Isoprene oxidation and OH recycling

从极地到赤道地区，地球表面温度变化很大。引起这种温度变化的因素很多，但主要是：太阳到达地表的热能(两极比赤道小)，地球的反射率(称为反照率)，它决定了有多少太阳的能量简单地反射回太空(包括表面的云和冰)，从而冷却了表面，以及大气中充当地球毯子的温室气体的数量(防止地球的热量逃逸到太空)和加热表面的量。植物在地球系统中扮演着至关重要的角色，在光合作用过程中将二氧化碳和水转化为糖和氧气(对生命至关重要)。它们还可以吸收表面的一系列污染物，并被种植在城市地区，部分原因是为了减少颗粒物的水平。然而，植物也会出于各种原因释放一种混合的化学物质，例如吸引传粉者、防御捕食者和保护免受臭氧等各种污染物的侵害。羟基自由基(OH)是一种在大气中产生的物种，其作用类似于化学洗涤剂，清除污染物并净化大气。人们认为，植物释放的这些化学物质抑制了羟基自由基，因此会增加温室气体的水平。然而，最近对热带地区羟基水平的测量表明，这种想法是错误的，这些化学物质实际上导致了羟基循环。如果这是正确的，那么植物，特别是热带地区的植物，将在抵消气候变化方面发挥重要作用。如果OH的循环是正确的，那么这些工厂排放的气体正在导致大气中存在的温室气体数量的减少。此外，人们认为这些排放还可能导致气溶胶物种，这将有助于形成云并进一步冷却地球。因此，这种影响的组合对于我们理解地球气候(过去、现在和未来)可能是极其重要的。当然，它还将对森林生态系统、热带地区森林砍伐带来的更严重的负面影响以及总体土地利用战略产生重要影响。不同的科学家推测这些化学物质可能如何导致OH的循环，其中一些是基于实验室实验。然而，那些似乎具有最大潜在影响并可能至少部分解决测量和计算机模拟之间的差异的方法，是基于计算机计算本身的。因此，这些理论研究在实验室中得到验证是至关重要的。这些反应很难研究，因此我们建议在我们想要研究的一些化学物质上增加标签(用氢换氢)，这样我们就可以更容易地跟踪反应路径。我们将使用一系列探测器与流动系统和静态反应室配合使用。这两个系统将允许我们研究化学系统的不同方面。我们将使用的探测器包括质谱学(我们通过化合物的重量来识别化合物)和光谱学(我们通过化合物吸收的特定颜色的光的量来识别化合物)。这些仪器是由相关的两所大学(布里斯托尔和曼彻斯特)开发的，使它们处于独特的地位，成为世界上少数能够进行这些研究的团队之一。

The surface temperature of the Earth varies dramatically from polar regions through to equatorial ones. There are many factors that give rise to this temperature variation but the main ones are; the amount of heat energy arriving at the surface from the sun (which is smaller at the poles than the equator), the reflectivity of the Earth (called the albedo) which determines how much of the sun's energy is simply reflected back to space (and includes clouds and ice at the surface) which cool the surface and the amount of greenhouse gases in the atmosphere which act as a blanket around the Earth (preventing heat from the Earth from escaping to space) and warm the surface up. Plants play a vital role in the Earth system, converting carbon dioxide and water into sugars and oxygen (essential for life) during photosynthesis. They also absorb a range of pollutants on their surfaces and are planted in urban areas in part to reduce the levels of particulate matter. However, plants also release a cocktail of chemicals for a variety of reasons, e.g. attracting pollinators, defence against predators and protection against a variety of pollutants such as ozone. The hydroxyl radical (OH) is a species produced in the atmosphere that acts like a chemical detergent, mopping up pollutants and cleansing the atmosphere. It was believed that these chemicals released by plants suppressed the hydroxyl radical and therefore would increase the level of greenhouse gases. However, recent measurements of the level of OH in the tropics suggest that this idea is wrong and that these chemicals actually lead to OH recycling. If this is correct then plants and in particular those in tropical regions, will be playing a significant role in off-setting climate change. If the recycling of OH is correct then these plant emissions are leading to a reduction in the amount of greenhouse gases present in the atmosphere.In addition, it is believed that these emissions may also lead to aerosol species that will help to form cloud and further cool the planet. Therefore, this combination of effects could be extremely important to our understanding of the Earth's climate (past, present and future). It will also of course have important implications for forest ecosystems, the enhanced negative impact of deforestation in tropical regions and land-use strategies in general. A variety of scientists have speculated about how these chemicals may be leading to a recycling of OH, some based on laboratory experiments. However, the ones that appear to have the biggest potential impact and may resolve, at least in part, the discrepancy between measurements and computer simulations, are based on computer based calculations themselves. Therefore, it is vital that these theoretical studies be verified in the laboratory. These reactions are difficult to study and so we propose to add tags (swapping hydrogen for deuterium)to some of the chemicals we wish to study so that we can follow the reaction pathway more easily. We will use a range of detectors in concert with both a flow system and a static reaction chamber. Both systems will allow us to stufy different aspects of the chemical system. The detectors we will use include mass spectrometry (where we identify compounds by their weight) and spectroscopy (where we identify compounds by the amount of a specific colour of light that they absorb). These instruments have been developed at the two Universities involved (Bristol and Manchester) and allow them to be uniquely placed to be one of the few teams in the world able to carry out these studies.