Department of Chemistry, State University of New York, College of Environmental Science and Forestry , 1 Forestry Drive, Syracuse, New York 13210, United States.
Environ Sci Technol. 2018 Feb 20;52(4):1929-1939. doi: 10.1021/acs.est.7b05462. Epub 2018 Jan 30.
Photolysis of dissolved organic matter is the main source of carbonyl compounds in sunlit seawater, but rates and photoefficiences are poorly constrained. Wavelength- and temperature-dependent apparent quantum yields (AQYs) were determined for photochemical production of acetaldehyde, glyoxal, and methylglyoxal in North Pacific Ocean seawater. Wavelength-dependent AQYs at 20 °C decreased exponentially with increasing wavelength between 290 and 380 nm, from 1.29 × 10 to 4.12 × 10, 2.52 × 10 to 6.89 × 10, and 4.37 × 10 to 1.25 × 10 mol (mol quanta) for acetaldehyde, glyoxal, and methylglyoxal, respectively. AQYs decreased after 6 h irradiation at 310 nm, possibly due to depletion of photochemical precursors or carbonyl photolysis. Average activation energies (95% CI) for photochemical production at 320 nm were 9.31 (±9.3), 26.0 (±7.5), and 34.7 (±12.8) kJ mol for acetaldehyde, glyoxal, and methylglyoxal, respectively. The peak response for photochemical production rates in surface seawater was ∼325 nm, with ∼30% contribution from UV-B and ∼70% from UV-A. Computed noontime wavelength-integrated photoproduction rates were 0.5-0.8, 0.04-0.2, and 0.03-0.06 nmol L h for acetaldehyde, glyoxal, and methylglyoxal, respectively, under cloudless conditions in August. Results can be used to determine regional-scale photochemical production rates for these compounds in the surface ocean.
溶解有机物的光解是阳光照射海水中海羰基化合物的主要来源，但速率和光效率约束较差。在北太平洋海水中，确定了光化学产生乙醛、乙二醛和甲基乙二醛的波长和温度依赖性表观量子产率（AQY）。在 20°C 时，波长依赖性 AQY 随 290 至 380nm 之间的波长增加呈指数下降，分别为 1.29×10 至 4.12×10、2.52×10 至 6.89×10 和 4.37×10 至 1.25×10 mol（mol 量子），对于乙醛、乙二醛和甲基乙二醛分别为。在 310nm 下照射 6 小时后，AQY 下降，可能是由于光化学前体耗尽或羰基光解。在 320nm 下光化学产生的平均活化能（95%CI）分别为 9.31（±9.3）、26.0（±7.5）和 34.7（±12.8）kJ mol，用于乙醛、乙二醛和甲基乙二醛。在表层海水中，光化学产生速率的峰值响应约为 325nm，其中来自 UV-B 的贡献约为 30%，来自 UV-A 的贡献约为 70%。在 8 月无云条件下，计算得出正午波长积分光生产量分别为 0.5-0.8、0.04-0.2 和 0.03-0.06 nmol L h，用于乙醛、乙二醛和甲基乙二醛。结果可用于确定这些化合物在表层海洋中的区域尺度光化学产生速率。
