Influence of mineral dust on the concentration and composition of PM10 in the city of Constantine

Abstract

Abstract Measurements of Saharan dust (SD) inputs are very scarce in the vicinity of the Saharan desert. This work aims to identify Saharan dust intrusions and evaluate their contribution to annual and daily PM10 at an urban background site located in the city of Constantine in Algeria. A reliable identification of SD days was carried out using aerosol maps provided by BSC-DREAM model and the information provided by HYSPLIT air mass back trajectories. SD is mainly composed of mineral dust (MD) due to the proximity of the Sahara to the study site. MD was determined by chemical speciation analysis and was estimated on SD days and non SD days. The contribution of MD on SD days was about 50% higher than that observed on non SD days. The observed average PM10 concentration during the study period was 56 ± 32.0 μg/m3. During SD days, the average PM10 concentration was 70 ± 36.1 µg/m3. On average, the PM10 concentration increased by 17.05 ± 12.7 μg/m3 on SD days. SD events contributed between 0.6 and 41.5 µg/m3 to the daily PM10 concentrations, whereas the average contribution to the annual PM10 concentration was 7.2 ± 11.8 μg/m3 i.e., 12.8 ± 15.5%. After the extraction of the SD load, the annual WHO air quality guideline (AQG) was still exceeded. SD incursions led to an increase of most metal elements concentrations by a factor ranging from 1.05 to 3.33. Our results point out that SD outbreaks are quite frequent as they occurred 42.2% of the annual days.