Colored dissolved natural organic matter (CDOM) and effluent organic matter (EfOM) are important aquatic photosensitizers. They can alter the fate of organic pollutants through the production of reactive oxygen species, including singlet oxygen (1O2). Recent reports demonstrate higher 1O2 quantum yields (Φ1O2) for EfOM than CDOM, suggesting that PPCPs in wastewater-impacted waterways may photodegrade more rapidly. Predicting 1O2 production rates requires knowledge of the Φ1O2 wavelength dependence. Traditionally, a discrete wavelength approach using band pass filters has been used to determine the spectral distribution of Φ1O2. This approach, however, is time-consuming due to low intensities of light and the limitation that only one sample can be irradiated at a time. Recently, a polychromatic approach was used to determine the wavelength dependence of hydrogen peroxide quantum yields in seawater (Kieber et al., 2014), but this approach has not been applied to other reactive species generated by CDOM. We are exploring the polychromatic approach as a method to determine the wavelength dependence of Φ1O2 for CDOM and EfOM isolated with Bond Elut PPL cartridges. A solar simulator and a series of eight long pass filters with increasing cutoff wavelengths are used to simultaneously irradiate up to 16 samples at a time. To generate the spectral distribution of Φ1O2, furfuryl alcohol (FFA) is used as a chemical probe to determine the steady state concentration of 1O2. CDOM samples showed an increase in Φ1O2 (ranging from 2.9 to 6.5%) with decreasing wavelength, 390 to 315nm. The EfOM samples displayed a similar trend but the Φ1O2 ranged from 3.1 to 10.5% over the same wavelengths. The trend obtained with the polychromatic system generally agrees with the discrete wavelength approach, but there are some discrepancies. These are suspected to arise from the method used to estimate the light intensity at wavelengths where the para-nitroanisole/pyridine actinometer had limited applicability. Ongoing work is aimed at refining the actinometry method by exploring other actinometers, such as ferrioxalate for longer wavelengths and coupling actinometry with radiometry. 1. Kieber, D.J.; Miller, G.W.; Neale, P.J.; Mopper, K. Environ. Sci.: Processes Impacts, 2014, 16, 777-791

Polychromatic method to determine the wavelength dependence of singlet oxygen quantum yields for natural and effluent organic matter

249th National Meeting (2015)

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