Utah Water Research Laboratory, Department of Civil and Environmental Engineering, Utah State University, Logan, Utah 84322, United States.
Environ Sci Technol. 2024 Jan 16;58(2):1265-1273. doi: 10.1021/acs.est.3c03976. Epub 2023 Dec 29.
Wildfires or prescribed fires release pyrogenic dissolved organic matter (pyDOM) into the environment, which can photochemically produce singlet oxygen (O) in sun-lit surface waters. O quantum yields (Φ) are well-studied for non-pyrogenic DOM, but little is understood about the O generation from pyDOM, especially the Φ values from real wildfire samples and their wavelength dependence. In this study, time-resolved O phosphorescence was used to determine the wavelength-dependent Φ values for pyDOM generated from wildfire char and a series of lab-prepared chars produced by combusting oak and pine wood. Wildfire and most lab-prepared pyDOM generally had similar Φ values (2.1-2.7%) at 365 nm compared to the reference Suwannee River Natural Organic Matter (SRNOM) isolate (2.4%). Interestingly, pyDOM from the highest combustion temperature char was found to possess extremely low Φ values compared to SRNOM and other pyDOM at all excitation wavelengths. In addition, it was revealed that the predicted steady-state concentration of O from pyDOM was similar to that from SRNOM, indicating that the addition of pyDOM from wood chars may not strongly impact surface water photochemistry.
野火或有意林火会将热解溶解性有机质（pyDOM）释放到环境中，在阳光照射的地表水中，这些有机质可能通过光化学反应产生单线态氧（1O2）。非热解 DOM 的 1O2 量子产率（Φ）已有大量研究，但对于源自 pyDOM 的 1O2 生成，特别是实际野火样本的 Φ 值及其波长依赖性，人们知之甚少。在这项研究中，我们使用时间分辨 1O2 磷光法来确定源自野火炭和一系列通过燃烧橡木和松木制备的实验室炭的 pyDOM 的波长依赖性 Φ 值。与参考苏万尼河天然有机物（SRNOM）分离物（2.4%）相比，野火和大多数实验室制备的 pyDOM 在 365nm 处的 Φ 值（2.1%-2.7%）通常相似。有趣的是，与 SRNOM 和其他 pyDOM 相比，来自最高燃烧温度炭的 pyDOM 被发现具有极低的 Φ 值，在所有激发波长下均如此。此外，还揭示了源自 pyDOM 的预测稳态 1O2 浓度与源自 SRNOM 的浓度相似，这表明来自木质炭的 pyDOM 的添加可能不会强烈影响地表水光化学。
