Assessment of annual air pollution levels with PM1, PM2.5, PM10 and associated heavy metals in Algiers, Algeria

Abstract

Concentrations of particulate matter less than 1 μm, 2.5 μm, 10 μm and their contents of heavy metals were investigated in two different stations, urban and roadside at Algiers (Algeria). Sampling was conducted during two years by a high volume samplers (HVS) equipped with a cascade impactor at four levels stage, for one year sampling. The characterization of the heavy metals associated to the particulate matter (PM) was carried out by X-Ray Fluorescence analysis (XRF). The annual average concentration of PM1, PM2.5 and PM10 in both stations were 18.24, 32.23 and 60.01 μg m−3 respectively. The PM1, PM2.5 and PM10 concentrations in roadside varied from 13.46 to 25.59 μg m−3, 20.82–49.85 μg m−3 and 45.90–77.23 μg m−3 respectively. However in the urban station, the PM1, PM2.5 and PM10 concentrations varied from 10.45 to 26.24 μg m−3, 18.53–47.58 μg m−3 and 43.8–91.62 μg m−3. The heavy metals associated to the PM were confirmed by Scanning Electron Microscopy-Energy Dispersive X-Ray analyses (SEM-EDX). The different spots of PM2.5 analysis by SEM-EDX shows the presence of nineteen elements with anthropogenic and natural origins, within the heavy metal detected, the lead was found with maximum of 5% (weight percent). In order to determine the source contributions of PM levels at the two sampling sites sampling, principal compound analysis (PCA) was applied to the collected data. Statistical analysis confirmed anthropogenic source with traffic being a significant source and high contribution of natural emissions. At both sites, the PM2.5/PM10 ratio is lower than that usually recorded in developed countries. The study of the back-trajectories of the air masses starting from Sahara shows that desert dust influences the concentration and the composition of the PM measured in Algiers.