Radon in groundwater in Tumkur district of Karnataka with special reference to sampling sensitivity

Radon is a naturally occurring colourless and odourless radioactive gas that is soluble in water and is the main source of radioactivity of groundwater. Use of radon contaminated groundwater increased the radon levels in the air, especially in poorly ventilated houses, which is hazardous to health. Ingestion of such water for quite long period may lead to stomach cancer. The drinking water standards proposed by the Bureau of Indian Standards (BIS) exclude the permissible concentration of radon in drinking water. The US Environmental Protection Agency (USEPA) in 1991 proposed a Maximum Concentration Level (MCL) of 11.1 Bq/l for public water supply. The water samples from the bore wells in Tumkur district of Karnataka show radon concentrations in the range of 5 to 250 Bq/l. Ninety percentages of the samples show radon levels above the permissible limit as per USEPA. The spatial variation and geological control over radon concentration in groundwater in the area and sampling sensitivity are discussed here. The study was conducted during March 2012.     

Estimation of Sediment Properties during Benthic Impact Experiments

Sediment properties, such as water content and density, have been used to estimate the dry and wet weights, as well as the volume of sediment recovered and discharged, during benthic impact experiments conducted in the Pacific and Indian Oceans. The estimates show that the weights of dry (355-1332 t) and wet sediment (1651-4888 t) recovered during the experiments, are not only a function of the total duration and distance covered during the experiment, but also depend on water content and density of the sediment. Estimation of dry sediment and its volumetric ratio in the discharge, are key parameters for calculating the discharged volume. The estimated volume of wet sediment recovered (1427-4049 m 3 ) as well as discharged (2693-6951 m 3 ) during the experiments, provide important inputs to evaluate the sediment resettlement and migration. Using these estimates, the average depth of excavation on the seafloor, can also been calculated. However, the stages of sediment recovery and discharge are expressed differently in some of the experiments. In order to standardize these, different stages have been identified, and definitions of certain terms have been suggested, for use in the future. The methods of calculating different properties, as well as weight and volume of discharged sediment are described in the paper for use in other applications concerning deep-sea discharges.     

Coccolithophores from the central Arabian Sea: Sediment trap results

Sediment trap samples collected from a depth of 1018 m in the Central Arabian Sea Trap (CAST) at 14°28.2′N, 64°35.8′E were analyzed for temporal variation of coccolithophore fluxes from October 1993 to August 1994. Out of the twenty species of coccolithophores encountered,Gephyrocapsa oceanica, Emiliania huxleyi, Umbilicosphaera sibogae andUmbellosphaera irregularis were the most abundant. The total coccolithophore fluxes ranged from 28.5 × 10⁶m^-2d^-1 to 50.3 × 10⁶m^-2d^-1 showing seasonality with higher fluxes during the northeast (NE) monsoon and lower fluxes during the spring intermonsoon. The higher fluxes were attributed to the enhancement of primary production in the central Arabian Sea due to southward extent of nutrients from the northeast Arabian Sea by the prevailing surface currents. Similarly, the occurrences of relatively lower coccolithophore fluxes during the spring intermonsoon and southwest (SW) monsoon were attributed to the low nutrients in the warm, shallow surface mixed layer and downwelling to the south of Findlater Jet respectively in the central Arabian Sea. Some of the coccolithophore species such asE. huxleyi, G. oceanica, Calcidiscus leptoporus andUmbellosphaera tenuis showed signs of dissolution.     

SPIN: An Inversion Code for the Photospheric Spectral Line

Inversion codes are the most useful tools to infer the physical properties of the solar atmosphere from the interpretation of Stokes profiles. In this paper, we present the details of a new Stokes Profile INversion code (SPIN) developed specifically to invert the spectro-polarimetric data of the Multi-Application Solar Telescope (MAST) at Udaipur Solar Observatory. The SPIN code has adopted Milne–Eddington approximations to solve the polarized radiative transfer equation (RTE) and for the purpose of fitting a modified Levenberg–Marquardt algorithm has been employed. We describe the details and utilization of the SPIN code to invert the spectro-polarimetric data. We also present the details of tests performed to validate the inversion code by comparing the results from the other widely used inversion codes (VFISV and SIR). The inverted results of the SPIN code after its application to Hinode/SP data have been compared with the inverted results from other inversion codes.     

Quantitative estimation of seafloor features from photographs and their application to nodule mining

