Mercury and trace metal wet deposition across five stations in Alaska: controlling factors, spatial patterns, and source regions
A total of 1360 weeks of mercury (Hg) wet deposition data were collected by the state of Alaska Department of Environmental Conservation and the U.S. National Park Service across five stations spanning up to 8 years. Here, we analyze concentration patterns, source regions, and seasonal and annual Hg...
Published in: | Atmospheric Chemistry and Physics |
---|---|
Main Authors: | , , , |
Format: | Text |
Language: | English |
Published: |
2019
|
Subjects: | |
Online Access: | https://doi.org/10.5194/acp-19-6913-2019 https://www.atmos-chem-phys.net/19/6913/2019/ |
id |
ftcopernicus:oai:publications.copernicus.org:acp72932 |
---|---|
record_format |
openpolar |
spelling |
ftcopernicus:oai:publications.copernicus.org:acp72932 2023-05-15T15:05:51+02:00 Mercury and trace metal wet deposition across five stations in Alaska: controlling factors, spatial patterns, and source regions Pearson, Christopher Howard, Dean Moore, Christopher Obrist, Daniel 2019-05-23 application/pdf https://doi.org/10.5194/acp-19-6913-2019 https://www.atmos-chem-phys.net/19/6913/2019/ eng eng doi:10.5194/acp-19-6913-2019 https://www.atmos-chem-phys.net/19/6913/2019/ eISSN: 1680-7324 Text 2019 ftcopernicus https://doi.org/10.5194/acp-19-6913-2019 2019-12-24T09:49:11Z A total of 1360 weeks of mercury (Hg) wet deposition data were collected by the state of Alaska Department of Environmental Conservation and the U.S. National Park Service across five stations spanning up to 8 years. Here, we analyze concentration patterns, source regions, and seasonal and annual Hg deposition loadings across these five sites in Alaska, along with auxiliary trace metals including Cr, Ni, As, and Pb. We found that Hg concentrations in precipitation at the two northernmost stations, Nome (64.5 ∘ N) along the coast of the Bering Sea and the inland site of Gates of the Arctic (66.9 ∘ N), were statistically higher (average of 5.3 and 5.5 ng L −1 , respectively) than those at the two lowest-latitude sites, Kodiak Island (57.7 ∘ N, 2.7 ng L −1 ) and Glacier Bay (58.5 ∘ N, 2.6 ng L −1 ) . These differences were largely explained by different precipitation regimes, with higher precipitation at the lower-latitude stations leading to dilution effects. The highest annual Hg deposition loads were consistently observed at Kodiak Island ( 4.80±1.04 µ g m −2 ) , while the lowest annual deposition was at Gates of the Arctic ( 2.11±0.67 µ g m −2 ) . Across all stations and collection years, annual precipitation strongly controlled annual Hg deposition, explaining 73 % of the variability in observed annual Hg deposition. The data further showed that annual Hg deposition loads across all five Alaska sites were consistently among the lowest in the United States, ranking in the lowest 1 % to 5 % of over 99 monitoring stations. Detailed back-trajectory analyses showed diffuse source regions for most Hg deposition sites suggesting largely global or regional Hg sources. One notable exception was Nome, where we found increased Hg contributions from the western Pacific Ocean downwind of East Asia. Analysis of other trace elements (As, Cr, Cu, Ni, Pb, Se, Zn) from Dutch Harbor, Nome, and Kodiak Island showed generally higher trace metal concentrations at the northern station Nome compared to Kodiak Island further to the south, with concentrations at Dutch Harbor falling in between. Across all sites, we find two distinct groups of correlating elements: Cr and Ni and As and Pb. We attribute these associations to possibly different source origins, whereby sources of Ni and Cr may be derived from crustal (e.g., dust) sources while As and Pb may include long-range transport of anthropogenic pollution. Hg was not strongly associated with either of these two groups. Text Arctic Bering Sea glacier Kodiak Nome Alaska Copernicus Publications: E-Journals Arctic Bering Sea Glacier Bay Pacific Atmospheric Chemistry and Physics 19 10 6913 6929 |
institution |
Open Polar |
collection |
Copernicus Publications: E-Journals |
op_collection_id |
ftcopernicus |
language |
English |
description |
