三峡库区汉丰湖水体氮磷及化学计量比季节变化特征

在分析2017年3月至2018年2月汉丰湖水体氮磷营养盐质量浓度季节性变化的基础上，利用氮磷化学计量摩尔比评估水体氮磷养分限制状态.结果表明：湖体TN、DN和NO₃^--N平均质量浓度分别为1.60、1.25和0.91 mg·L^-1，三者季节变化过程相似，均呈现出冬季最高、夏季最低的特点.NO₃^--N对水体TN贡献较大，NH₄⁺-N和NO₂^--N质量浓度维持在较低水平且变化平稳.TP、DP和PO₄^3--P平均质量浓度分别为0.13、0.09和0.06 mg·L^-1，TP和DP质量浓度变化相似，呈春夏季升高，秋冬季先降低再升高的趋势，而PO₄^3--P质量浓度则波动降低.TN/TP范围在11.07~56.02之间，均值为29.23，TN/TP呈季节性波动变化，最高值出现在冬季，最低值出现在夏季.汉丰湖水体多数时间适宜藻类生长繁殖，少数时间处于N限制状态，极少数时间处于P限制状态.降雨径流、肥料使用、污水排放和水生生物活动等因素皆会影响TN/TP的季节变化，同时根据汉丰湖水质特征提出保护建议.

Seasonal Variations in Nitrogen and Phosphorus Concentration and Stoichiometry of Hanfeng Lake in the Three Gorges Reservoir Area

Based on the seasonal changes in the nitrogen and phosphorus concentrations in Hanfeng Lake from March 2017 to February 2018, the nutrient limitation status was evaluated by the stoichiometric molar ratio of nitrogen and phosphorus. The results showed that the average concentrations of TN, DN, and NO₃^--N were 1.60, 1.25, and 0.91 mg·L^-1 in Hanfeng Lake, respectively. The seasonal changes of those indicators were similar, showing the highest concentration in winter and lowest in summer. NO₃^--N accounted for TN significantly in the water body, and the concentrations of NH₄⁺-N and NO₂^--N remained at low levels and changed steadily. The average concentrations of TP, DP, and PO₄^3--P were 0.13, 0.09, and 0.06 mg·L^-1, respectively. The changes in the concentrations of TP and DP were similar, showing a trend of increasing in spring and summer, and then decreasing in autumn and winter, while the PO₄^3--P concentration showed the trend of fluctuated decrease. TN/TP varied from 11.07 to 56.02, with an average value of 29.23. TN/TP changed seasonally, with the highest value occurring in winter and the lowest value in summer. The conditions of the water body were conducive to growth and reproduction of algae for most of the time during sampling months. The water body was occasionally nitrogen limited and rarely phosphorus limited. The seasonal variation in TN/TP ratio was affected by several factors such as rainfall runoff, fertilizer use, sewage discharge, and aquatic biological activities. Further, protection strategies were proposed for the improvement of the water body in terms of present water quality characteristics in Hanfeng Lake.