Estimation of nutrient atmospheric deposition to Long Island Sound

Anthropogenic nutrient sources (especially nitrogen and phosphorus) released into the Long Island Sound (LIS) causes excessive phytoplankton growth resulting in hypoxic conditions. Atmospheric deposition (both wet and dry deposition) has significant effect on aquatic and terrestrial ecosystems. Two dry deposition monitoring sites were established along the north shore of LIS in February 1991. Wet and dry deposition samples were collected since then. A dry deposition velocity model, based on the characteristics of the water surface, was used to estimate the loading as well as the seasonal variability (dynamics) of nutrients in atmospheric deposition to LIS. The average nitrogen flux from each site was 6.64 kg (as-N) ha-yr(-1). The total atmospheric nitrogen loading was estimated to be 2240 metric tons yr(-1) which corresponds to 2.5% of the estimated total nitrogen loading to the Sound from all sources. The average phosphorus flux was 37.44 g (as-P) ha-yr(-1). The total atmospheric phosphorus loading to the Sound was estimated to be 12.62 metric tons yr(-1). The results show that wet deposition was the predominant source of atmospheric contribution to the Sound.