Trace elements and metal pollution in aerosols at an alpine site, New Zealand: Sources, concentrations and implications

Abstract

Atmospheric aerosol samples were collected at a remote site in New Zealand's Southern Alps. Collected samples were found to be a mixture of New Zealand and Australian sourced sediment, using their trace element signatures. Aerosol concentrations and the relative contribution of different sources was found to be a function of specific air-mass trajectories influencing the study site, dust entrainment rates in source areas and rainfall. Results show that Australian dust is a major source of particulate matter in New Zealand, particularly in remote alpine locations; however, locally derived dust is also important. Metal pollutants, including Pb, Cu and Sn, were enriched in the samples by approximately 15 times and up to >100 times expected natural concentrations, confirming that metal pollution is a ubiquitous component of the atmosphere, even in relatively remote locations. Moreover, pollutants were highly enriched in otherwise clean air, i.e. during and following rainfall. Additionally, high concentrations of elements naturally enriched in sea water, e.g. Sr, Ba and Rb, were deposited alongside mineral dust, reflecting the oceanic origin of air influencing the site and the role of sea spray in contributing aerosol to the atmosphere. These elements experienced the greatest enrichment during rainfall, implying sea spray and pollution become relatively important during otherwise clean air conditions.