PM10 concentration levels at an urban and background site in Cyprus: the impact of urban sources and dust storms

Abstract

Air quality in Cyprus is influenced by both local and transported pollution, including desert dust storms. We examined PM10 concentration data collected in Nicosia (urban representative) from April 1, 1993, through December 11, 2008, and in Ayia Marina (rural background representative) from January 1, 1999, through December 31, 2008. Measurements were conducted using a Tapered Element Oscillating Micro-balance (TEOM). PM10 concentrations, meteorological records, and satellite data were used to identify dust storm days. We investigated long-term trends using a Generalized Additive Model (GAM) after controlling for day of week, month, temperature, wind speed, and relative humidity. In Nicosia, annual PM10 concentrations ranged from 50.4 to 63.8 μg/m3 and exceeded the EU annual standard limit enacted in 2005 of 40 μg/m3 every year A large, statistically significant impact of urban sources (defined as the difference between urban and background levels) was seen in Nicosia over the period 2000-2008, and was highest during traffic hours, weekdays, cold months, and low wind conditions. Our estimate of the mean (standard error) contribution of urban sources to the daily ambient PM10 was 24.0 (0.4) μg/m3. The study of yearly trends showed that PM10 levels in Nicosia decreased from 59.4 μg/m3 in 1993 to 49.0 μg/m3 in 2008, probably in part as a result of traffic emission control policies in Cyprus. In Ayia Marina, annual concentrations ranged from 27.3 to 35.6 μg/m3, and no obvious time trends were observed. The levels measured at the Cyprus background site are comparable to background concentrations reported in other Eastern Mediterranean countries. Average daily PM10 concentrations during desert dust storms were around 100 μg/m3 since 2000 and much higher in earlier years. Despite the large impact ofdust storms and their increasing frequency over time, dust storms were responsible for a small fraction of the exceedances of the daily PM10 limit. Implications: This paper examines PM10 concentrations in Nicosia, Cyprus, from 1993 to 2008. The decrease in PM10 levels in Nicosia suggests that the implementation of traffic emission control policies in Cyprus has been effective. However, particle levels still exceeded the European Uion annual standard, and dust storms were responsible for a small fraction of the daily PM10 limit exceedances. Other natural particles that are not assessed in this study, such as resuspended soil and sea salt, may be responsible in part for the hig particle levels.

Figures

Figure 1

Location of the two measuring sites: Nicosia (urban) and Ayia Marina (background).

Figure 2

Annual PM10 levels for Nicosia (1993–2008) and Ayia Marina (1999–2008) in μg/m3. Dashed line shows the EU annual standard of 40 μg/m3 and error bars correspond to the 95% confidence intervals for the dust contribution.

Figure 3

Monthly PM10 concentrations for Nicosia (urban), Ayia Marina (background) and urban contribution in μg/m3. Error bars correspond to the 95% confidence intervals for the dust contribution.

Figure 4

Annual PM10 trends adjusted for month, day of week, desert dust storm effect, temperature, wind speed and relative humidity for Nicosia (urban), Ayia Marina (background) and urban contribution. Dashed lines represent the 95% confidence intervals for the estimate.

Figure 5

Number of observed dust days per year in Cyprus and fitted linear trend (dashed line).

Figure 6

Urban source contributions to PM10 hourly concentrations in the (a) cold and (b) warm season, μg/m3.