Estimates of Australian dust flux into New Zealand: Quantifying the eastern Australian dust plume pathway using trace element calibrated 210Pb as a monitor
Weekly average atmospheric 210Pb flux data collected between March 1989 and February 2001 are used to construct a record of Australian dust incursions onto the west coast, South Island, New Zealand. Dusts collected from New Zealand glaciers were found to contain a mixture of local New Zealand and long range Australian material, based on novel binary and tertiary mixing models of their ultra trace element chemistries. Trace element characteristics further allowed determination of the provenance of the long range dust component within Australia to better than 200 km resolution. 210Pb analyses of these chemically characterised dust samples show that activity is related to the percentage of Australian dust in a linear fashion. However, 210Pb activity of Australian dusts collected in New Zealand is orders of magnitude greater than that measured in the alluvial sediments of the provenance areas. Australian dusts collected in New Zealand are also highly enriched in 210Pb compared to dusts collected in Australia. This shows that dust scavenges atmospheric 210Pb which can therefore be used as an effective tracer of long range dust transport. Previously obtained average atmospheric 210Pb flux data can thus be converted into the first record of long range Australian dust flux in New Zealand. Results show that the average atmospheric concentration of Australian dust in New Zealand is 5.3 μg m-3. There is a clear seasonality with the highest concentrations occurring in autumn-winter, preceding Australia's major dust storm season, which occurs in winter-spring. We propose that while meteorological factors control the occurrence of major dust storms, the availability of sediment in source areas is a major control on Australian dust flux in New Zealand. Dust flux is greatest after seasonal river flows when transport of extremely fine grained dust occurs. This is followed by transport of larger particles in the more spectacular winter-spring dust storms. Our results provide information on the characteristics and seasonality of dust transport in the Australian region, which had previously been difficult to quantify by other methods (e.g., satellite imagery). Results also attest to the effectiveness of 210Pb as a tracer in this region. © 2005 Elsevier B.V. All rights reserved.