1 research outputs found
Photochemical Alteration of Dissolved Organic Sulfur from Sulfidic Porewater
Sulfidic sediments are a source of
dissolved organic sulfur (DOS)
to the ocean but the fate of sedimentary DOS in the oxic, sunlit water
column is unknown. We hypothesized that photodegradation after discharge
from the dark sedimentary environment results in DOS molecular transformation
and decomposition. To test this hypothesis, sulfidic porewater from
a saltmarsh was exposed to potential abiotic transformations of dissolved
organic matter (DOM) in the water column. We quantitatively investigated
DOM transformations via elemental analysis and molecularly via ultrahigh-resolution
mass spectrometry. Our study indicated that photoreactivity is dependent
on DOM elemental composition as DOS molecular formulas were more photolabile
than those without sulfur. Prior to solar irradiation, of the 6451
identified molecular formulas in sulfidic porewater, 39% contained
sulfur. After 29 days of irradiation, the DOS concentration was depleted
from 13 to 1 μM, together with a 9% decrease in the number of
DOS molecular formulas. Comparing porewater and oceanic DOS molecular
formulas, solar irradiation increased the similarity due to the removal
of photolabile DOS formulas not present in the ocean. In conclusion,
DOS from sulfidic sediments is preferentially photolabile and solar
irradiation can be a potential mechanism controlling the stability
and fate of porewater DOS