کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5746038 1618785 2017 12 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Photochemical oxidation of dimethylsulphide to dimethylsulphoxide in estuarine and coastal waters
ترجمه فارسی عنوان
اکسیداسیون عکس شیمیایی از دی متیل سولفید به دی متیل سولفوکسید در آب های استواری و ساحلی
موضوعات مرتبط
علوم زیستی و بیوفناوری علوم محیط زیست شیمی زیست محیطی
چکیده انگلیسی


- We observed 1:1 M conversion of DMS to DMSO in estuarine waters.
- This suggests that DMS photo-oxidation occurred via the CDOM sensitised 1O2 pathway.
- Photochemical rate constants decreased ∼10-fold from river to seawater.
- Rate constants were strongly correlated with CDOM absorption coefficients (a350).
- a350-normalised rate constants increased ∼10-fold from river to seawater.

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−1 to 0.345 h−1) and DMSO photo-production (0.017 h−1 to 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 a350 explained 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−1 for 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.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Chemosphere - Volume 186, November 2017, Pages 805-816
نویسندگان
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