富营养化饮用水源地山仔水库限制性营养元素研究

世界范围内关于水体富营养化的研究表明,流域尺度上营养盐的控制和削减是修复富营养化水体的关键措施,甄别水体限制性营养元素进而采取相应的控制措施是修复富营养化水体的有效途径.本文在时空格局上分析了富营养化饮用水源地山仔水库的限制性营养元素.结果表明,2003—2012年,山仔水库初级生产力的关键限制性营养元素为磷.秋、冬、春季,水体总磷浓度在0.02~0.09 mg·L-1左右,TN/TP原子比值在35~72之间,表明TP浓度相对低,磷为限制性营养元素;夏季表层水TP浓度在0.06~0.13 mg·L-1左右,TN/TP原子比值在11~13之间,表层水溶解性磷的浓度较低,磷主要蓄积在藻细胞内,由于温跃层的存在,底层释放的磷无法向表层水补给,故溶解态磷相对缺乏.总之季节变化对磷的限制性作用有显著影响.通过对山仔水库2003—2012年水体TP浓度和叶绿素a浓度相关性分析得出,修复水体需要控制的TP浓度阈值为0.028 mg·L-1.根据上述结果综合分析了已采取修复措施的效果,从而进一步提出了山仔水库富营养化的修复策略.

Research on the limiting nutrient in Shanzi Reservoir, an eutrophied drinking water source

Previous research on eutrophication has identified the control and reduction of water nutrients are the key solution to restore the quality of water bodies. Recent experience showed that the characterization of limiting nutrient factors benefits the engineering and management strategies for highly efficient water quality restoration. Based on the water quality variation of Shanzi reservoir as a drinking water source, this work revealed the spatial and temporal distribution of limiting nutrients. Based on the analysis of the seasonal fluctuation of nitrogen and phosphorus from 2003 to 2012, the limiting nutrient factor for primary productivity was identified as phosphorus in Shanzi reservoir. In autumn, winter and spring, the total phosphorus ranged from 0.02 to 0.09 mg·L^-1 and the TN/TP ratio fluctuated between 35 and 72, indicating relatively limited phosphorus condition for eutrophication. The total phosphorus concentration increased to 0.06~0.13 mg·L^-1 in summer, consequently resulting in the declining TN/TP ratio from 11 to 13. The dominant phosphorus was accumulated in the algae, and the low concentration of dissolved phosphorus attributed to the thermocline which limited the phosphorus releasing process from the sediment to surface water. The water soluble phosphorus was therefore still the restriction factor for controlling water quality. The dominant influencing factor for limiting nutrients was seasonal fluctuation, rather than vertical diffusion. The correlation analysis between TP and chlorophyll-a concentration further suggested the control concentration of total phosphorus was 0.028 mg·L^-1 in Shanzi reservoir. Further evaluation on different restoration measures and strategies provided the technical reference for the water quality management of eutrophic Shanzi reservoir.