Methyl from wetlands

Natural acidity is contributed from emissions of acidic or acidifying compounds from volcanoes (Pyle et al., 1996 Camuffo, 1992), including compounds of S, N, Cl (chloride), and NH3 (ammonia), from the ocean (e.g., methyl sulfonate) (Charlson et al., 1987), and from wetlands (e.g., H2S) (Gorham et al., 1987). 

In random samples of soil taken from five Alabama counties, only 3 of 46 soil samples contained methyl parathion. The concentration in these samples was <0.1 ppm (Albright et al. 1974). Aspartofthe National Soils Monitoring Program, soil and crop samples from 37 states were analyzed for methyl parathion during 1972. Methyl parathion was detected in only 1 soil sample, at a concentration of <0.1 ppm and taken from South Dakota, out of 1,246 total samples taken from the 37 states (Carey et al. 1979). In soil and sediment samples collected from a watershed area in Mississippi, methyl parathion was not detected in the soil samples. In three wetland sediment cores, however, measurable concentrations of methyl parathion were detected during application season (Cooper 1991). 

Mercury in soil is not only likely to have a different potential for evasion and methylation than Hg in runoff, but soil Hg may be perturbed by land disturbance. Land disturbances that are particularly relevant to Hg cycling include the formation of wetlands and flooding of reservoirs (Rudd 1995 see Chapter 3). Disturbances such as clear-cutting can also result in marked increases in the release of THg and MeHg from soils (Munthe and Hultbeig 2003 Porvari et al. 2003). Fire can result in large Hg losses by volatilization (Grigal 2002). 

Three novel phenanthrenes have been isolated from the wetland plant Juncus acutus. The structures of the novel phenanthrenes were established as 2-hydroxy-l,6-dimethyl-5-vinyl-phenanthrene (320), 2,7-dimethoxy-l,6-dimethyl-5-vinylphenanthrene (321) and 2-hydroxy-6-hydroxymethyl-l-methyl-5-vinyl-phenanthrene (322) [164, 165]. In spite of the great number of 9,10-dihydrophenanthrenes, only quite a small number of phenanthrenes have been reported until now as constituents of Juncaceae. 

Typical organic precursors for COS, CS2 and the methylated sulfur gases include methionine and cysteine from proteins and isothiocyanates and thiocyanates from plant secondary metabolites. Methanethiol and DMS are also formed in anoxic freshwater sediments from reactions based on H2S and various methyl donors, for example, methoxylated aromatic acids, such as syringic acid from lignins. The rates of DMS emission per unit area are similar for both the oceans and Sphagnum-AommattA wetlands. Only the area of this peat land limited the relative importance of the latter source. 

The work performed in Kejimkujik Park, Nova Scotia demonstrates that substantial mercury bioaccumulation can occur in remote areas where no abnormal sources of mercury exist. The mass balance preformed at BDW Lake in Kejimkujik Park, showed that movement of atmospheric mercury from the terrestrial catchment to wetland areas is the primary source of methyl mercury to the lake. Mercury volatilization was found to be an important process in this basin with annual volatilization equaling 46% of the mercury deposited by precipitation over the entire lake basin. This paper demonstrates that mercury speciation must be known to reliably predict the effect of anthropogenic influences on a regional and global scale. 

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