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.

在2017年12月的托马斯大火（加利福尼亚州圣塔芭芭拉县）中燃烧的流水集中的水样品将在大火后的第一次降雨中收集，这可能发生在2018年1月至3月。总有机碳和热源性碳（即来自这些燃烧的生物量）将与这些型号相比，这些含量将与这些相比，这些含量是这些含量，并且这些含量是这些含量，并且这些含量是这些含量，并且在这些样品中，这些含量是在这些量中的含量，并且在这些范围内与这些含量相比，这些含量是在这些含量中的水平。不受火灾影响的毗邻的流域。这些测量的目的是确定火对溶解有机物对海洋的供应和组成的影响。特别是，研究人员希望知道是否将溶解的充气碳出口到海洋，因为这是一个有争议的科学主题。如果溶解的热原C与最近的研究所表明的那样丰富且流动性，则可能对海洋化学，长期C循环以及相关的气候变化和污染物转运产生强烈的影响。另一方面，如果在排水的小溪中未检测到这些被燃烧的流域的小溪，其数量大于未开枪的流域，则生物地球运动员将不得不质疑当前用作火灾生产有机物标记的方法。该项目的另一个重要影响是为研究生提供机会，为他的解散的充气碳的论文研究增加现场成分。近年来，人们对热产固体的性质的了解有所增加，但对黄铁蛋白溶解有机物的性质和循环的研究相对较少。最常用的用于热源溶解有机碳（PYDOC）分析的方法涉及将凝结的芳香族成分氧化成较小的可量化单体（即苯二苯甲酸羧酸或BPCAS）。 使用这种方法，已经提出PYDOC代表全球河流DOC的恒定比例（〜10％PYDOC/DOC）。这个结论是有问题的，因为人们期望该比率随区域气候和燃烧政权而变化。可能是所有这些先前的测量方法都是在相当大的河流中进行的，即大流域，因此火的影响已被生物量生长，降水量的其他变化所隐藏。而且，PYC也可以从过去的火灾中不断释放。 2017年12月的Thomas Fire提供了一种理想的情况，用于检测和表征PYC从陆地系统到海洋系统的出口。在圣塔芭芭拉河道（Santa Barbara）频道上有几条短跑小河，这些小河在燃烧区域内完全有小流域，在几个毗邻的流域中类似的小溪，由于抑制火灾，过去60年中没有大火。研究人员还可以使用在托马斯大火之前从这些小溪中存储的水样。可能没有更好的方案来检测无疑的证据或反对大量出口热源C向海洋出口的声明，以及如果存在，则可以量化出口通量。