Adverse health effects from exposure to air pollution are a global challenge and of widespread concern. Recent high ambient concentration episodes of air pollutants in European cities highlighted the dynamic nature of human exposure and the gaps in data and knowledge about exposure patterns. In order to support health impact assessment it is essential to develop a better understanding of individual exposure pathways in people's everyday lives by taking account of all environments in which people spend time. Here we describe the development, validation and results of an exposure method applied in a study conducted in Scotland. A low-cost particle counter based on light-scattering technology - the Dylos 1700 was used. Its performance was validated in comparison with equivalent instruments (TEOM-FDMS) at two national monitoring network sites (R(2)=0.9 at a rural background site, R(2)=0.7 at an urban background site). This validation also provided two functions to convert measured PNCs into calculated particle mass concentrations for direct comparison of concentrations with equivalent monitoring instruments and air quality limit values. This study also used contextual and time-based activity data to define six microenvironments (MEs) to assess everyday exposure of individuals to short-term PM2.5 concentrations. The Dylos was combined with a GPS receiver to track movement and exposure of individuals across the MEs. Seventeen volunteers collected 35 profiles. Profiles may have a different overall duration and structure with respect to times spent in different MEs and activities undertaken. Results indicate that due to the substantial variability across and between MEs, it is essential to measure near-complete exposure pathways to allow for a comprehensive assessment of the exposure risk a person encounters on a daily basis. Taking into account the information gained through personal exposure measurements, this work demonstrates the added value of data generated by the application of low-cost monitors.

No abstract

An intercomparison was made between eddy covariance flux measurements of ammonia by a quantum cascade laser absorption spectrometer (QCLAS) and a lead-salt tunable diode laser absorption spectrometer (TDLAS). The measurements took place in September 2004 and again in April 2005 over a managed grassland site in Southern Scotland, U.K. These were also compared with a flux estimate derived from an "Ammonia Measurement by ANnular Denuder with online Analysis" (AMANDA), using the aerodynamic gradient method (AGM). The concentration and flux measurements from the QCLAS correlated well with those of the TDLAS and the AGM systems when emissions were high, following slurry application to the field. Both the QCLAS and TDLAS, however, underestimated the flux when compared with the AMANDA system, by 64%. A flux loss of 41% due to chemical reaction of ammonia in the QCLAS (and 37% in the TDLAS) sample tube walls was identified and characterized using laboratory tests but did not fully accountforthis difference. Recognizing these uncertainties, the agreement between the systems was nevertheless very close (R2 = 0.95 between the QCLAS and the TDLAS; R2 = 0.84 between the QCLAS and the AMANDA) demonstrating the suitability of the laser absorption methods for quantifying the temporal dynamics of ammonia fluxes.

Abstract. The global nitrogen (N) cycle at the beginning of the 21st century has been shown to be strongly influenced by the inputs of reactive nitrogen (N r ) from human activities, including combustion-related NO x , industrial and agricultural N fixation, estimated to be 220 Tg N yr −1 in 2010, which is approximately equal to the sum of biological N fixation in unmanaged terrestrial and marine ecosystems. According to current projections, changes in climate and land use during the 21st century will increase both biological and anthropogenic fixation, bringing the total to approximately 600 Tg N yr −1 by around 2100. The fraction contributed directly by human activities is unlikely to increase substantially if increases in nitrogen use efficiency in agriculture are achieved and control measures on combustion-related emissions implemented.Some N-cycling processes emerge as particularly sensitive to climate change. One of the largest responses to climate in the processing of N r is the emission to the atmosphere of NH 3 , which is estimated to increase from 65 Tg N yr −1 in 2008 to 93 Tg N yr −1 in 2100 assuming a change in global surface temperature of 5 • C in the absence of increased anthropogenic activity. With changes in emissions in response to increased demand for animal products the combined effect would be to increase NH 3 emissions to 135 Tg N yr −1 . Another major change is the effect of climate changes on aerosol composition and specifically the increased sublimation of NH 4 NO 3 close to the ground to form HNO 3 and NH 3 in a warmer climate, which deposit more rapidly to terrestrial surfaces than aerosols. Inorganic aerosols over the polluted regions especially in Europe and North America were dominated by (NH 4 ) 2 SO 4 in the 1970s to 1980s, and large reductions in emissions of SO 2 have removed most of the SO 2− 4 from the atmosphere in these regions. Inorganic aerosols from anthropogenic emissions are now dominated by NH 4 NO 3 , a volatile aerosol which contributes substantially to PM 10 and human health effects globally as well as eutrophication and climate effects. The volatility of NH 4 NO 3 and rapid dry deposition of the vapour phase dissociation Published by Copernicus Publications on behalf of the European Geosciences Union. D. Fowler et al.: Effects of global change during the 21st century on the nitrogen cycleproducts, HNO 3 and NH 3 , is estimated to be reducing the transport distances, deposition footprints and inter-country exchange of N r in these regions.There have been important policy initiatives on components of the global N cycle. These have been regional or country-based and have delivered substantial reductions of inputs of N r to sensitive soils, waters and the atmosphere. To date there have been no attempts to develop a global strategy to regulate human inputs to the nitrogen cycle. However, considering the magnitude of global N r use, potential future increases, and the very large leakage of N r in many forms to soils, waters and the atmosphere, international action is re...

No abstract