Old groundwater in parts of the upper Patapsco aquifer, Atlantic Coastal Plain, Maryland, USA: evidence from radiocarbon, chlorine-36 and helium-4

Plummer, L. Niel; Eggleston, Jack; Andreasen, David C.; Raffensperger, Jeff P.; Hunt, Andrew G.; Casile, Gerolamo C.

doi:10.1007/s10040-012-0871-1

Cited by 48 publications

(13 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Concentrations of 14 C ranged from 0.1 to 47% modern carbon (pmc), and concentrations of terrigenic 4 He ranged from 0.3 × 10 −8 to 5790 × 10 −8 cm 3 STP/g 1 (STP, standard temperature and pressure) (Table ). The observed pattern of decreasing 14 C concentrations with increasing terrigenic 4 He concentrations (Figure B) implies that the flow system contained groundwater with considerable age (Andrews and Lee ; Plummer et al ). Carbon‐14 ages unadjusted for geochemical reactions ranged from <1000 years in well 6 to >30,000 years in wells 4 and 17 (Table ).…”

Section: Resultsmentioning

confidence: 88%

Quality and Age of Shallow Groundwater in the Bakken Formation Production Area, Williston Basin, Montana and North Dakota

McMahon¹,

Caldwell

Galloway

et al. 2014

Groundwater

View full text Add to dashboard Cite

The quality and age of shallow groundwater in the Bakken Formation production area were characterized using data from 30 randomly distributed domestic wells screened in the upper Fort Union Formation. Comparison of inorganic and organic chemical concentrations to health based drinking-water standards, correlation analysis of concentrations with oil and gas well locations, and isotopic data give no indication that energy-development activities affected groundwater quality. It is important, however, to consider these results in the context of groundwater age. Most samples were recharged before the early 1950s and had 14C ages ranging from <1000 to >30,000 years. Thus, domestic wells may not be as well suited for detecting contamination associated with recent surface spills as shallower wells screened near the water table. Old groundwater could be contaminated directly by recent subsurface leaks from imperfectly cemented oil and gas wells, but horizontal groundwater velocities calculated from 14C ages imply that the contaminants would still be less than 0.5 km from their source. For the wells sampled in this study, the median distance to the nearest oil and gas well was 4.6 km. Because of the slow velocities, a long-term commitment to groundwater monitoring in the upper Fort Union Formation is needed to assess the effects of energy development on groundwater quality. In conjunction with that effort, monitoring could be done closer to energy-development activities to increase the likelihood of early detection of groundwater contamination if it did occur.

show abstract

Section: Resultsmentioning

confidence: 88%

Quality and Age of Shallow Groundwater in the Bakken Formation Production Area, Williston Basin, Montana and North Dakota

McMahon¹,

Caldwell

Galloway

et al. 2014

Groundwater

View full text Add to dashboard Cite

show abstract

“…During both icehouse and greenhouse times, groundwater storage in deep levels of continental reservoirs might provide an alternative to the effect of residence time of carbon (cf. Plummer et al, ; Sturchio et al, ), wherein the impact on δ 13 C 0 could be mediated by eustasy (cf. Hay & Leslie, ; Wagreich et al, ; Wendler & Wendler, ) and/or terrestrial carbon burial (cf.…”

Section: Discussion: Practical Implications and Case Examplesmentioning

confidence: 99%

Orbital Signals in Carbon Isotopes: Phase Distortion as a Signature of the Carbon Cycle

