城市湖泊氮磷沉降输入量及影响因子——以武汉东湖为例

城市湖泊是受人类影响最严重生态系统之一,正面临着水体污染和生态系统退化的双重压力.研究氮、磷沉降输入量及影响因素对城市湖泊管理具有重要的实践意义.本文通过对中国最大的城市湖泊之一——武汉东湖进行为期1年的氮、磷沉降连续监测,研究了大气混合沉降对武汉东湖的氮、磷输入动态,并探讨了氮、磷沉降的影响因素.结果表明:武汉东湖大气氮、磷年沉降通量分别为22.80、1.37 kg·hm~(-2)·a~(-1);总氮年沉降负荷为76.94 t·a~(-1),氨氮年沉降负荷为31.83 t·a~(-1),总磷年沉降负荷为4.61 t·a~(-1),分别占其东湖年入湖污染物的7.28%、7.61%和4.41%.从时间格局看,总氮沉降通量的季节性差异较为明显,表现为:春季(9.03 kg·hm~(-2))夏季(6.01 kg·hm~(-2))秋季(3.90 kg·hm~(-2))冬季(3.86 kg·hm~(-2));而总磷沉降通量呈现出仅春季较高(0.52 kg·hm~(-2)),占全年的38%,其他三季总磷沉降通量变化较小的特征.相关性分析显示,氮、磷沉降负荷量与降雨量、降雨时间间隔及空气颗粒物浓度(PM_(10)、PM_(2.5))等因素呈显著正相关,与相对湿度呈显著负相关.分析表明,随着控源、截污等措施对城市湖泊氮、磷输入的控制,氮、磷沉降对城市湖泊的生态影响应引起足够的重视.

Nitrogen and phosphorus deposition in urban lakes and its impact factors: A case study of East Lake in Wuhan

Urban lake is one of the ecosystems vulnerable to the influence of anthropogenic activities, and is under a dual-threat from water pollution and ecosystem deterioration. Thus, it is of great practical significance to study the nitrogen and phosphorus deposition in urban lakes and the influencing factors. Based on a one-year monitoring nitrogen and phosphorus deposition in East Lake in Wuhan, the nitrogen and phosphorus input dynamics of East Lake and influencing factors were analyzed. Results show that the atmospheric nitrogen and phosphorus deposition fluxes of East Lake were 22.80 and 1.37 kg·hm^-2·a^-1 respectively. The annual deposition load of total nitrogen (TN), ammonia nitrogen (NH₃-N) and total phosphorus (TP) were 76.94, 31.83, and 4.61 t·a^-1, which take up 7.28%, 7.61% and 4.41% of the annual TN, NH₃-N and TP pollution load in East lake respectively. From the time pattern, there is an obvious seasonal variation of total nitrogen deposition flux, i.e. spring (9.03 kg·hm^-2)>summer (6.01 kg·hm^-2)>autumn (3.90 kg·hm^-2)>winter (3.86 kg·hm^-2). However, the seasonal variation of TP deposition flux shows higher only in spring (0.52 kg·hm^-2), which accounts for 38% of annual TP deposition. Correlation analysis results show that nitrogen and phosphorus deposition are positively correlated with rainfall, rainfall interval and air particulate matter (PM₁₀, PM_2.5), and are negatively correlated with relative humidity. Our results suggest that enough attentions are needed on the ecological influences on urban lake caused by atmospheric nitrogen and phosphorus deposition, because their influence will become more and more serious.