K. Kourtidis et al., Benzene and toluene levels measured with a commercial DOAS system in Thessaloniki, Greece, ATMOS ENVIR, 34(9), 2000, pp. 1471-1480
Benzene, toluene and p-xylene were measured above the buildings level in Th
essaloniki, Greece for around eight months during the period December 1993-
August 1994 by means of a commercial differential optical absorption spectr
ometer (OPSIS DOAS). Daily mean mixing ratios for benzene and toluene varie
d between 1-6 and 1-32 ppb, respectively. The data indicate that the annual
mean benzene concentrations most probably lie in the range 2-3 ppb, which
is below the guide values but above the target values of European countries
that have set limits for benzene. Mean diurnal variations of benzene and t
oluene during summer and winter months reflect the effects of emission, pho
tochemical degradation and mixing. Benzene and toluene hourly values correl
ated well with each other and with NO2. Toluene and benzene hourly values w
ere negatively correlated with ozone during summertime. During wintertime,
considerable enhancements of benzene and toluene mixing ratios might be ass
ociated with the passage of synoptic weather systems of fair weather. Altho
ugh the measurement of p-xylene is, in principle, efficiently performed wit
h the DOAS technique, the OPSIS instrument p-xylene measurements contradict
current understanding of its sources and sinks and are thus attributed to
errors of the instrument in the evaluation of this substance. (C) 2000 Else
vier Science Ltd. All rights reserved.