Search

Black carbon aerosol (BC), which is emitted from natural and anthropogenic sources (e.g., wildfires, coal burning), can contribute to magnify climate warming at high latitudes by darkening snow- and ice-covered surfaces, and subsequently lowering their albedo. Therefore, modeling the atmospheric transport and deposition of BC to the Arctic is important, and historical archives of BC accumulation in polar ice can help to validate such modeling efforts. Here we present a > 250-year ice-core record of refractory BC (rBC) deposition on Devon ice cap, Canada, spanning the years from 1735 to 1992. This is the first such record ever developed from the Canadian Arctic. The estimated mean deposition flux of rBC on Devon ice cap for 1963-1990 is 0.2 mgm-2 a-1, which is at the low end of estimates from Greenland ice cores obtained using the same analytical method (~ 0:1-4 mgm-2 a-1). The Devon ice cap rBC record also differs from the Greenland records in that it shows only a modest increase in rBC deposition during the 20th century. In the Greenland records a pronounced rise in rBC is observed from the 1880s to the 1910s, which is largely attributed to midlatitude coal burning emissions. The deposition of contaminants such as sulfate and lead increased on Devon ice cap in the 20th century but no concomitant rise in rBC is recorded in the ice. Part of the difference with Greenland could be due to local factors such as melt- freeze cycles on Devon ice cap that may limit the detection sensitivity of rBC analyses in melt-impacted core samples, and wind scouring of winter snow at the coring site. Air back-trajectory analyses also suggest that Devon ice cap receives BC from more distant North American and Eurasian sources than Greenland, and aerosol mixing and removal during long-range transport over the Arctic Ocean likely masks some of the specific BC source-receptor relationships. Findings from this study suggest that there could be a large variability in BC aerosol deposition across the Arctic region arising from different transport patterns. This variability needs to be accounted for when estimating the large-scale albedo lowering effect of BC deposition on Arctic snow/ice. [ABSTRACT FROM AUTHOR]

Black carbon aerosol (BC) emitted from natural and anthropogenic sources (e.g., wildfires, coal burning) can contribute to magnify climate warming at high latitudes by darkening snow- and ice-covered surfaces, thus lowering their albedo. Modeling the atmospheric transport and deposition of BC to the Arctic is therefore important, and historical archives of BC accumulation in polar ice can help to validate such modeling efforts. Here we present a 190-year ice-core record of refractory BC (rBC) deposition on Devon ice cap, Canada, spanning calendar years 1810-1990, the first such record ever developed from the Canadian Arctic. The estimated mean deposition flux of rBC on Devon ice cap for 1963-1990 is 0.2 mg m-2 a-1, which is low compared to most Greenland ice-core sites over the same period. The Devon ice cap rBC record also differs from existing Greenland records in that it shows no evidence of a substantial increase in rBC deposition during the early-mid 20th century, which, for Greenland, has been attributed to mid-latitude coal burning emissions. The deposition of other contaminants such as sulfate and Pb increased on Devon ice cap in the 20th century but without a concomitant rise in rBC. Part of the difference with Greenland may be due to local factors such as wind scouring of winter snow at the coring site on Devon ice cap. Air back-trajectory analyses also suggest that Devon ice cap receives BC from more distant North American and Eurasian sources than Greenland, and aerosol mixing and removal during long-range transport over the Arctic Ocean likely masks some of the specific BC source-receptor relationships. Findings from this study underscore the large variability in BC aerosol deposition across the Arctic region that may arise from different transport patterns. This variability needs to be accounted for when estimating the large-scale albedo lowering effect of BC deposition on Arctic snow/ice. [ABSTRACT FROM AUTHOR]

Increases in global anthropogenic emissions are far reaching, and are a concern even in remote areas. Tasmania, Australia is an island state that hosts the only Southern Hemisphere premier Baseline Air Pollution Station as part of the World Meteorological Organization-Global Atmosphere Watch network. Despite Tasmania's importance as a baseline location, little is known about atmospheric nitrogen (N) and sulfur (S) deposition and sources across the state. Here we investigate total N and S content and isotopic compositions (δ 15 N, δ 34 S) in the lichen Cladia retipora as a bio-indicator to identify whether atmospheric N and S deposition in Tasmania is affected by anthropogenic pollution. Both TN and TS were extremely low in all 66 samples collected across the state, averaging 0.29 ± 0.28% and 0.03 ± 0.05%, respectively. The average δ 15 N value was −2.8 ± 1.9‰ and there was no correlation with TN, but values were highest towards the denser populated SE of Tasmania. Lichens collected from sites within 500 m of salt marshes revealed a strong local source of microbially-reduced S as indicated by δ 34 S values as low as −21.9‰. All other lichen samples had a mean value of δ 34 S value of 13.7 ± 2.2‰, indicating mixing of marine biogenic S and anthropogenic S. This study represents the first baseline study of atmospheric N and S in C. retipora across Tasmania, and demonstrates the suitability of lichen bio-monitoring for future studies in this region. [ABSTRACT FROM AUTHOR]