An instrument for high time resolution and chemically speciated monoterpene atmospheric measurements

生物圈的排放(特别是植物和树木的排放)在全球有机化合物进入地球大气层的流量中占主导地位，远远超过了人为来源的排放。单萜烯是一类重要的化学物质，由自然过程释放，其化学结构以十个碳原子为基础。在这类单萜中有数百种不同的化学物种，根据其化学结构的确切性质，它们的反应活性和性质有很大的不同。这类化合物占自然有机排放总量的很大一部分(高达三分之一)，在大气中具有很高的活性；它们在对流层中发生转化，导致臭氧的形成，并作为可凝聚材料的来源，用于形成和改变气雾剂。在陆地环境中，生物萜类和人为排放的混合在一定条件下会导致非常糟糕的空气质量，即使在英国等北欧国家也是如此。为了正确地模拟单萜类化合物对大气的影响以及这种影响在未来可能如何变化--例如通过土地利用的变化或森林砍伐、气候或水循环变化--需要特定于单个化学结构的信息，而不是更简单地以单萜类形式对碳的总质量进行求和。进行这样的测量是一项非常重大的分析科学挑战，过去20年来使用的方法几乎没有变化。对于异戊二烯和甲醇等其他生物化合物，直接进气质谱仪等创新的新仪器使快速测量和从飞机等平台进行调查成为可能。然而，这些技术不适合于从一个单萜结构中拆分另一个单萜结构，而且现有的萜类技术已经落后。目前，绝大多数化学分解的测量都是通过在现场采集样品，然后收集到捕集器和样品容器中，然后使用标准的台式实验室设备返回实验室进行分析。然而，这种方法存在许多分析问题，这是由于单萜在运输过程中具有很高的化学反应活性造成的。该项目建议将一些与热解吸、气相色谱和质谱分析相关的现有最先进的商业现成组件整合到一个专门为快速和现场分析单萜而设计的单一设备中。该项目利用了与快速和直接的阻性柱加热相关的技术能力的一些关键最新发展，以及紧凑、高稳定性和MS航班的灵敏时间的演变。我们的目标是实现至少比现有仪器好一个数量级的测量时间分辨率，并为自己设定了分析周期不超过180秒的目标。该仪器将专门为飞机使用而开发，以实现广域单萜调查，并将安装在NERC FAAM 146研究飞机上，以提供新的测量能力。该项目将由约克大学、NCAS(国家大气科学中心)、Markes International(一家英国中小企业)和国家物理实验室合作完成。该项目遵循了最初的实验室分析研究、仪器设计阶段、制造和测试、验证和国际比较以及最终集成到146飞机上的发展道路。

Emissions from the biosphere (in particular from plants and trees) dominate the global flux of organic compounds into the Earth's atmosphere, far exceeding those of man-made origin. Monoterpenes are an important sub-class of chemicals released by natural processes with chemical structures based around ten carbon atom building blocks. Within this monoterpene class are many hundred distinct chemical species which have greatly differing reactivities and properties dependant on the exact nature of their chemical structure. This group of compounds contribute a significant fraction (up to one third) of total natural organic emissions and are highly reactive in the atmosphere; they undergo transformations in the troposphere leading to the formation of ozone, and act as a source of condensable material for the formation and modification of aerosols. In terrestrial environments, the mixing of biogenic terpenes and man-made emissions can under certain conditions lead to very poor air quality episodes, even in North European countries such as the UK. To correctly simulate the influence monoterpenes have on the atmosphere and how this might change in the future - for example through land-use change or deforestation, climate or water cycle change - requires information which is specific to the individual chemical structures, rather than a more simple summation of the total mass of carbon in monoterpene forms. Making such measurements is a very significant analytical science challenge, and there has been little change in methods used over the past two decades. For other biogenic compounds such as isoprene and methanol, innovative new instruments such as direct inlet mass spectrometers have enabled rapid measurements and surveying from platforms such as aircraft. These techniques however are not suitable for resolving one monoterpene structure from another, and the available terpene technology has lagged behind. At present the vast majority of chemically resolved measurements are made through the collection of samples in the field on to traps and into sample vessels then returned to the laboratory for analysis using standard bench-top lab equipment. There are many analytical problems with this approach however which result from the high chemical reactivity of monoterpenes during transit. This projects proposes to take a number of existing state of the art but commercial off the shelf components associated with thermal desorption, gas chromatography and mass spectrometry and integrate them into a single device designed specifically for the rapid and in situ analysis of monoterpenes. The project exploits some key recent developments in technological capability associated with fast and direct resistive column heating and the evolution of compact, high stability and sensitivity Time of Flight MS. We aim to achieve a time resolution for measurement at least one order of magnitude better than existing instruments and have set ourselves the target of an analytical cycle taking no longer than 180s. The instrument will be developed specifically for aircraft use to allow wide area monoterpene surveys and will be installed aboard the NERC FAAM 146 research aircraft to provide a new measurement capability. The project will be a collaboration between the University of York, NCAS (National Centre for Atmospheric Science), Markes International (a UK SME) and the National Physical Laboratory. The project follows a developmental path of initial lab analytical research, instrument design phase, fabrication and testing, validation and international comparison, and final integration onto the 146 aircraft.