Isoprene oxidation and OH recycling

从极地到赤道地区，地球表面的温度变化很大。有许多因素引起这种温度变化，但主要的是;从太阳到达地表的热能（在两极比赤道小），地球的反射率它决定了有多少太阳能被反射回太空（包括地表的云和冰），它冷却了地表，大气中的温室气体量就像地球周围的毯子（防止地球的热量逃逸到太空），并使地表变暖。植物在地球系统中起着至关重要的作用，在光合作用过程中将二氧化碳和水转化为糖和氧气（生命所必需的）。它们还吸收表面的一系列污染物，并在城市地区种植，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出混合化学物质，例如吸引传粉者，抵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）是大气中产生的一种物质，其作用就像化学洗涤剂，清除污染物并清洁大气。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OH水平的测量表明，这种想法是错误的，这些化学物质实际上会导致OH再循环。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的循环利用是正确的，那么这些植物排放物将导致大气中温室气体的减少。此外，据信这些排放物还可能导致气溶胶物种，这将有助于形成云，进一步冷却地球。因此，这种效应的组合对我们理解地球的气候（过去，现在和未来）非常重要。当然，这也将对森林生态系统、热带地区砍伐森林的更大负面影响和一般土地使用战略产生重要影响。许多科学家已经推测了这些化学物质如何导致OH的再循环，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希望研究的一些化学物质中添加标签（将氢交换为氘），以便我们可以更容易地跟踪反应途径。我们将使用一系列的检测器与流动系统和静态反应室。这两个系统都能让我们研究化学系统的不同方面。我们将使用的检测器包括质谱法（我们通过它们的重量来识别化合物）和光谱法（我们通过它们吸收的特定颜色的光的量来识别化合物）。这些仪器是在两所大学（布里斯托和曼彻斯特）开发的，使他们成为世界上少数几个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.