Elemental composition in source identification of brown haze in Auckland, New Zealand

Abstract

A brown haze, which builds up over Auckland, New Zealand under calm and cold weather conditions, causes public concern. This study identifies the major sources of this brown haze using variations in the elemental composition of airborne particulate matter between those collected during brown haze days, and normal days in the year 2001. Airborne particulate matter was collected in a site in southeast Auckland, using a versatile air pollution sampler (VAPS) and a PM10 hi-volume sampler. The elemental composition of the samples, collected using the hi-volume sampler, was quantitatively determined for 14 elements using ICP/MS. The elemental composition of the coarse and fine fractions of the particulate matter collected using the VAPS, was quantitatively determined using ion beam analysis for 16 elements. Elemental carbon was quantitatively determined by a light reflection/transmission technique. For source determination, the VAPS was found to be more useful that the hi-volume sampler. Enrichment factors (EF) for each element of the PM10 samples were calculated to identify the sources. Further, principal component factor analysis with Varimax rotation was performed using some selected elements in the coarse and fine fractions of particulate samples collected using the VAPS to identify major sources of PM10 in Auckland. The analysis yielded six significant sources: sea spray, suspended soil/road dust, fine soil, domestic emissions, diesel, and petrol emissions. EF values for brown haze samples revealed that diesel emissions were the major sources responsible for the build-up of brown haze. Coal combustion emissions were also found to contributed, but to a lesser extent. Furthermore, source apportionment using absolute principal component analysis on brown haze and normal days confirmed that accumulation of diesel emissions contributed most to the appearance of brown haze and coal combustion emissions to a lesser extent.