Concentrations, sources, and fluxes of trace elements in the remote marine atmosphere of New Zealand

Abstract

The concentrations of trace elements were determined for aerosol particle, dry deposition, and precipitation samples collected from Ninety Mile Beach on the North Island of New Zealand. Major objectives for the studies, which were conducted as part of the SEAREX (Sea/Air Exchange) Program, were to investigate the concentrations, sources and geochemical cycling of trace elements in the westerly wind field over the South Pacific Ocean. Many of the trace elements were associated with natural materials such as atmospheric sea salt or mineral aerosol. The mean concentration of atmospheric sea salt (∼7.9 μg m −3) was 5 to 30% higher than that predicted by models based on relationships between salt concentrations and wind speed. Mineral aerosol particles were transported through the atmosphere from Australia, and the concentration of atmospheric dust (∼200 ng m −3) was lower than the expected long‐term average due to the fact that the sampling at Ninety Mile Beach was conducted during the climatological low‐dust season. Estimates of the atmospheric deposition rates suggest that eolian material constitutes a significant fraction of the nonbiogenic deep‐sea sediments of the region. Certain trace elements, including Ag, Cd, Cu, I, Mo, Pb, Sb, Se, Ni, and Zn, were enriched over the concentrations expected from natural sources. Anthropogenic emissions from Australia and New Zealand evidently affected the concentrations of several of these elements on local to regional scales.