Photo‐Reactivity of Surfactants in the Sea‐Surface Microlayer and Subsurface Water of the Tyne Estuary, UK
Philippa Rickard, G Uher, Robert C. Upstill‐Goddard
Abstract
Abstract We report the first estimates of total surfactant photo‐reactivity in the sea‐surface microlayer (SML) and in subsurface water (SSW) (Tyne estuary, UK; salinity 0.3–32.0). In addition to temperature, a known driver of surfactant adsorption kinetics, we show that irradiation contributes independently to enhanced interfacial surfactant activity (SA), a notion supported by coincident CDOM photodegradation. We estimate a mean SA production via irradiation of 0.064 ± 0.062 mg l −1 T‐X‐100 equivalents h −1 in the SML and 0.031 ± 0.025 mg l −1 T‐X‐100 equivalents h −1 in the SSW. Using these data, we derive first‐order estimates of the potential suppression of the gas transfer velocity ( k w ) by photo‐derived surfactants ∼12.9%–22.2% in coastal North Sea water. Given the ubiquitous distribution of natural surfactants in the oceans, we contend that surfactant photochemistry could be a hitherto unrecognized additional driver of air‐sea gas exchange, with potential implications for global trace gas budgets and climate models.