Evidence for significant photochemical production of carbon monoxide by particles in coastal and oligotrophic marine waters

Abstract

Carbon monoxide (CO) photoproduction from particulate and chromophoric dissolved organic matter (CDOM) was determined in seawater from open-ocean and coastal areas. In confirmatory tests, poisoned or non-poisoned filtered and unfiltered blue-water samples, were exposed to sunlight. CO photoproduction was 21–42% higher in the unfiltered than in the filtered samples. In a more thorough study utilizing concentrated particles prepared by 0.2-μm cross-flow filtration, samples containing varying levels of particles were irradiated under simulated solar radiation. Their CO photoproduction rates increased linearly with particle concentration factor. Particulate CO production was 11–35% of CDOM-based CO production. On an absorbed-photons basis, the former was 30–108% more efficient than the latter. This study suggests that in both coastal and blue waters these new-found particulate photoprocesses are of similar biogeochemical importance to the well-known CDOM photoproduction term.