Molecular Identification of Water-Extractable Organic Carbon from Thermally Heated Soils: C-13 NMR and Accurate Mass Analyses Find Benzene and Pyridine Carboxylic Acids.,Environmental Science & Technology

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Molecular Identification of Water-Extractable Organic Carbon from Thermally Heated Soils: C-13 NMR and Accurate Mass Analyses Find Benzene and Pyridine Carboxylic Acids.
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2020-02-12 , DOI: 10.1021/acs.est.9b05230
E Michael Thurman ₁ , Yun Yu ₁ , Imma Ferrer ₁ , Kevin A Thorn ₂ , Fernando L Rosario-Ortiz ₁

Affiliation

To simulate the effects of wildfire on the combustion process in soils and their potential to leach organic compounds into streams and groundwater, mineral soil samples were heated at temperatures of 150-550 °C. Then, the soils were leached with deionized water, filtered, and analyzed for dissolved organic carbon. The water extract was concentrated by both XAD-8 and XAD-4 resins and analyzed by C-13 nuclear magnetic resonance and liquid chromatography time-of-flight mass spectrometry. Approximately 15-20% of the water-extractable organic carbon was identified as benzene dicarboxylic acids, tricarboxylic acids, and tetracarboxylic acid isomers, commonly called BPCAs. Also identified were isomers of pyridine dicarboxylic acids and tricarboxylic acids (PCAs). The conversion of soil organic carbon to BPCAs occurs at 250 °C and reaches a maximum between 350 and 450 °C. At higher temperatures (>450 °C), the BPCA concentrations decrease, suggesting decarboxylation and conversion to carbon dioxide and water. This is the first report of BPCAs and PCAs in water-extractable organic carbon from thermally altered soil and suggest that these compounds are possible candidates for further water-quality studies in watersheds affected by wildfire. Finally, BPCAs and PCAs could contribute to the black carbon and nitrogen in seawater and are worthy of future investigation.

中文翻译：

热加热土壤中可水萃取的有机碳的分子鉴定：C-13 NMR和精确的质量分析可发现苯和吡啶羧酸。

为了模拟野火对土壤燃烧过程的影响以及它们将有机化合物浸出到河流和地下水中的潜力，将矿物土壤样品加热到150-550°C。然后，用去离子水淋洗土壤，过滤，并分析溶解的有机碳。水提取物通过XAD-8和XAD-4树脂浓缩，并通过C-13核磁共振和液相色谱飞行时间质谱分析。约15-20％的水可萃取有机碳被鉴定为苯二羧酸，三羧酸和四羧酸异构体，通常称为BPCA。还鉴定出吡啶二羧酸和三羧酸（PCA）的异构体。土壤有机碳向BPCAs的转化发生在250°C，最高达到350至450°C。在较高温度（> 450°C）下，BPCA浓度降低，表明脱羧并转化为二氧化碳和水。这是BPCA和PCA在热改变后的土壤中可从水中提取的有机碳中的第一份报告，表明这些化合物可能是受野火影响的流域中进一步水质研究的候选者。最后，BPCAs和PCA可能有助于海水中的黑碳和氮，值得今后进行研究。这是BPCA和PCA在热改变后的土壤中可从水中提取的有机碳中的第一份报告，表明这些化合物可能是受野火影响的流域中进一步水质研究的候选者。最后，BPCAs和PCA可能有助于海水中的黑碳和氮，值得今后进行研究。这是BPCA和PCA在热改变后的土壤中可从水中提取的有机碳中的第一份报告，表明这些化合物可能是受野火影响的流域中进一步水质研究的候选者。最后，BPCAs和PCA可能有助于海水中的黑碳和氮，值得今后进行研究。

更新日期：2020-02-13

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