Origin, transport and deposition of aerosol iron to Australian coastal waters

Atmospheric Trace Metal Deposition near the Great Barrier Reef, Australia

“…The FFeS results reported in this section are similar to data reported by Winton et al [28] for aerosols collected at a coastal site in the Northern Territory (Australia) (2-12%) and lie in the lower range of solubilities observed in Tasmania (0.5-56%) [29]. The labile fraction of Fe in aerosols collected at Mission Beach is similar to those reported in aerosols collected at sea during the same period (4-33%) [68]. Our results are higher than those reported by Mackie et al [57] for readily soluble Fe (dissolving in the time range from minutes to hours) from soil samples collected in Thargomindah in Southwest Queensland (0.9 ± 0.3%).…”

“…The mean flux of labile Fe in this study was 0.213 ± 0.107 µmol m −2 day −1 , which is lower than results of marine aerosols collected at sea (Coral Sea Marine Region) during the same time period, 0.303 ± 0.590 µmol m −2 day −1 [68] calculated based on the same deposition velocity. Fluxes reported in this case are also similar to the lower results reported by Winton et al [28] for Northern Territory, 0.2 ± 0.1-4 ± 2 µmol m −2 day −1 (also calculated for the same deposition velocity).…”

“…A value of dry deposition velocity (V dry ) (4) is sensitive to the wind speed and humidity as well as particle size profile. For coarse crustal particulates, V dry has been estimated to range from 0.3 to 3.0 cm s −1 [66] and was assumed of 2 cm s −1 for coastal regions of Australia [28,67,68] with uncertainty of 50% [28,29]. The calculated dry deposition Fe flux ranged from 0.055 ± 0.027 to 0.258 ± 0.129 µmol m −2 day −1 (mean 0.143 ± 0.072) for the soluble, 0.017 ± 0.008 to 0.138 ± 0.069 µmol m −2 day −1 (mean 0.070 ± 0.035) for the leachable, and 0.802 ± 0.401 to 6.27 ± 3.14 µmol m −2 day −1 (mean 2.73 ± 1.37) for the refractory Fe fraction.…”

“…Aerosol particulates were accumulated by pumping the air through an acid-cleaned full sheet (20 cm × 25 cm) cellulose filter (Whatman 41, W41) without a size cut-off (TSP). As a result, we directly measured concentrations of trace metals in air, and use these data to estimate trace metal deposition fluxes using the methods previously described [28,[66][67][68]. Before sampling, filters were cleaned for TM analysis according to GEOTRACES procedures [69,70].…”

Atmospheric Trace Metal Deposition from Natural and Anthropogenic Sources in Western Australia

“…A higher FFeS was observed in aerosol containing fresh bushfire emissions from both Gingin and GI sites, where the labile Fe fraction contributed 3.8 and 4.0% of total Fe, respectively. The Fe solubility reported here is lower than reported for aerosols collected along the south and north sector of Western Australia's coast, where the fraction of labile Fe ranged from 7% to 16% (median 8%) and from 3% to 15% (median 5%), respectively [69]. However, aerosols analysed by Perron et al [69] were collected at sea on a research vessel, while aerosols analysed here were collected on land.…”