Geochemical characteristics of deposits from the 2011 Tohoku-oki tsunami at Hasunuma, Kujukuri coastal plain
Geochemical characteristics of deposits from the 2011 Tohoku-oki tsunami at Hasunuma, Kujukuri coastal plain
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2011年东北冲海啸九十九里滨海平原莲沼沉积物的地球化学特征
DOI：
10.1111/iar.12159
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发表时间：
2016
期刊：
影响因子：
1.5
通讯作者：
Tanigawa K.
中科院分区：
文献类型：
--
作者：
Shinozaki T.;Sawai Y.;Hara J.;Ikehara M.;Matsumoto D.;Tanigawa K.
我们研究了与 2011 年东北冲海啸相关的沉积物的地球化学特征和时间变化。 2011 年和 2014 年，在日本九十九里沿海平原莲沼的沙质海啸沉积物和相关土壤中测量了稳定碳同位素比、生物标志物和水可浸出离子。2011 年的海啸在该地点形成了 10-30 厘米厚的极细至中砂层。海啸沉积物有机质贫乏，并且没有样品含有任何可检测到的陆地或海洋生物标志物。在下面的土壤中，我们鉴定出了来自陆地植物的碳氢化合物和甾醇，但没有检测到海洋来源的生物标志物。在 2011 年收集的样本中，海啸产生的水可浸出离子的浓度在海啸沉积物正下方的土壤中最高，然后随着深度的增加逐渐降低。由于其质地更细，有机含量更高，土壤比沙质海啸沉积物具有更高的持水能力。这种分布表明，海啸产生的离子迅速穿透沙层并集中在下面的土壤中。在 2014 年收集的样品中，土壤和沙子中可水浸出离子的浓度都非常低。我们将离子浓度的下降归因于海啸后的降雨、渗漏和地下水位的季节性变化。尽管海啸淹没后，来自海水的水可浸出离子集中在海啸沉积物下方的土壤中，但它们的保留时间不会超过几年。为了阐明与海啸相关的地球化学特征行为，需要对富含有机物的泥质沉积物（泥质海啸沉积物和砂质海啸沉积物下方的土壤）以及砂质海啸沉积物进行进一步研究。
We examined the geochemical characteristics and temporal changes of deposits associated with the 2011 Tohoku‐oki tsunami. Stable carbon isotope ratios, biomarkers, and water‐leachable ions were measured in a sandy tsunami deposit and associated soils sampled at Hasunuma, Kujukuri coastal plain, Japan, in 2011 and 2014. At this site, the 2011 tsunami formed a 10–30 cm ‐thick layer of very fine to medium sand. The tsunami deposit was organic‐poor, and no samples contained any detectable biomarkers of either terrigenous or marine origin. In the underlying soil, we identified hydrocarbons and sterols derived from terrestrial plants, but detected no biomarkers of marine origin. In the samples collected in 2011, concentrations of tsunami‐derived water‐leachable ions were highest in the soil immediately beneath the tsunami deposit and then decreased gradually with depth. Because of its finer texture and higher organic content, the soil has a higher water‐holding capacity than the sandy tsunami deposit. This distribution suggests that ions derived from the tsunami quickly penetrated the sand layer and became concentrated in the underlying soil. In the samples collected in 2014, concentrations of water‐leachable ions were very low in both soil and sand. We attribute the decrease in ion concentrations to post‐tsunami rainfall, seepage, and seasonal changes in groundwater level. Although water‐leachable ions derived from seawater were concentrated in the soil beneath the tsunami deposit following the tsunami inundation, they were not retained for more than a few years. To elucidate the behavior of geochemical characteristics associated with tsunamis, further research on organic‐rich muddy deposits (muddy tsunami deposits and soils beneath sandy tsunami deposits) as well as sandy tsunami deposits is required.