Investigating Atmospheric Inputs of Dissolved Black Carbon to the Santa Barbara Channel During the Thomas Fire (California, USA)
Investigating Atmospheric Inputs of Dissolved Black Carbon to the Santa Barbara Channel During the Thomas Fire (California, USA)
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DOI：
10.1029/2021jg006442
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发表时间：
2021-08-01
影响因子：
3.7
通讯作者：
Stubbins, Aron
中科院分区：
文献类型：
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作者：
Wagner, Sasha;Harvey, Elizabeth;Stubbins, Aron
托马斯大火于2017年12月4日点燃，燃烧了一个多月。随着托马斯大火的燃烧，圣安娜大风将浓烟和火山灰带到了圣巴巴拉海峡上空。我们试图确定托马斯火山灰沉积到圣巴巴拉海峡是否对沿海水域中溶解的黑碳(DBC)的浓度和稳定的碳同位素组成(增量C-13)产生了可测量的影响。DBC是用苯多羧酸(BPCA)方法定量的热蚀变有机碳的缩合芳香族组分。通过BPCA特定的稳定碳同位素分析确定了DBC Delta C-13的特征。烟羽下的地表水DBC浓度比其他采样站高出13%。通过控制浸出实验，我们发现Thomas Fire ash在海水中释放了相当数量的DBC(每公斤灰有机碳1.4g-DBC)，光溶解进一步增强了DBC的释放。通过将现场数据和实验数据相结合，我们构建了一个同位素混合模型来估计灰分衍生的DBC对海洋表层水域的输入。尽管我们能够探测到烟羽下DBC浓度的轻微上升，但来自火山灰的贡献太小，不能有意义地移动增量C-13特征，这导致观察到的DBC增量C-13值与模型之间的不匹配。很少有研究调查野火对沿海生物地球化学的直接影响。因此，我们的工作为了解火灾衍生的DBC对海岸边缘的大气贡献提供了重要的基础。
The Thomas Fire ignited on December 4, 2017 and burned for over one month. As the Thomas Fire burned, Santa Ana winds carried a thick plume of smoke and ash over the Santa Barbara Channel. We sought to determine whether the deposition of Thomas Fire ash to the Santa Barbara Channel had a measurable effect on the concentration and stable carbon isotopic composition (delta C-13) of dissolved black carbon (DBC) in coastal waters. DBC is the condensed aromatic fraction of thermally altered organic carbon quantified using the benzenepolycarboxylic acid (BPCA) method. DBC delta C-13 signatures were determined via BPCA-specific stable carbon isotopic analysis. Surface water DBC concentrations beneath the smoke plume were up to 13% higher than other sampling stations. Via controlled leaching experiments, we found that Thomas Fire ash released a considerable amount of DBC in seawater (1.4 g-DBC per kg of ash organic carbon), which was further enhanced by photodissolution. By combining in situ and experimental data, we constructed an isotopic mixing model to estimate inputs of ash-derived DBC to marine surface waters. Although we were able to detect slight elevations in DBC concentrations beneath the smoke plume, the ash-derived contributions were too small to meaningfully shift the delta C-13 signature, which resulted in an observed mismatch between modeled and measured DBC delta C-13 values. Few studies have investigated the immediate impacts of wildfire on coastal biogeochemistry. Therefore, our work provides an important foundation for understanding atmospheric contributions of fire-derived DBC to coastal margins.