学術雑誌論文 Aerosol black carbon over Svalbard regions of Arctic

10 ( 1 )  , pp.60 - 70 , 2016-03
ISSN:1873-9652
内容記述
In view of the climate impact of aerosol Black Carbon (BC) over snow covered regions (through enhanced absorption of radiation as well as snow-albedo forcing), and in view of the increasing anthropogenic presence and influence in the northern polar regions, continuous long term measurements of airborne BC have been undertaken from the Svalbard region of Norwegian Arctic (Ny-Ålesund, 79°N, 12°E, 8 m a.s.l.). This study, employing data over a period of 4-years (2010–2013) have shown a consistent spring-time enhancement in BC concentrations, having a (climatological) seasonal mean value of ∼50.3 ± 19.5 ng m−3, nearly 3-times higher than the lowest BC concentrations in summer (∼19.5 ± 6.5 ng m−3). Spectral variation of absorbance indicates that long-range transported biomass burning aerosols contribute as high as 25% to the high BC concentrations in the Arctic atmosphere in spring. Concurrent estimates of BC concentrations in the Arctic snow (for an ensemble of snow samples collected over a period of time during spring) showed values ranging from 0.6 ppb to 4.1 ppb. These values have been used to estimate the BC scavenging ratio (SR). Our studies revealed a mean value of SR ∼98 ± 46, which varied over wide range from 40 to 184 for individual samples. In a broader perspective, the seasonal variations of atmospheric BC concentrations at the Arctic are similar to those seen at the high altitude Himalayas; even though the concentrations are much lower at Arctic. It is found that synoptic conditions mainly influence the high altitude Himalayas, while the influences of local anthropogenic influences are not negligible at the Arctic in modulating the seasonal variations of absorbing aerosols.
ノルウェイ北極のスバールバル地域で、大気中ブラック・カーボン(BC)濃度の連続測定を行った。2010–2012年の4年間のデータから、夏の最低値(〜19.5 ± 6.5 ng m−3)より3倍もの春季の増大(平均50.3 ± 19.5 ng m−3)が一貫して見られた。吸収物質の波長特性から、春季の大気中BC濃度のうち最大25%は、長距離輸送された森林火災によるエアロゾルが貢献している。同時に見た、北極積雪中のBC濃度は0.6〜4.1 ppbであった。これらの値を使って、BC沈着率を求めたところ、平均でも98 ± 46となり、個々のサンプルでは40–184と大きくばらついた。比較すると、北極の大気中BC濃度の季節変化はヒマラヤ高山域で見られるものと同様であるが、濃度そのものは北極の方がはるかに低い。ヒマラヤ高山域では、総観規模の現象が影響するが、北極域では局所的な人為起源の影響が無視できない。

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