Methods developed for quantitative estimation of seafloor features from seabed photographs and their application for estimation of nodule sizes, coverage, abundance, burial, sediment thickness, extent of rock exposure, density of benthic organisms, and their lebensspuren have been presented. Digitization of the photographs shows variable nodule size (< 1 to 10 cm), coverage (< 1 to 75%) and abundance (< 1 to 20 kg/m²). Nodule population is inversely proportional to the coverage of the sediment (10–100%) and its thickness (0 to > 10 cm), which causes differential burial (0–100%) of nodules. Correlation between nodule parameters (diameter and coverage) in the photographs and grab recovery is used to evolve empirical relationships for estimating nodule abundance in different seabed settings. The rock outcrops (basalts) with a coverage of 6–100% are the sources of nuclei for the nodules, the distribution of which is controlled by the local topography. Higher concentrations of nodules are observed along the slopes, followed by the crests of seamounts, and are lowest in the valleys and plains. A population density of 6–7 benthic organisms per 100 m² belonging to 7 different phyla is observed, with a high frequency of lebensspuren (4–12 traces/m²) in association with nodules. Estimation of these parameters can be used as important inputs in the design of the nodule collector, as it will have to encounter a variety of seafloor conditions, such as patchy nodule distribution, rock outcrops, steep slopes, and frequent microtopographic changes, as well as benthic life. The distribution and relation of various features with one another can also be used to understand the possible impact of nodule mining on the seabed. Estimates show that for a yield of 3 million tonnes of nodules per year, the volume of sediment disturbed will be between 200 × 10⁷ and 500 × 10⁷ m³over an area of 300–600 km², depending upon the average abundance of nodules. Hence, the nodule collector will have to be a self‐propelled system, with photographic and acoustic sensors, to enable selective mining and avoid unfavorable areas.     

Turbulence, suspension and downstream fining over a sand-gravel mixture bed

Flume experiments were carried out to study the turbulence and its impact on suspension and segregation of grain-sizes under unidirectional flow conditions over the sand-gravel mixture bed. The components of fluid velocity with fluctuations were measured vertically using 3-D Micro-acoustic Doppler velocimeter (ADV). The theoretical models for velocity and sediment suspension have been developed based on the concept of mixing length that includes the damping effect of turbulence due to sediment suspension in the flow over the sand-gravel mixture bed. Statistical analysis of segregation of grain-sizes along downstream of the bed has been performed using the principle of unsupervised learning or clustering problem. Exploratory data analysis suggests that there is a progressive downstream fining of sediment sizes with selective depositions of gravels, sand-gravels and sand materials along the stream, which may be segmented into three regions such as, the upstream, the transitional and the downstream respectively. This contribution is relevant to understand the direction of ancient rivers, the bed material character in the river form, sorting process and its role in controlling the sediment flux through landscape.     

Response of Sandy Lake in Schirmacher Oasis,East Antarctica to the glacial-interglacial climate shift

Freshwater lakes in Antarctica fluctuate from ice-free state (during austral summer) to ice-cover state (during austral winter). Hence the lakes respond instantly to the seasonal climate of the region. The Antarctic seasons respond sharply to the glacial and interglacial climates and these signatures are archived in the lake sediments. A sediment core from Sandy Lake, a periglacial lake located in Schirmacher Oasis of East Antarctica records distinct changes in grain-size, C, N, C/N ratios (atomic), δ¹³C_OM and δ¹⁵N_OM contents during the last 36 ky. The contents of the sedimentary organic matter (OM) proxies (C_org ~ 0.3 ± 0.2%, C/N ratios ~9 ± 5 and δ¹³C_OM ~?18 ± 6‰) indicate that the OM in this lake sediment is a product of mixing of terrestrial and lacustrine biomass. Distinctly lower contents of C_org (~0.2%) and sand (~50%), low C/N ratios (~8) and depleted δ¹³C_OM (~?20‰) during the Last Glacial Maximum (LGM: 32–17 ky BP based on Vostok Temperatures) suggest greater internal (autochthonous) provenance of organic matter and limited terrestrial (allochthonous) inputs probably due to long and intense winters in the Antarctic. Such intense winters might have resulted the lake surface to be ice-covered for most part of the year when the temperatures remained consistently colder than the Holocene temperatures. The denitrification within the lake evident by enriched δ¹⁵N_OM (>10‰) during Antarctic LGM might have resulted from oxygen-limitation within the lake environment caused by insulated lake surface. The gradual increases in δ¹³C_OM, C/N and sand content starting at ~11 ky BP and attaining high values (~?11‰, ~10 and ~80% respectively) at ~6 ky BP together suggest a subtle change in the balance of sources of organic matter between algal and macrophyte/bryophyte nearly 8–9 ky later to the beginning of the deglaciation. Thus the seasonal opening-up of the Sandy Lake similar to the modern pattern started with the establishment of the optimum temperature conditions (i.e., 0 °C anomaly) in the Antarctic, prior to which the lake environment might have remained mostly insulated or closed.     

Talkoot: software tool to create collaboratories for earth science

“Open science,” where researchers share and publish every element of their research process in addition to the final results, can foster novel ways of collaboration among researchers and has the potential to spontaneously create new virtual research collaborations. Based on scientific interest, these new virtual research collaborations can cut across traditional boundaries such as institutions and organizations. Advances in technology allow for software tools that can be used by different research groups and institutions to build and support virtual collaborations and infuse open science. This paper describes Talkoot, a software toolkit designed and developed by the authors to provide Earth Science researchers a ready-to-use knowledge management environment and an online platform for collaboration. Talkoot allows Earth Science researchers a means to systematically gather, tag and share their data, analysis workflows and research notes. These Talkoot features are designed to foster rapid knowledge sharing within a virtual community. Talkoot can be utilized by small to medium sized groups and research centers, as well as large enterprises such a national laboratories and federal agencies.