Atmospheric phosphorus in the northern part of Lake Taihu, China

Eutrophication, which has been linked to enhanced nutrient loading in lakes, estuarine and coastal waters, is common to many water bodies in China, including Lake Taihu. The atmosphere is an important and growing source of new nutrients entering water bodies. To assess the impact of atmospheric phosphorus (P) on water quality of Lake Taihu, we have estimated the atmospheric input of P by measuring its concentrations in aerosols and in rainwater. Samples were collected at the northeastern part of the lake. The P concentration in total suspended particle ranged from 0.054 to 0.300μgm^-3. Concentrations of P in aerosols in the winter and autumn samples were higher than those in the spring and summer samples. Soluble inorganic P (SIP), which provides direct nutrient sources to algae, accounts for 4.9%-83.4% of the total P. Principal Component Analysis of the measured aerosol constituents and examination of inter-species correlation indicate that SIP was correlated with elemental carbon, water soluble organic carbon, NO3-, and Ca²⁺. Such correlations could be explained if two nearby coal-fired power plants were a major aerosol P sources. The average concentration of the total P in rain water samples was 0.082±0.058mg P/L. The annual deposition flux of P into the northern part of Lake Taihu was estimated to be in the range of 0.04-0.44kgha^-1year^-1 through dry deposition and 0.33kgha^-1year^-1 through wet deposition. The combined wet and dry deposition was less than 8% of riverine P input, therefore the atmospheric deposition was only a minor contributor to P in Lake Taihu at the time of this study.