Detection of dissolved pyrogenic carbon export following the Southern California fires of 2017

2017 年南加州火灾后溶解热解碳输出的检测

• 批准号: 1824133
• 负责人: Andrew Zimmerman
• 金额: $ 3.87万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-02-15 至 2022-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1824133&HistoricalAwards=false
• 关键词: Detection; dissolved; pyrogenic; carbon; export

Water from stream samples draining watersheds burned in the Thomas fire of December 2017 (Santa Barbara County, California) will be collected during the first rains following the fire, which are likely to occur in January-March, 2018. Total organic carbon and pyrogenic carbon (i.e. derived from burned biomass) will be measured in these samples and compared with quantities of these components in water of these streams prior to the fire, and in streams of adjoining watersheds not affected by the fire. The objective of these measurements is to determine the influence of fire on the supply and composition of dissolved organic matter to the ocean. In particular, the investigator wishes to know whether dissolved pyrogenic carbon will be exported to the ocean as this is a controversial scientific subject. If dissolved pyrogenic C is as abundant and mobile as recent studies suggest, it may have a strong impact on marine chemistry, long-term C cycling and associated climate changes and pollutant transport. On the other hand, if pyrogenic C is not detected in the creeks draining these burned watershed in amounts greater than that of the unburned watersheds, biogeochemists will have to question the methods currently used as markers for fire-produced organic matter. Another important impact of the project will be to provide the opportunity for a graduate student to add a field component to his dissertation research on dissolved pyrogenic carbon.While knowledge of the properties of pyrogenic solids has increased in recent years, there has been relatively little study of the properties and cycling of pyrogenic dissolved organic matter. The method most commonly used for pyrogenic dissolved organic carbon (pyDOC) analysis involves the oxidation of condensed aromatic constituents into smaller, quantifiable monomers (i.e., benzenepolycarboxylic acids or BPCAs). Using this method, it has been suggested that pyDOC represents a constant proportion of riverine DOC globally (~10% pyDOC/DOC). This conclusion is problematic since one would expect this ratio to vary with regional climate and burning regimes. It may be that all these previous measurements were made in fairly large rivers, i.e. large watersheds, so the effects of fire have been hidden by other variations in biomass growth, precipitation etc. Also, pyC may be continually released from charcoals made during past fires. The Thomas fire of December 2017 provides an ideal scenario for detecting and characterizing pyC export from terrestrial to marine systems. There are several short-run creeks draining coastal catchments along the Santa Barbara Channel that have small watershed completely within the burned area, and similar creeks in several adjoining watershed that saw no fire for the past 60 years due to fire suppression. The investigator also has access to water samples that have been in storage from these creeks taken prior to the Thomas fire. There is probably no better scenario for detecting indisputable evidence for, or against, the claim of significant export of pyrogenic C to the ocean, as well as quantifying that export flux if it exists.

2017年12月托马斯火灾（加州圣巴巴拉县）中烧毁的流域的溪流样本中的水将在火灾后的第一场降雨期间收集，这可能发生在2018年1月至3月。将测量这些样本中的总有机碳和热解碳（即来自燃烧的生物质），并与火灾前这些溪流中的这些成分的数量以及未受火灾影响的相邻流域的溪流中的这些成分的数量进行比较。这些测量的目的是确定火灾对海洋溶解有机物的供应和组成的影响。特别是，调查人员希望知道溶解的热解碳是否会被输出到海洋，因为这是一个有争议的科学问题。如果溶解的热解碳像最近的研究表明的那样丰富和移动的，它可能对海洋化学、长期的碳循环以及相关的气候变化和污染物迁移产生强烈影响。另一方面，如果在排出这些燃烧过的流域的小溪中没有检测到比未燃烧过的流域更大量的热原C，地球化学家将不得不质疑目前用作火产生的有机物的标记的方法。该项目的另一个重要影响是为研究生提供机会，增加一个领域的组成部分，他的论文研究溶解热解carbon.While热解固体的属性的知识增加，近年来，有相对较少的研究热解溶解有机物的属性和循环。最常用于热解溶解有机碳（pyDOC）分析的方法涉及将稠合芳族组分氧化成较小的可定量单体（即，苯多羧酸或BPCA）。 使用这种方法，已经表明，pyDOC代表了恒定比例的河流DOC全球（~10% pyDOC/DOC）。这一结论是有问题的，因为人们会期望这个比例随区域气候和燃烧制度而变化。这可能是所有这些以前的测量是在相当大的河流，即大流域，所以火的影响已被隐藏的其他变化，生物量的增长，降水等，此外，pyC可能会不断释放的木炭在过去的火灾。2017年12月的托马斯火灾为检测和表征从陆地到海洋系统的pyC输出提供了理想的场景。沿圣巴巴拉海峡有几条短溪流排放沿着集水区，这些溪流的小流域完全位于燃烧区域内，在几个相邻流域中也有类似的小溪，由于灭火，过去60年来没有发生火灾。调查人员还可以获得在托马斯火灾前从这些小溪中采集的储存的水样。可能没有更好的方案来检测无可争议的证据，支持或反对，大量出口到海洋的热原C的说法，以及量化出口通量（如果存在）。