Intercomparison of submarine groundwater discharge estimates from a sandy unconfined aquifer

Mulligan, Ann E.; Charette, Matthew A.

doi:10.1016/j.jhydrol.2005.11.056

Cited by 192 publications

(163 citation statements)

References 50 publications

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“…For example, we observed Ra values at salinities of 1 and 25 that had the same activity-an unexpected result given what we know about Ra cycling in surface estuaries. In addition, at salinities <1, we observed measurable radium, hence even "fresh" groundwater may be a source of radium to surface waters, especially when fresh groundwater represents a significant portion of total SGD (as in Mulligan and Charette, 2006 considerably, even when bulk Ra shows little change. We recommend a simple approach for determining this quantity using 222 Rn equilibration.…”

Section: Discussionmentioning

confidence: 70%

“…Radium isotopes have been employed to determine the magnitude of SGD (0.035 m 3 s -1 , Mulligan and Charette, 2006) and several studies report considerable variability in groundwater radium activities (Charette et al, 2001;Abraham et al, 2003;Gonneea et al, 2006;Mulligan and Charette, 2006). Samples for this study were collected in June 2006, when aquifer levels were dropping and the fresh/saline groundwater interface was moving landward, inundating sediments that had been exposed to freshwater during the winter recharge period of the aquifer with higher salinity groundwater.…”

Section: Study Areamentioning

confidence: 99%

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New perspectives on radium behavior within a subterranean estuary

et al. 2008

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Abstract:Over the past decade, radium isotopes have been frequently applied as tracers of submarine groundwater discharge (SGD). The unique radium signature of SGD is acquired within the subterranean estuary, a mixing zone between fresh groundwater and seawater in coastal aquifers, yet little is known about what controls Ra cycling in this system. The focus of this study was to examine controls on sediment and groundwater radium activities within permeable aquifer sands (Waquoit Bay, MA, USA) through a combination of field and laboratory studies. In the field, a series of sediment cores and corresponding groundwater profiles were collected for analysis of the four radium isotopes, as well as dissolved and sediment associated manganese, iron, and barium. We found that in addition to greater desorption at increasing salinity, radium was also closely tied to manganese and iron redox cycling within these sediments. A series of laboratory adsorption/desorption experiments helped elucidate the importance of 1) contact time between sediment and water, 2) salinity of water in contact with sediment, 3) redox conditions of water in contact with sediment, and 4) the chemical characteristics of sediment on radium adsorption/desorption. We found that these reactions are rapid (on the order of hours), desorption increases with increasing salinity and decreasing pH, and the presence of Fe and Mn (hydr)oxides on the sediment inhibit the release of radium.These sediments have a large capacity to sorb radium from fresh water. Combined with these experimental results, we present evidence from time series groundwater sampling 2 that within this subterranean estuary there are cyclic periods of Ra accumulation and release controlled by changing salinity and redox conditions.

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Section: Discussionmentioning

confidence: 70%

Section: Study Areamentioning

confidence: 99%

New perspectives on radium behavior within a subterranean estuary

et al. 2008

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“…Infrared imaging has been used to identify the location and spatial variability of SGD by exploiting the temperature difference between surface water and groundwater at certain times of the year (Portnoy et al, 1998;Miller and Ullman, 2004;Mulligan and Charette, 2006). While this technique is quite useful for identifying spatial discharge patterns, it has not yet been applied to estimating flow rates.…”

Section: Infrared Thermographymentioning

confidence: 99%

“…Locations of SGD can be seen in the infrared image as locations along the beach face with cooler temperature than the surrounding surface water. The image clearly shows spatial variability in SGD along the beach face, information that is extremely valuable in designing an appropriate field sampling campaign (e.g., Mulligan and Charette, 2006). …”

Section: Infrared Thermographymentioning

confidence: 99%

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Groundwater Flow to the Coastal Ocean

Mulligan

Charette

2009

Encyclopedia of Ocean Sciences

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Effects of alongshore morphology on groundwater flow and solute transport in a nearshore aquifer

Zhang

Erler

et al. 2016

Water Resources Research

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Variations of beach morphology in both the cross-shore and alongshore directions, associated with tidal creeks, are common at natural coasts, as observed at a field site on the east coast of Rarotonga, Cook Islands. Field investigations and three-dimensional (3-D) numerical simulations were conducted to study the nearshore groundwater flow and solute transport in such a system. The results show that the beach morphology, combined with tides, induced a significant alongshore flow and modified local pore water circulation and salt transport in the intertidal zone substantially. The bathymetry and hydraulic head of the creek enabled further and more rapid landward intrusion of seawater along the creek than in the aquifer, which created alongshore hydraulic gradient and solute concentration gradient to drive pore water flow and salt transport in the alongshore direction within the aquifer. The effects of the creek led to the formation of a saltwater plume in groundwater at an intermediate depth between fresher water zones on a cross-shore transect. The 3-D pore water flow in the nearshore zone was also complicated by the landward hydraulic head condition, resulting in freshwater drainage across the inland section of the creek while seawater infiltrating the seaward section. These results provided new insights into the complexity, intensity, and time scales of mixing among fresh groundwater, recirculating seawater and creek water in three dimensions. The 3-D characteristics of nearshore pore water flow and solute transport have important implications for studies of submarine groundwater discharge and associated chemical input to the coastal sea, and for evaluation of the beach habitat conditions. Key Points:3-D nearshore groundwater flow and solute transport at a field site are examined Tidal creek causes complex morphological and hydraulic variations, inducing alongshore flow and solute transport Cross-shore and alongshore flow and solute transport processes interact strongly in the near-creek area Supporting Information:Supporting Information S1 (2016), Effects of alongshore morphology on groundwater flow and solute transport in a nearshore aquifer, Water Resour.

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Intercomparison of submarine groundwater discharge estimates from a sandy unconfined aquifer

Cited by 192 publications

References 50 publications

New perspectives on radium behavior within a subterranean estuary

New perspectives on radium behavior within a subterranean estuary

Groundwater Flow to the Coastal Ocean

Effects of alongshore morphology on groundwater flow and solute transport in a nearshore aquifer

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