2017

View full text Add to dashboard Cite

Isotopic mass balance models are employed here to study the response of carbon isotope composition (δ13C) of the ocean‐atmosphere system to amplitude‐modulated perturbations on Milankovitch time scales. We identify a systematic phase distortion, which is inherent to a leakage of power from the carrier precessional signal to the modulating eccentricity terms in the global carbon cycle. The origin is partly analogous to the simple cumulative effect in sinusoidal signals, reflecting the residence time of carbon in the ocean‐atmosphere reservoir. The details of origin and practical implications are, however, different. In amplitude‐modulated signals, the deformation is manifested as a lag of the 405 kyr eccentricity cycle behind amplitude modulation (AM) of the short (~100 kyr) eccentricity cycle. Importantly, the phase of AM remains stable during the carbon cycle transfer, thus providing a reference framework against which to evaluate distortion of the 405 kyr term. The phase relationships can help to (1) identify depositional and diagenetic signatures in δ13C and (2) interpret the pathways of astronomical signal through the climate system. The approach is illustrated by case studies of Albian and Oligocene records using a new computational tool EPNOSE (Evaluation of Phase in uNcertain and nOisy SEries). Analogous phase distortions occur in other components of the carbon cycle including atmospheric CO2 levels; hence, to fully understand the causal relationships on astronomical time scales, paleoclimate models may need to incorporate realistic, amplitude‐modulated insolation instead of monochromatic sinusoidal approximations. Finally, detection of the lagged δ13C response can help to reduce uncertainties in astrochronological age models that are tuned to the 405 kyr cycle.

show abstract

“…River sediments sampled in the above studies included both coarse and fine grained fractions, whereas our study was focused on aquifer settings. Moreover, our radiogenic 4 He accumulation rate is also within the range of rates (1–3 × 10 −12 ccSTP

{normalg}_{GW}^{- 1}

yr −1 ) reported for a fluvial‐deltaic formation in the Atlantic Coastal Plain of Maryland based on measured U‐Th concentrations, 14 C ages, and 36 Cl ages [ Plummer et al ., ].…”

Section: Discussionmentioning

confidence: 99%

Recharge of low‐arsenic aquifers tapped by community wells in Araihazar, Bangladesh, inferred from environmental isotopes

Mihajlov

Stute

Schlosser

et al. 2016

Water Resources Research

View full text Add to dashboard Cite

More than 100,000 community wells have been installed in the 150–300 m depth range throughout Bangladesh over the past decade to provide low-arsenic drinking water (<10 μg/L As), but little is known about how aquifers tapped by these wells are recharged. Within a 25 km2 area of Bangladesh east of Dhaka, groundwater from 65 low-As wells in the 35–240 m depth range was sampled for tritium (3H), oxygen and hydrogen isotopes of water (18O/16O and 2H/1H), carbon isotope ratios in dissolved inorganic carbon (DIC, 14C/12C and 13C/12C), noble gases, and a suite of dissolved constituents, including major cations, anions, and trace elements. At shallow depths (<90 m), 24 out of 42 wells contain detectable 3H of up to 6 TU, indicating the presence of groundwater recharged within 60 years. Radiocarbon (14C) ages in DIC range from modern to 10 kyr. In the 90–240 m depth range, however, only 5 wells shallower than 150 m contain detectable 3H (<0.3 TU) and 14C ages of DIC cluster around 10 kyr. The radiogenic helium (4He) content in groundwater increases linearly across the entire range of 14C ages at a rate of 2.5×10−12 ccSTP 4He g−1 yr−1. Within the samples from depths >90 m, systematic relationships between 18O/16O, 2H/1H, 13C/12C and 14C/12C, and variations in noble gas temperatures, suggest that changes in monsoon intensity and vegetation cover occurred at the onset of the Holocene, when the sampled water was recharged. Thus, the deeper low-As aquifers remain relatively isolated from the shallow, high-As aquifer.

show abstract

Old groundwater in parts of the upper Patapsco aquifer, Atlantic Coastal Plain, Maryland, USA: evidence from radiocarbon, chlorine-36 and helium-4

Cited by 48 publications

References 37 publications

Quality and Age of Shallow Groundwater in the Bakken Formation Production Area, Williston Basin, Montana and North Dakota

Quality and Age of Shallow Groundwater in the Bakken Formation Production Area, Williston Basin, Montana and North Dakota

Orbital Signals in Carbon Isotopes: Phase Distortion as a Signature of the Carbon Cycle

Recharge of low‐arsenic aquifers tapped by community wells in Araihazar, Bangladesh, inferred from environmental isotopes

Contact Info

Product

Resources

About