Watershed 'Chemical Cocktails': Forming Novel Elemental Combinations in Anthropocene Fresh Waters
Citation:
Kaushal, S., A. Gold, S. Bernal, T. Newcomer-Johnson, K. Adddy, A. Burgin, D. Burns, A. Coble, E. Hood, Y. Lu, P. Mayer, E. Minor, A. Schroth, H. Wilson, M. Xenopoulos, T. Doody, J. Galella, P. Goodling, K. Haviland, S. Haq, B. Wessel, K. Wood, N. Jaworski, AND K. Belt. Watershed 'Chemical Cocktails': Forming Novel Elemental Combinations in Anthropocene Fresh Waters. BIOGEOCHEMISTRY. Springer, New York, NY, 141(3):281-305, (2018). https://doi.org/10.1007/s10533-018-0502-6
Impact/Purpose:
Watershed transport of pollutants can become increasingly dominated by groups of elements which are hydrologically linked together biogeochemically. Shifts in the timing and magnitude of drying/rewetting events amplify these patterns and links, potentially exacerbating pollution problems. We explored the questions of whether we could develop a framework to pollutant transformation under drying and rewetting cycles and what role do these linked chemical transformations mean for pollution risk in increasingly urbanized aquatic ecosystems. To address these questions, we first analyzed global trends in carbon, nutrient, trace metals, and salt concentrations in watersheds over a century. Next, we explored how drying/rewetting contribute to these trend, and we analyzed abiotic and biotic mechanisms that may drive the co-evolution of these cycles in watersheds. We found that over repeated and synchronous drying and wetting cycles, elements such as nutrients and heavy metals oxidize, form complexes, and/or accumulate in soils. Elements undergo reduction, dissolution, flushing, and/or volatilization before repeating the drying-rewetting cycle over again. Our analysis and review suggest that a changes to biogeochemical cycles due to urbanization has altered global river chemistry over 100 years and that understanding these linkages is important for managing water quality under climate and landscape modification.
Description:
In the Anthropocene, watershed chemical transport is increasingly dominated by novel combinations of elements, which are hydrologically linked together as 'chemical cocktails.' Chemical cocktails are novel because human activities greatly enhance elemental concentrations and their probability for biogeochemical interactions and shared transport along hydrologic flowpaths. A new chemical cocktail approach advances our ability to: trace contaminant mixtures in watersheds, develop chemical proxies with high-resolution sensor data, and manage multiple water quality problems. We explore the following questions: (1) Can we classify elemental transport in watersheds as chemical cocktails using a new approach? (2) What is the role of climate and land use in enhancing the formation and transport of chemical cocktails in watersheds? To address these questions, we first analyze trends in concentrations of carbon, nutrients, metals, and salts in fresh waters over 100 years. Next, we explore how climate and land use enhance the probability of formation of chemical cocktails of carbon, nutrients, metals, and salts. Ultimately, we classify transport of chemical cocktails based on solubility, mobility, reactivity, and dominant phases: (1) sieved chemical cocktails (e.g., particulate forms of nutrients, metals and organic matter); (2) filtered chemical cocktails (e.g., dissolved organic matter and associated metal complexes); (3) chromatographic chemical cocktails (e.g., ions eluted from soil exchange sites); and (4) reactive chemical cocktails (e.g., limiting nutrients and redox sensitive elements). Typically, contaminants are regulated and managed one element at a time, even though combinations of elements interact to influence many water quality problems such as toxicity to life, eutrophication, infrastructure corrosion, and water treatment. A chemical cocktail approach significantly expands evaluations of water quality signatures and impacts beyond single elements to mixtures. High-frequency sensor data (pH, specific conductance, turbidity, etc.) can serve as proxies for chemical cocktails and improve real-time analyses of water quality violations, identify regulatory needs, and track water quality recovery following storms and extreme climate events. Ultimately, a watershed chemical cocktail approach is necessary for effectively co-managing groups of contaminants and provides a more holistic approach for studying, monitoring, and managing water quality in the Anthropocene
URLs/Downloads:
DOI: Watershed 'Chemical Cocktails': Forming Novel Elemental Combinations in Anthropocene Fresh Waters