title: Spatial distributions of and diurnal variations in low molecular weight carbonyl compounds in coastal seawater, and the controlling factors.
abstract: We studied the spatial distributions of and the diurnal variations in four low molecular weight (LMW) carbonyl compounds, formaldehyde, acetaldehyde, propionaldehyde, and glyoxal, in coastal seawater. The samples were taken from the coastal areas of Hiroshima Bay, the Iyo Nada, and the Bungo Channel, western Japan. The formaldehyde, acetaldehyde, and glyoxal concentrations were higher in the northern part of Hiroshima Bay than at offshore sampling points in the Iyo Nada and the Bungo Channel. These three compounds were found at much higher concentrations in the surface water than in deeper water layers in Hiroshima Bay. It is noteworthy that propionaldehyde was not detected in any of the seawater samples, the concentrations present being lower than the detection limit (1 nanomole per liter (nM)) of the high performance liquid chromatography (HPLC) system we used. Photochemical and biological experiments were performed in the laboratory to help understand the characteristic distributions and fates of the LMW carbonyl compounds. The primary process controlling their fate in the coastal environment appears to be their biological consumption. The direct photo degradation of propionaldehyde, initiated by ultraviolet (UV) absorption, was observed, although formaldehyde and acetaldehyde were not degraded by UV irradiation. Our results suggest that the degradation of the LMW carbonyl compounds by photochemically formed hydroxyl radicals is relatively insignificant in the study area. Atmospheric deposition is a possible source of soluble carbonyl compounds in coastal surface seawater, but it may not influence the carbonyl concentrations in offshore waters.
authors: Graduate School of Biosphere Science, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan. Electronic address: takedaq@hiroshima-u.ac.jp.
authors: Kazuhiko
authors: K
authors: Takeda
authors: Graduate School of Biosphere Science, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan.
authors: Shinya
authors: S
authors: Katoh
authors: Graduate School of Biosphere Science, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan.
authors: Yumi
authors: Y
authors: Mitsui
authors: Graduate School of Biosphere Science, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan.
authors: Shinichi
authors: S
authors: Nakano
authors: Graduate School of Biosphere Science, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan; Department of Environmental and Symbiotic Sciences, Rakuno Gakuen University, 582 Bunkyodai-Midorimachi, Ebetsu, Hokkaido 069-8501, Japan.
authors: Nobutake
authors: N
authors: Nakatani
authors: Graduate School of Biosphere Science, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan.
authors: Hiroshi
authors: H
authors: Sakugawa
mesh_terms: D000079:Acetaldehyde / Q000032:analysis*; D000447:Aldehydes / Q000032:analysis*; D004784:Environmental Monitoring; D005557:Formaldehyde / Q000032:analysis*; D007564:Japan; D008970:Molecular Weight; D012623:Seawater / Q000737:chemistry; D062211:Spatio-Temporal Analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D000447:Aldehydes; D014874:Water Pollutants, Chemical; D005557:Formaldehyde; C005556:propionaldehyde; D000079:Acetaldehyde
keywords: Coastal seawater; Hydroxyl radical; Low molecular weight carbonyl compounds; Photochemical reaction