Photochemical production of reactive oxygen species from dissolved organic matter in ice.

摘要

Dissolved natural organic matter (DOM) is a ubiquitous component of natural waters and an important photosensitizer. A variety of reactive oxygenated species (ROS) are known to be produced from DOM photolysis, including singlet oxygen, 1O2. Recently, it has been determined that humic-like substances and unknown chromophores are significant contributors to sunlight absorption in snowpack; however, DOM photochemistry in snow/ice has received little attention in the literature. Here we examine 1 O2 photochemically produced from DOM in frozen and liquid solutions. We have found that steady-state 1O2 production is enhanced 34-129 times in frozen DOM samples (10-13 M) compared to liquid samples (10-15 M). 1O2 production is dependent on the concentration of DOM. Generally, as DOM concentration increases, steady-state 1O2 production increases. However, we have found that DOM source (microbial vs terrestrial) does not have an effect on 1O2 production in liquid or frozen samples, with different source types producing similar concentrations of 1O2. Although 1O2 production is enhanced in frozen samples, the temperature of frozen samples has no statistically significant effect on steady-state 1O2 production. The large enhancement in 1O2 production in frozen samples suggests that 1O2 plays a significant role in the photochemical processes that occur in snow and ice and that DOM photolysis in snow and ice may be a significant source of 1O2 production in the environment.