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Original scientific paper

Photochemical Pollution Indicators in the Subtropics

Leo Klasinc ; Ruđer Bošković Institute, Bijenička cesta 54, HR-10000 Zagreb, Croatia
Tomislav Cvitaš ; Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, HR-10000 Zagreb, Croatia
Sean P. McGlynn ; Chemistry Department, Louisiana State University, Baton Rouge, USA
Min Hu ; Peking University, Beijing, China
Xiaoyan Tang ; Peking University, Beijing, China
Yuanhang Zhang ; Peking University, Beijing, China

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page 11-16

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Indicators evaluated from the long-term hourly averages of ozone volume fractions at air monitoring
sites are proposed as measures of the photochemical pollution exposure at those sites. These indicators
are based on the average of the daily maximum-to-minimum ratio during the period of maximum ozone production
and are corrected a), for the average maximum to average total ozone ratio (indicator P1) and b), for
the number of hours the limit ozone volume ratio limit of 80 ppb was exceeded (indicator P2). These indicators
are then combined into P3 as their geometrical mean. The rationale for the introduction of a new set of
indicators is based on the suspicion that ozone volume fractions do not provide information either on the total
daily ozone that is produced or on the fraction of it that has produced other photochemical pollution components
despite that ozone correlates quite well with some of them. Unlike the European stations, where every
case in excess of the 80 ppb limit occurs within the April to September "growth period", stations in the subtropics
have longer periods (e.g. at Greater Baton Rouge (GBR), USA, for 2001 to 2008) are shifted towards
later months June to November (e.g. the Pearl River Delta (PRD) in China for 2006). While GBR and the rural
PRD stations exhibit indicators close to those of polluted stations in northern Italy (Po Valley), the
(sub)urban PRD stations have high photochemical pollution indicators. However, a surprisingly low indicator
level occurs for the coastal Hong Kong stations for reasons possibly attributable to the prevailing easterly
winds which bring fresh air and airborne sea-salt particulates. (doi: 10.5562/cca1807)


ambient ozone, photochemical pollution, pollution indicators

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