Time filter

Source Type

Tallahassee, FL, United States

Missimer T.M.,King Abdullah University of Science and Technology | Maliva R.G.,Schlumberger | Dehwah A.H.A.,King Abdullah University of Science and Technology | Phelps D.,Florida Geological Survey
Desalination and Water Treatment | Year: 2014

Desalination of seawater using the reverse osmosis process can be made less costly by the use of subsurface intake systems. Use of conventional open-ocean intakes requires the addition of a number of pretreatment processes to protect the primary RO process. Despite using the best designs possible for the pretreatment, seawater RO membranes tend to biofoul because of the naturally-occurring organic material and small bacteria present in seawater. These materials are not completely removed by the pretreatment system and they pass through the cartridge filters into the membranes, thereby causing frequent and expensive cleaning of the membranes. Quality of the raw water can be greatly improved by the use of subsurface intakes which can substantially reduce the overall treatment cost. There are a number of possible subsurface designs that can be used including conventional vertical wells, horizontal wells, collector wells, beach galleries, and seabed filters. The key selection criteria for the type of subsurface intake most suited and most cost-effective for a site are based on the required volume of raw water and the local geology. The active shorelines of Florida are very well-suited for the development of beach gallery intake systems. These systems are installed beneath the active beach between the high and low tide zones of the beach. Since they are constructed with a depth to the screens between 3 and 5 m, they cannot be observed at surface and persons using the beach would be unaware of their existence. These galleries are simple to construct and they tend not to clog because the active wave action within the intertidal zone provides mechanical energy that continuously cleans the filter face. They also have other advantages, including: the water quality is seawater unaffected by substances present in freshwater aquifers occurring landward of the shoreline, the salinity of the water is generally constant, and there are no impacts on water users located inland from the shoreline. A comprehensive study of the grain size characteristics of Florida beaches has allowed an assessment to be made of the hydraulic conductivities of the Florida beach sands. Hydraulic conductivity values generally range from 1.8 to 24 m/day, which is more than sufficient to allow the design and construction of high-capacity galleries at a reasonable cost. This type of intake is particularly relevant to the northeast Florida shoreline adjacent to an area being considered for development of a large-capacity seawater desalination system. © 2013 © 2013 Balaban Desalination Publications. All rights reserved. Source

Jin J.,University of Florida | Zimmerman A.R.,University of Florida | Norton S.B.,Florida Geological Survey | Annable M.D.,University of Florida | Harris W.G.,University of Florida
Science of the Total Environment | Year: 2016

While aquifer storage and recovery (ASR) is becoming widely accepted as a way to address water supply shortages, there are concerns that it may lead to release of harmful trace elements such as arsenic (As). Thus, mechanisms of As release from limestone during ASR operations were investigated using 110-day laboratory incubations of core material collected from the Floridan Aquifer, with treatment additions of labile or refractory dissolved organic matter (DOM) or microbes. During the first experimental phase, core materials were equilibrated with native groundwater lacking in DO to simulate initial non-perturbed anaerobic aquifer conditions. Then, ASR was simulated by replacing the native groundwater in the incubations vessels with DO-rich ASR source water, with DOM or microbes added to some treatments. Finally, the vessels were opened to the atmosphere to mimic oxidizing conditions during later stages of ASR. Arsenic was released from aquifer materials, mainly during transitional periods at the beginning of each incubation stage. Most As released was during the initial anaerobic experimental phase via reductive dissolution of Fe oxides in the core materials, some or all of which may have formed during the core storage or sample preparation period. Oxidation of As-bearing Fe sulfides released smaller amounts of As during the start of later aerobic experimental phases. Additions of labile DOM fueled microbially-mediated reactions that mobilized As, while the addition of refractory DOM did not, probably due to mineral sorption of DOM that made it unavailable for microbial utilization or metal chelation. The results suggest that oscillations of groundwater redox conditions, such as might be expected to occur during an ASR operation, are the underlying cause of enhanced As release in these systems. Further, ASR operations using DOM-rich surface waters may not necessarily lead to additional As releases. © 2016 Elsevier B.V. Source

