Modification of an Isotope Dilution GC/MS System for Atmospheric Chemistry Experiments on Ships and Aircrafts Under Turbulent Conditions

PIS在美国国家科学基金会授予ATM-8717861的资助下开发了一种气相色谱/质谱仪(GC/MS)，并将其与同位素标记的内标联用，用于近实时测定大气中的二氧化硫、二甲基硫化物、二硫化碳和羰基硫化物。在目前的配置中，GC/MS可用于在相对温和的湍流条件下进行测量，例如在海洋混合层中遇到的情况。这四种化合物可以用同时采集的空气样本以每8分钟一种的平均频率进行测量。PIS计划改装样品处理和校准系统，以实现3分钟的响应时间，检测下限为1pptv(以体积计)，精度为1pptv。他们还计划安装涡轮分子泵，允许在大陆边界层的飞机和大范围海况下的船舶上出现湍流条件下不间断地使用GC/MS。有了这一增加的能力，GC/MS可以用于进行大气化学实验，这些实验旨在评估硫气体的通量和收支，测量硫气体的海洋-大气交换，研究OCS和CS2的源和汇，以及研究二甲基硫和二氧化硫的化学转化及其通过对流层气溶胶形成影响气候的作用。

The PIs developed a gas chromatograph/mass spectrometer (GC/MS) under NSF grant ATM-8717861 and coupled it with isotopically labeled internal standards for near real-time determinations of sulfur dioxide (SO2), dimethyl sulfide (DMS), carbon disulfide (CS2), and carbonyl sulfide (OCS) in the atmosphere. In its present configuration, the GC/MS can be used for measurements in relatively mild turbulent conditions such as those encountered in the marine mixed layer. These four compounds can be measured with an average frequency of one per 8 minutes using simultaneously collected air samples. The PIs plan to modify the sample handling and calibration systems to achieve response times of three minutes with detection limits of 1 part-per-trillion by volume (pptv) with a precision of 1 pptv. They also plan to install a turbomolecular pump that will allow uninterrupted use of the GC/MS under the turbulent conditions that occur in aircraft in the continental boundary layer and on ships under a wide range of sea states. With this added capability the GC/MS could be used to conduct atmospheric chemistry experiments which are designed to evaluate fluxes and budgets of sulfur gases, to measure ocean-atmosphere exchange of sulfur gases, to study sources and sinks of OCS and CS2, and to study chemical transformation of dimethyl sulfide and sulfur dioxide and their role in affecting climate via aerosol formation in the troposphere.