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<p>There is a critical need for a springshed-specific, 3-dimensional (3-D) contaminant fate and transport (CFT) model for the Volusia Blue Spring (VBS), given the complex hydrogeology of Florida’s karst aquifers and the substantial anthropogenic nutrient pollution. In this study, an integrated 3-D CFT model was developed to track the sources and predict impacts of nutrient and an anthropogenic marker (caffeine) loading on the springshed. While nitrate was present in all groundwater samples (0.048–0.417&#xa0;mg/L), primarily attributed to total Kjeldahl nitrogen in septic tank supernatant, caffeine was absent in groundwater but reached concentrations as high as 22&#xa0;µg/L in septic systems. A coupled MODFLOW-2005/MT3DMS model, incorporating a four-layer aquifer system and a karst conduit network, was calibrated and validated with satisfactory results. Model simulations showed that, despite the very low caffeine concentration in VBS discharge (~ 0.024&#xa0;µg/L) compared to global river levels, its presence indicates domestic wastewater as a contamination source. Simulated Management scenarios showed that in the baseline scenario (Scenario 1), without any intervention, both caffeine and nitrate levels are expected to rise slightly. Scenario 2 [directing septic tank effluent to the nearest wastewater treatment plant (WWTP)] lowered nitrate levels by 27% relative to the baseline but did not sufficiently reduce caffeine levels due to the assumed limited removal efficiency of WWTP. In Scenario 3, upgrading septic systems to achieve a 30% improvement in nutrient removal led to reductions of approximately 80% in caffeine and 14% in nitrate compared to the baseline, showing its greater effectiveness in reducing contamination.</p>

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Modeling contaminant transport in karst aquifer for spring water quality management

  • 期刊论文

  • 发表日期：

    2026年4月7日

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  • Lili Yao,
  • Md Touhidul Islam,
  • Nicholas Damigella,
  • Dingbao Wang,
  • A. H. M. Anwar Sadmani

摘要

There is a critical need for a springshed-specific, 3-dimensional (3-D) contaminant fate and transport (CFT) model for the Volusia Blue Spring (VBS), given the complex hydrogeology of Florida’s karst aquifers and the substantial anthropogenic nutrient pollution. In this study, an integrated 3-D CFT model was developed to track the sources and predict impacts of nutrient and an anthropogenic marker (caffeine) loading on the springshed. While nitrate was present in all groundwater samples (0.048–0.417 mg/L), primarily attributed to total Kjeldahl nitrogen in septic tank supernatant, caffeine was absent in groundwater but reached concentrations as high as 22 µg/L in septic systems. A coupled MODFLOW-2005/MT3DMS model, incorporating a four-layer aquifer system and a karst conduit network, was calibrated and validated with satisfactory results. Model simulations showed that, despite the very low caffeine concentration in VBS discharge (~ 0.024 µg/L) compared to global river levels, its presence indicates domestic wastewater as a contamination source. Simulated Management scenarios showed that in the baseline scenario (Scenario 1), without any intervention, both caffeine and nitrate levels are expected to rise slightly. Scenario 2 [directing septic tank effluent to the nearest wastewater treatment plant (WWTP)] lowered nitrate levels by 27% relative to the baseline but did not sufficiently reduce caffeine levels due to the assumed limited removal efficiency of WWTP. In Scenario 3, upgrading septic systems to achieve a 30% improvement in nutrient removal led to reductions of approximately 80% in caffeine and 14% in nitrate compared to the baseline, showing its greater effectiveness in reducing contamination.