Scavenging of atmospheric trace metal pollutants by mineral dusts: Inter-regional transport of Australian trace metal pollution to New Zealand

Abstract

Dust samples collected from the surface of glaciers and in dust traps on the remote West Coast of New Zealand's South Island can reliably be identified as being of both Australian and New Zealand origin. Most are, however, found to be enriched in Cu, Zn, Cd, Sb, Sn, Pb, Ni and Cr, when compared with their source-area sediments. The degree of metal enrichment in the dust samples is proportionally related to the percentage of Australian dust implying that the pollutants were transported with dust from eastern Australia. Pollution enrichment factors for these metals in dusts were calculated with a high degree of certainty, because the specific source regions of the dust could be identified. Rates of trace metal pollution transport were then calculated using a record of Australian dust transport over New Zealand. Results show that significant concentrations of trace metal pollutants are transported to New Zealand at levels that are between 1.5 and 100 times background conditions. Results also show that Sb, Pb and Cr are highly particle reactive and their transport in this region is almost exclusively associated with dust scavenging (up-take of pollutants by dust). By comparison, Cu, Zn, Cd, Sn and Ni may also be transported independently of dust. While the rates of pollution metal transport reported here are lower than in more industrialised regions of the globe, the majority of these metals are being deposited in a region internationally recognised for its environmental and conservation values.