About

Dr. Michael Annable has been a faculty member in the Department of Environmental Engineering Sciences at the University of Florida since 1992. His research interests are in physical-chemical processes related to field scale application of innovative technologies for subsurface remediation. His work also focuses on innovative methods for measuring contaminant and water flux in hydrologic systems.

Research topics

• Environmental science
• Computer Science
• Environmental chemistry
• Chemistry
• Geology
• Environmental engineering
• Ecology
• Waste management
• Geotechnical engineering
• Cartography
• Soil science
• Geography

Selected publications

• Per- and polyfluoroalkyl substances (PFAS) mass flux and mass balance at an aqueous film-forming foam release site in semiarid eastern New Mexico, USA

  Journal of Contaminant Hydrology · 2025-03-22 · 4 citations

  articleOpen accessSenior author

  Passive flux meters (PFMs) directly measure groundwater chemistry mass flux and Darcy flux, providing insight into contaminant source-zone architecture and transport properties. This study uses PFMs to characterize PFAS flux in groundwater at a semiarid site with a thick (greater than 90-m) unsaturated zone where groundwater has been contaminated with per- and polyfluoroalkyl substances (PFAS) related to the use of aqueous film-forming foam (AFFF) for fire training and fire suppression. PFAS mass discharge (PFAS mass flux integrated over a control plane) in groundwater downgradient from several PFAS release areas is calculated using PFM results. In groundwater downgradient from fire-training areas, total PFAS mass discharge (summed across 14 compounds) was estimated to be between 6.0 and 31 g per day in 2020 and between 5.9 and 23 g per day in 2021. Site-specific documentation, generic information on AFFF properties, and literature values of PFAS concentration in AFFF are used to estimate site-specific PFAS-application rates at fire-training areas. These PFAS-application rates are compared to groundwater PFAS-discharge rates. Results suggest that transformation processes (exact pathways unknown) have led to increased discharge of measured PFAS in groundwater relative to initial AFFF formulations. The mass balance approach has broad applicability as a high-level approach that can provide insight into PFAS transport at AFFF sites.

  PublisherDOI

• A Reduced‐Complexity Model to Predict Seasonal Variation in Estuarine Salinity

  Geophysical Research Letters · 2025-11-14

  articleOpen access

  Abstract Accurate prediction of seasonal variations in salinity is essential for assessing the health of estuarine environments. Traditional estuarine salinity models face challenges such as high computational demands and extensive data requirements. Here, we introduce a novel, reduced‐complexity model that computes seasonal variations in estuarine salinity based on three key inputs: river discharge, tidal water levels, and marine salinity. The model predicts the seasonal (monthly moving average) salinity at a given location using a single dimensionless variable that represents the ratio of freshwater discharge to tidally driven discharge. The model is validated using data from 11 estuaries globally, showing strong predictive performance for seasonal salinity time series in each estuary, with mean absolute errors (MAEs) of 2.5 ± 1.3 psu across all estuaries. Moreover, we also show that our reduced‐complexity model predicts seasonal estuarine salinity with comparable accuracy as a fully three‐dimensional Delft3D simulation in one estuary.

  PublisherDOI

• Assessment of <scp>Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)</scp> Mass Flux and Distributions in a Lake System Using Sediment Bed Passive Flux Meters and Ceramic Dosimeters

  Groundwater Monitoring & Remediation · 2024-07-15 · 3 citations

  articleOpen access

  Abstract Per‐ and polyfluoroalkyl substances (PFAS) are persistent in the environment due to their chemical stability and can spread quickly in a lake system due to mixing. Passive samplers allow for time‐weighted average concentration monitoring and the ability to detect low concentrations, which are difficult to measure with conventional grab sampling. This study demonstrates the feasibility of deploying both ceramic dosimeters and Sediment Bed Passive Flux Meters (SBPFMs) to assess time integrated PFAS concentrations and fluxes, respectively, at a historically contaminated PFAS lake near Baden‐Baden, Germany. Long‐term surface water grab samples resulted in the detection of PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFBS, PFHxS, and PFOS at a total concentration of approximately 1 μg/L. Dosimeters were deployed for 66 and 126 d, resulting in detected concentrations ranging from approximately 250 to 380 ng/L and 120 to 460 ng/L, respectively. The 66 d deployment resulted in the detection of PFPeA, PFHxA, PFHpA, and PFOA, whereas the 126 d deployment additionally detected PFBA, PFNA, PFDA, PFUnDA, PFDoDA, PFTeDA, PFBS, PFPeS, PFOS, PFNS, and PFDS. SBPFMs resulted in the detection of PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFUnA, PFTrDA, and PFBS and the determination of a total mass discharge of 5.6 g/d into the lake. Overall, dosimeters and SBPFMs are more sensitive than grab samples at detecting PFAS at low concentrations and can be used to better understand spatial distribution of PFAS in a lake system.

