An Analysis of Heavy Metals of Atmospheric Aerosols in Makkah

Abstract

Heavy metals in atmospheric aerosols make an important group of air pollutants, which adversely affect human health, building materials and the natural environment. In this study the levels of six heavy metals are assessed in Mina, Makkah during the Hajj season of 2010 (1431 H). The heavy metals considered in this study are lead (Pb), nickel (Ni), cadmium (Cd), chromium (Cr), vanadium (V) and arsenic (As), which are the most predominant heavy metals in the atmosphere. The concentrations of Total Suspended Particulate (TSP), PM10 and PM2.5 are compared and their heavy metals contents are analysed. The concentration of TSP was much greater than that of PM10 and PM2.5, which probably indicate resuspension of particles being the predominant source of particles in the study area. However, the difference in their heavy metal content was relatively less prominent, indicating a high proportion of heavy metal in PM2.5, which pose potentially greater health risk due to their ability to penetrate deeper into the respiratory system. Correlation analysis revealed two distinct clusters in heavy metals: (a) Pb, Ni, Cd and Cr; (b) V and As. Elements in each group had stronger correlation with each other and relatively weaker correlation with the elements in the other cluster. V was negative, whereas As was positively correlated with Pb, Cd, Cr and Ni. Variations in TSP, PM10 and PM2.5 concentrations during different days of the Hajj and their possible reasons have been discussed. Further work is recommended to analyse spatial and temporal variations in heavy metals concentrations over longer periods of time and to quantify the contribution of each source of emission, which is part of the ongoing research project for the improvement of air quality in Makkah.