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SALT WATER INTRUSION IN COASTAL AREAS OF VOLUSIA BREVARD AND INDIAN RIVER COUNTIES
... The hydrostratigraphy of Florida can be broadly divided into three principle units including from deepest to shallowest, the Floridan, Intermediate, and Surficial aquifers (Miller 1986, Scott 1992, Groszos et al. 1992 (Scott 1988). To the south of the Indian River Lagoon, the Intermediate aquifer is thin and relatively non-productive (Toth 1988). ...
... The Surficial aquifer has been subdivided into separate units informally named the Shallow Rock aquifer and Shallow Clastic aquifer (Toth 1988). These aquifers consist largely of mixtures of sand, coquina and clay layers, with the clay layers providing the confining layers between the aquifers. ...
... The boundary between confined and semi-confined Floridan aquifer cuts across the northern portion of the Indian River Lagoon north of Melbourne, and this boundary is missing in the northernmost reaches of the Indian River Lagoon and the Mosquito Lagoon (Scott 1988, Toth 1988 ...
... The surficial aquifer system is the uppermost water-bearing unit, and consists of sand, shell beds, silt, clay, and indurated shell or coquina of Pliocene to Quaternary age. The Floridan aquifer system consists of limestone and dolomite rocks of Eocene and Miocene age and is the primary source of potable water in the basin (Toth, 1988). A confining unit composed of clays of Miocene age separates the surficial aquifer system from the Floridan aquifer system (Toth, 1988). ...
... The Floridan aquifer system consists of limestone and dolomite rocks of Eocene and Miocene age and is the primary source of potable water in the basin (Toth, 1988). A confining unit composed of clays of Miocene age separates the surficial aquifer system from the Floridan aquifer system (Toth, 1988). The depth to the top of the Floridan aquifer system ranges from about 100 to 200 ft below NGVD 1929 within the basin (Toth, 1988) and is deeper toward the south. ...
... A confining unit composed of clays of Miocene age separates the surficial aquifer system from the Floridan aquifer system (Toth, 1988). The depth to the top of the Floridan aquifer system ranges from about 100 to 200 ft below NGVD 1929 within the basin (Toth, 1988) and is deeper toward the south. The Floridan aquifer system is further subdivided into two highly transmissive zones, the Upper Floridan aquifer and Lower Floridan aquifer, which are separated by a less permeable middle semiconfining unit. ...
... The hydrostratigraphy of peninsular Florida is divided into three main units—the Floridan, Intermediate, and Surficial aquifers (Miller 1986; Scott 1988; Groszos et al. 1992). At the study site, the Floridan Aquifer is confined by the Miocene Hawthorn Group (Scott 1988), and the Intermediate Aquifer is thin and relatively nonproductive (Bermes 1958; Toth 1988). Consequently, the major source of fresh ground water available for discharge to the Banana River Lagoon is from the Surficial Aquifer, which is locally subdivided into informal units called the Shallow Rock, Terrace, Atlantic Coastal Ridge, Ten-Mile Ridge, and Inter-Ridge aquifers (Toth 1988). ...
... At the study site, the Floridan Aquifer is confined by the Miocene Hawthorn Group (Scott 1988), and the Intermediate Aquifer is thin and relatively nonproductive (Bermes 1958; Toth 1988). Consequently, the major source of fresh ground water available for discharge to the Banana River Lagoon is from the Surficial Aquifer, which is locally subdivided into informal units called the Shallow Rock, Terrace, Atlantic Coastal Ridge, Ten-Mile Ridge, and Inter-Ridge aquifers (Toth 1988). These aquifers are Pliocene in age, are recharged by local rainfall, and consist largely of mixtures of sands and coquina, separated by thin confining clay layers (Toth 1988). ...
