A 200-year 210Pb record from Greenland

A continuous profile of 210Pb activity extending back to 1766 has been developed for a firn/ice core collected at Site D in central Greenland in 1984. Unexpectedly high activities of 210Pb were found at the base of this core (0.032 pCi kg−1 in samples more than 200 years old), calling into question the common assumption that supported 210Pb can be neglected when constructing chronologies in glacial snow and ice. It is problematic to assert that all of the 210Pb measured at depth should be attributed to the supported fraction, given previous estimates of dust loading in Greenland ice cores. However, even if an estimated constant value of 0.032 pCi supported210Pb kg−1 is subtracted from the measured values to estimate excess 210Pb, the 210Pb chronology for Site D yields ages that are significantly younger (mean accumulation rate too high) than an independent depth-age scale based on annual layer counting. It is apparent that the flux of excess and/or supported 210Pb to this site must have decreased over the past 2 centuries, with decreasing trends in both fractions most likely. Previously published 210Pb profiles for cores from Summit and Dye 3, Greenland, show similar trends, which had been interpreted as decreasing fluxes of excess 210Pb only. For all three sites, it is not possible to separate variations in the fluxes of the excess and supported fractions of 210Pb, but variations in the total 210Pb flux will impact 210Pb-based chronologies generally if these variations have not been restricted to the Greenland ice sheet

Ice accumulation rate in Changme-Khangpu glacier, Sikkim

Vertical profiles of 137Cs and 210Pb have been determined in a 9 m column of ice from accumulation zone of Changme-Khangpu glacier in north Sikkim valley. 137Cs activity varies from 4 to 22 dpm/ L. In many samples 210Pb occurs at a level of 20 to 65 dpm/ L which is much higher than the expected fallout value. 137Cs and 210Pb activities correlate well with each other but not with the dust content. Possibility of 210Pb production in the nuclear explosions is discussed. Several peaks appear in the depth profile of 137Cs and 210Pb which can be matched with Chinese atmospheric nuclear explosions with some phase difference if a uniform ice accumulation rate of 0.7 m per year is assumed since 1969

Randomized Clinical Trial of High-Dose Rifampicin With or Without Levofloxacin Versus Standard of Care for Pediatric Tuberculous Meningitis: The TBM-KIDS Trial

Background. Pediatric tuberculous meningitis (TBM) commonly causes death or disability. In adults, high-dose rifampicin may reduce mortality. The role of fluoroquinolones remains unclear. There have been no antimicrobial treatment trials for pediatric TBM. Methods. TBM-KIDS was a phase 2 open-label randomized trial among children with TBM in India and Malawi. Participants received isoniazid and pyrazinamide plus: (i) high-dose rifampicin (30 mg/kg) and ethambutol (R30HZE, arm 1); (ii) high-dose rifampicin and levofloxacin (R30HZL, arm 2); or (iii) standard-dose rifampicin and ethambutol (R15HZE, arm 3) for 8 weeks, followed by 10 months of standard treatment. Functional and neurocognitive outcomes were measured longitudinally using Modified Rankin Scale (MRS) and Mullen Scales of Early Learning (MSEL). Results. Of 2487 children prescreened, 79 were screened and 37 enrolled. Median age was 72 months; 49%, 43%, and 8% had stage I, II, and III disease, respectively. Grade 3 or higher adverse events occurred in 58%, 55%, and 36% of children in arms 1, 2, and 3, with 1 death (arm 1) and 6 early treatment discontinuations (4 in arm 1, 1 each in arms 2 and 3). By week 8, all children recovered to MRS score of 0 or 1. Average MSEL scores were significantly better in arm 1 than arm 3 in fine motor, receptive language, and expressive language domains (P < .01). Conclusions. In a pediatric TBM trial, functional outcomes were excellent overall. The trend toward higher frequency of adverse events but better neurocognitive outcomes in children receiving high-dose rifampicin requires confirmation in a larger trial. Clinical Trials Registration. NCT02958709

Oxygen isotopic ratios of some Himalayan glaciers

&#948; 18O in ice cores taken from two temperate glaciers, Changme-Khangpu (CK) and Nehnar. located in the eastern and the western Himalayas respectively, and in fresh precipitation and surface ice at different altitudes on the Changme-Khangpu glacier has been measured. The fresh precipitation in CK has &#948;18O in the narrow range of -19 &#177; 2% which is similar to the ice core values. &#948;18O and dust concentration in Nehnar core is found to be variable. The &#948;18O values lie in the narrow range of -9.5 &#177; 1% in the upper 46 m section and the fluctuations increase in the 66-102 m section of the ice core

An improved method of silicon-32 measurement of groundwaters

A rapid method of separation of 32P from 32Si by hydrofluorisation saves considerable amount of time besides being more efficient in the chemical recovery of phosphorus. Similarly, 4π beta counting of 32P activity allows a more accurate estimation of small amounts of this activity. These improvements make it possible to reliably measure amounts of 32Si as low as 0.1 dpm present in about 10 tons of water

Chemical composition of snow and ice from Chhota Shigri glacier, central Himalaya

A systematic study of the chemical composition of snow, firn from a shallow core, surface ice and of meltwater samples collected from the Chhota Shigri glacier, Central Himalaya, is reported here. The average concentrations of Na and Cl in snow are 402 and 753 µgl-1, respectively; whereas those in old surface ice are relatively low, 185 µg l-1 and 375 µg l-1, respectively. The average Cl/Na weight ratio in these samples is ≈1.9, quite similar to that in the sea salts suggesting that both Cl and Na are predominantly of marine origin. The concentrations of other major ions such as K, Mg, Ca, NO3 and SO4 in snow and ice samples are generally less than 1 mg l-1. The major ion concentrations, when normalized to Na, indicate that the abundances of K and Ca are dominated by terrestrial sources whereas Mg appears to have both marine and terrestrial sources. Based on the seasonal variations of Na and Cl concentrations observed in the ice core samples, an approximate accumulation rate at the core site has been estimated to be 1.6 m year-1) 640 kg m-2 year-1)