Towards a UK Airborne Bioaerosol Climatology

原生生物气溶胶（PBA）或生物气溶胶是有机碳质气溶胶（OC）的一个鲜为人知的组成部分，对空气中的颗粒物（PM）贡献很大一部分，由数千种有机化合物组成。PBA包括活的或死的细胞和细胞碎片，真菌孢子和花粉，以及植物、昆虫和动物的碎片。它们对大气气溶胶和化学过程的物理化学、生物、健康甚至与气候有关的行为具有重大影响。这些气溶胶的检测、表征和分类以及它们在大气输送模型中的描述仍然是科学界面临的主要挑战。事实上，美国国家科学院得出的结论是，“对它们对大气成分、气候和人类健康的影响的全面了解仍然薄弱。”(NAS, 2016)。全球和区域生物气溶胶（PBA）排放和输送模拟研究显示了很大的不确定性，因此对这些重要的大气成分的了解有限。这主要是由于缺乏关于许多不同生态系统的它们的通量和空气中浓度的观测数据。最近提出的一些重要但尚未得到解答的问题包括：PBA连续排放和向环境浓度转移的相对重要性与随后的影响；PBA是否通过“生物沉淀”假说显著影响云和降水过程；它们通过从热带到极地的大气生态位进行繁殖的程度；以及它们是否能通过降解有机化合物来影响化学过程。最近的所有研究和审查都得出了类似的结论，即为了开始解决与PBA相关的许多和日益增长的挑战，我们需要更好地了解它们的大气浓度和分布，特别是它们的垂直浓度分布。最近对PBA的深入回顾，Fröhlich-Nowoisky等人（2016）得出结论，“主要挑战包括地表、行星边界层和自由对流层之间交换的定量表征。为此，地面测量必须与高塔和飞机测量相结合。获取生物颗粒的垂直和水平分布信息。”我们的目标就是做到这一点，提供新的数据集，使英国环境的排放建模。我们将利用NERC FAAM飞机上现有的测量设施以及地面测量数据，提供英国地区（包括城市、农村农田、草地、森林和沿海地区）的垂直和水平PBA浓度曲线。我们将使用最近在美国开发的飞机生物气溶胶采样方法以及实时生物气溶胶仪器。这些数据将提供50多年来英国生物气溶胶边界层浓度剖面的首次此类信息。高质量的英国机载数据集适合约束和测试英国生物排放模型的第一次。我们新的垂直和水平分辨率的pba气候数据库将支持大量的科学研究和政策应用，远远超出了项目的时间尺度。现场PBA浓度将与机载气象、微量气体和其他气溶胶成分数据相关联，用于气团分类，使用多年来为FAAM飞机开发的工具进行来源跟踪和识别。这将使我们能够提供有质量控制的、易于同化的案例研究，能够限制广泛的潜在PBA排放模型。我们还将进行实验室实验，提供英国特定的生物气溶胶参考数据集，旨在改进使用实时UVLIF生物气溶胶仪器收集的当前和未来PBA现场数据的解释。

Primary biological aerosols (PBA), or bioaerosols, are a poorly understood component of organic carbonaceous aerosols (OC), contributing a significant fraction to airborne particulate matter (PM) and comprising mixtures of many thousands of organic compounds. PBA include live or dead cells and cell fragments, fungal spores and pollens, and plant, insect and animal fragments. They have a major influence on the physico-chemical, biological, health and even climate related behaviour of atmospheric aerosols and chemical processes. The detection, characterization and classification of these aerosols and their descriptions in atmospheric transport models has remained a major challenge to the science community. Indeed the US national Academies of Science concluded that "The overall understanding of their impacts on atmospheric composition, climate, and human health remains weak." (NAS, 2016). Global and regional bioaerosol (PBA) emission and transport modelling studies have demonstrated very large uncertainties and thus provide limited understanding of these important atmospheric constituents. This is primarily due to a lack lack of observational data on their fluxes and airborne concentrations for many different ecosystems. Important, as yet unanswered, questions raised recently include: the relative importance of continuous versus intermittent emission and transport of PBA to ambient concentrations and subsequent impacts; whether PBA significantly influence cloud and precipitation processes via the "bioprecipitation" hypothesis; the degree to which they can reproduce via atmospheric ecosystem niches from the tropics to the poles; and whether they can influence chemical processes through degradation of organic compounds. All recent studies and reviews have similarly concluded that in order to start to address the many and growing challenges associated with PBA we need to acquire a better knowledge of their atmospheric concentrations and distributions and in particular knowledge of their vertical concentration profiles. The most recent in depth review of PBA, Fröhlich-Nowoisky et al. (2016), concluded that "major challenges include the quantitative characterization of exchange between surface, planetary boundary layer, and free troposphere. For this purpose, ground based measurements have to be combined with tall tower and aircraft measurements... to obtain information on the vertical and horizontal distribution of bioparticles." We aim to do just this, delivering new data sets to enable emissions modelling for the UK environment. We will use existing measurement facilities on the NERC FAAM aircraft together with surface measurements to deliver vertical and horizontal PBA concentration profiles over UK regions including urban, rural-cropland, grassland, forest & coastal. We will use aircraft bioaerosol sampling methodologies recently developed in the US together with real-time bioaerosol instruments. These data will provide the first such information on UK boundary layer concentration profiles of bioaerosol for over 50 years. High quality UK airborne data sets suitable for constraining & testing UK bio-emissions models for the first time.Our new vertically & horizontally resolved PBA-climate database will support a raft of scientific research and policy applications well beyond the timescale of the project. In situ PBA concentrations will be correlated with airborne meteorological, trace gas and other aerosol composition data, for air mass classification, using tools developed for the FAAM aircraft over many years for source tracking & identification. This will allow us to deliver quality controlled, assimilation-ready case studies able to constrain a wide range of potential PBA emissions models. We will also conduct laboratory experiments to deliver UK specific bioaerosol reference data sets designed to improve interpretation of current and future PBA field data collected using real-time UVLIF bioaerosol instruments.