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How do ship emissions (NOx, SO2, particulate matter) cause eutrophication?

My research models nitrogen deposition impacts on coastal seas. While agricultural runoff is a well-documented source, the contribution from shipping emissions is less clear in our regional models. I understand the basic concept, but I need to articulate the precise atmospheric chemistry and marine biogeochemical pathway to strengthen the methodology section of my paper.

 

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By Rinku Answered 1 year ago

From my work on Baltic Sea models, the pathway is clear but involves several steps. Ship stacks emit NOx and SO2. In the atmosphere, NOx oxidizes to form nitric acid (HNO3) and nitrate aerosols, while SO2 forms sulfuric acid. These compounds are then deposited onto the sea surface via dry or wet deposition. This is a direct input of bioavailable reactive nitrogen. In nitrogen-limited coastal waters, this new N influx acts like fertilizer, promoting phytoplankton blooms. The subsequent decay of this organic matter consumes dissolved oxygen, leading to hypoxia. I've seen modeling studies where shipping contributes 10-30% of the total N load in major shipping lanes

 

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