Role of organic matter in uranium mineralisation in Vempalle dolostone; Cuddapah basin,India

Dolostone of Vempalle Formation near Tummalapalle hosts large uranium deposit (>100,000 tonnes with an average grade of 0.045%U₃O₈). It is a unique type of uranium deposit because carbonate formations have been considered to be among the least uraniferous of all the rocks of the Earth’s crust due to mobility of uranium in aqueous fluid in the presence of carbonate and bicarbonate ions. Vempalle dolostone hosts syn-sedimentary uranium mineralization in the form of discrete uranium phases (pitchblende and coffinite) associated with collophane, and adsorbed uranium in organic matter. The organic matter has played dual role of concentrating uranium from solution and also chemically reducing it to pitchhblende and coffinite.     

Simulation of Indian summer monsoon intraseasonal oscillations in a superparameterized coupled climate model: need to improve the embedded cloud resolving model

The characteristic features of Indian summer monsoon (ISM) and monsoon intraseasonal oscillations (MISO) are analyzed in the 25 year simulation by the superparameterized Community Climate System Model (SP-CCSM). The observations indicate the low frequency oscillation with a period of 30–60 day to have the highest power with a dominant northward propagation, while the faster mode of MISO with a period of 10–20 day shows a stationary pattern with no northward propagation. SP-CCSM simulates two dominant quasi-periodic oscillations with periods 15–30 day and 40–70 day indicating a systematic low frequency bias in simulating the observed modes. Further, contrary to the observation, the SP-CCSM 15–30 day mode has a significant northward propagation; while the 40–70 day mode does not show prominent northward propagation. The inability of the SP-CCSM to reproduce the observed modes correctly is shown to be linked with inability of the cloud resolving model (CRM) to reproduce the characteristic heating associated with the barotropic and baroclinic vertical structures of the high-frequency and the low-frequency modes. It appears that the superparameterization in the General Circulation Model (GCM) certainly improves seasonal mean model bias significantly. There is a need to improve the CRM through which the barotropic and baroclinic modes are simulated with proper space and time distribution.     

Trace element distribution and risk assessment in South Indian surface waterways

The concentrations of 27 major and trace elements are determined in surface water samples collected from 48 sites of diverse waterways in four states (Tamil Nadu, Kerala, Karnataka, and Telangana) of South India. The aims of this study are to identify the element distribution, comparatively assess the pollution risk, and evaluate human health risks related to diverse waterways in the study area. The results indicate that elements such as Cr, Se, As, Fe, and Mn are the major pollutants, as their concentrations exceeded the acceptable national and international water quality standards in several sites of Ennore, Adyar, Cooum, Periyar, and Vrishabhavathi rivers. Furthermore, statistical analysis reveals that the Ennore, Adyar, Cooum, Periyar, and Kaveri river basins are affected by various anthropogenic activities, leading to moderate-to-high pollution by As, Cr, Mn, Fe, and Se. Potential pollution sources are industrial waste, sewage intrusion, paint industry waste, and automobile runoff. Overall, the investigated sites are categorized into three major groups: highly, moderately, and least polluted. Risk on human health by metals is then evaluated using hazard quotients (HQs) and carcinogenic risk evaluation; the results indicated that As with HQ >1 is the most hazardous pollutant, which could lead to non-carcinogenic and carcinogenic concerns, particularly in children. This study helps in establishing pollutant loading reduction goal and the total maximum daily loads and consequently contributes to preserving public health and developing water conservation strategies.     

The sensitivity of the northern hemisphere summer mean meridional circulation to changes in the large scale eddy forcing

A zonally averaged version of the Goddard Laboratory for Atmospheric Sciences (GLAS) climate model is used to study the sensitivity of the northern hemisphere (NH) summer mean meridional circulation to changes in the large scale eddy forcing. A standard solution is obtained by prescribing the latent heating field and climatological horizontal transports of heat and momentum by the eddies. The radiative heating and surface fluxes are calculated by model parameterizations. This standard solution is compared with the results of several sensitivity studies. When the eddy forcing is reduced to 0.5 times or increased to 1.5 times the climatological values, the strength of the Ferrel cells decrease or increase proportionally. It is also seen that such changes in the eddy forcing can influence the strength of theNH Hadley cell significantly. Possible impact of such changes in the large scale eddy forcing on the monsoon circulation via changes in the Hadley circulation is discussed. Sensitivity experiments including only one component of eddy forcing at a time show that the eddy momentum fluxes seem to be more important in maintaining the Ferrel cells than the eddy heat fluxes. In the absence of the eddy heat fluxes, the observed eddy momentum fluxes alone produce subtropical westerly jets which are weaker than those in the standard solution. On the other hand, the observed eddy heat fluxes alone produce subtropical westerly jets which are stronger than those in the standard solution.     

Quantitative treatment of annealing of charged particle tracks in common minerals

A semi-empirical approach has been used to obtain an analytical expression for the annealing of charged particle tracks in minerals as a function of time and temperature. The new formalism allows quantitative evaluation of the extent of annealing in samples for any specified temperature and track production history. The validity of the present approach depends upon the applicability of the Arrhenius equation to the process of annealing of nuclear tracks in solids. Laboratory track annealing studies confirm the predictive aspects of the present approach and also the applicability of Arrhenius' equation to track annealing over a wide time-temperature range (5 seconds/1200 K to 5 × 10⁶ seconds/500 K). The present quantitative treatment of track annealing in rock minerals should permit an in-depth study of a variety of problems in meteoritics and earth sciences.     

The once and future pulse of Indian monsoonal climate

We present a comprehensive assessment of the present and expected future pulse of the Indian monsoon climate based on observational and global climate model projections. The analysis supports the view that seasonal Indian monsoon rains in the latter half of the 21th century may not be materially different in abundance to that experienced today although their intensity and duration of wet and dry spells may change appreciably. Such an assessment comes with considerable uncertainty. With regard to temperature, however, we find that the Indian temperatures during the late 21st Century will very likely exceed the highest values experienced in the 130-year instrumental record of Indian data. This assessment comes with higher confidence than for rainfall because of the large spatial scale driving the thermal response of climate to greenhouse gas forcing. We also find that monsoon climate changes, especially temperature, could heighten human and crop mortality posing a socio-economic threat to the Indian subcontinent.