Browsing by Author "Likens, Gene E."
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- The anthropogenic salt cycleKaushal, Sujay S.; Likens, Gene E.; Mayer, Paul M.; Shatkay, Ruth R.; Shelton, Sydney A.; Grant, Stanley B.; Utz, Ryan M.; Yaculak, Alexis M.; Maas, Carly M.; Reimer, Jenna E.; Bhide, Shantanu V.; Malin, Joseph T.; Rippy, Megan A. (SpringerNature, 2023-10-31)Increasing salt production and use is shifting the natural balances of salt ions across Earth systems, causing interrelated effects across biophysical systems collectively known as freshwater salinization syndrome. In this Review, we conceptualize the natural salt cycle and synthesize increasing global trends of salt production and riverine salt concentrations and fluxes. The natural salt cycle is primarily driven by relatively slow geologic and hydrologic processes that bring different salts to the surface of the Earth. Anthropogenic activities have accelerated the processes, timescales and magnitudes of salt fluxes and altered their directionality, creating an anthropogenic salt cycle. Global salt production has increased rapidly over the past century for different salts, with approximately 300 Mt of NaCl produced per year. A salt budget for the USA suggests that salt fluxes in rivers can be within similar orders of magnitude as anthropogenic salt fluxes, and there can be substantial accumulation of salt in watersheds. Excess salt propagates along the anthropogenic salt cycle, causing freshwater salinization syndrome to extend beyond freshwater supplies and affect food and energy production, air quality, human health and infrastructure. There is a need to identify environmental limits and thresholds for salt ions and reduce salinization before planetary boundaries are exceeded, causing serious or irreversible damage across Earth systems.
- Five state factors control progressive stages of freshwater salinization syndromeKaushal, Sujay S.; Mayer, Paul M.; Likens, Gene E.; Reimer, Jenna E.; Maas, Carly M.; Rippy, Megan A.; Grant, Stanley B.; Hart, Ian; Utz, Ryan M.; Shatkay, Ruth R.; Wessel, Barret M.; Maietta, Christine E.; Pace, Michael L.; Duan, Shuiwang; Boger, Walter L.; Yaculak, Alexis M.; Galella, Joseph G.; Wood, Kelsey L.; Morel, Carol J.; Nguyen, William; Querubin, Shane Elizabeth C.; Sukert, Rebecca A.; Lowien, Anna; Houde, Alyssa Wellman; Roussel, Anais; Houston, Andrew J.; Cacopardo, Ari; Ho, Cristy; Talbot-Wendlandt, Haley; Widmer, Jacob M.; Slagle, Jairus; Bader, James A.; Chong, Jeng Hann; Wollney, Jenna; Kim, Jordan; Shepherd, Lauren; Wilfong, Matthew T.; Houlihan, Megan; Sedghi, Nathan; Butcher, Rebecca; Chaudhary, Sona; Becker, William D. (Wiley, 2022-03-16)Factors driving freshwater salinization syndrome (FSS) influence the severity of impacts and chances for recovery. We hypothesize that spread of FSS across ecosystems is a function of interactions among five state factors: human activities, geology, flowpaths, climate, and time. (1) Human activities drive pulsed or chronic inputs of salt ions and mobilization of chemical contaminants. (2) Geology drives rates of erosion, weathering, ion exchange, and acidification-alkalinization. (3) Flowpaths drive salinization and contaminant mobilization along hydrologic cycles. (4) Climate drives rising water temperatures, salt stress, and evaporative concentration of ions and saltwater intrusion. (5) Time influences consequences, thresholds, and potentials for ecosystem recovery. We hypothesize that state factors advance FSS in distinct stages, which eventually contribute to failures in systems-level functions (supporting drinking water, crops, biodiversity, infrastructure, etc.). We present future research directions for protecting freshwaters at risk based on five state factors and stages from diagnosis to prognosis to cure.
- Linking water age and solute dynamics in streamflow at the Hubbard Brook Experimental Forest, NH, USABenettin, Paolo; Bailey, Scott W.; Campbell, John L.; Green, M. B.; Rinaldo, Andrea; Likens, Gene E.; McGuire, Kevin J.; Botter, Gianluca (American Geophysical Union, 2015-11-01)We combine experimental and modeling results from a headwater catchment at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA, to explore the link between stream solute dynamics and water age. A theoretical framework based on water age dynamics, which represents a general basis for characterizing solute transport at the catchment scale, is here applied to conservative and weatheringderived solutes. Based on the available information about the hydrology of the site, an integrated transport model was developed and used to compute hydrochemical fluxes. The model was designed to reproduce the deuterium content of streamflow and allowed for the estimate of catchment water storage and dynamic travel time distributions (TTDs). The innovative contribution of this paper is the simulation of dissolved silicon and sodium concentration in streamflow, achieved by implementing first-order chemical kinetics based explicitly on dynamic TTD, thus upscaling local geochemical processes to catchment scale. Our results highlight the key role of water stored within the subsoil glacial material in both the short-term and long-term solute circulation. The travel time analysis provided an estimate of streamflow age distributions and their evolution in time related to catchment wetness conditions. The use of age information to reproduce a 14 year data set of silicon and sodium stream concentration shows that, at catchment scales, the dynamics of such geogenic solutes are mostly controlled by hydrologic drivers, which determine the contact times between the water and mineral interfaces. Justifications and limitations toward a general theory of reactive solute circulation at catchment scales are discussed.
