Wavelength- and Temperature-Dependent Apparent Quantum Yields for Photochemical Production of Carbonyl Compounds in the North Pacific Ocean.
Wavelength- and Temperature-Dependent Apparent Quantum Yields for Photochemical Production of Carbonyl Compounds in the North Pacific Ocean.
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DOI：
10.1021/acs.est.7b05462
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发表时间：
2017-12
影响因子：
11.4
通讯作者：
Yuting Zhu;D. Kieber
中科院分区：
文献类型：
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作者：
Yuting Zhu;D. Kieber
溶解有机物的光解是阳光照射下的海水中羰基化合物的主要来源，但速率和光效率受到很大的限制。测定了北太平洋海水中乙醛、乙二醛和甲基乙二醛光化学生成的波长和温度依赖的表观量子产率（AQY）。在290 ~ 380 nm波长范围内，20 °C时的波长依赖性AQY随波长的增加呈指数下降，乙醛、乙二醛和丙酮醛的AQY分别从1.29 × 10-4下降到4.12 × 10-6、2.52 × 10-5下降到6.89 × 10-7和4.37 × 10-6下降到1.25 × 10-7 mol（mol quanta）-1。AQYs在310 nm处照射6 h后下降，可能是由于光化学前体或羰基光解的耗尽。乙醛、乙二醛和甲基乙二醛在320 nm处光化学生成的平均活化能（95% CI）分别为9.31（±9.3）、26.0（±7.5）和34.7（±12.8）kJ mol-1。表层海水中光化学产生率的峰值响应为λ 325 nm，其中λ 30%来自UV-B，λ 70%来自UV-A。计算中午波长积分光产率分别为0.5-0.8，0.04-0.2，和0.03-0.06 nmol L-1 h-1的乙醛，乙二醛，和甲基乙二醛，分别在8月无云条件下。结果可用于确定这些化合物在海洋表面的区域规模的光化学生产率。
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 × 10-4 to 4.12 × 10-6, 2.52 × 10-5 to 6.89 × 10-7, and 4.37 × 10-6 to 1.25 × 10-7 mol (mol quanta)-1 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-1 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-1 h-1 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.