Dissolved Organic Matter Quality from a Discontinuous Permafrost Area and its Susceptibility to Photolytic and Microbial Degradation

English Abstract:

Northern environments are some of the most susceptible to a warming climate, experiencing increased active-layer thickness and permafrost degradation. Such changes can influence subsurface carbon cycling. Particularly, previously-frozen carbon can become mobilized into the hydrosphere as dissolved organic matter (DOM) and make its way into surrounding surface waters. Dissolved organic matter plays a number of important environmental roles including absorbing harmful ultra-violet radiation in surface waters, affecting the pH, and acting as an important nutrient source for microbes. Furthermore, DOM can influence water quality by binding and transporting heavy metals, as well as potentially forming carcinogenic disinfection by-products during the chlorination of drinking water. Reactivity of DOM is dependent upon its quality, which can vary depending on source, amount of degradation, and season. In northern environments, it is uncertain how degrading permafrost will influence DOM quantity and quality and the subsequent effect upon drinking water and aquatic health, especially in ice-poor permafrost areas. Our research used a variety of DOM characterization methods and geochemical techniques to quantify DOM quality from four different sources (subsurface peat porewater, ponds, streams, and rivers) in an area with degrading permafrost near Yellowknife, NWT. In addition, we conducted microbial and photolytic degradation experiments to determine whether the lability of DOM differs with source, how DOM quality changes with environmental processing, and how this ultimately influences parameters linked with drinking water quality and aquatic health.