- Network analysis reveals multiscale controls on streamwater chemistryMcGuire, Kevin J.; Torgersen, C. E.; Likens, Gene E.; Buso, D. C.; Lowe, W. H.; Bailey, Scott W. (National Academy of Sciences, 2014-05-13)By coupling synoptic data from a basin-wide assessment of streamwater chemistry with network-based geostatistical analysis, we show that spatial processes differentially affect biogeochemical condition and pattern across a headwater stream network. We analyzed a high-resolution dataset consisting of 664 water samples collected every 100 m throughout 32 tributaries in an entire fifth-order stream network. These samples were analyzed for an exhaustive suite of chemical constituents. The fine grain and broad extent of this study design allowed us to quantify spatial patterns over a range of scales by using empirical semivariograms that explicitly incorporated network topology. Here, we show that spatial structure, as determined by the characteristic shape of the semivariograms, differed both among chemical constituents and by spatial relationship (flow-connected, flowunconnected, or Euclidean). Spatial structure was apparent at either a single scale or at multiple nested scales, suggesting separate processes operating simultaneously within the stream network and surrounding terrestrial landscape. Expected patterns of spatial dependence for flow-connected relationships (e.g., increasing homogeneity with downstream distance) occurred for some chemical constituents (e.g., dissolved organic carbon, sulfate, and aluminum) but not for others (e.g., nitrate, sodium). By comparing semivariograms for the different chemical constituents and spatial relationships, we were able to separate effects on streamwater chemistry of (i ) fine-scale versus broad-scale processes and (ii ) in-stream processes versus landscape controls. These findings provide insight on the hierarchical scaling of local, longitudinal, and landscape processes that drive biogeochemical patterns in stream networks.
- Network analysis reveals multiscale controls on streamwater chemistryMcGuire, Kevin J.; Torgersen, C. E.; Likens, Gene E.; Buso, D. C.; Lowe, W. H.; Bailey, Scott W. (National Academy of Sciences, 2014-05-13)By coupling synoptic data from a basin-wide assessment of streamwater chemistry with network-based geostatistical analysis, we show that spatial processes differentially affect biogeochemical condition and pattern across a headwater stream network. We analyzed a high-resolution dataset consisting of 664 water samples collected every 100 m throughout 32 tributaries in an entire fifth-order stream network. These samples were analyzed for an exhaustive suite of chemical constituents. The fine grain and broad extent of this study design allowed us to quantify spatial patterns over a range of scales by using empirical semivariograms that explicitly incorporated network topology. Here, we show that spatial structure, as determined by the characteristic shape of the semivariograms, differed both among chemical constituents and by spatial relationship (flow-connected, flowunconnected, or Euclidean). Spatial structure was apparent at either a single scale or at multiple nested scales, suggesting separate processes operating simultaneously within the stream network and surrounding terrestrial landscape. Expected patterns of spatial dependence for flow-connected relationships (e.g., increasing homogeneity with downstream distance) occurred for some chemical constituents (e.g., dissolved organic carbon, sulfate, and aluminum) but not for others (e.g., nitrate, sodium). By comparing semivariograms for the different chemical constituents and spatial relationships, we were able to separate effects on streamwater chemistry of (i ) fine-scale versus broad-scale processes and (ii ) in-stream processes versus landscape controls. These findings provide insight on the hierarchical scaling of local, longitudinal, and landscape processes that drive biogeochemical patterns in stream networks.
- Young runoff fractions control streamwater age and solute concentration dynamicsBenettin, Paolo; Bailey, Scott W.; Rinaldo, Andrea; Likens, Gene E.; McGuire, Kevin J.; Botter, Gianluca (2017-07-31)We introduce a new representation of coupled solute and water age dynamics at the catchment scale, which shows how the contributions of young runoff waters can be directly referenced to observed water quality patterns. The methodology stems from recent trends in hydrologic transport that acknowledge the dynamic nature of streamflow age and explores the use of water age fractions as an alternative to the mean age. The approach uses a travel time-based transport model to compute the fractions of streamflow that are younger than some thresholds (e.g., younger than a few weeks) and compares them to observed solute concentration patterns. The method is here validated with data from the Hubbard Brook Experimental Forest during spring 2008, where we show that the presence of water younger than roughly 2 weeks, tracked using a hydrologic transport model and deuterium measurements, mimics the variation in dissolved silicon concentrations. Our approach suggests that an age-discharge relationship can be coupled to classic concentration-discharge relationship, to identify the links between transport timescales and solute concentration. Our results highlight that the younger streamflow components can be crucial for determining water quality variations and for characterizing the dominant hydrologic transport dynamics.