Large-scale spatial variability of major ions in the atmospheric wet deposition along the China–Antarctica transect (31°N–69°S)

Abstract

A B S T R A C T Twenty-two atmospheric wet deposition samples were collected along the large-scale transect from China to Antarctica, and the major ion components as well as their sources were analysed. It is the first time that chemical composition variation of precipitation has been investigated on such a large-scale transect. The results show that the precipitations exhibit near-neutral pH on the average. On the whole, ionic levels on an equivalent basis are presented as Cl ( , and ionic contents of rainfall are generally higher compared with values of snowfall. Ionic concentrations vary greatly on the study transect, and the values of the Northern Hemisphere are relatively higher. Both enrichment factor and principal component analyses reveal that Cl ( , Na ' , K ' and Mg 2 ' are mainly related to sea salt, namely, the marine source. The good correlations between marine-sourced ions and wind speed indicate that seawater sprays are important sources of precipitation ions. Land-based sources, for example, human activities, are the primary sources of NO À 3 , NH þ 4 and Ca 2 ' . SO 2À 4 partly originates from sea salt, but anthropogenic and biogenic sources are also important contributors. Backward trajectories illustrate well the different main sources and transport routes of the precipitation ions.

Isotope Fractionation of Nitrate During Volatilization in Snow: A Field Investigation in Antarctica

“…Details on this method are described in Shi et al (2012). Details on this method are described in Shi et al (2012).…”

“…In the laboratory, analyses of major ions (Na + , NH 4 + , K + , Mg 2+ , Ca 2+ , Cl − , NO 3 − , and SO 4 2− ) were performed using a Dionex ICS-3000 ion chromatograph. Details on this method are described in Shi et al (2012). Repeated measurements within and across different runs were conducted to check the analysis precision.…”

Nitrate deposition and preservation in the snowpack along a traverse from coast to the ice sheet summit (Dome A) in East Antarctica

“…Significant losses can account for NO − 3 profiles at inland sites, i.e., NO − 3 concentration decreasing with increasing depths. Previous observations and modeling works suggested that photolysis dominates the losses Erbland et al, 2013;Shi et al, 2015). During photolysis of NO − 3 , some of the photoproducts (NO x ) are emitted into the gas phase France et al, 2011), and these products could undergo reoxidation by the local oxidants (e.g., hydroxyl radical (OH), NO 2 + OH + M → HNO 3 + M), forming gas-phase HNO 3 .…”

“…Gas-phase and snow concentration studies and recent isotopic investigations and modeling have shown that NO − 3 , particularly in snow on the Antarctic plateau, is a combination of deposition of HNO 3 and post-depositional loss or recycling of NO − 3 (e.g., Röthlisberger et al, 2002;Davis et al, 2004;Dibb et al, 2004;Erbland et al, 2013Erbland et al, , 2015Shi et al, 2015;Bock et al, 2016;Zatko et al, 2016). Based upon a suite of isotopic studies in the field and laboratory, it has been demonstrated that under cold, sunlit conditions ultraviolet photolysis dominates NO − 3 post-depositional processing, whereas HNO 3 volatilization may become more important at warmer temperatures > −20 • C (Röthlisberger et al, 2002;Frey et al, 2009;Erbland et al, 2013;Berhanu et al, 2015).…”

“…Field measurements at Dome C on the East Antarctic plateau suggest a z e of 10 to 20 cm (France et al, 2011), and the depth is dependent upon the concentration of impurities contained in the snow (Zatko et al, 2013). In the inland regions with low snow accumulation rates, particularly on the East Antarctic plateaus, photolysis has been shown to lead to significant post-depositional loss of NO − 3 , demonstrated by significant enrichment in 15 N of snow NO − 3 (i.e., high δ 15 N) Erbland et al, 2013Berhanu et al, 2015;Shi et al, 2015), as well as a decrease in δ 18 O and 17 O due to reformation of NO − 3 in the condensed phase (Erbland et al, 2013;Shi et al, 2015, and references therein). The transport and recycling of NO x sourced from photolysis of snow NO − 3 in the summertime has been invoked to model the distribution of snowpack NO − 3 across the Antarctic plateau (Zatko et al, 2016).…”