Helium, neon, and tritium in the Black Sea

Measurements of the 3He/4He ratio, and concentrations of helium, neon, and tritium have been made in samples collected at station 1355 in the Black Sea during the 1975 cruise of R/V Chain. Helium concentrations increase rapidly from 400 m to about 1000 m and then less rapidly below 1000 m. The maximum He concentration excess is about 16% above solubility equilibrium. Neon concentrations are constant, within a few percent of solubility equilibrium, below 400 m. The He-Ne data thus clearly indicate a large component of radiogenic 4He in the deep water from decay of U and Th in the bottom sediments. Tritium concentrations decrease from 67.2 T.U. at the surface to near-zero values at 726 m, 968 m, and 1358 m. Two deeper samples at 1745 m and 1939 m contain some tritium—0.6 ± 0.3 T.U. and 0.7 ± 0.2 T.U. respectively, which shows that a small amount of high-tritium surface water has descended to the bottom during the past twenty years. A one-dimensional three-box model using our tritium concentrations and the geothermal heat flux values measured by Erickson and Simmons (1974) gives vertical exchange times of 440 ± 180 years between the deep water (1000 m-2000 m) and the middle water (400 m-1000 m), and 125 ± 75 years between the middle water and a layer above from 200 m to 400 m in the salinity interval 21.50‰-22.00‰. The fluxes of radiogenic 4He and primordial 3He into the deep water are found to be 1.3 ± 0.5 × 105 atoms cm—2 sec—1 and 1.1 ± 0.6 atoms cm—2 sec—1 respectively which may be compared with world-ocean estimates of Craig et al. (1975)—3 ± 1.5 x 105 atoms cm—2 sec—1 and 4 ± 1 atoms cm—2 sec—1

Radiogenic helium in Baffin Bay bottom water

3He-4He ratios, dissolved He and Ne, and tritium have been measured in 87 seawater samples collected at 14 stations in Baffin Bay, Davis Strait, and in the sounds through which Arctic water flows into Baffin Bay…

An evaluation of submarine groundwater discharge along the continental shelf of Louisiana using a multiple tracer approach

Natural geochemical tracers (222Rn, 3H, 3He, and 4He) were used to assess submarine groundwater discharge (SGD) along the continental shelf west of the Mississippi River. In order to assess SGD, groundwater, surface water, and sediment samples were collected on land and during six 4-day cruises aboard the R/V Pelican between Match 2003 and May 2004. A box model approach was used to quantify sources and sinks of 222Rn in the study area and to calculate SGD rates. SGD estimates were we based on two end member values for the potential advecting fluids: (1) that supported by 226Ra in the sediments; and (2) groundwater activities measured in monitoring wells. Calculated 222Rn SGD rates based on sediment supported activities ranged from 0.04 to 0.14 cm d-1, and estimates based on monitoring well activities ranged from 0.01 to 0.07 cm d-1 and corresponds to 1.41 km3 yr-1 of discharged water over our study area, equivalent to <1% of the Mississippi River during the same time frame. 3He and 4He, longer-lived tracers, exhibited significantly greater anomalies in the eastern portion of the study area which corresponds with greater oil and gas extraction and the release of formation water into the water column in this region. While the total SGD was relatively minor, potential sources of SGD are many and we suggest formation water associated with oil and gas extraction, geothermal convection, and seawater recirculation are the primary sources with a minimal contribution from terrestrially derived topography driven flow

Precision electroweak calculation of the production of a high transverse-momentum lepton pair at hadron colliders

We present a detailed study of the production of a high transverse-momentum lepton pair at hadron colliders, which includes the exact O(alpha) electroweak corrections properly matched with leading logarithmic effects due to multiple photon emission, as required by the experiments at the Fermilab Tevatron and the CERN LHC. Numerical results for the relevant observables of single Z-boson production at hadron colliders are presented. The impact of the radiative corrections is discussed in detail. The presence in the proton of a photon density is considered and the effects of the photon-induced partonic subprocesses are analyzed. The calculation has been implemented in the new version of the event generator HORACE, which is available for precision simulations of the neutral and charged current Drell-Yan processes.Comment: October 2007, 22p

Coastal groundwater discharge – an additional source of phosphorus for the oligotrophic wetlands of the Everglades

In this manuscript we define a new term we call coastal groundwater discharge (CGD), which is related to submarine groundwater discharge (SGD), but occurs when seawater intrudes inland to force brackish groundwater to discharge to the coastal wetlands. A hydrologic and geochemical investigation of both the groundwater and surface water in the southern Everglades was conducted to investigate the occurrence of CGD associated with seawater intrusion. During the wet season, the surface water chemistry remained fresh. Enhanced chloride, sodium, and calcium concentrations, indicative of brackish groundwater discharge, were observed in the surface water during the dry season. Brackish groundwaters of the southern Everglades contain 1–2.3μM concentrations of total phosphorus (TP). These concentrations exceed the expected values predicted by conservative mixing of local fresh groundwater and intruding seawater, which both have TPμM. The additional source of TP may be from seawater sediments or from the aquifer matrix as a result of water–rock interactions (such as carbonate mineral dissolution and ion exchange reactions) induced by mixing fresh groundwater with intruding seawater. We hypothesize that CGD maybe an additional source of phosphorus (a limiting nutrient) to the coastal wetlands of the southern Everglades

Isotopic, geophysical and biogeochemical investigation of submarine groundwater discharge : IAEA-UNESCO intercomparison exercise at Mauritius Island

