کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
26573 | 43964 | 2011 | 7 صفحه PDF | دانلود رایگان |
Low molecular weight carbonyl compounds are produced photochemically from chromophoric dissolved organic matter (CDOM) in natural waters. Photoproduction rates for formaldehyde, acetaldehyde and acetone were measured in the laboratory using a pre-column 2,4-dinitrophenylhydrazine derivitization HPLC method as a function of optical properties (absorption coefficient, spectral slope) and irradiation time. Rates decreased linearly with decreasing absorption coefficient at 350 nm (a(350 nm)), a measure of CDOM levels, with substantial variability in low a(350 nm) beach waters. Apparent quantum yields (Θ) were unchanged for a(350 nm) = 2–16 m−1, but increased rapidly (×5) for beach waters with low a(350 nm) values. Θ increased linearly with increasing spectral slope for beach waters, consistent with enhanced production efficiency with photobleaching of CDOM in coastal waters. Θ trends with oxygen and molecular reaction probes (hydroxyl radical scavengers and producers) suggested a combination of direct photolysis and singlet oxygen quenching as primary production mechanisms.
► Low molecular weight carbonyl compounds are produced photochemically from CDOM.
► Photoproduction rates decrease linearly with absorbance in estuarine source waters.
► Photoproduction rates vary significantly in coastal waters with low absorbance values
► Apparent quantum yields increase for coastal waters with higher spectral slopes.
► Direct photolysis and singlet oxygen quenching are primary production mechanisms.
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 226, Issue 1, 15 December 2011, Pages 16–22