Current research

Chemical composition of rain and cloud in upland areas

Weekly measurements of rain and cloud composition are made at an upland site in the Scottish Borders (Bowbeat) and a nearby lower-altitude site (Auchencorth Moss) to study the role of seeder-feeder processes in determining the chemical composition of precipitation in upland areas of the UK. The data are used to underpin the mapping of wet deposition across the UK. This work is funded by the Department for Environment, Food and Rural Affairs (Defra).

Artefacts in sampling precipitation (dry deposition on collectors)

The UK monitoring network for precipitation composition uses "bulk" collectors - funnels that are open all the time. When it is not raining, gases and particles are deposited on funnel surfaces and then washed into the sample bottle the next time rain falls. The contribution of dry deposition to the total "bulk" composition of rainfall is being measured at three sites using a novel collector that flushes the funnel surface when rain is detected. The rinse water is collected and analysed separately from the rainfall collected by the cleaned funnel to assess how much of the "bulk" composition is accounted for by "contamination" of the funnel surface. This work is funded by Defra.

Reactions of ozone at leaf surfaces

Long-term measurements of the flux of ozone from the atmosphere to plants have shown that well over half of the deposited ozone molecules do not enter leaves through stomata, but are retained or destroyed on leaf surfaces. Laboratory measurements under controlled conditions, using artificial leaves, are being used to understand the chemical processes responsible for these observations. This knowledge will be used to improve models of the deposition and loss of ozone from the boundary layer of the atmosphere.

Fluxes of oxygenated volatile organic compounds (OVOCs)

Although the emissions and fluxes of many biogenic volatile organic compounds (VOCs) have been measured for many plant species over many years, knowledge of the sources and sinks of OVOCs are much less well understood. A proton-transfer reaction mass spectrometer (PTR-MS) is being used to measure both concentrations and fluxes of OVOCs in agricultural and urban areas.

Monitoring of particulate and gaseous mercury in the UK atmosphere
This project forms part of the Heavy Metals project funded by Defra.

Effects of oxidised and reduced nitrogen on moorland species
Moorland vegetation is sensitive to airborne nitrogen, whether as ammonia gas (NH3) or ammonium (NH4+) or nitrate (NO3-) ions in rain. A major experimental field site, unique in the world, has been established in eastern Scotland to study the effects of gaseous ammonia and wet-deposited N (ammonium and nitrate, separately) on a mire ecosystem. Results already show that, gram for gram, gaseous ammonia has bigger effects than wet deposited N, and there are large differences in the way that different plant species react. These studies are supplemented by experimental measurements in open-top chambers using similar types of vegetation - we are currently observing how plants exposed to different levels of N from 1998 to 2002 are recovering now that the experimental treatments have been stopped. The open-top chambers also provide a means of looking at the processes that control the uptake of ammonia gas from the air by such plants. This information allows us to calculate how much ammonia is deposited to UK vegetation. This work is part-funded by Defra.

Development and field trialling of N biomonitor methods
Methods were tested at point sources of N deposition and at nature conservation sites throughout the UK with diffuse N sources. The methods examined were tissue N concentration and soluble NH4-N concentration in pleurocarpous mosses, Ellenberg Index, standardised grass biomonitors and lichen diversity. This work was jointly funded by JNCC and SNIFFER.

Air quality outcomes for regulatory purposes
We are reviewing the use of biomonitoring in the assessment and operation of statutory regulations controlling the emission of atmospheric pollutants. This work is funded by the Environment Agency