Source variability of WSOC in atmospheric precipitation

一系列有机（含碳）化合物既可以通过生物和化学过程自然产生，也可以通过人类活动（火灾，车辆和工业排放等）产生。易溶于水。这些化合物统称为“水溶性有机碳”，简称WSOC。在某种意义上，WSOC可以被认为是一个有点模糊和包罗万象的术语，因为它是一种复杂的有机分子混合物，这些有机分子对总量的贡献各不相同，并且极难单独分离和分析。然而，作为所谓的“散装”成分，WSOC是大气水的重要组成部分，并且是反应性的。其组成分子在阳光下发生（光化学）反应，产生一系列影响大气化学过程的反应性产物，从而影响当地和全球范围的气候。WSOC可以是云形成所需的云凝结核（CCN）的重要来源，它有助于雨水的酸度，它可以是湖泊，河流和海洋的营养源。最近在英国和世界各地的降雨量增加的趋势意味着需要详细研究WSOC将变得越来越重要。为了预测其对环境的影响，需要更好地确定其各种单独来源，并从其组成和时空可变性方面对其进行定性。WSOC的详细化学分析是昂贵的，不容易获得，并且在任何情况下都不能提供高水平的识别;而只是“平均成分”。最近发现大部分WSOC是荧光的，这意味着如果受到来自某些源的入射辐射的吸收的刺激，它会发射电磁辐射，特别是可见光。发射的波长光谱可以被分析并用作“指纹”以识别不同“类型”（所谓的“荧光团”）的WSOC（和其他形式的溶解有机物质），这使得能够推断关于对样品有贡献的不同WSOC源的信息并提供它们的相对重要性的测量（从它们的荧光强度）。荧光的优点是相对简单和成本低。这项工作的想法是从特定的降雨“事件”中收集雨水样本，并通过荧光分析这些样本，以确定荧光团的存在及其强度。使用这些测量数据沿着来自邻近气象桅杆的气象数据和使用这些数据预测气团起源区域的软件，将有可能确定所识别的各种源“类型”起源的区域。这将是更好地了解WSOC在环境中的起源和随后的命运的重要的第一步。这项短期研究的结果将用于帮助在不久的将来制定更详细的WSOC研究方案。

A wide range of organic (carbon containing) compounds produced both naturally by biological and chemical processes but also by mans activities (fires, vehicle and industrial emissions etc.) readily dissolve in water. Together these compounds are termed 'water soluble organic carbon', or WSOC for short. In some senses WSOC can be considered as a somewhat vague and all-encompassing term because it is a complex mixture of organic molecules which vary in their contributions to the total and are extremely difficult to isolate and analyse individually. Nevertheless, as a so-called 'bulk' component, WSOC is an important constituent of atmospheric water and is reactive. Its constituent molecules undergo sunlight-induced (photochemical) reactions that result in a range of reactive products which influence atmospheric chemical processes, influencing the climate on both local and global scales. WSOC can be an important source of cloud condensation nuclei (CCN) which are required for cloud formation, it contributes to rainwater acidity, and it can be a nutrient source to lakes, rivers and the ocean. Recent trends of increasing rainfall in the UK and worldwide mean that the need for detailed study of WSOC will become ever more important. In order to predict its impact on the environment, its various individual sources need to be better identified and characterised in terms of their composition and variabilty in time and space. Detailed chemical analysis of WSOC is costly, not readily accesible and in any case does not provide a high level of identification; rather only 'average compositions'. Recently a large fraction of WSOC was found to be fluorescent, which means that it emits electromagnetic radiation, especially visible light, if stimulated by the absorption of incident radiation from some source. The wavelength spectrum emitted can be analysed and used as a 'fingerprint' to characterise WSOC (and other forms of dissolved organic matter) of different 'types' (so-called 'flourophores') that enable a means to deduce information about different WSOC sources contributing to a sample and provide a measure of their relative importance (from their fluorescence intensities). The advantages of fluorescence are its relative simplicity and low cost. The idea of this work is to collect rainwater samples from specific rainfall 'events' and analyse these by fluorecence to identify the fluorophores present and their intensities. Using these measurements along with meteorological data from an adjacent meteorological mast and software that uses these data to predict areas from which air masses have originated, it will be possible to determine the regions in which the various source 'types' identified originated. This will be an important first step towards a better understanding of the origin and subsequent fate of WSOC in the environment. The results from this short-duration study will be used to help formulate a more detailed programme of WSOC research in the near future.