太湖流域小型水源性湖泊氮、磷时空分布及营养状态评价

2009年11月至2010年10月,对太湖流域小型水源性湖泊20个采样点水体的TN、TP、NO3--N、NH4+-N、NO2--N以及PO43-等水质因子进行测定分析,讨论了氮、磷时空分布特征,并评价其富营养化程度。结果表明,TN、TP年均值分别为1.50、0.05mg/L;TN、TP的季节性变化规律具有一定差异,TN浓度为冬、春季高于夏、秋季,而TP浓度为2009年11月至2010年3月高于其他月份。由于受入湖河流的影响,TN、TP的空间分布格局较为相似,均表现为西南部高于东北部、入湖口分别高于湖中心和出湖口。NO3--N年均值为0.68mg/L,浓度变化趋势呈双峰型(2010年3、9月为峰值),基本同TN的变化趋势一致,空间分布表现为入湖口分别低于湖中心和出湖口(除冬季外),显示水体硝化过程对硝酸盐的贡献。NH4+-N年均值为0.23mg/L,从2010年4月开始浓度逐渐升高,到2010年7月达到全年最高值,其浓度空间分布特征表现为入、出湖口均高于湖中心(除秋季外)。NO2--N和PO43-的年均值都较低,均为0.01mg/L(以P计),时空差异不明显。根据CARLSON提出的营养状态指数法计算分析可知,该湖泊冬、春季处于中营养状态,夏、秋季营养状态略高,且磷是全年初级生产力的限制因子。

Temporal and spatial distribution of nitrogen and phosphorus and evaluation of trophic status of a water supply lake in Taihu basin

Total nitrogen(TN),total phosphorus(TP),nitrate-nitrogen(NO-3-N),ammonium-nitrogen(NH+4-N),nitrite-nitrogen(NO-2-N) and phosphate(PO3-4) of water samples collected at 20 points of a water supply lake in Taihu basin were measured monthly from November 2009 to October 2010.Temporal and spatial distributions of nitrogen,phosphorus and their different forms were discussed and the trophic status was evaluated.The results showed that annual average concentrations of TN and TP were 1.50,0.05 mg/L,respectively.TN concentration in winter and spring was higher than that in summer and autumn,while the highest TP concentration was found in winter.The overall spatial distribution pattern of TN and TP was similar;they both higher in Southwest than in Northeast,higher in inlet of lake than in outlet and center of lake.The concentration of NO-3-N presented a double-peak profile with annual average concentration was 0.68 mg/L,the peak value was found in March and September.NO-3-N in winter and spring was higher than in summer and autumn,it was also higher in inlet of lake than in outlet and center of the lake,which showed the contribution of denitrification to NO-3-N.The annual average concentration of NH+4-N was 0.23 mg/L,the concentration of NH+4-N was gradually increased from spring and reach maximum value at July.The concentrations of NO-2-N and PO3-4 were relatively low(0.01 mg/L),and their temporal and spatial distribution was not obvious.According to Carlson trophic state index,the lake in winter and spring was mesotrophic,and eutrophic in summer and autumn,and phosphorus was the limiting factor of eutrophication.