scholarly journals Comparison of 14C Collected by Precipitation and Gas-Strip Methods for Dating Groundwater

Radiocarbon ◽  
2016 ◽  
Vol 58 (3) ◽  
pp. 491-503 ◽  
Author(s):  
Kotaro Nakata ◽  
Takuma Hasegawa ◽  
Teruki Iwatsuki ◽  
Toshihiro Kato
Keyword(s):  
Residence Time ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Precipitation Method ◽  
Strip Method ◽  
Naoh Solution ◽  
C Value ◽  
The Difference ◽  
Predicted Values

AbstractDissolved inorganic carbon (DIC) in groundwater is used to estimate the residence time based on radiocarbon concentration. DIC is usually extracted by a gas-strip or precipitation (SrCO3 or BaCO3) method. In this study, the gas-strip and precipitation methods of DIC were applied to both artificially prepared NaHCO3 solutions and natural groundwater to estimate the certainty of the two methods for 14C dating. 14C values obtained by the gas-strip method for NaHCO3 solutions with distinct salinity, DIC, and 14C concentrations were close to the theoretically predicted 14C value based on the 14C value of NaHCO3 powder. Conversely, the 14C value obtained by the precipitation method always showed higher values than the predicted values. The difference in 14C value between the gas-strip and precipitation methods was assumed to be caused by the contamination of modern carbon in the NaOH solution used in the precipitation method. The contamination of modern carbon derived from the NaOH solution during precipitation was found to range from less than 1 mg/L to about 1 mg/L. The applicability of the precipitation method for groundwater should be considered carefully according to the DIC, 14C concentration of groundwater, and purpose of the study being conducted.

scholarly journals Dynamics of dissolved inorganic carbon in the Yenisey gulf during open water period

2019 ◽  
Vol 59 (5) ◽  
pp. 701-713
Author(s):  
P. N. Makkaveev ◽  
Yu. R. Nalbandov ◽  
A. A. Polukhin ◽  
S. A. Schuka
Keyword(s):  
Suspended Matter ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Open Water ◽  
Bottom Layer ◽  
Sediment Layer ◽  
Almost Everywhere ◽  
Mineral Suspension ◽  
The Difference ◽  
The Many

On the materials of several SIO RAS cruises and archival hydrological and hydrochemical data, the dynamics of dissolved inorganic carbon in the Yenisey Gulf was investigated. There are 3 main areas, where mass sedimentation of suspended matter and oxidation of organic matter (OM) in the upper sediment layer takes place. The first region of oxidation of OM was south of 72 N, its existence is associated with mass sedimentation of dissolved and suspended matter on the geochemical barrier. Two other areas of decomposition of the OM (elevated dCtot) are located downstream (between 73 and 74 and north of 75 N) and most likely originated at the orographic barrier, where the change in the dynamic characteristics of the riverine flow and the topography of the bay bottom creates conditions for sedimentation. Comparison of the difference in the observed Ctot value with the AOU value showed that in 1993, the change in the Ctot content was provided by the oxidation processes of OM. In 2011, carbon emission into water was most likely associated with the transformation of mineral suspension and/or carbon exchange in bottom water with bottom sediments. In 2016, a decrease in the Ctot content was observed almost everywhere in bottom layer. It is most realistic to assume that such a distribution is associated with carbon sorption on suspensions. Despite the many similar features of the distribution of hydrochemical characteristics in the bay, the change in the content of dissolved inorganic carbon in the investigated area has differed greatly in different years. In our opinion, the reason for the fact is the variability of the discharge of the Yenisey River in different years.

