Controls on River Salinization and its Relationship to Nitrogen

Abstract:

Many watersheds in the US and elsewhere are experiencing episodic salinization due to extreme climate events, and long-term salinization due to land use change and anthropogenic salt inputs. Previous research suggests that changes in salinization have the potential to release stored nutrients from sediments and alter biogeochemical cycling. We compared and contrasted controls on salinity over varying temporal scales (e.g. daily scales, seasonal scales, and inter-annual scales). We observed long-term increases in specific conductance at all sites, and there were significant increases in baseflow salinity over years. There were also significant relationships between nitrate and specific conductance (which varied across streamflow) at some sites potentially due to mobilization of nitrogen from sediments to streams. Laboratory incubation experiments showed that salt additions could rapidly mobilize nitrate and other contaminants from sediments over a day. The magnitude and frequency of riverine salt loads may be amplified in the near future due the interactive effects of extreme climate events (i.e. snowstorms, droughts, and floods) and urban development growth.