Photochemical oxidation of dimethylsulphide to dimethylsulphoxide in estuarine and coastal waters.
Photochemical oxidation of dimethylsulphide to dimethylsulphoxide in estuarine and coastal waters.
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DOI：
10.1016/j.chemosphere.2017.08.050
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发表时间：
2017-11
期刊：
影响因子：
8.8
通讯作者：
G. Uher;J. Julian Pillans;Angela D. Hatton;R. Upstill‐Goddard
中科院分区：
文献类型：
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作者：
G. Uher;J. Julian Pillans;Angela D. Hatton;R. Upstill‐Goddard
对英格兰东北部(泰恩河口)和苏格兰西部(泰恩河和泰努伊尔特纳特河)的26个海岸样品的二甲基硫化物(DMS)光氧化和二甲基亚硫醚(DMSO)光产生进行了估算。二甲基亚砜光氧化(0.038 h−1~0.345 h−1)和二甲基亚砜光解(0.017 h−1~0.283 h−1)的准一级速率常数变化一个数量级，北海沿岸最低。河口样品(盐度S)的平均DMSO产率为96%±116%(n=414)，符合单线态氧光敏氧化1：1 Mm的转化率。光化学速率常数与有色溶解有机物(CDOM)在350 nm、A350处的吸收系数密切相关。A350的变异分别解释了DMS光氧化和DMSO产生的61%(R2=0.61，n=0.26)和73%(R2=0.73，n=0.17)的变异。然而，CDOM归一化光化学速率常数在CDOM吸光度最低的沿海水域急剧增加，表明具有海洋性质的水样(S)对DMS光氧化反应最活跃。水柱平均DMS光氧化速率常数的估计，通过尺度到平均日辐照度(英格兰东北部7月)和中UV水下辐照度，估计为0.012 d−1，0.019 d−1和0.017 d−1，在以前观测的下端，在河口上游(S)，河口下部(20)和S(30)和近海(S)。将我们的水柱平均DMS光氧化速率常数与通过气-海气体交换估计的DMS损失以及之前报道的生物消耗进行比较，表明DMS的光化学去除在我们的研究区域中只是次要的。
Dimethylsulphide (DMS) photo-oxidation and dimethylsulphoxide (DMSO) photoproduction were estimated in 26 laboratory irradiations of coastal samples from NE England (Tyne estuary) and W Scotland (Loch Linnhe and River Nant at Taynuilt). Pseudo-first order rate constants of DMS photo-oxidation (0.038 h−1to 0.345 h−1) and DMSO photo-production (0.017 h−1to 0.283 h−1) varied by one order of magnitude and were lowest in the coastal North Sea. Estuarine samples (salinity S < 30) had a mean DMSO yield of 96 ± 16% (n = 14), consistent with 1:1 M conversion via photosensitised oxidation by singlet oxygen. Photochemical rate constants were strongly correlated with coloured dissolved organic matter (CDOM) absorption coefficients at 350 nm, a350. Variations in a350explained 61% (R2= 0.61, n = 26) and 73% (R2= 0.73, n = 17) of the variability in DMS photo-oxidation and DMSO production, respectively. However, CDOM normalised photochemical rate constants increased strongly towards coastal waters exhibiting lowest CDOM absorbance, indicating water samples of marine character (S > 30) to be most reactive with respect to DMS photo-oxidation. Estimates of water column averaged DMS photo-oxidation rate constants, obtained by scaling to mean daily irradiance (July, NE England) and mid-UV underwater irradiance, were 0.012 d−1, 0.019 d−1, and 0.017 d−1for upper estuary (S < 20), lower estuary (20 < S < 30) and coastal waters (S > 30), at the lower end of previous observations. Comparing our water column averaged DMS photo-oxidation rate constants with estimated DMS losses via air-sea gas exchange and previously reported biological consumption implies that DMS photochemical removal is of only minor importance in our study area.