A Survey of the 14C Content of Dissolved Inorganic Carbon in Chinese Lakes

Radiocarbon ◽  
2017 ◽  
Vol 60 (2) ◽  
pp. 705-716 ◽  
Author(s):  
Taibei Liu ◽  
Weijian Zhou ◽  
Peng Cheng ◽  
G S Burr
Keyword(s):  
Steady State ◽  
Simple Model ◽  
Residence Time ◽  
Surface Waters ◽  
Lake Water ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Water Cycle ◽  
Average Residence Time ◽  
Exchange Character

AbstractWe present radiocarbon (14C) measurements of dissolved inorganic carbon (DIC) from surface waters of 11 lakes, widely distributed in China. Surface lake water DIC F14C values show distinct differences, and we relate these to the physical exchange character (“open” or “closed”) of each lake. Open lakes studied here generally have lower DIC F14C values than closed lakes. We present a simple model of a lake water cycle to calculate an average residence time for each lake. Comparisons between lake DIC F14C and average residence time shows that the DIC F14C increases with the average residence time and reflects a steady-state.

scholarly journals Groundwater residence time estimates obscured by anthropogenic carbonate

2021 ◽  
Vol 7 (17) ◽  
pp. eabf3503
Author(s):  
Alan M. Seltzer ◽  
David V. Bekaert ◽  
Peter H. Barry ◽  
Kathryn E. Durkin ◽  
Emily K. Mace ◽  
...  
Keyword(s):  
Residence Time ◽  
Open System ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Soil Amendments ◽  
Flow Models ◽  
Time Estimates ◽  
Drinking And Irrigation ◽  
Carbonate Soil ◽  
Agricultural Regions

Groundwater is an important source of drinking and irrigation water. Dating groundwater informs its vulnerability to contamination and aids in calibrating flow models. Here, we report measurements of multiple age tracers (14C, 3H, 39Ar, and 85Kr) and parameters relevant to dissolved inorganic carbon (DIC) from 17 wells in California’s San Joaquin Valley (SJV), an agricultural region that is heavily reliant on groundwater. We find evidence for a major mid-20th century shift in groundwater DIC input from mostly closed- to mostly open-system carbonate dissolution, which we suggest is driven by input of anthropogenic carbonate soil amendments. Crucially, enhanced open-system dissolution, in which DIC equilibrates with soil CO2, fundamentally affects the initial 14C activity of recently recharged groundwater. Conventional 14C dating of deeper SJV groundwater, assuming an open system, substantially overestimates residence time and thereby underestimates susceptibility to modern contamination. Because carbonate soil amendments are ubiquitous, other groundwater-reliant agricultural regions may be similarly affected.

scholarly journals Temporal Changes of the 14C Reservoir Effect in Lakes

Radiocarbon ◽  
1997 ◽  
Vol 40 (2) ◽  
pp. 921-931 ◽  
Author(s):  
Mebus A. Geyh ◽  
U. Schotterer ◽  
M. Grosjean
Keyword(s):  
Arid Regions ◽  
Climate Changes ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Temporal Changes ◽  
Organic Fraction ◽  
Radiocarbon Dates ◽  
Reservoir Effect ◽  
Plant Remains ◽  
C Value

Conventional radiocarbon dates for sediment samples from aquatic systems and of coeval terrestrial samples deviate from each other due to the reservoir effect. The reservoir correction is usually assumed to be constant with time for a specific aquatic system. Our studies confirm that seasonal and secular changes are frequent and are governed by the limnological conditions. Lakes have two principal sources of 14C: atmospheric CO2 and the total dissolved inorganic carbon (TDIC) of the entering groundwater and runoff. The former has values of ca. 100 pMC; the latter usually has a 14C value well below 100 pMC. Atmospheric CO2 enters the lake by exchange via its surface. The proportions of these two kinds of input determine the magnitude of the reservoir correction in freshwater lakes. It is mainly a function of the volume/surface ratio of the lake and, consequently a function of the water depth. The surface of lakes with outflow does not change when sedimentation decreases the depth of the water. The depth of Schleinsee Lake in southern Germany has decreased from 30 to 15 m since ca. 9000 bp. As a result, the reservoir correction has decreased from ca. -1550 to -580 yr. In contrast, the depth of Lake Proscansko in Croatia increased with growth of the travertine dam and the reservoir correction changed from ca. -1790 to -2650 yr during the last 8800 yr. The largest fluctuations of lake levels occur in closed lakes in arid regions when the climate changes from humid to arid and vice versa. As a result, the reservoir correction of the 14C dates for the total organic fraction from Lejía Lake in the Atacama Desert of Chile varied between <-1800 yr and -4700 yr over a period of only 1800 yr between 11,500 and 9700 bp. The corresponding reservoir correction for the marl fraction is much higher. In summary, accurate and reliable 14C dating of lake sediments requires a study of the temporal changes of the reservoir effect by analysis of both the organic and marl fractions. The most reliable 14C dates are obtained from terrestrial plant remains.

