Quantifying the atmosphere-biosphere exchange of inorganic and organic acids.

Quantifying the exchange, or “flux”, of atmospheric acids between the air and the Earth’s surface is important for understanding atmospheric chemistry, ecosystem inputs and pollutant deposition. These processes directly impact human health and environmental change. For example, nitric acid (HNO3) is the pre-cursor for ammonium nitrate aerosol, which underlies many of the exceedances of Air Quality Standards in the UK; and organic acids dominate the route by which volatile organic compounds in the atmosphere partition into the aerosol phase and are deposited to the surface. According to current estimates HNO3 alone contributes 30% of the UK's nitrogen deposition and 10% of UK acid deposition, causing ecosystem impacts due to eutrophication and acidification. Evidence suggests that hydrochloric acid (HCl) provides as much input as HNO3 in summer, but the measurement database for HCl is poor. Atmospheric acids also play key roles in atmospheric chemistry, by regulating the oxidant budget and by contributing to the formation of atmospheric aerosols with direct impacts on human health and the climate system. The behaviour of every one of these compounds is poorly understood and virtually no atmosphere-biosphere flux measurements exist for HONO and organic acids.


This PhD studentship will make novel measurements of atmospheric chemicals as part of national and international experiments in order to test these hypotheses:
1. Inorganic atmospheric acids make a significant contribution to the acid dry deposition component of input to European sensitive ecosystems.
2. Agricultural point source emissions are a significant source of organic acids to the UK atmosphere.
3. Sensitive upland ecosystems are subjected to higher acid inputs than lowland areas because they remain more closely coupled to the atmosphere above.
4. Atmospheric acids do not always deposit at the maximum rate permitted by turbulence, as suggested by current deposition parameterisations.
5. Heterogeneous processes on vegetation surfaces and urban areas provide a significant daytime source for HONO and organic acids.


The student will use a chemical ionisation mass spectrometer (CIMS), to make concentration measurements of a range of acids (HNO3, HCl, HONO, organic acids) very selectively from which fluxes can be calculated. Planned experiments include using the Centre for Ecology & Hydrology’s (CEH) mobile laboratory at UK locations, to look at point sources of organic acids and altitude gradients of nitric acid; and collaborative campaign experiments at Harwell, Oxfordshire; and within the experimental components of the ECLAIRE project (http://www.eclaire-fp7.eu/).

CEH and the University of Manchester are committed to a high quality graduate training programme to ensure that the successful candidate has opportunities to develop their career skills and experience. The successful candidate will be trained in mass spectrometry, field work, micrometeorology, data acquisition and analysis, UK and European environmental science and policy. Through collaboration with scientists involved in UK and international projects, the student will learn to work in teams and benefit from the scientific exchange within the international atmospheric chemistry community. The successful candidate will be supported to attend the UK Summer School in Atmospheric Measurement, on the Isle of Arran.