Changes in light absorption and composition of chromophoric marine-dissolved organic matter across a microbial bloom

Abstract

Marine chromophoric dissolved organic matter (m-CDOM) mediates many vital photochemical processes in the surface ocean. Isolating m-CDOM within the chemical complexity of marine dissolved organic matter has remained an analytical...

Enhanced HONO Formation from Aqueous Nitrate Photochemistry in the Presence of Marine Relevant Organics: Impact of Marine-Dissolved Organic Matter (m-DOM) Concentration on HONO Yields and Potential Synergistic Effects of Compounds within m-DOM

“…To further understand mechanisms of the enhancement, mixtures of molecular models, 4-benzoylbenzoic acid (4-BBA) and ethylene glycol (EG), for light-absorbing and non-light-absorbing components within m-DOM, respectively, were added to nitrate solutions and irradiated to determine if the enhancement of HONO in these mixtures was simply additive or if synergistic effects could play a role, as discussed below. The selection of the proxies is based on previous characterization of the chemical and optical properties of m-DOM, which shows absorbance by aromatic groups in the range between 280 to 500 nm, similar to that of 4-BBA. ,, …”

“…This finding not only confirms that these mechanisms are responsible for the enhancement but also gives insight into its synergistic nature. This understanding is crucial when assessing this effect in environmental samples like m-DOM and other organics within SSA, which include various compounds acting as photosensitizers or aliphatic substances. ,, …”

“…Marine-dissolved organic matter (m-DOM), present in the acidic environment of sea spray aerosols (SSA), has been shown to enhance the formation of HONO in the MBL due to the presence of light-absorbing, photosensitizer molecular species . The photosensitized reduction of NO 2 to HONO has been extensively investigated using humic acid as a chemically complex environmental photosensitizer. ,,, Importantly, studies combining computation and experiment have found that the UV–vis absorption of m-DOM falls within the actinic region and therefore opens up a potential photosensitization pathway due to m-DOM. − Additionally, we have recently shown that broadband irradiation (λ > 280 nm) of aqueous nitrate solutions containing m-DOM, as well as solutions containing the known photosensitizer 4-benzoyl benzoic acid (4-BBA), enhance HONO formation by a factor of 5 and 3, respectively . The proposed mechanism involves the photosensitizer in its triplet state, abstracting hydrogen from water and producing hydroxyl radicals.…”

Heterogeneous and Photosensitized Oxidative Degradation Kinetics of the Plastic Additive Bisphenol-A in Sea Spray Aerosol Mimics

“…Mimicking the complexity of SSA, we added to the mixture of BPA and NaCl two photosensitizing molecules as substitutes for the chromophoric dissolved organic matter found in SSA: 4-benzoylbenzoic acid (4-BBA) and more complex humic acid (HA). Both 4-BBA and HA have been employed in previous work as representative photosensitizing molecules but notably may lack some of the key photosensitizing properties and chemical features of real chromophoric material present at the ocean surface, which includes enriched levels of nitrogen. , These experiments were performed in the absence and in the presence of NaCl to elucidate possible additive effects on the degradation of BPA by NaCl and the photosensitizers. The decay rates of BPA in the ternary-component aerosol composed of either photosensitizer were considerably higher than those in the binary-component BPA + NaCl aerosol.…”

pH Dependence of the speciation and optical properties of 4-benzoylbenzoic acid

“…A recent analysis by Alves et al shows that CDOM is rich in aromatic ketones, aldehydes, carboxyl alicyclic molecules, among other classes of compounds. 37 Theoretical and experimental investigations of small molecules matching these molecular moieties can provide insights into the optical properties of these more complex light absorbing substances and the role of environmental factors (pH, hydration state etc. ) in these properties.…”