Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Biogeosciences, 12, 7331-7347, 2015
https://doi.org/10.5194/bg-12-7331-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
15 Dec 2015
Salinization alters fluxes of bioreactive elements from stream ecosystems across land use
S. Duan and S. S. Kaushal Department of Geology and Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
Abstract. There has been increased salinization of fresh water over decades due to the use of road salt deicers, wastewater discharges, saltwater intrusion, human-accelerated weathering, and groundwater irrigation. Salinization can mobilize bioreactive elements (carbon, nitrogen, phosphorus, sulfur) chemically via ion exchange and/or biologically via influencing of microbial activity. However, the effects of salinization on coupled biogeochemical cycles are still not well understood. We investigated potential impacts of increased salinization on fluxes of bioreactive elements from stream ecosystems (sediments and riparian soils) to overlying stream water and evaluated the implications of percent urban land use on salinization effects. Two-day incubations of sediments and soils with stream and deionized water across three salt levels were conducted at eight routine monitoring stations across a land-use gradient at the Baltimore Ecosystem Study Long-Term Ecological Research (LTER) site in the Chesapeake Bay watershed. Results indicated (1) salinization typically increased sediment releases of labile dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), total dissolved Kjeldahl nitrogen (TKN) (ammonium + ammonia + dissolved organic nitrogen), and sediment transformations of nitrate; (2) salinization generally decreased DOC aromaticity and fluxes of soluble reactive phosphorus from both sediments and soils; (3) the effects of increased salinization on sediment releases of DOC and TKN and DOC quality increased with percentage watershed urbanization. Biogeochemical responses to salinization varied between sediments and riparian soils in releases of DOC and DIC, and nitrate transformations. The differential responses of riparian soils and sediments to increased salinization were likely due to differences in organic matter sources and composition. Our results suggest that short-term increases in salinization can cause releases of significant amounts of labile organic carbon and nitrogen from stream substrates and organic transformations of nitrogen and phosphorus in urban watersheds. Given that salinization of fresh water will increase in the future due to human activities, significant impacts on carbon and nutrient mobilization and water quality should be anticipated.

Citation: Duan, S. and Kaushal, S. S.: Salinization alters fluxes of bioreactive elements from stream ecosystems across land use, Biogeosciences, 12, 7331-7347, https://doi.org/10.5194/bg-12-7331-2015, 2015.
Publications Copernicus
Download
Short summary
There has been increased salinization of fresh water over decades during the urban evolution of watersheds. This study finds that salinization consistently increased sediment releases of labile organic carbon and total dissolved Kjeldahl nitrogen and sediment transformations of nitrate, and the salinization effects increased with percentage watershed urbanization. These findings are will be critical for forecasting changes in carbon and nutrient exports due to salt use in urban watersheds.
There has been increased salinization of fresh water over decades during the urban evolution of...
Share