Determination of atmospheric methyl bromide by cryotrapping-gas chromatography and application to soil kinetic studies using a dynamic dilution system.
Determination of atmospheric methyl bromide by cryotrapping-gas chromatography and application to soil kinetic studies using a dynamic dilution system.
复制标题
通过冷冻捕集气相色谱法测定大气中的甲基溴，并使用动态稀释系统应用于土壤动力学研究。
作者：
Ruth A. Kerwin;P. Crill;Robert W. Talbot;Mark E. Hines;J. Shorter;Charles E. Kolb;R. Harriss
甲基溴（CH(3)Br）被认为是平流层Br的主要来源，它有助于破坏臭氧。因此，有必要了解这种化合物的自然汇，并准确地测量环境混合比。介绍了低温俘获-气相色谱法测定大气中CH(3)Br的方法及其在土壤动力学中的应用。使用2-丙醇/干冰冷冻器在标准样品和空气样品中预浓缩CH(3)Br，随后使用配备O(2)掺杂电子捕获检测器（GC-ECD）的气相色谱仪进行检测。GC-ECD低温捕集法的检出限为0.23 pmol。这相当于500毫升环境空气样本中CH(3)Br的含量，估计北半球大气混合比为11万亿分之一（pptv）。开发了一种动态稀释系统，以产生混合比在4和1000 pptv之间的CH(3)Br。采用动态土壤培养法，利用稀释系统产生的校准的CH(3)Br混合比来确定土壤吸收动力学。
Methyl bromide (CH(3)Br) is considered to be a major source of stratospheric Br, which contributes to the destruction of ozone. It is therefore necessary to understand the natural sinks of this compound and to accurately measure ambient mixing ratios. Methodology is described for the measurement of atmospheric CH(3)Br by cryotrapping-gas chromatography and its application to soil kinetics. A 2-propanol/dry ice cryotrap was used to preconcentrate CH(3)Br in standard and air samples, with subsequent detection using a gas chromatograph equipped with an O(2)-doped electron capture detector (GC-ECD). The GC-ECD cryotrapping method had a detection limit of 0.23 pmol of CH(3)Br. This is equivalent to the amount of CH(3)Br in a 500 mL sample of ambient air at the estimated northern hemisphere atmospheric mixing ratio of 11 parts per trillion by volume (pptv). A dynamic dilution system was developed to produce mixing ratios of CH(3)Br ranging between 4 and 1000 pptv. Calibrated mixing ratios of CH(3)Br produced with the dilution system were used to determine soil uptake kinetics employing a dynamic soil incubation method.