A total of 1360 weeks of mercury (Hg) wet deposition data were collected by the state of Alaska Department of Environmental Conservation and the U.S. National Park Service across five stations spanning up to 8 years. Here, we analyze concentration patterns, source regions, and seasonal and annual Hg deposition loadings across these five sites in Alaska, along with auxiliary trace metals including Cr, Ni, As, and Pb. We found that Hg concentrations in precipitation at the two northernmost stations, Nome (64.5 ∘ N) along the coast of the Bering Sea and the inland site of Gates of the Arctic (66.9 ∘ N), were statistically higher (average of 5.3 and 5.5 ng L −1 , respectively) than those at the two lowest-latitude sites, Kodiak Island (57.7 ∘ N, 2.7 ng L −1 ) and Glacier Bay (58.5 ∘ N, 2.6 ng L −1 ) . These differences were largely explained by different precipitation regimes, with higher precipitation at the lower-latitude stations leading to dilution effects. The highest annual Hg deposition loads were consistently observed at Kodiak Island ( 4.80±1.04 µ g m −2 ) , while the lowest annual deposition was at Gates of the Arctic ( 2.11±0.67 µ g m −2 ) . Across all stations and collection years, annual precipitation strongly controlled annual Hg deposition, explaining 73 % of the variability in observed annual Hg deposition. The data further showed that annual Hg deposition loads across all five Alaska sites were consistently among the lowest in the United States, ranking in the lowest 1 % to 5 % of over 99 monitoring stations. Detailed back-trajectory analyses showed diffuse source regions for most Hg deposition sites suggesting largely global or regional Hg sources. One notable exception was Nome, where we found increased Hg contributions from the western Pacific Ocean downwind of East Asia. Analysis of other trace elements (As, Cr, Cu, Ni, Pb, Se, Zn) from Dutch Harbor, Nome, and Kodiak Island showed generally higher trace metal concentrations at the northern station Nome compared to Kodiak Island further to the south, with concentrations at Dutch Harbor falling in between. Across all sites, we find two distinct groups of correlating elements: Cr and Ni and As and Pb. We attribute these associations to possibly different source origins, whereby sources of Ni and Cr may be derived from crustal (e.g., dust) sources while As and Pb may include long-range transport of anthropogenic pollution. Hg was not strongly associated with either of these two groups. |
format |
Text |
author |
Pearson, Christopher Howard, Dean Moore, Christopher Obrist, Daniel |
spellingShingle |
Pearson, Christopher Howard, Dean Moore, Christopher Obrist, Daniel Mercury and trace metal wet deposition across five stations in Alaska: controlling factors, spatial patterns, and source regions |
author_facet |
Pearson, Christopher Howard, Dean Moore, Christopher Obrist, Daniel |
author_sort |
Pearson, Christopher |
title |
Mercury and trace metal wet deposition across five stations in Alaska: controlling factors, spatial patterns, and source regions |
title_short |
Mercury and trace metal wet deposition across five stations in Alaska: controlling factors, spatial patterns, and source regions |
title_full |
Mercury and trace metal wet deposition across five stations in Alaska: controlling factors, spatial patterns, and source regions |
title_fullStr |
Mercury and trace metal wet deposition across five stations in Alaska: controlling factors, spatial patterns, and source regions |
title_full_unstemmed |
Mercury and trace metal wet deposition across five stations in Alaska: controlling factors, spatial patterns, and source regions |
title_sort |
mercury and trace metal wet deposition across five stations in alaska: controlling factors, spatial patterns, and source regions |
publishDate |
2019 |
url |
https://doi.org/10.5194/acp-19-6913-2019 https://www.atmos-chem-phys.net/19/6913/2019/ |
geographic |
Arctic Bering Sea Glacier Bay Pacific |
geographic_facet |
Arctic Bering Sea Glacier Bay Pacific |
genre |
Arctic Bering Sea glacier Kodiak Nome Alaska |
genre_facet |
Arctic Bering Sea glacier Kodiak Nome Alaska |
op_source |
eISSN: 1680-7324 |
op_relation |
doi:10.5194/acp-19-6913-2019 https://www.atmos-chem-phys.net/19/6913/2019/ |
op_doi |
https://doi.org/10.5194/acp-19-6913-2019 |
container_title |
Atmospheric Chemistry and Physics |
container_volume |
19 |
container_issue |
10 |
container_start_page |
6913 |
op_container_end_page |
6929 |
_version_ |
1766337480299118592 |