... Consequently, the major source of fresh ground water available for discharge to the Banana River Lagoon is from the Surficial Aquifer, which is locally subdivided into informal units called the Shallow Rock, Terrace, Atlantic Coastal Ridge, Ten-Mile Ridge, and Inter-Ridge aquifers (Toth 1988). These aquifers are Pliocene in age, are recharged by local rainfall, and consist largely of mixtures of sands and coquina, separated by thin confining clay layers (Toth 1988). A few previous attempts have been made to measure ground water discharge to the Indian River Lagoon system, and these include both direct measurements and modeling (Belanger and Walker 1990; Pandit and El-Khazen 1990; Martin et al. 2002). ...
Submarine ground water discharge is suggested to be an important pathway for contaminants from continents to coastal zones, but its significance depends on the volume of water and concentrations of contaminants that originate in continental aquifers. Ground water discharge to the Banana River Lagoon, Florida, was estimated by analyzing the temporal and spatial variations of Cl− concentration profiles in the upper 230 cm of pore waters and was measured directly by seepage meters. Total submarine ground water discharge consists of slow discharge at depths > ∼70 cm below seafloor (cmbsf) of largely marine water combined with rapid discharge of mixed pore water and estuarine water above ∼70 cmbsf. Cl− profiles indicate average linear velocities of ∼0.014 cm/d at depths > ∼70 cmbsf. In contrast, seepage meters indicate water discharges across the sediment-water interface at rates between 3.6 and 6.9 cm/d. The discrepancy appears to be caused by mixing in the shallow sediment, which may result from a combination of bioirrigation, wave and tidal pumping, and convection. Wave and tidal pumping and convection would be minor because the tidal range is small, the short fetch of the lagoon limits wave heights, and large density contacts are lacking between lagoon and pore water. Mixing occurs to ∼70 cmbsf, which represents depths greater than previously reported. Mixing of oxygenated water to these depths could be important for remineralization of organic matter.
... The study site is a shore-normal transect that extends across the seepage face of Indian River Lagoon, Florida (Fig. 1). Details of hydrostratigraphy, hydrogeology, and non-local exchange are discussed elsewhere Martin et al., 2004Martin et al., , 2006Martin et al., , 2007Pandit and El-Khazen, 1990;Toth, 1988). The hydraulic conductivity of the upper several meters of sediment ranges from 10 − 2 to 10 − 8 cm/s but is more homogenous in the upper 70 cm sediments ranging from 10 − 2 to 10 − 4 cm/s (data based on 28 cores, Hartl, 2006). ...
Iron oxides are important terminal electron acceptors for organic carbon (OC) remineralization in subterranean estuaries, particularly where oxygen and nitrate concentrations are low. In Indian River Lagoon, Florida, USA, terrestrial Fe-oxides dissolve at the seaward edge of the seepage face and flow upward into overlying marine sediments where they precipitate as Fe-sulfides. The dissolved Fe concentrations vary by over three orders of magnitude, but Fe-oxide dissolution rates are similar across the 25-m wide seepage face, averaging around 0.21 mg/cm2/yr. The constant dissolution rate, but differing concentrations, indicate Fe dissolution is controlled by a combination of increasing lability of dissolved organic carbon (DOC) and slower porewater flow velocities with distance offshore. In contrast, the average rate constants of Fe-sulfide precipitation decrease from 21.9 × 10- 8 s- 1 to 0.64 × 10- 8 s- 1 from the shoreline to the seaward edge of the seepage face as more oxygenated surface water circulates through the sediment. The amount of OC remineralized by Fe-oxides varies little across the seepage face, averaging 5.34 × 10- 2 mg/cm2/yr. These rates suggest about 3.4 kg of marine DOC was remineralized in a 1-m wide, shore-perpendicular strip of the seepage face as the terrestrial sediments were transgressed over the past 280 years. During this time, about 10 times more marine solid organic carbon (SOC) accumulated in marine sediments than were removed from the underlying terrestrial sediments. Indian River Lagoon thus appears to be a net sink for marine OC.
