Towards a UK Airborne Bioaerosol Climatology

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.

Airborne bioparticles are an important component of our Earth-Atmosphere system that continues to evolve and as we experience and attempt to adapt to our changing climate. There is now an urgent need to improve models to include these particles to understand and anticipate their likely future impacts due to changing emission patterns of these particles and pathogens. These particles impact areas as wide ranging as food security, disease spread and climate feedback. In a recent comprehensive review, the US National Academies of Science (NAS 2016) concluded, "The understanding of the sources and impacts of bioparticles has increased in recent years but the overall understanding of their impacts on atmospheric composition, climate, and human health remains weak. The first attempts to model emissions and transport of fungal spores, bacteria, and pollen are now starting to be tested against new observational constraints from fluorescence measurements." BIOARC is designed to directly address this science gap with specific focus on the UK. It therefore has potential for significant impact on many UK economic and ecosystem applications within a discovery science framework.

Who will benefit & how?
Scientific community. Quantifying bioparticle emissions and long-range transport of biological containing materials as warming alters emission patterns and distributions is key to understanding the influence these particles will have on human health and ecosystem management. Whilst there have been many detailed studies of the biological characterisation of these particles, few if any have been quantitative with respect to actual atmospheric bioparticle concentrations or fluxes that can be assimilated routinely by dispersion and climate models as non-biological particles currently are. This work will be of scientific interest in the UK and Northern/Arctic Europe, which will likely be more sensitive to climate warming. Better understanding of these particles as highlighted by the NAS review is an important goal in its own right; this work will have added benefit as it will help to understand the response internationally to such problems. Thus the work will improve our knowledge across the whole hemisphere. Results from this project will be an important step forward for the scientific community in the UK especially. It adds to the capability of the FAAM aircraft encouraging its use by the biomolecular community. Better bioparticle emission data will improve models currently under development now including bioparticles, to inform future UK societal needs. Results will be reported in publications and conferences. The project is cross-disciplinary, relevant to biologists, ecologists health scientists, and regional and global climate modellers.

Policymakers. Policymakers in government and scientific bodies (such as IPCC) will be users of the project outcomes. DEFRA and EPA are among those interested in monitoring changing bioparticle emissions for human, plant and animal health. Development of better methodologies to assess emissions and forecast incursions will have much relevance in the UK and EU and will in turn advise on new technologies for surface monitoring of bioparticles being considered for pollution networks.

Business. Health impacts, both plant, animal and human are significant economic drivers and better model forecasts will contribute to mitigation. Instrument companies are collaborating with us in the development of UVLIF technologies (some developed in the UK). The proposed laboratory experiments will generate "training" data sets available to many in the community now using new UVLIF instruments for monitoring and passing UK PBA emissions.

General public/media. Partnerships with instrument manufacturers in the proposed work will improve sensors for bioparticle detection. There is increasing public and media interest in recent years on the impacts of bioparticle/pathogens and this is forecast to increase.