Rhew R C, Miller B R, Weiss R F
Scripps Institution of Oceanography, University of California at San Diego, La Jolla 92093-0244, USA.
Nature. 2000 Jan 20;403(6767):292-5. doi: 10.1038/35002043.
Atmospheric methyl bromide (CH3Br) and methyl chloride (CH3Cl), compounds that are involved in stratospheric ozone depletion, originate from both natural and anthropogenic sources. Current estimates of CH3Br and CH3Cl emissions from oceanic sources, terrestrial plants and fungi, biomass burning and anthropogenic inputs do not balance their losses owing to oxidation by hydroxyl radicals, oceanic degradation, and consumption in soils, suggesting that additional natural terrestrial sources may be important. Here we show that CH3Br and CH3Cl are released to the atmosphere from all vegetation zones of two coastal salt marshes. We see very large fluxes of CH3Br and CH3Cl per unit area: up to 42 and 570 micromol m(-2) d(-1), respectively. The fluxes show large diurnal, seasonal and spatial variabilities, but there is a strong correlation between the fluxes of CH3Br and those of CH3Cl, with an average molar flux ratio of roughly 1:20. If our measurements are typical of salt marshes globally, they suggest that such ecosystems, even though they constitute less than 0.1% of the global surface area, may produce roughly 10% of the total fluxes of atmospheric CH3Br and CH3Cl.
大气中的甲基溴（CH₃Br）和甲基氯（CH₃Cl）是与平流层臭氧消耗有关的化合物，它们源于自然和人为来源。目前对海洋源、陆地植物和真菌、生物质燃烧以及人为输入所产生的CH₃Br和CH₃Cl排放量的估计，无法平衡因羟基自由基氧化、海洋降解和土壤消耗而导致的损失，这表明可能还存在重要的额外自然陆源。在此，我们表明CH₃Br和CH₃Cl从两个沿海盐沼的所有植被区释放到大气中。我们观察到单位面积的CH₃Br和CH₃Cl通量非常大：分别高达42和570微摩尔·米⁻²·天⁻¹。这些通量表现出很大的昼夜、季节和空间变异性，但CH₃Br通量与CH₃Cl通量之间存在很强的相关性，平均摩尔通量比约为1:20。如果我们的测量结果在全球盐沼中具有代表性，那么这表明此类生态系统尽管占全球表面积不到0.1%，却可能产生大气中CH₃Br和CH₃Cl总通量的约10%。
