Dissolved Organic Carbon in Arctic Rivers: Reduced Model with Functional Groups

Abstract:

Boreal river systems play a crucial role in high latitude change as they carry the highest terrestrial input of all aquatic flow to the sea. This includes a massive dissolved organic flux, injected directly to the climatologically sensitive Arctic Ocean. The dissolved organics imply chemical functional groups that interact with coastal and open ocean biophysical properties such as light attenuation, surface tension, trace metal chelation and aerosol formation. We have performed reduced kinetic modeling for organic matter evolution along an idealized Siberian river. We studied reactivity, networking and fate for the major macromolecular groups based on their diverse structures: sugar, lipids, proteins, heteropolycondensate and humic substance are all considered. We found that along the stream course, chemical reactivity is slow relative to the coastal or open ocean, but mixing at tributary nodes plays a dominant role. Concentrations for the various carbon compounds stagger at connecting points based specifically on sourcing from the different Arctic sub-ecosystems: taiga, tundra, woodland, peat, bog and others. Even so, photochemical and microbial losses contribute to the final mix and along coastlines biophysical impacts are extreme. For example the chromophoric dissolved organic matter or CDOM attenuates at a one versus ten meter e-fold depending on upstream ecology. Soil-runoff and deltaic (pre- versus post-) processing also exert discrimination on the functional distribution and aquatic chemical influence. Further investigation is necessary and ongoing, through an increase in the number of connection points dictating dilution and mixing. And we are hoping to investigate the interaction of humics as flocculants with mineral particles, since they are capable of removing turbidity as ionic strength rises in the plume.