A high volume sampling system for isotope determination of volatile halocarbons and hydrocarbons
A high volume sampling system for isotope determination of volatile halocarbons and hydrocarbons
复制标题
用于挥发性卤化碳和碳氢化合物同位素测定的大容量采样系统
DOI：
10.5194/amt-4-2073-2011
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发表时间：
2011
影响因子：
3.8
通讯作者：
W. Michaelis
中科院分区：
文献类型：
--
作者：
E. Bahlmann;I. Weinberg;R. Seifert;C. Tubbesing;W. Michaelis
抽象。挥发性有机化合物（VOCs）的同位素组成可以提供有价值的信息，其来源和命运不能推断出单独的混合比。特别是已报道的不同来源的氯甲烷和溴甲烷的碳稳定同位素比值覆盖了几乎100‰的δ 13 C范围，使得同位素比值成为研究这些化合物的地球化学的非常有前途的工具。迄今为止，C1和C2卤代烃的同位素组成的测定，而不是氯甲烷是阻碍了他们的混合比低。为了确定混合比低至1 pptv的C1和C2卤代烃的碳同位素组成，开发并验证了（i）适合现场的低温大容量采样系统和（ii）用于处理这些样品的色谱装置。在北方德国的城市和沿海两个不同的采样点对采样系统进行了测试。城市地区溴甲烷的平均δ 13 C值为−42.9 ± 1.1‰，与先前发表的结果一致。但在沿海地区，溴甲烷的13 C含量大大增加了近10‰。二氟氯甲烷、1，1，1-三氯乙烷和氯甲烷的差异不太明显。我们认为，这些差异与这些化合物在海洋表面沃茨的营业额。此外，我们还首次报道了碘甲烷（−40.4‰至−79.8‰）、溴仿（−13.8‰至22.9‰）和其他卤烃的碳同位素比值。
Abstract. The isotopic composition of volatile organic compounds (VOCs) can provide valuable information on their sources and fate not deducible from mixing ratios alone. In particular the reported carbon stable isotope ratios of chloromethane and bromomethane from different sources cover a δ13C-range of almost 100‰ making isotope ratios a very promising tool for studying the biogeochemistry of these compounds. So far, the determination of the isotopic composition of C1 and C2 halocarbons others than chloromethane is hampered by their low mixing ratios. In order to determine the carbon isotopic composition of C1 and C2 halocarbons with mixing ratios as low as 1 pptv (i) a field suitable cryogenic high volume sampling system and (ii) a chromatographic set up for processing these samples have been developed and validated. The sampling system was tested at two different sampling sites, an urban and a coastal location in Northern Germany. The average δ13C-values for bromomethane at the urban site were −42.9 ± 1.1‰ and agreed well with previously published results. But at the coastal site bromomethane was substantially enriched in 13C by almost 10‰. Less pronounced differences were observed for chlorodifluoromethane, 1,1,1-trichloroethane and chloromethane. We suggest that these differences are related to the turnover of these compounds in ocean surface waters. Furthermore we report first carbon isotope ratios for iodomethane (−40.4‰ to −79.8‰), bromoform (−13.8‰ to 22.9‰), and other halocarbons.