Occurrence and fate of semivolatile organic compounds (SVOCs) in the tropical atmosphere

Abstract

Semi-volatile organic compounds (SVOCs) such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) are of global concern as they are persistent, ubiquitous and toxic. The dominant transport pathways occur via the atmospheric compartment where these compounds co-exist in both gas and particulate phases and may undergo long-term cycles between the atmosphere and the earth surface. Long range transport of SVOCs has been shown to occur through a series of deposition/volatilization "hops", commonly referred to as the grasshopper effect, in response to climatic parameters especially the temperature. The fate and transport of SVOCs have been widely studied around the world. However, very little information exists on their environmental levels in different compartments in South-East Asia and there are no previous studies on the gas-particle partitioning of SVOCs which is an important mechanism affecting their environmental fate and transport. <br><br>This doctoral study has investigated (1) occurrence of atmospheric PAHs, PCBs and OCPs in Singapore under different weather conditions and define possible contributing sources, (2) their gas/particle partitioning employing different absorption and adsorption-based models, and (3) the role of air-water exchange of these compounds in the tropical environment by taking into consideration various processes such as mass transfer process, precipitation scavenging of vapour and particle-sorbed chemicals, and dry deposition with aerosol particles.<br>