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Bedrock weathering contributes to subsurface reactive nitrogen and nitrous oxide emissions

Nature Geoscience volume 14, pages 217–224 (2021)Cite this article

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Abstract

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 probably 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 vadose 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.

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Fig. 1: The East River watershed study site and instrumentation.
Fig. 2: Rock weathering occurs primarily below soil, within the depth zone of the annually oscillating water table.
Fig. 3: The hillslope subsurface reactive-N is primarily from bedrock weathering, not from soil.
Fig. 4: Measurements and rate calculations of bedrock weathering, dissolved-N export to hydrosphere and N2O to atmosphere.
Fig. 5: Conceptual model for hillslope bedrock-N weathering release and exports with N mass balance.

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Data availability

Data used in this paper are published on ESS-DIVE (https://doi.org/10.15485/1766328), which is freely accessible to the public, and a part of the DataONE network registered with fairsharing.org.

References

  1. Bremner, J. M. Sources of nitrous oxide in soils. Nutr. Cycl. Agroecosystems 49, 7–16 (1997).

    Article  Google Scholar 

  2. Bouwman, A. F. et al. Global trends and uncertainties in terrestrial denitrification and N2O emissions. Philos. Trans. R. Soc. B 368, https://doi.org/10.1098/rstb.2013.0112 (2013).

  3. Ravishankara, A. R., Daniel, J. S. & Portmann, R. W. Nitrous oxide (N2O): the dominant ozone-depleting substance emitted in the 21st century. Science 326, 123–125 (2009).

    Article  Google Scholar 

  4. Thompson, R. L. et al. Acceleration of global N2O emissions seen from two decades of atmospheric inversion. Nat. Clim. Change 9, 993 (2019).

    Article  Google Scholar 

  5. Tian, H. Q. et al. Global soil nitrous oxide emissions since the preindustrial era estimated by an ensemble of terrestrial biosphere models: magnitude, attribution, and uncertainty. Global Change Biol. 25, 640–659 (2019).

    Article  Google Scholar 

  6. Butterbach-Bahl, K., Baggs, E. M., Dannenmann, M., Kiese, R. & Zechmeister-Boltenstern, S. Nitrous oxide emissions from soils: how well do we understand the processes and their controls? Philos. Trans. R. Soc. B 368, 1621 (2013).

    Article  Google Scholar 

  7. Johnson, B. & Goldblatt, C. The nitrogen budget of Earth. Earth Sci. Rev. 148, 150–173 (2015).

    Article  Google Scholar 

  8. Holloway, J. M. & Dahlgren, R. A. Nitrogen in rock: occurrences and biogeochemical implications. Global Biogeochem. Cycles 16, https://doi.org/10.1029/2002gb001862 (2002).

  9. Houlton, B. Z., Morford, S. L. & Dahlgren, R. A. Convergent evidence for widespread rock nitrogen sources in Earth’s surface environment. Science 360, 58–62 (2018).

    Article  Google Scholar 

  10. Morford, S. L., Houlton, B. Z. & Dahlgren, R. A. Direct quantification of long-term rock nitrogen inputs to temperate forest ecosystems. Ecology 97, 54–64 (2016).

    Article  Google Scholar 

  11. Sullivan, P. J., Sposito, G., Strathouse, S. M. & Hansen, C. L. Geologic nitrogen and the occurrence of high nitrate soils in the western San-Joaquin Valley, California. Hilgardia 47, 15–49 (1979).

    Article  Google Scholar 

  12. Butterbach-Bahl, K. et al. in The European Nitrogen Assessment (eds M. A. Sutton et al.) Ch. 6 (Cambridge Univ. Press, 2011).

  13. Van Breemen, N. et al. Where did all the nitrogen go? Fate of nitrogen inputs to large watersheds in the northeastern USA. Biogeochemistry 57, 267–293 (2002).

    Article  Google Scholar 

  14. Williams, L. B., Wilcoxon, B. R., Ferrell, R. E. & Sassen, R. Diagenesis of ammonium during hydrocarbon maturation and migration, Wilcox-Group, Louisiana, USA. Appl. Geochem. 7, 123–134 (1992).

