Comprehensive Analytical System for Measuring Isoprene-derived Nitrates

全面了解生物圈和大气之间的相互作用对于：(i)地球系统科学（ii）预测未来气候变化的影响至关重要。异戊二烯是大气中最重要的生物源性挥发性有机化合物（VOC），其排放量占全球VOC总排放量的1/3（即自然和人为结合）。异戊二烯通过其降解化学作用，影响臭氧和气溶胶的形成，两者共同影响全球变暖和大气净化污染物的能力。最近的模型研究表明，计算出的异戊二烯对臭氧的影响在很大程度上取决于模型异戊二烯化学方案，特别是处理异戊二烯衍生硝酸盐的方式。这些硝酸盐形成了多少以及随后发生了什么，这是相当不确定的。特别重要的是，与硝酸盐结合在一起的氮氧化物是否会在以后被循环利用或从大气中消失。这会影响随后形成的臭氧量。实际上，关于硝酸异戊二烯化学的所有已知知识都是基于理论计算，而大多数观测限制都是基于对硝酸盐群总数的测量，或者是来自不止一种反应和前体物质的降解产物。为了取得实质性的科学进展，需要对单个硝酸盐进行全面的测量，在实验室研究中需要正确地了解单个硝酸盐的化学性质，在实地研究中需要确定异戊二烯对臭氧和气溶胶的真正影响。异戊二烯降解化学的研究受到测量技术的极大限制，它们无法识别和量化单个有机硝酸盐。因此，我们建议：开发一种能够检测和鉴定单个异戊二烯衍生硝酸盐的分析气相色谱质谱仪2。合成18种单独的异戊二烯衍生硝酸盐，使其能够明确检测和鉴定，并将其浓度量化到大气水平。这项“技术主导”提案的最终产品将是新的合成方案和一个分析系统，该系统将允许校准测量18种单个硝酸异戊二烯的浓度低至大气水平。该系统随后可用于实验室和实地研究。这种分析系统将是独特的，并将使异戊二烯化学在个别反应和产物的水平上进行研究。这将有助于在评估用于预测空气质量和气候的模式化学机制方面取得重大进展。通过量化这些反应方案的单个分支的速率和产物，它将使限制这些机制的能力发生一步变化。此外，它将允许在真实大气中测量单个硝酸异戊二烯的浓度，并根据这些数据测试模型。总之，这将使硝酸异戊二烯对氮氧化物再循环和臭氧的影响能够用约束良好的模型进行量化。2003年热浪期间英国臭氧浓度升高的部分原因是异戊二烯浓度升高。未来气候和土地利用的变化可能会影响异戊二烯的排放，因此了解异戊二烯如何影响氮氧化物的再循环对于预测未来的臭氧浓度非常重要。因此，随着本提案中技术的发展，在科学认识方面可能取得的进步对于制定排放控制战略的决策者至关重要。

A comprehensive understanding of the interactions between the biosphere and the atmosphere is crucial for: (i) Earth System science (ii) predicting the impact of future climate change. Isoprene is the most important biogenic volatile organic compound (VOC) in the atmosphere, with its emissions accounting for 1/3 of the global total VOC emissions (i.e. natural and anthropogenic combined). Through its degradation chemistry, isoprene impacts ozone and the formation of aerosols, which together impact global warming and the atmosphere's ability to cleanse itself of pollutants.Recent model studies show that the calculated impact of isoprene on ozone is critically dependent on the model isoprene chemical scheme, in particular the way the isoprene derived nitrates are treated. There is considerable uncertainty over how much of these nitrates are formed and what subsequently happens to them. Of particular importance is whether the nitrogen oxides, which are tied up in the nitrates, are later recycled or are lost from the atmosphere. This then impacts the amount of ozone that can be subsequently formed. Virtually everything that is known about isoprene nitrate chemistry is based on theoretical calculations, with most observational constraints based on measurements of either groups of nitrates as totals, or degradation products that come from more than one reaction and precursor species. For any substantial scientific progress to be made comprehensive measurement of individual nitrates is required, in laboratory studies to properly understand the chemistry of individual nitrates, and in the field to determine the true impact of isoprene on ozone and aerosol.Studies of isoprene degradation chemistry have been greatly limited by measurement techniques and their inability to identify and quantify individual organic nitrates. We therefore propose to:1. Develop an analytical gas chromatography mass spectrometry instrument capable of detecting and identifying individual isoprene derived nitrates2. Synthesise 18 individual isoprene derived nitrates to enable their unambiguous detection and identification and for their concentrations to be quantified down to atmospheric levels.The final products of this "Technology Led" proposal will be novel synthesis protocols and an analytical system that will allow calibrated measurements of 18 individual isoprene nitrates at concentrations down to atmospheric levels. The system can then subsequently be used in both laboratory and field studies. Such an analytical system will be unique and will enable isoprene chemistry to be studied at the level of individual reactions and products. This will facilitate a major advancement in the evaluation of model chemical mechanisms used to predict air quality and climate. It will enable a step change in the ability to constrain these mechanisms by allowing quantification of the rates and products of individual branches of these reaction schemes. Further it will allow the concentrations of individual isoprene nitrates to be measured in the real atmosphere and models tested against these data. Altogether this will enable the impact of isoprene nitrates on nitrogen oxide recycling and ozone to be quantified with well constrained models.The elevated ozone in England during the 2003 heatwave was attributed, in part, to elevated concentrations of isoprene. Future changes in climate and land-use are likely to affect isoprene emissions so understanding how isoprene impacts nitrogen oxide recycling is important for predicting future ozone concentrations. The potential advancements in scientific understanding that can be made following the development of the technology within this proposal are therefore essential for policy makers developing emission control strategies.