... The study site (28 o 08.0 0 N and 80 o 37.5 0 W) is in the central part of the main lagoon. Hydrostratigraphy of the field area is subdivided into three units: (1) the unconfined Surficial Aquifer, which is composed of sand, silt, clay, shell and dolomitic limestones of the Holocene Anastasia Formation; (2) the confined Floridan Aquifer, which is composed of Late Paleocene to Oligocene limestone; and (3) the confining unit separating the Floridan and Surficial aquifers, which is composed of sand, silt and clay of the Miocene Hawthorn Group (Toth, 1988;Scott, 1992). The Hawthorn Group is more than 30 m thick in the study area, fully confining the Floridan Aquifer, and thus all terrestrial SGD in the study area is from the Surficial Aquifer. ...
Subterranean estuary occupies the transition zone between hypoxic fresh groundwater and oxic seawater, and between terrestrial and marine sediment deposits. Consequently, we hypothesize, in a subterranean estuary, biogeochemical reactions of Fe respond to submarine groundwater discharge (SGD) and sea level rise. Porewater and sediment samples were collected across a 30-m wide freshwater discharge zone of the Indian River Lagoon (Florida, USA) subterranean estuary, and at a site 250 m offshore. Porewater Fe concentrations range from 0.5 μM at the shoreline and 250 m offshore to about 286 μM at the freshwater–saltwater boundary. Sediment sulfur and porewater sulfide maxima occur in near-surface OC-rich black sediments of marine origin, and dissolved Fe maxima occur in underlying OC-poor orange sediments of terrestrial origin. Freshwater SGD flow rates decrease offshore from around 1 to 0.1 cm/day, while bioirrigation exchange deepens with distance from about 10 cm at the shoreline to about 40 cm at the freshwater–saltwater boundary. DOC concentrations increase from around 75 μM at the shoreline to as much as 700 μM at the freshwater–saltwater boundary as a result of labile marine carbon inputs from marine SGD. This labile DOC reduces Fe-oxides, which in conjunction with slow discharge of SGD at the boundary, allows dissolved Fe to accumulate. Upward advection of fresh SGD carries dissolved Fe from the Fe-oxide reduction zone to the sulfate reduction zone, where dissolved Fe precipitates as Fe-sulfides. Saturation models of Fe-sulfides indicate some fractions of these Fe-sulfides get dissolved near the sediment–water interface, where bioirrigation exchanges oxic surface water. The estimated dissolved Fe flux is approximately 0.84 μM Fe/day per meter of shoreline to lagoon surface waters. Accelerated sea level rise predictions are thus likely to increase the Fe flux to surface waters and local primary productivity, particularly along coastlines where groundwater discharges through sediments.
... The aquifer in the model domain had a mainly sandy geological structure. The porosity of the aquifer sand, ne, typically ranged from 0Ð25 to 0Ð53 (Zheng and Bennett, 1995), and hydraulic conductivities, K, ranged from 10 m d 1 to 127 m d 1 (Toth, 1988). By assuming that the aquifer was isotropic and homogeneous (zone A), constant parameters, K D 20 m d 1 and ne D 0 Ð 25, were used to achieve more accurate simulations. ...
Effect of freshwater discharge on the long-term salt balance in the Northern and Central Indian River Lagoon (IRL) is successfully simulated by a new analytical solution to a water balance-based one-dimensional salt conservation equation. Sensitivity tests show that the salinity levels drop abruptly even during the dry season (November to May) due to the high surface runoff discharge caused by tropical storms, depressions, and passage of cold fronts. Increasing surface runoff and direct precipitation by ten times lowers the salinity level down to 12 psu in the Northern Central zone, and to 17 psu in the Northern zone. However, the salinity level in the Southern Central zone has decreased to 25 psu. High sensitivity of the Northern Central zone to freshwater discharge can be partially explained by a rapid urbanization in this zone. During the dry season, less sensitivity of the Southern Central zone to the increased surface runoff is attributed to the proximity to the Sebastian Inlet and a strong diffusion condition possibly resulting from the seawater intrusion to the surficial aquifer at the Vero Beach. During the wet season, however, the whole study area is highly sensitive to freshwater discharge due to the weak diffusion conditions. High sensitivity of the IRL to the given diffusion conditions suggests that the freshwater release should be executed during strong wind condition for both flood control in the drainage basin and a proper salinity regime in the IRL.
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