Burdette K.E.,McMaster University | Rink W.J.,McMaster University | Mallinson D.J.,East Carolina University | Means G.H.,Florida Geological Survey | Parham P.R.,University of Malaysia, Terengganu
Quaternary Research (United States) | Year: 2013

For the first time, electron spin resonance optical dating (ESROD) has been conducted on littorally transported and aeolian siliciclastic sediments in Florida. ESROD utilizes light-sensitive radiation-sensitive defects at silicon sites that have been replaced by aluminum and titanium atoms to give rise to a time-dependant signal. These defects saturate at higher levels of radiation dose, compared to optically stimulated luminescence, and therefore extend the optical dating range back into the millions of years. Our results show that the Trail Ridge Sequence is a multi-depositional unit that began deposition around 2.2. Ma and continued until 6. ka. The Osceola Cape, of the Effingham Sequence, was deposited around 1.5. Ma, and the Chatham Sequence was a multi-depositional terrace with at least three events preserved. © 2012 University of Washington. Source

Froede C.R.,U.S. Environmental Protection Agency | Reed J.K.,2936 Summerwood Circle | Means G.H.,Florida Geological Survey
Southeastern Geology | Year: 2015

The Chattahoochee Anticline, Gordon Anticline, and Decatur Arch are three subsurface structural features identified on the southeastern Gulf Coastal Plain by geologists in the 20th century. The Chattahoochee Anticline was first identified in 1911 as a southward plunging structure extending along the Chattahoochee River from south of Columbus, Georgia, to the juncture of Alabama, Georgia, and Florida. Later, Hager (1918) described the Gordon Anticline as a small feature along the river near Gordon, Alabama. In 1947, Pressler dismissed the Chattahoochee Anticline but identified a similarly trending feature, the Decatur Arch, to the east and further south but parallel to the Chattahoochee and Apalachicola Rivers. Evidence in support of these structural features, such as basement uplift, subsurface faulting, sediment compaction, or one or more subsurface diapirs, remains elusive. This study examines existing basement maps, subsurface cross sections, and geophysical data across the southeastern Coastal Plain. We construct a new basement map and cross sections to test the location and orientation of reported structural features. Our analysis reveals no evidence that supports the existence of the Chattahoochee Anticline, Gordon Anticline, or Decatur Arch. © 2015, Duke University. All rights reserved. Source

Sarthou G.,European University of Brittany | Sarthou G.,French National Center for Scientific Research | Bucciarelli E.,European University of Brittany | Bucciarelli E.,French National Center for Scientific Research | And 9 more authors.
Biogeosciences | Year: 2011

Labile Fe(II) distributions were investigated in the Sub-Tropical South Atlantic and the Southern Ocean during the BONUS-GoodHope cruise from 34 to 57° S (February-March 2008). Concentrations ranged from below the detection limit (0.009 nM) to values as high as 0.125 nM. In the surface mixed layer, labile Fe(II) concentrations were always higher than the detection limit, with values higher than 0.060 nM south of 47° S, representing between 39 % and 63 % of dissolved Fe (DFe). Apparent biological production of Fe(II) was evidenced. At intermediate depth, local maxima were observed, with the highest values in the Sub-Tropical domain at around 200 m, and represented more than 70 % of DFe. Remineralization processes were likely responsible for those sub-surface maxima. Below 1500 m, concentrations were close to or below the detection limit, except at two stations (at the vicinity of the Agulhas ridge and in the north of the Weddell Sea Gyre) where values remained as high as ∼0.030-0.050 nM. Hydrothermal or sediment inputs may provide Fe(II) to these deep waters. Fe(II) half life times (t 1/2) at 4°C were measured in the upper and deep waters and ranged from 2.9 to 11.3 min, and from 10.0 to 72.3 min, respectively. Measured values compared quite well in the upper waters with theoretical values from two published models, but not in the deep waters. This may be due to the lack of knowledge for some parameters in the models and/or to organic complexation of Fe(II) that impact its oxidation rates. This study helped to considerably increase the Fe(II) data set in the Ocean and to better understand the Fe redox cycle. © Author(s) 2011. Source

Discover hidden collaborations