage culture sites and reference sites showed that the MeHg production and distribution in the water column were affected by the water discharge and water exchange activities in the reservoir rather than by the cage culture activities, whereas the anaerobic condition of bottom water and the variation of water temperature caused by the seasonal stratification of water column could be the main factors affecting the methylmercury production and distribution.

Key words: nitrogen use efficiency (NUE), subtraction method, ¹⁵N labeling method, substituted calculating method, comprehensive evaluation index system.