    Article  Google Scholar 

  15. Muller, P. J. C/N ratios in Pacific deep-sea sediments: effect of inorganic ammonium and organic nitrogen compounds sorbed by clays. Geochim. Cosmochim. Acta 41, 765–776 (1977).

    Article  Google Scholar 

  16. Morrison, S. J., Goodknight, C. S., Tigar, A. D., Bush, R. P. & Gil, A. Naturally occurring contamination in the Mancos Shale. Environ. Sci. Technol. 46, 1379–1387 (2012).

    Article  Google Scholar 

  17. Tuttle, M. L. W., Fahy, J. W., Elliott, J. G., Grauch, R. I. & Stillings, L. L. Contaminants from Cretaceous black shale: II. Effect of geology, weathering, climate, and land use on salinity and selenium cycling, Mancos Shale landscapes, southwestern United States. Appl. Geochem. 46, 72–84 (2014).

    Article  Google Scholar 

  18. Riebe, C. S., Kirchner, J. W. & Finkel, R. C. Long-term rates of chemical weathering and physical erosion from cosmogenic nuclides and geochemical mass balance. Geochim. Cosmochim. Acta 67, 4411–4427 (2003).

    Article  Google Scholar 

  19. Montgomery, D. R. & Brandon, M. T. Topographic controls on erosion rates in tectonically active mountain ranges. Earth Planet. Sci. Lett. 201, 481–489 (2002).

    Article  Google Scholar 

  20. Morford, S. L., Houlton, B. Z. & Dahlgren, R. A. Geochemical and tectonic uplift controls on rock nitrogen inputs across terrestrial ecosystems. Global Biogeochem. Cycles 30, 333–349 (2016).

    Article  Google Scholar 

  21. West, A. J., Galy, A. & Bickle, M. Tectonic and climatic controls on silicate weathering. Earth Planet. Sci. Lett. 235, 211–228 (2005).

    Article  Google Scholar 

  22. Holloway, J. M. & Smith, R. L. Nitrogen and carbon flow from rock to water: regulation through soil biogeochemical processes, Mokelumne River watershed, California, and Grand Valley, Colorado. J. Geophys. Res. Earth 110, F01010 (2005).

    Google Scholar 

  23. Hubbard, S. S. et al. The East River, Colorado, watershed: a mountainous community testbed for improving predictive understanding of multiscale hydrological-biogeochemical dynamics. Vadose Zone J. 17, 180061 (2018).

    Article  Google Scholar 

  24. Gaskill, D. L., Mutschler, F. E., Kramer, J. H., Thomas, J. A. & Zahoney, S. G. Geologic Map of the Gothic Quadrangle, Colorado, Gunnison County, Department of Interior (USGS, 1991).

  25. Carroll, R. W. H. et al. Factors controlling seasonal groundwater and solute flux from snow-dominated basins. Hydrol. Process. 32, 2187–2202 (2017).

    Article  Google Scholar 

  26. Winnick, M. J. et al. Snowmelt controls on concentration-discharge relationships and the balance of oxidative and acid–base weathering fluxes in an alpine catchment, East River, Colorado. Water Resour. Res. 53, 2507–2523 (2017).

    Article  Google Scholar 

  27. Wan, J. M. et al. Predicting sedimentary bedrock subsurface weathering fronts and weathering rates. Sci. Rep. 9, https://doi.org/10.1038/s41598-019-53205-2 (2019).

  28. Tokunaga, T. K. et al. Depth- and time-resolved distributions of snowmelt-driven hillslope subsurface flow and transport and their contributions to surface waters. Water Resour. Res. 55, 9474–9499 (2019).

    Article  Google Scholar 

  29. CASTNET (US Environmental Protection Agency, 2019).

  30. Darrouzet-Nardi, A., Erbland, J., Bowman, W. D., Savarino, J. & Williams, M. W. Landscape-level nitrogen import and export in an ecosystem with complex terrain, Colorado Front Range. Biogeochemistry 109, 271–285 (2012).