  PublisherOA PDFDOI

• Temporary hydraulic barriers using organic gel for enhanced aquifer remediation during groundwater flushing: Bench-scale experiments

  Journal of Contaminant Hydrology · 2023-02-01 · 3 citations

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  PublisherDOI

• Nitrate attenuation potential in karst conduits and aquifer matrix

  Journal of Hydrology · 2023-07-01 · 6 citations

  article
  PublisherDOI

• Rainfall-Runoff Time Lags from Saltwater Interface Interactions in Atlantic Coastal Plain Basins

  Water · 2022-12-30

  articleOpen accessCorresponding

  The dynamic behavior of the freshwater-saltwater interface (FSI) in coastal aquifers can introduce unexpected lags between recharge and stream discharge, especially when recharge is forced by long-term cyclical precipitation patterns. This work seeks to assess these FSI impacts at the watershed scale. Recharge-discharge time lags were evaluated in 68 watersheds overlying the Floridan Aquifer System in the coastal region of the southeastern United States (Florida, Georgia, and South Carolina). Utilizing the strength of the Atlantic multidecadal oscillation (AMO) signal in this region, 10–20 year averaged recharge and discharge time series were used for the selected watersheds. Lags of 10–25 years between recharge and discharge were found in 16% of the basins considered, possibly induced by a dynamic FSI which responded slowly to the AMO-scale recharge signal. Freshwater storage coefficients (S) were estimated from time series of change-in-storage and groundwater level, with 11 basins showing S&gt;1.5 indicating water storage well above that expected for unconfined aquifers. These 11 basins with both multidecadal recharge-discharge time lags and high S values showed a positive linear relationship between time lag and FSI depth with slope 0.016 yr/m (R-squared = 0.30). These large time lags may be directly impacting the management of these basins as they obscure water and solute mass balances in the southeastern US.

  PublisherOA PDFDOI

• Aquifer remediation using surfactant-enhanced gas sparging applied to target the contaminant source

  Journal of Contaminant Hydrology · 2022-03-23 · 5 citations

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  PublisherDOI

• Analysis of Facilitated Air Intrusion during Surfactant-enhanced Air Sparging Using Surface Tension-reducing Chemicals: Surfactants and Alcohols

  Soil and Sediment Contamination An International Journal · 2021-04-25 · 8 citations

  articleSenior author

  The effect of lowered groundwater surface tension using alcohols and surfactants, and increased viscosity using a thickener on the performance of the air sparging (AS) process was investigated, and the mechanism of facilitated air intrusion into the saturated zone during surfactant-enhanced air sparging (SEAS) was proposed.When aqueous solutions of alcohols (e.g., ethyl alcohol) displaced the resident water in a sand-packed column, the air saturation slightly decreased during AS, whereas the addition of surfactants increased air saturation. During the AS process, a significant difference in the air pressure measurements was observed, depending on the chemicals (alcohols and surfactants). Significantly higher air pressure was measured during SEAS than AS process with alcohol solutions. In this study, it is proposed that the foam formation and displacement through the soil interstices during the SEAS process increases air pressure. And this additional air pressure is responsible for the additional air intrusion into the smaller pores at lowered surface tension. Increased hydraulic pressure or water viscosity showed no significant effect on the air saturation during alcohol-applied AS. However, during SEAS, the increased viscosity using a thickener increased the viscosity of the foam inducing high air pressure, resulting in further enhanced air saturation.

  PublisherDOI

• Sediment Bed Borehole Advection Method

  Water · 2020-12-02 · 1 citations

  articleOpen accessSenior authorCorresponding

  This paper introduces and tests the Sediment Bed Borehole Advection Method (SBBAM), a low cost, point-measurement technique which utilizes a push-point probe to quantify the vertical direction and magnitude of Darcy flux at the surface water—groundwater sediment interface. The Darcy flux measurements are derived from the residence-time analysis of tracer arrival calculated from measured tracer concentration time-series data. The technique was evaluated in the laboratory using a sediment bed simulator tank at eight flow rates (1–90 cm/day). Triplicate test runs for each flow rate returned average errors between 4–20 percent; r2 = 0.9977.

  PublisherOA PDFDOI

• Natural attenuation of a chlorinated ethene plume discharging to a stream: Integrated assessment of hydrogeological, chemical and microbial interactions

  Water Research · 2020 · 30 citations

  • Environmental science
  • Environmental chemistry
  • Environmental engineering
  PublisherOA PDFDOI

Frequent coauthors

• J.F. Devlin

  101 shared

• G Lavorgna

  IRCCS Ospedale San Raffaele

  98 shared

• William G. Rixey

  98 shared

• C Schaefer

  Zentrum für Qualität in der Pflege

  98 shared

• Aldrich Lahvis

  Ecolyse (United States)

  98 shared

• David C. Major

  Film Independent

  98 shared

• Brooke M. Smith

  98 shared

• Neil R. Thomson

  98 shared