Jiamin Wan Lawrence Berkeley National Laboratory jmwan@lbl.gov https://orcid.org/0000-0003-4847-5577 Tetsu Tokunaga Lawrence Berkeley National Laboratory tktokunaga@lbl.gov https://orcid.org/0000-0003-0861-6128 Kenneth H. Williams Lawrence Berkeley National Laboratory khwilliams@lbl.gov https://orcid.org/0000-0002-3568-1155 contributor Wendy Brown wsbrown@frontier.net https://orcid.org/0000-0002-7237-1797 contributor Alexander M. Newman alexnewman760@gmail.com contributor Wenming Dong Lawrence Berkeley National Laboratory wenmingdong@lbl.gov https://orcid.org/0000-0003-2074-8887 contributor Markus Bill Lawrence Berkeley National Laboratory mbill@lbl.gov https://orcid.org/0000-0001-7002-2174 contributor Curtis A. Beutler curtis.Beutler@colorado.edu contributor Amanda N. Henderson Rocky Mountain Biological Laboratory amanda.henderson3@gmail.com https://orcid.org/0000-0001-9613-5003 contributor Nydra Harvey-Costello contributor U.S. DOE > Office of Science > Biological and Environmental Research (BER) http://dx.doi.org/10.13039/100006206 fundingOrganization 2021 Atmospheric nitrous oxide contributes directly to global warming, yet models of the nitrogen cycle do not account for bedrock, the largest pool of terrestrial nitrogen, as a source of nitrous oxide. Although it is known that release rates of nitrogen from bedrock are large, there is an incomplete understanding of the connection between bedrock-hosted nitrogen and atmospheric nitrous oxide. Here, we quantify nitrogen fluxes and mass balances at a hillslope underlain by marine shale. We found that at this site bedrock weathering contributes 78% of the subsurface reactive nitrogen, while atmospheric sources (commonly regarded as the sole sources of reactive nitrogen in pristine environments) account for only the remaining 22%. About 56% of the total subsurface reactive nitrogen denitrifies, including 14% emitted as nitrous oxide. The remaining reactive nitrogen discharges in porewaters to a floodplain where additional denitrification likely occurs. We also found that the release of bedrock nitrogen occurs primarily within the zone of the seasonally fluctuating water table and suggest that the accumulation of nitrate in the vadoes zone, often attributed to fertilization and soil leaching, may also include contributions from weathered nitrogen-rich bedrock. Our hillslope study suggests that under oxygenated and moisture-rich conditions, weathering of deep, nitrogen-rich bedrock makes an important contribution to the nitrogen cycle. The data files are in Excel, which can be accessed using Microsoft Office, and consist of many data sets from the Pumphouse Hillslope PLM (Pumphouse Lower Montane) 1, 2, 3, and 4. They include soil to rock (0-10 meters) solid phase minerals and elements compositions; time- and depth-resolved pore-water chemistry and pore-gas compositions; time- and depth-resolved water table depths and water fluxes; subsurface weathering rates; nitrogen influxes and effluxes and mass balance. The attached paper is in a Word document, which can be accessed using Microsoft Office, and in pdf format. bedrock weathering rock nitrogen subsurface reactive nitrogen nitrous oxide emissions shale bedrock watershed hillslope CATEGORICAL:NONE Anion Cation Dissolved Ammonia Mineralogy Dissolved Inorganic Carbon Dissolved Organic Carbon Total Dissolved Nitrogen Total Nitrogen Total Organic Carbon Groundwater Flux Groundwater Level Tensiometer Head VARIABLE:NONE EARTH SCIENCE > TERRESTRIAL HYDROSPHERE > GROUND WATER > GROUNDWATER CHEMISTRY EARTH SCIENCE > LAND SURFACE > SOILS > HYDRAULIC CONDUCTIVITY VARIABLE:GCMD This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. The East River (ER) is a snow‐dominated, headwater basin of the Upper Colorado River Basin (UCRB) located in the western United States. The ER is the designated testbed of Lawrence Berkeley National Laboratory's Watershed Function Scientific Focus Area (WFSFA). Through WFSFA, observational networks have been established to measure stream discharge and precipitation chemistry.The ER is considered representative of many snow‐dominated headwaters of the Rocky Mountains. The study domain encompasses nearly 85 square km, a 1.4‐km vertical drop in elevation (4,120 to 2,760 m) and pristine alpine, subalpine, montane, and riparian ecosystems. The ER contains high‐energy mountain streams to low‐energy meandering floodplains and is eroding primarily into the Cretaceous, carbon‐rich, marine shale of the Mancos Formation. Specific locations sampled were at PLM 1, PLM 2, PLM 3, and PLM 4. -107.05 -106.88 39.034 38.88 2017-05-10 2020-08-30 Jiamin Wan Lawrence Berkeley National Laboratory jmwan@lbl.gov https://orcid.org/0000-0003-4847-5577 Watershed Function SFA Samples of soil to bedrock, porewater and pore gas samples were collected and the hydrological properties were measured at the Pumphouse Hillslope PLM1, 2, 3, and 4 of the East River Watershed, and samples were analyzed in many labs in and out of the LBNL (See methods attached for more details). Susan Hubbard Lawrence Berkeley National Laboratory sshubbard@lbl.gov principalInvestigator DOE:DEAC0205CH11231 JWan_2_10_21_Final_N_MS_single_space_with_figs.pdf application/pdf JWan_2_10_21_Complete_Date_for_N_MS.xlsx application/vnd.openxmlformats-officedocument.spreadsheetml.sheet JWan_2_10_21_Final_N_MS_single_space_with_figs.docx application/vnd.openxmlformats-officedocument.wordprocessingml.document