Estimation of the contribution of atmospheric deposition to coastal water eutrophication

Abstract

Human activities often lead to increased inputs of nutrients from point and/or distributed sources into the coastal environment, causing eutrophication. Recent research has suggested that atmospheric deposition can be a major source of nutrients to the aquatic ecosystems where these nutrient species can play a critical role in major biogeochemical cycles. This study was initiated with an aim to improve our quantitative understanding of the processes related to the transfer of nutrients from the atmosphere to aquatic systems under different weather conditions for prediction of the occurrence of coastal eutrophication. Both field-based investigations and eutrophication modeling work were undertaken in the present research work. The role of atmospheric deposition of elements and substances of biogeochemical interest, particularly nitrogen (N) & phosphorus (P) species, was studied. The effects of atmospheric nutrient deposition on biogeochemical processes in coastal waters were investigated through the development and use of a three dimensional (3-D) numerical eutrophication model. It was observed that the average concentrations of nutrients in atmospheric aerosols and rainwater increased by a factor of 3 to 8 in biomass burning-impacted air masses as compared to those during non-hazy days. The occurrences of increased atmospheric deposition of nutrients during smoke haze episodes were found to have negative consequences on receiving aquatic ecosystems with cascading impacts on water quality, and trophic and biogeochemical alterations. This study provides the estimates of both inorganic and organic fractions of water soluble N and P species in dry atmospheric deposition and wet atmospheric deposition to the coastal waters of Singapore and surrounding regions for the first time. The environmental implications of this comprehensive study are also discussed.