posted on 2023-12-29, 20:13authored byMonika Madhiyan, Kyle J. Moor
Wildfires or prescribed fires release
pyrogenic dissolved organic
matter (pyDOM) into the environment, which can photochemically produce
singlet oxygen (1O2) in sun-lit surface waters. 1O2 quantum yields (ΦΔ) are
well-studied for non-pyrogenic DOM, but little is understood about
the 1O2 generation from pyDOM, especially the
ΦΔ values from real wildfire samples and their
wavelength dependence. In this study, time-resolved 1O2 phosphorescence was used to determine the wavelength-dependent
ΦΔ 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 ΦΔ 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 ΦΔ values compared to SRNOM and other pyDOM at all excitation wavelengths.
In addition, it was revealed that the predicted steady-state concentration
of 1O2 from pyDOM was similar to that from SRNOM,
indicating that the addition of pyDOM from wood chars may not strongly
impact surface water photochemistry.