Towards a UK Airborne Bioaerosol Climatology

初级生物气溶胶（PBA）或生物气溶胶是有机碳质气溶胶（OC）的一种知之甚少的成分，对空气中的颗粒物（PM）有很大的贡献，并包含数千种有机化合物的混合物。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产生重大影响。对这些气溶胶的探测、定性和分类及其在大气传输模型中的描述仍然是科学界面临的一个重大挑战。事实上，美国国家科学院的结论是：“对它们对大气成分、气候和人类健康的影响的总体认识仍然薄弱。（NAS，2016）。全球和区域生物气溶胶排放和迁移模型研究表明存在很大的不确定性，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通量和空气中浓度的观测数据。最近提出的重要但尚未得到解答的问题包括：持久性有机污染物的连续排放和向环境浓度的迁移与间歇性排放和迁移的相对重要性以及随后的影响;持久性有机污染物是否通过“生物沉淀”假说对云和降水过程产生重大影响;持久性有机污染物通过从热带到两极的大气生态系统小生境繁殖的程度;以及它们是否可以通过降解有机化合物来影响化学过程。所有最近的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其大气浓度和分布，特别是其垂直浓度分布的知识。Fröhlich-Nowoisky等人（2016年）对PBA进行了最新的深入审查，得出的结论是：“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。以获得关于生物颗粒的垂直和水平分布的信息。“我们的目标就是这样，提供新的数据集，为英国环境建立排放模型。我们将使用NERC FAAM飞机上现有的测量设施以及地面测量，在英国地区提供垂直和水平的PBA浓度分布，包括城市，农村耕地，草原，森林和沿海地区。我们将使用飞机生物气溶胶采样方法最近在美国开发的实时生物气溶胶仪器一起。这些数据将提供50多年来关于英国生物气溶胶边界层浓度分布的第一个此类信息。高质量的英国空气数据集首次适用于约束和测试英国生物排放模型。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，远远超出项目的时间范围。现场PBA浓度将与空中气象、痕量气体和其他气溶胶成分数据相关联，用于空气质量分类，使用多年来为FAAM飞机开发的用于源跟踪和识别的工具。这将使我们能够提供质量受控，同化准备的案例研究，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，以提供英国特定的生物气溶胶参考数据集，旨在改善使用实时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.