Chemical speciation of fine airborne particles in Abu Dhabi.

PM2.5 was sampled at two urban background sites in Abu Dhabi (Khalifa in the city of Abu Dhabi and Bida Zayed) and analysed chemically for further source identification and quantification. Understanding of source contributions to PM2.5 is a prerequisite for the formulation of effective control strategies for PM2.5 emissions. For both sites, five source factors were identified. Long-range transported aerosol is the largest contributor (~41%) to average PM2.5 mass concentrations at both sites. It gradually forms from SO2, which is possibly emitted into ambient in the Arabian Gulf area, while it is transported to the sites. Mineral dust was found to be the second most important source, contributing ~25% at both sites. It represents an ubiquitous natural contribution of mainly regional origin to particulate matter in Abu Dhabi. Other source contributions to particle concentrations found at Khalifa identified were: local traffic (15.1%), shipping/industry (10.5%) and sea salt (4.0%). The latter is a natural contribution. At Bida Zayed, a mixed traffic/industry factor (13.2%) was found, as well as another two factors of natural origin, explaining 11.4% and 8.7%