Potential effect of atmospheric condition on incident light and photo-production of reactive intermediates in freshwater systems

Abstract

The effect of local atmospheric conditions on aquatic photochemical reactions has been rarely explored because of the difficulty in field observation. Thus, this study aimed to elucidate the effects of atmospheric conditions, which are inorganic air pollution, aerosol pollution, and ozone layer depletion, on the incident light and photo-production of reactive intermediates (RIs). Models of SMARTS (Simple Model for the Atmospheric Radiative Transfer of Sunshine) and APEX (Aqueous Photochemistry of Environmentally occurring Xenobiotics) were used to simulate the changes in wavelength profile and steady-state concentrations of RIs, which are hydroxyl radical, carbonate radical, singlet oxygen, and triplet-state of dissolved organic matter. Results showed that inorganic air pollution and aerosol pollution have a reduction effect on the production of RIs, while ozone layer depletion increases the production of RIs. Among them, inorganic air pollution has the largest influence on the production of RIs which were expected to reduce by 80%–90% in extreme pollution. This study also investigated the potential effect of water constituents (i.e., NO3−, dissolved organic matter, and HCO3−) on the relation between atmospheric conditions and the production of RIs. NO3− concentration under different atmospheric conditions showed the most influence on the production of RIs. This study highlighted the importance of considering atmospheric conditions when assessing the photochemical persistence of organic pollutants. Even though these results are model output, they quantitatively revealed the potential influence of atmospheric conditions on the production of RIs in freshwater systems.