Impacts of pH on NSAID adsorption to microplastics in the North Pacific Gyre

Abstract

The adsorption of non-steroidal anti-inflammatory drugs (NSAIDs) to microplastics, and subsequent ingestion by marine organisms, has many detrimental impacts on the marine organisms, including behavioral changes, reproduction disruption, and mortality. In this study, I researched the impacts of pH on the capacity of NSAID adsorption to microplastics. I anticipated that lower pH levels would coincide with a higher adsorption capacity due to a more protonated microplastic surface area being present in low pH levels. To test this hypothesis, I added microfiber filters and NSAIDs to seawater samples from the North Pacific Gyre – a convergence zone of microplastics – allowed for adsorption to occur and analyzed the results via mass spectrometry. There was extremely strong and nearly irreversible adsorption between the NSAIDs and the plastics. Only the NSAIDs with the simplest chemical compounds, aspirin, Naproxen, and Ibuprofen, were found to desorb and only under highly acidic conditions (pH ≤4). This is important due to how, as NSAIDs travel through the food web, they may enter and desorb in the acidic (pH 1.5-3.5) digestive tract of large mammals.