Abstract
Sandy beach aquifers are complex hydrological and biogeochemical systems where fresh groundwater and seawater mix. The extent of the intertidal mixing zone and the rates of circulating flows within beaches are a primary control on porewater chemistry and microbiology of the intertidal subsurface. Interplay between the hydrological and biogeochemical processes at these land-sea transition zones moderate fluxes of chemicals, particulates, heavy metals, and biota across the aquifer-ocean interface, affecting coastal water quality and nutrient loads to marine ecosystems. Thus, it is important to characterize hydrological and biogeochemical processes in beach aquifers when estimating material fluxes to the ocean. This can be achieved through a suite of cross-disciplinary measurements of beach groundwater flow and chemistry. In this review, we present measurement approaches that have been developed and employed to characterize the physical (geology, topography, subsurface hydrology) and biogeochemical (solute and particulate distributions, reaction rates) properties of and processes occurring within sandy intertidal aquifers. As applied to beach systems, we discuss vibracoring, sample collection, laboratory experiments, variable-density considerations, instrument construction, and sensor technologies. We discuss advantages and limitations of typical hydrologic field sampling methods when used to investigate beach aquifers and provide a measurement framework for researchers seeking to sample and collect data from these systems.
Highlights
Beaches mark the terminal end of terrestrial groundwater flow paths and comprise approximately 1/3 of the world’s ice-free coastline [1]
Fresh groundwater flows through the beach aquifer before discharging to the coastal ocean as fresh submarine groundwater discharge (SGD)
While few manufacturers (e.g., Solinst Inc., Georgetown, ON, USA) do produce pressure transducers that can record at intervals down to 1/8 s, manufacturers that cater to oceanographic applications produce sensors that are capable of sampling at very high frequencies (e.g., 32 Hz)
Summary
Citation: Kim, K.H.; Heiss, J.W. Methods in Capturing the Spatiotemporal Dynamics of Flow and Biogeochemical Reactivity in Sandy Beach Aquifers: A Review. Department of Environmental, Earth and Atmospheric Sciences, University of Massachusetts Lowell, Lowell, MA 01854, USA
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