Analysis of the air pollution climate at a central urban background site |
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| Authors: | Alessandro Bigi Roy M Harrison |
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| Institution: | 1. School of Public Health, Key Lab of Public Health Safety of the Ministry of Education, Fudan University, Shanghai, China;2. Research Institute for the Changing Global Environment and Fudan Tyndall Centre, Fudan University, Shanghai, China;4. Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA;5. Shanghai Key Laboratory of Meteorology and Health, Shanghai Meteorological Bureau, Shanghai, China;1. Department of Building Science, Tsinghua University, Beijing, China;2. Institute on the Environment, University of Minnesota, St. Paul, MN, USA;3. Environmental Chemistry and Technology Program, University of Wisconsin, Madison, WI, USA;4. Department of Civil and Environmental Engineering, University of Wisconsin, Madison, WI, USA;5. MRC-PHE Center for Environment and Health, Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, UK;6. College of Resources and Environment, University of the Chinese Academy of Sciences, Beijing, China;7. Institute for Health and Social Policy, Department of Epidemiology, Biostatistics & Occupational Health, McGill University, Montréal, QC, Canada |
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| Abstract: | Measurements of air pollutants from a background site in central London are analysed. These comprise hourly data for CO, NO, NO2, O3, SO2 and PM10 from 1996 to 2008 and particle number count from 2001 to 2008. The data are analysed in terms of long-term trends, annual, weekly and diurnal cycles, and autocorrelation and cross-correlation functions. CO, NO and NO2 show a typical traffic-associated pattern with two daily peaks and lesser concentrations at the weekend. Particle number count and PM10 show a similar cycle, but with smaller amplitude. Ozone has an annual cycle with a maximum in May, influenced by the spring maximum in background ozone, but the diurnal and weekly cycles are dominated by losses through reaction with nitric oxide. Particle number count shows a minimum corresponding with maximum air temperatures in August, whereas the CO, NO NO2 and SO2 show a minimum in June/July. There is a lower particle count to NOx ratio at the background site compared to a central London kerbside site (Marylebone Road) and a seasonal pattern in particle count to NOx and PM10 ratios consistent with loss of nanoparticles by evaporation during atmospheric transport. Sulphur dioxide peaks in the morning in summer, but at midday in winter consistent with emissions from elevated sources mixing down from aloft as the diurnal mixed layer deepens. Implications for epidemiological studies of air quality and health are discussed. Sulphur dioxide, carbon monoxide, nitric oxide and nitrogen dioxide show clear downward trends over the measurement period, PM10 declines initially before levels stabilised, and ozone concentrations increased. |
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