Isotopic fingerprints of carbonyl sulfide (COS) in atmosphere and biosphere

羰基硫化物（COS）是二氧化碳的硫类似物。它是大气中最丰富的含硫化合物，寿命为2至4年。COS有工业和自然来源，主要是海洋。其主要吸收源是植物和土壤的吸收，但由于其寿命长，一些COS到达平流层，在平流层进行光解和氧化成硫酸盐，形成平流层气溶胶层（图1）。这一层对臭氧化学、辐射平衡和地球气候至关重要。就像CO2一样，COS在光合作用过程中被吸收，但在呼吸过程中不被释放，使其成为总初级生产力的示踪剂（Asaf et al. 2013）。然而，植物和土壤吸收的重叠限制了COS浓度单独用于这一目的。同位素测量最近被用于指纹识别COS源和汇，包括大气氧化途径，并可能区分植物和土壤的吸收。一种新的在线COS同位素分析方法将用于13C和34S的测量（Hattori et al. 2015），并进一步扩展到多同位素（13C16O34S），使用世界范围内独特的分析仪和检测器配置的质谱仪。利用富含COS的大气测定土壤和植被对COS的吸收过程中的同位素分馏，从而对不同COS汇的相对贡献提供约束条件。在实际光照条件下，COS光解过程中的同位素分馏将被测量并用于验证平流层硫酸盐气溶胶收支。最后，该方法将应用于存档的对流层和平流层样品，以改善用于总光合速率量化的COS全球预算。人员规格和培训本项目需要良好的定量分析和实验技能。化学、物理或地球科学专业毕业。将提供同位素质谱、气体和真空系统、仪器控制和数值数据分析方面的培训。任何科学知识的空白都可以通过参加讲授的课程来填补，例如生物地球化学循环和大气化学。该项目包括访问荷兰的国际合作者。

BackgroundCarbonyl sulfide (COS) is a sulfur-analogue of CO2. It is the most abundant atmospheric sulfur compound and has a lifetime of 2 to 4 years. COS has industrial and natural sources, mostly the oceans. Its main sinks are plant and soil uptake, but due to its long lifetime, some COS reaches the stratosphere where it undergoes photolysis and oxidation to sulfate and forms the stratospheric aerosol layer (Fig. 1). This layer is of key importance for ozone chemistry, the radiation balance and Earth's climate. Just as CO2, COS is taken up during photosynthesis, but not released during respiration, making it a tracer for gross primary productivity (Asaf et al. 2013). However, overlap of plant and soil uptake limit the use of COS concentration alone for this purpose. Isotope measurements have recently found applications in fingerprinting COS sources and sinks including atmospheric oxidation pathways, and can potentially distinguish between plant and soil uptake.MethodologyA novel online method for isotope analysis of COS will be used for 13C and 34S measurements (Hattori et al. 2015) and further extended to polyisotopologues (13C16O34S) on mass-spectrometers with worldwide unique analyser and detector configurations.The isotope fractionation during COS uptake by soils and vegetation will be determined using COS-enriched atmospheres, in order to provide constraints on the relative contributions of different COS sinks. Isotope fractionation during COS photolysis under realistic light conditions will be measured and used to verify the stratospheric sulfate aerosol budget.Finally, the new method will be deployed on archived tropospheric and stratospheric samples to improve the global budget of COS for the quantification of gross photosynthesis rates.Person specification and trainingThis project requires good quantitative-analytical and experimental skills. A degree in chemistry, physics or earth sciences is desirable. Training will be provided in isotope mass spectrometry, gas and vacuum systems, instrument control and numerical data analysis. Any scientific knowledge gaps can be filled by attending taught courses, e.g. in biogeochemical cycles and atmospheric chemistry. The project includes visits to international collaborators in the Netherlands.