Dimethyl sulfide seawater

Dimethyl sulfoxide occurs widely at levels of <3 ppm. It has been isolated from spearmint oil, com, barley, malt, alfalfa, beets, cabbage, cucumbers, oats, onion, Swiss chard, tomatoes, raspberries, beer, coffee, milk, and tea (5). It is a common constituent of natural waters, and it occurs in seawater in the 2one of light penetration where it may represent a product of algal metaboHsm (6). Its occurrence in rainwater may result from oxidation of atmospheric dimethyl sulfide, which occurs as part of the natural transfer of sulfur of biological origin (7,8). 

Sulfur dioxide occurs in industrial and urban atmospheres at 1 ppb—1 ppm and in remote areas of the earth at 50—120 ppt (27). Plants and animals have a natural tolerance to low levels of sulfur dioxide. Natural sources include volcanoes and volcanic vents, decaying organic matter, and solar action on seawater (28,290,291). Sulfur dioxide is beHeved to be the main sulfur species produced by oxidation of dimethyl sulfide that is emitted from the ocean. 

The vast majority of sulfur at any given time is in the lithosphere. The atmosphere, hydrosphere, and biosphere, on the other hand, are where most transfer of sulfur takes place. The role of the biosphere often involves reactions that result in the movement of sulfur from one reservoir to another. The burning of coal by humans (which oxidizes fossilized sulfur to SO2 gas) and the reduction of seawater sulfate by phytoplankton which can lead to the creation of another gas, dimethyl sulfide (CH3SCH3), are examples of such processes. 

Dimethyl sulfide is derived primarily from the enzymatic hydrolysis of dimethylsulfoniopropionate(CH3)2S+CH2CH2COO DMSP),an osmoregulatory compound produced by a wide variety of marine phytoplankton [313,317]. Intracellular DMSP hydrolysis has been shown in phytoplankton [318], in macro algae [319], and also in bacteria following uptake of DMSP from seawater [320]. Reported seawater concentrations of dissolved dimethyl sulfide (< 0.1-90 nM) and DMSP (1 -1000 nM) vary with increasing depth, spatially from coastal areas to the open ocean, and also temporally from winter to summer [313-316]. 

Dimethyl sulfide (DM) and dimethyl disulfide have been measured in seawater and in the atmosphere by gas chromatography [309] and by GC-MS [310]. Some variety of cryogenic trapping is often used. 

Leek and Baagander [311] determined reduced sulfide compounds in seawater by gas chromatography using a flame ionisation detector. Substances determined include methyl mercaptan, dimethyl sulfide, hydrogen sulfide and carbon disulfide. Detection limits range from 0.2ng/l (carbon disulfide) to 0.6 ng/1 (methyl mercapton). 

Andreae [324,325] has described a gas chromatographic method for the determination of nanogram quantities of dimethyl sulfoxide in natural waters, seawater, and phytoplankton culture waters. The method uses chemical reduction with sodium borohydride to dimethyl sulfide, which is then determined gas-chromatographically using a flame photometric detector. 

Dimethyl sulfide and other volatile organic compounds have been determined in amounts down to 0.1pg/l in seawater in a method described by Watanabe et al. [329]. 

Similar data for sulfate have been reported in many studies. Figure 9.36, for example, shows overall average sulfate distributions measured in marine areas as well as at continental sites (Milford and Davidson, 1987). The marine data show two modes, a coarse mode associated with sea salt and a fine mode associated with gas-to-particle conversion. Sulfate in seawater, formed, for example, by the oxidation of sulfur-containing organics such as dimethyl sulfide, can be carried into the atmosphere during the formation of sea salt particles by processes described earlier and hence are found in larger particles. The continental data show only the fine particle mode, as expected for formation from the atmospheric oxidation of the S02 precursors. 

Wong, P.K., Wang, Y.H. (1997) Determination of the Henry s law constant for dimethyl sulfide in seawater. Chemosphere 35, 535-544. 

Kiene, R.P. (1990) Dimethyl sulfide production from dimethylsulfoniopropionate in coastal seawater samples and bacterial cultures. Appl. Environ. Microbiol. 56, 3292-3297. 

Turner SM, Nightingale PD, Spokes LJ, Liddicoat MI, and Liss PS (1996) Increased dimethyl sulfide concentrations in seawater from in situ iron enrichment. Nature 383 513-517. 

Other organic components of seawater have also been the subject of intercalibrations. Two laboratories compared their methods of analysis for dimethyl sulfide in water [54]. The values found for seawater samples were comparable, but heavy cultures of phytoplankton produced differences which may have been related to the physiological state of the organisms and the methods used in sample preparation. 

Measurements of dimethyl sulfide (DMS) along smface transects and on vertical profiles across the East China Sea (ECS) continental shelf show that its concentrations in the smface seawater ranged from 64 to 180 ng/L and that its vertical distribution was divided into 3 types. Model calculations of a stagnant film show a DMS flux of 10.6 p,mol/(m -d) across the air-sea interface (Yang et al., 1996). 

Well over 100 compounds have been determined in seawater (and sediments) using a considerable variety of techniques (Table 2). Methods include n-and branched alkanes (up to about C20, pristane/ phytane), alkenes and aromatic compounds (up to the disubstituted naphthalenes), halocarbons and chlorinated aromatic species, low relative molecular mass alcohols, organic sulfur compounds (notably dimethyl sulfide, a major product of some phytoplankton species, but ranging up to dimethyl trisulfide), and freons (11, 12, and 113 used in studies of oceanic mixing). 

In 2003, the HLCs for six volatile coffee flavor compounds in pure water and in liquid coffee were measured with dynamic measurements [145]. The partition coefficients in pure water and coffee were significantly different for ethyl-2-methylbutyrate and barely different for 2-methylpropanal. For 2-methyIbutanal, 3-methylbutanal, dimethyl sulfide, and dimethyl disulfide, however, the values were indistinguishable in pure water and coffee within the experimental precision. Moreover, this method was first used to measure acetone concentrations in the surface seawater by Holzinger et al. [194]. At present, the detailed description about the quantification of dissolved dimethyl sulfide in seawater using HLC was reported in 2009, and the HLC of dimethyl sulfide and its temperature dependence were considered [196] ... 

Kameyama, S., Tanimoto, H., Inomata, S., Tsunogai, U., Ooki, A., Yokouchi, Y, Takeda, S., Obata, H., Uematsu, M. (2009) Equilibrator inlet-proton transfer reaction-mass spectrometry (EI-PTR-MS) for sensitive, high-resolution measurement of dimethyl sulfide dissolved in seawater. Analytical Chemistry, 81, 9021-9026. 

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