Photochemical pollution indicators—an analysis of 12 European monitoring stations

Abstract

Indicators were devised to classify air pollution monitoring sites according to the type of expected photochemical pollution. The indicators are based on measured ozone volume fractions, the most frequently monitored component of photochemical pollution, and in particular on two contributions: one due to the ratio of daily maximum-to-minimum ozone volume fractions and the other to observed peak values. The two contributions regarded as independent are logically connected by "and" and therefore mathematically combined by multiplication. The criterion of classification is mainly described by the mentioned ratio and incidences of ozone volume fractions exceeding the limit of 80 ppb. Twelve monitoring stations within the European network (Cooperative programme for monitoring and evaluation of long-range transmission of air pollutants in Europe, EMEP) were classified according to this indicator predicting what ozone levels can be expected at the particular sites during the growth season (April through September) into three groups: clean, medium, and polluted, based on the data for the 7 years (1997 to 2003).

Growth Season Photochemical Pollution over the UK Based on 1990-2006 Ozone Data

“…All covered stations at altitudes above 200 m have very low indicator values, in agreement with the findings for continental stations 6,13 that elevated sites show lower indicator values. Note that in the British Isles, the definition of "elevated" is different than in continental Europe where only sites above 800 m are considered as elevated.…”

“…This decrease, as shown also by Jenkin, would have been even more pronounced if the year 2003 had not been so exceptional. 12 As reported earlier, 6 sites with indicator values below 10 should be classified as "clean," with 10 -40 as "medium" and sites with values above 100 as "polluted." Thus, all rural sites Bottesford, Glazeburry, Harwell and Lough Navar would be classified as medium PP (the last two probably only up to 2003).…”

“…If we compare the indicator values for stations covered in this report with those for some other regions during the early 2000s, for example, those in central Europe, 6 Croatia, Italy and Slovenia, 13 where P 3 is generally higher than 40 at urban sites (with the exception of Osijek and Rijeka where industries shrunk in the early 1990s), we conclude that the PP indicator values for the UK sites are lower than those of central and southern Europe and show a tendency of becoming even lower in future. Production of ozone in Mediterranean area is dominated by huge photochemical production of ozone in this area due to larger number of sunny days which is combined with hemispheric-scale spring maximum.…”

“…The calculation method has been described previously 6 and was developed by analysing 10 years of ozone data from 12 European Monitoring and Evaluation of air Pollutants program (EMEP) stations over Europe. Originally, two indicators were proposed,…”

“…3 Ozone can be easily and reliably monitored, and based on the average hourly ozone volume fractions at many locations over long periods of time, a number of indices, directives and air quality standards and limits have been put forward in order to quantify the air quality affecting humans, vegetation and materials. 4,5 Long-term ozone monitoring results at various European locations 6 have shown that along with a high daily value of ozone volume fractions, the extent of the diurnal variation expressed as the ratio of maximum to minimum ozone volume fractions gives a much better insight into the atmospheric condition known as photochemical pollution (PP). The recent analysis of more than 14 years of whole-year ozone data from 18 monitoring stations in the UK by Jenkin 7 revealed interesting results on trends in the ozone concentration distribution as well as on local, regional and global influences.…”