Deposition of sulfur and nitrogen components in Louisiana in August, 2011

Dry and wet deposition of sulfur and nitrogen contained air pollutants lead to increase of sulfur and nitrogen to the surface, causing acidification of surface water bodies and subsequent damage to aquatic and terrestrial ecosystems. Louisiana has abundant water resources and it is important to protect water resources from excessive atmospheric deposition of sulfur and nitrogen. However, the information for understanding sulfur and nitrogen deposition and adverse effects in Louisiana is limited. In this study, a source-oriented version of the Community Multi-scale Air Quality (CMAQ) model was used to simulate emission, formation, transport, and deposition of sulfur and nitrogen species in Louisiana in August 2011 to understand the forms and quantities of sulfur and nitrogen deposition due to wet and dry processes in Louisiana, to show the spatial and temporal variations of deposition fluxes, and to quantify the contributions of different sources to sulfur and nitrogen deposition. Aerosol phase sulfate (AeroSO₄) has the highest monthly total flux of 6 kg S/ha in wet deposition of sulfur. Major forms of sulfur dry depositions are AeroSO₄ (~1 kg S/ha) and SO₂ (~3 kg S/ha). Nitrogen deposition is mainly in forms of NO₂, HNO₃, NH₃, and aerosol phase nitrate (AeroNO₃). Electric generating utilities (EGU) are the largest contributor to sulfur depositions with monthly total flux of 1.6 kg S/ha, followed by industry (1 kg S/ha) and upwind sources. On-road vehicles and industry are important to nitrogen (except ammonia) depositions with maximum contributions of 0.6 kg N/ha and 0.8 kg N/ha, respectively. The dominate source of ammonia is "Other" implicit sector including agricultural activities.