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Environmental Radioactivity 104 (2012): 24-45, doi:10.1016/j.jenvrad.2011.09.009.Submarine groundwater discharge (SGD) into a shallow lagoon on the west coast of Mauritius Island (Flic-en-Flac) was investigated using radioactive (3H, 222Rn, 223Ra, 224Ra, 226Ra, 228Ra) and stable (2H, 18O) isotopes and nutrients. SGD intercomparison exercises were carried out to validate the various approaches used to measure SGD including radium and radon measurements, seepage-rate measurements using manual and automated meters, sediment bulk conductivity and salinity surveys. SGD measurements using benthic chambers placed on the floor of the Flic-en-Flac Lagoon showed discharge rates up to 500 cm/day. Large variability in SGD was observed over distances of a few meters, which were attributed to different geomorphological features. Deployments of automated seepage meters captured the spatial and temporal variability of SGD with a mean seepage rate of 10 cm/day. The stable isotopic composition of submarine waters was characterized by significant variability and heavy isotope enrichment and was used to predict the contribution of fresh terrestrially derived groundwater to SGD (range from a few % to almost 100 %). The integrated SGD flux, estimated from seepage meters placed parallel to the shoreline, was 35 m3/m day, which was in a reasonable agreement with results obtained from hydrologic water balance calculation (26 m3/m day). SGD calculated from the radon inventory method using in situ radon measurements were between 5 and 56 m3/m per day. Low concentrations of radium isotopes observed in the lagoon water reflected the low abundance of U and Th in the basalt that makes up the island. High SGD rates contribute to high nutrients loading to the lagoon, potentially leading to eutrophication. Each of the applied methods yielded unique information about the character and magnitude of SGD. The results of the intercomparison studies have resulted a better understanding of groundwater-seawater interactions in coastal regions. Such information is an important pre-requisite for the protection management of coastal freshwater resources.The financial support provided by the IOC and IHP of UNESCO for travel arrangements, and by the IAEA’s Marine Environment Laboratories for logistics is highly acknowledged. MAC and MEG were supported in part by the US National Science Foundation (OCE-0425061 and OCE-0751525). PPP acknowledges a support provided by the EU Research & Development Operational Program funded by the ERDF (project No. 26240220004), and the Slovak Scientific Agency VEGA (grant No. 1/108/08). The International Atomic Energy Agency is grateful to the Government of the Principality of Monaco for support provided to its Marine Environment Laboratories

Characterization of the Metabolically Modified Heavy Metal-Resistant Cupriavidus metallidurans Strain MSR33 Generated for Mercury Bioremediation

BACKGROUND: Mercury-polluted environments are often contaminated with other heavy metals. Therefore, bacteria with resistance to several heavy metals may be useful for bioremediation. Cupriavidus metallidurans CH34 is a model heavy metal-resistant bacterium, but possesses a low resistance to mercury compounds. METHODOLOGY/PRINCIPAL FINDINGS: To improve inorganic and organic mercury resistance of strain CH34, the IncP-1β plasmid pTP6 that provides novel merB, merG genes and additional other mer genes was introduced into the bacterium by biparental mating. The transconjugant Cupriavidus metallidurans strain MSR33 was genetically and biochemically characterized. Strain MSR33 maintained stably the plasmid pTP6 over 70 generations under non-selective conditions. The organomercurial lyase protein MerB and the mercuric reductase MerA of strain MSR33 were synthesized in presence of Hg(2+). The minimum inhibitory concentrations (mM) for strain MSR33 were: Hg(2+), 0.12 and CH(3)Hg(+), 0.08. The addition of Hg(2+) (0.04 mM) at exponential phase had not an effect on the growth rate of strain MSR33. In contrast, after Hg(2+) addition at exponential phase the parental strain CH34 showed an immediate cessation of cell growth. During exposure to Hg(2+) no effects in the morphology of MSR33 cells were observed, whereas CH34 cells exposed to Hg(2+) showed a fuzzy outer membrane. Bioremediation with strain MSR33 of two mercury-contaminated aqueous solutions was evaluated. Hg(2+) (0.10 and 0.15 mM) was completely volatilized by strain MSR33 from the polluted waters in presence of thioglycolate (5 mM) after 2 h. CONCLUSIONS/SIGNIFICANCE: A broad-spectrum mercury-resistant strain MSR33 was generated by incorporation of plasmid pTP6 that was directly isolated from the environment into C. metallidurans CH34. Strain MSR33 is capable to remove mercury from polluted waters. This is the first study to use an IncP-1β plasmid directly isolated from the environment, to generate a novel and stable bacterial strain useful for mercury bioremediation

Study of the doubly Cabibbo-suppressed decays Ds+→K+K+π−D^+_s\to K^+K^+\pi^- and Ds+→K+K+π−π0D^+_s\to K^+K^+\pi^-\pi^0

Based on 7.33 fb$^{-1}$ of $e^+e^-$ collision data collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, the experimental studies of the doubly Cabibbo-suppressed decays $D^+_s\to K^+K^+\pi^-$ and $D^+_s\to K^+K^+\pi^-\pi^0$ are reported. We determine the absolute branching fraction of $D^+_s\to K^+K^+\pi^-$ to be (${1.23^{+0.28}_{-0.25}}({\rm stat})\pm0.06({\rm syst})$) $\times 10^{-4}$. No significant signal of $D^+_s\to K^+K^+\pi^-\pi^0$ is observed and the upper limit on its decay branching fraction at 90\% confidence level is set to be $1.7\times10^{-4}$.Comment: 10 pages, 4 figures, 4 table