太湖氮磷营养盐大气湿沉降特征及入湖贡献率

2009年8月—2010年7月在太湖流域不同区域10个采样点收集降水样品230多个,测定其中不同形态N,P营养盐的质量浓度,分析太湖大气湿沉降中N,P营养盐沉降特征,计算N,P营养盐湿沉降率及其占太湖河流入湖负荷的贡献率.结果表明:湿沉降中ρ(TN)年均值为3.16 mgL,DTN(溶解性总氮)占TN的70%以上,其中以NH4+-N为主;湿沉降中ρ(TN)年均值最高值出现在南部湖区,最低值出现在北部湖区.湿沉降中ρ(TP)年均值为0.08 mgL,相对较低.5个区域湿沉降中不同形态N的质量浓度均表现为冬季高、夏季低,而不同形态N,P的湿沉降量均为夏季最大.南部、东部湖区TN的湿沉降率相对较大.各采样点湿沉降中NH4+-N沉降率约占DTN沉降率的30.4%～52.0%,NO3--N沉降率约占DTN的31.6%;各区域间湿沉降中DTP(溶解性总磷)占TP的比例差异较大.大气湿沉降中TN和TP的年沉降总量分别为10 868和247 t,为同期河流入湖负荷的18.6%和11.9%,湿沉降对太湖富营养化的贡献及可能带来的水生态系统的影响不容忽视.

Atmospheric Wet Deposition Characteristics of Nitrogen and Phosphorus Nutrients in Taihu Lake and Contributions to the Lake

To understand seasonal and spatial wet deposition characteristics of nutrients in Taihu Lake during precipitation,more than 230 precipitation samples were collected at ten monitoring sites from August 2009 to July 2010 in different regions around the Taihu Lake basin.Mass concentrations of total nitrogen(TN),dissolved total nitrogen(DTN),nitrate nitrogen(NO3——N),ammonia nitrogen(NH4+-N),total phosphorus(TP),dissolved total phosphorus(DTP) and dissolved inorganic phosphorus(DIP) in the precipitation samples were measured.The precipitation characteristics of nitrogen and phosphorus nutrients in atmospheric wet deposition,the deposition rates and their contributions compared with their counterparts from external loading of rivers to the lake were studied.The results indicated that the annual average mass concentration of TN in the wet deposition was 3.16 mg/L,in which that of DTN accounted for more than 70% of TN,with a major form of NH4+-N.The maximum values of TN appeared in the southern lake district,and the minimum in the north.The TP deposition mass concentrations were relatively lower,with an annual average value of 0.08 mg/L.Seasonally,mass concentrations of different forms of nitrogen in wet deposition in the five regions were high in winter and low in summer,although the wet deposition of different forms of nitrogen and phosphorus were all highest in summer.Spatially,the deposition rates of TN were relatively higher in the southern and eastern lake regions.The deposition rates of NH4+-N and NO3——N accounted for approximately 30.4%-52.0% and 31.6% of DTN,respectively,while the deposition rate proportion of DTP to TP varied greatly among these monitoring sites.The annual settlements of TN and TP in the precipitation were 10,868 and 247 t,respectively,accounting for 18.6% and 11.9% of the annual loading of rivers into Taihu Lake.These settlements could promote eutrophication and have strong impacts on the lake ecosystem.