    Article  Google Scholar 

  31. Vitousek, P. M., Menge, D. N. L., Reed, S. C. & Cleveland, C. C. Biological nitrogen fixation: rates, patterns and ecological controls in terrestrial ecosystems. Philos. Trans. R. Soc. B 368, https://doi.org/10.1098/rstb.2013.0119 (2013).

  32. Anderson, S. P., Dietrich, W. E. & Brimhall, G. H. Weathering profiles, mass-balance analysis, and rates of solute loss: linkages between weathering and erosion in a small, steep catchment. Geol. Soc. Am. Bull. 114, 1143–1158 (2002).

    Article  Google Scholar 

  33. Brimhall, G. H. & Dietrich, W. E. Constitutive mass balance relations between chemical-composition, volume, density, porosity, and strain in metasomatic hydrochemical systems – results on weathering and pedogenesis. Geochim. Cosmochim. Acta 51, 567–587 (1987).

    Article  Google Scholar 

  34. Littke, R., Klussmann, U., Krooss, B. & Leythaeuser, D. Quantification of loss of calcite, pyrite, and organic-matter due to weathering of toarcian black shales and effects on kerogen and bitumen characteristics. Geochim. Cosmochim. Acta 55, 3369–3378 (1991).

    Article  Google Scholar 

  35. Galy, A. & France-Lanord, C. Weathering processes in the Ganges–Brahmaputra Basin and the riverine alkalinity budget. Chem. Geol. 159, 31–60 (1999).

    Article  Google Scholar 

  36. Brantley, S. L. et al. Toward a conceptual model relating chemical reaction fronts to water flow paths in hills. Geomorphology 277, 100–117 (2017).

    Article  Google Scholar 

  37. Manning, A. H., Verplanck, P. L., Caine, J. S. & Todd, A. S. Links between climate change, water-table depth, and water chemistry in a mineralized mountain watershed. Appl. Geochem. 37, 64–78 (2013).

    Article  Google Scholar 

  38. Torres, M. A., West, A. J. & Clark, K. E. Geomorphic regime modulates hydrologic control of chemical weathering in the Andes–Amazon. Geochim. Cosmochim. Acta 166, 105–128 (2015).

    Article  Google Scholar 

  39. Holloway, J. M. & Dahlgren, R. A. Geologic nitrogen in terrestrial biogeochemical cycling. Geology 27, 567–570 (1999).

    Article  Google Scholar 

  40. Rodhe, A. On the generation of stream runoff in till soils. Nord Hydrol 20, 1–8 (1989).

    Article  Google Scholar 

  41. Horton, T. W., Chamberlain, C. P., Fantle, M. & Blum, J. D. Chemical weathering and lithologic controls of water chemistry in a high-elevation river system: Clark’s Fork of the Yellowstone River, Wyoming and Montana. Water Resour. Res. 35, 1643–1655 (1999).

    Article  Google Scholar 

  42. Holloway, J. M., Dahlgren, R. A., Hansen, B. & Casey, W. H. Contribution of bedrock nitrogen to high nitrate concentrations in stream water. Nature 395, 785–788 (1998).

    Article  Google Scholar 

  43. Seitzinger, S. et al. Denitrification across landscapes and waterscapes: a synthesis. Ecol. Appl. 16, 2064–2090 (2006).

    Article  Google Scholar 

  44. Tokunaga, T. K. et al. Deep vadose zone respiration contributions to carbon dioxide fluxes from a semiarid floodplain. Vadose Zone J. 15, https://doi.org/10.2136/vzj2016.02.0014 (2016).

  45. Ascott, M. J. et al. Global patterns of nitrate storage in the vadose zone. Nat. Commun. 8, 1416 (2017).

    Article  Google Scholar 

  46. Kendall, K. A., Shanley, J. B. & McDonnell, J. J. A hydrometric and geochemical approach to test the transmissivity feedback hypothesis during snowmelt. J. Hydrol. 219, 188–205 (1999).

