Abstract
Abstract. Size-segregated particulate air samples were collected during the austral summer of 2016–2017 at Palmer Station on Anvers Island, western Antarctic Peninsula, to characterize trace elements in aerosols. Trace elements in aerosol samples – including Al, P, Ca, Ti, V, Mn, Ni, Cu, Zn, Ce, and Pb – were determined by total digestion and a sector field inductively coupled plasma mass spectrometer (SF-ICP-MS). The crustal enrichment factors (EFcrust) and k-means clustering results of particle-size distributions show that these elements are derived primarily from three sources: (1) regional crustal emissions, including possible resuspension of soils containing biogenic P, (2) long-range transport, and (3) sea salt. Elements derived from crustal sources (Al, P, Ti, V, Mn, Ce) with EFcrust<10 were dominated by the coarse-mode particles (>1.8 µm) and peaked around 4.4 µm in diameter, reflecting the regional contributions. Non-crustal elements (Ca, Ni, Cu, Zn, Pb) showed EFcrust>10. Aerosol Pb was primarily dominated by fine-mode particles, peaking at 0.14–0.25 µm, and likely was impacted by air masses from southern South America based on air mass back trajectories. However, Ni, Cu, and Zn were not detectable in most size fractions and did not present clear size patterns. Sea-salt elements (Ca, Na+, K+) showed a single-mode distribution and peaked at 2.5–4.4 µm. The estimated dry deposition fluxes of mineral dust for the austral summer, based on the particle-size distributions of Al measured at Palmer Station, ranged from 0.65 to 28 mg m−2 yr−1 with a mean of 5.5±5.0 mg m−2 yr−1. The estimated dry deposition fluxes of the target trace elements in this study were lower than most fluxes reported previously for coastal Antarctica and suggest that atmospheric input of trace elements through dry deposition processes may play a minor role in determining trace element concentrations in surface seawater over the continental shelf of the western Antarctic Peninsula.
Highlights
Aerosols affect the climate through direct and indirect radiative forcing (Kaufman et al, 2002)
3.3.2 Bimodal distribution applied k-means clustering to the full data set, and the results indicate that aerosol trace elements in the austral summer at Palmer Station can be classified into five groups based on their normalized particle-size distributions (Fig. 6), with each group showing a unique size distribution pattern: (1) crustal elements from crustal weathering and wind-induced resuspension of soil particles, (2) Al dominated by local minerals, (3) Pb from anthropogenic sources as a result of long-range transport, (4) sea-salt elements from the ocean through bursting bubbles of seawater, and (5) P from local biogenic and soil resuspension
Results from this study indicate that trace elements in aerosols over Palmer Station during the austral summer were primarily derived from (1) the regional crustal sources, which includes P-enriched soil resuspension; (2) remote anthropogenic emissions in South America; and (3) seawater
Summary
Aerosols affect the climate through direct and indirect radiative forcing (Kaufman et al, 2002). The extent of such forcing depends on both physical and chemical properties of aerosols, including particle size and chemical composition (Pilinis et al, 1995). Over the Southern Ocean and Antarctica, aerosol particle-size distributions have been studied (Gras, 1995; Järvinen et al, 2013; Xu et al, 2013; Kim et al, 2017; Herenz et al, 2019; Lachlan-Cope et al, 2020). The maximum and minimum of the particle number concentrations at two sites were found in the austral summer and austral winter, respectively (Kim et al, 2017; Lachlan-Cope et al, 2020).
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