Natural C-14 provides new data for stream food-web studies: a comparison with C-13 in multiple stream habitats

2012 ◽  
Vol 63 (3) ◽  
pp. 210 ◽  
Author(s):  
Naoto F. Ishikawa ◽  
Masao Uchida ◽  
Yasuyuki Shibata ◽  
Ichiro Tayasu
Keyword(s):  
Food Web ◽  
Inorganic Carbon ◽  
Photosynthetic Activity ◽  
Dissolved Inorganic Carbon ◽  
Carbon Sources ◽  
Δ13c Values ◽  
Web Studies ◽  
The Difference

In stream food-web analysis, the contributions of carbon from periphyton (an autochthonous source) and terrestrial litter (an allochthonous source) are estimated by isotopic difference. We hypothesised that periphyton δ13C varies among stream habitats, whereas Δ14C does not because Δ14C is corrected with δ13C, by definition. To test this hypothesis, we compared the variability of δ13C and Δ14C of periphyton and dissolved inorganic carbon (DIC) in four habitats (open v. shaded, riffle v. pool) within a limestone-based upland stream in Japan. Periphyton δ13C values (from –31.9‰ to –16.3‰) were significantly different among the habitats whereas the Δ14C values (from –379‰ to –141‰) were not. Periphyton δ13C values depended on both algal photosynthetic activity and δ13C of the DIC, whereas periphyton Δ14C depended only on DIC Δ14C. The δ13C and Δ14C values of litter were constant. Thus, the difference between the periphyton and litter δ13C values (Δδ13C) varied among habitats, but their Δ14C differences (ΔΔ14C) did not. Our results indicate that Δ14C is spatially stable among stream habitats and that Δ14C measurements can be used to precisely determine carbon sources for stream food-web analysis within individual reaches.

scholarly journals A mechanistic account of increasing seasonal variations in the rate of ocean uptake of anthropogenic carbon

2010 ◽  
Vol 7 (1) ◽  
pp. 745-764
Author(s):  
T. Gorgues ◽  
O. Aumont ◽  
K. B. Rodgers
Keyword(s):  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Three Dimensional ◽  
Austral Summer ◽  
Circulation Model ◽  
Surface Fluxes ◽  
Anthropogenic Carbon ◽  
The Mean ◽  
The Difference ◽  
Increasing Trends

Abstract. A three-dimensional circulation model that includes a representation of anthropogenic carbon as a passive tracer is forced with climatological surface fluxes. This simulation is then used to compute offline the anthropogenic ΔpCO2 (defined as the difference between the atmospheric CO2 and its seawater partial pressure) trends over three decades between the years 1970 and 2000. It is shown that the mean increasing trends in ΔpCO2 reflects an increase of the seasonal amplitude of ΔpCO2. In particular, the ocean uptake of anthropogenic CO2 is decreasing (negative trends in ΔpCO2) in boreal (austral) summer in the Northern (Southern) Hemisphere in the subtropical gyres between 20° N(S) and 40° N(S). In our simulation, the increased amplitude of the seasonal trends of the ΔpCO2 is mainly explained by the seasonal sea surface temperature (SST) acting on the anthropogenic increase of the dissolved inorganic carbon (DIC). It is also shown that the seasonality of the anthropogenic DIC has very little effect on the decadal trends. This study underscores the need for surface CO2 measurements that resolve the seasonal cycle throughout much of the extratropical oceans.

PHYSIOLOGICAL EFFECTS OF DISSOLVED INORGANIC CARBON ON COMMON SUBMERGED MACROPHYTES

2010 ◽  
Vol 33 (6) ◽  
pp. 1020-1030 ◽  
Author(s):  
Yan-Hui ZHANG ◽  
Yan-Jie AN ◽  
Chi ZHU ◽  
Shao YANG
Keyword(s):  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Submerged Macrophytes ◽  
Physiological Effects
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