    Article  Google Scholar 

  47. Brooks, E. S., Boll, J. & McDaniel, P. A. A hillslope-scale experiment to measure lateral saturated hydraulic conductivity. Water Resour. Res. 40, W04208 (2004).

    Article  Google Scholar 

  48. Moldrup, P. et al. Predicting the gas diffusion coefficient in repacked soil: water-induced linear reduction model. Soil Sci. Soc. Am. J. 64, 1588–1594 (2000).

    Article  Google Scholar 

  49. Massman, W. J. A review of the molecular diffusivities of H2O, CO2, CH4, CO, O3, SO2, NH3, N2O, NO, and NO2 in air, O2 and N2 near STP. Atmos. Environ. 32, 1111–1127 (1998).

    Article  Google Scholar 

  50. Bowling, D. R. & Massman, W. J. Persistent wind-induced enhancement of diffusive CO2 transport in a mountain forest snowpack. J. Geophys. Res. Biogeosci. 116, G04006 (2011).

    Article  Google Scholar 

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Acknowledgements

The authors thank Rocky Mountain Biological Laboratory (RMBL) for helping with field research. This work was conducted as part of the Watershed Function Scientific Focus Area at Lawrence Berkeley National Laboratory and was supported by the US Department of Energy (DOE) Subsurface Biogeochemical Research Program, DOE Office of Science, Office of Biological and Environmental Research, under contract no. DE-AC02−05CH11231. Mention of trade names and commercial analytical services does not imply endorsement.

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Authors and Affiliations

  1. Earth and Environment Sciences Area, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

    Jiamin Wan, Tetsu K. Tokunaga, Wenming Dong, Markus Bill, Nydra Harvey-Costello, Mark E. Conrad, Nicholas J. Bouskill, Susan S. Hubbard & Kenneth H. Williams

  2. Rocky Mountain Biological Laboratory, Crested Butte, CO, USA

    Wendy Brown, Alexander W. Newman, Curtis A. Beutler, Amanda N. Henderson & Kenneth H. Williams

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Contributions

J.W. and T.K.T. designed the research, conducted the data analyses and wrote the manuscript; K.H.W. led the field team; T.K.T., K.H.W., A.W.N., W.B., C.A.B. and A.N.H. performed field instrumentation, monitoring and sampling; J.W., W.D., M.B., N.H.-C., M.E.C. and N.J.B. conducted laboratory measurements. S.S.H. contributed to the conceptual model and reviewed the manuscript.

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Correspondence to Jiamin Wan or Tetsu K. Tokunaga.

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Peer review information Nature Geoscience thanks Nina Bingham, JoAnn Holloway and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor: Rebecca Neely.

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Extended data

Extended Data Fig. 1 Correlations between the sum of separately measured base cations (∑BC) and the specific conductance (SC) in porewaters.

The measured SC values were used for weathering rates calculations.

Extended Data Fig. 2 Summary of calculated subsurface total dissolved nitrogen (TDN export rates).

The TDN concentrations and export rates are averaged from May 2017 to September 2019. Predictions using flow rates based on field-measured K and enhanced K (25x for soil, 1.5x for the WZ) are compared. In the table, WZ and FBR refer to the weathering zone and fractured bedrock, respectively. The importance of TDN export during the peak 2-month periods of snowmelt recharge is noteworthy, amounting to 39% and 49% of total exports, based on the measured and enhance K, respectively.

Extended Data Fig. 3 Hillslope N mass balance. Nitrogen fluxes along the lower montane hillslope.

The two different hydraulic conductivity (K) scenarios constrain N influxes from weathering and effluxes in groundwater flow and overall diffusion (N2 + N2O) to the atmosphere. The N2O flux is the three-year average of diffusion calculations with and without inclusion of winter 2018–2019, for three locations.

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Wan, J., Tokunaga, T.K., Brown, W. et al. Bedrock weathering contributes to subsurface reactive nitrogen and nitrous oxide emissions. Nat. Geosci. 14, 217–224 (2021). https://doi.org/10.1038/s41561-021-00717-0

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