Light absorption and the photoformation of hydroxyl radical and singlet oxygen in fog waters

Photochemistry of the Cloud Aqueous Phase: A Review

“…To our knowledge, little information is available in the literature concerning measurements of Some work also focuses on the determination of the main precursor of HO • : Kaur and Anastasio [113] determined that the main source of HO • in fog water is due to nitrate photolysis, while Bianco et al [93] showed that 70% to 90% of HO • in cloud water is due to H 2 O 2 . These results could seem to be in contrast but it should be considered that fog water samples collected by Kaur and Anastasio [113] in California and Louisiana (USA) were frozen before analysis and negative temperatures affect the concentration of H 2 O 2 . Moreover, the concentrations of nitrates were up to 1830 µM, one order of magnitude higher than the ones measured in cloud samples by Bianco et al [93].…”

Supplementary material to "Photooxidants from Brown Carbon and Other Chromophores in Illuminated Particle Extracts"

“…i Fraction of calculated sunlight absorption due to inorganic nitrogen (nitrite and nitrate) in each sample. Equations are in Kaur and Anastasio (2017). j Mass absorption coefficient of dissolved organic species at 300 nm for each sample (Eq.…”

“…A value of 1.0 indicates no light screening (Smith et al, 2014;Rehorek and Seidel, 1989). m Average values previously measured in Davis fog samples (n = 4) (Kaur and Anastasio, 2017 "Dilute" (PME1*-2*,3D2.5*) 953 (419) 2.4 (1.9) 749 (580) 80 (101) 20.9 (5.9) 3.8 (1.5) 541 (420) 93.2 (21.9) 38.5 (7.4) 5.2 (2.9) 1.2 (1.1)…”

“…13 (3) 4.8 (1.0) 4.0 (0.8) 0.25 (0.05) 3.3 (0.3) 1.1 (0.2) 11 (2) PME3D0.5 6.6 (1.6) e PME3D1.3 2.4 (0.6) e PME3D2.5* 3.1 (0.1) 1.1 (0.02) 1.3 (0.3) 0.78 (0.19) 2.3 (0.6) e 1.86 (0.03) 8.9 (2.2) PME3D10 0.47 (0.04) 0.17 (0.01) 0.24 (0.02) 4.3 (0.3) 2.0 (0.5) e 1.1 (0.1) 6.1 (0.5) Averages (±σ) "Standard" (PME3-6) 12 (5) 4.2 (1.7) 2.6 (1.0) 1.1 (0.2) 4.7 (1.9) 1.6 (1.3) 7.1 (2.5) "Dilute" (PME1*-2*,3D2.5*) Listed uncertainties (in parentheses) are ± 1 standard error from the errors in inverse plot (1/R * p vs. 1/[Benzene]) parameters, except for the averages (± 1σ) All equations used for these calculations are discussed in Kaur and Anastasio (2017) unless otherwise stated. * Samples extracted in 2.5 mL/filter square and referred to as the "dilute" extracts in the main text.…”

“…-↔ H + + CO 3 2-, K a2 = 4.7E-11 M (pKa2 = 10.3) Thus, the contributions of HCO 3 and CO 3 2to measured k' OH in all PME samples should be negligible. All equations involved in the technique are discussed in Kaur and Anastasio (2017). * Samples extracted in 2.5 mL/filter square and referred to as the "dilute" extracts in the main text.…”