Geological Survey of India

About: Geological Survey of India is a government organization based out in Kolkata, India. It is known for research contribution in the topics: Metamorphism & Mafic. The organization has 2007 authors who have published 1963 publications receiving 29408 citations.

Historically unprecedented global glacier decline in the early 21st century

Abstract: Observations show that glaciers around the world are in retreat and losing mass. Internationally coordinated for over a century, glacier monitoring activities provide an unprecedented dataset of glacier observations from ground, air and space. Glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass-balance data relating to the impact that glaciers exercise on global sea-level fluctuations or on regional runoff. In this study we provide an overview and analysis of the main observational datasets compiled by the World Glacier Monitoring Service (WGMS). The dataset on glacier front variations (�42000 since 1600) delivers clear evidence that centennial glacier retreat is a global phenomenon. Intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the Little Ice Age (or Holocene). Glaciological and geodetic observations (�5200since 1850) show that the rates of early 21st-century mass loss are without precedent on a global scale, at least for the time period observed and probably also for recorded history, as indicated also in reconstructions from written and illustrated documents. This strong imbalance implies that glaciers in many regions will very likely suffer further ice loss, even if climate remains stable.

Arsenic poisoning in the Ganges delta

Abstract: The natural contamination of drinking water by arsenic needs to be urgently addressed. The pollution by naturally occurring arsenic of alluvial Ganges aquifers, which are used for the public water supply in Bangladesh and West Bengal, has been discussed by Nickson et al.1. We agree with their main conclusion that arsenic is released by reductive dissolution of iron oxyhydroxides, as was proposed earlier2. Our observations indicate that arsenic- rich pyrite and other arsenic minerals, which were proposed in previous models (cited by Nickson et al.1) to give rise to arsenic pollution, are rare or even absent in the sediments of the Ganges delta. We believe that arsenic is more likely to be co-precipitated with or scavenged by iron (III) and manganese (IV) in the sedimentary environment.

A Review of the Different Methods Applied in Environmental Geochemistry For Single and Sequential Extraction of Trace Elements in Soils and Related Materials

Abstract: A comprehensive review of the single and sequential extraction schemes for metal fractionation in environmental samples such as soil and industrially contaminated soils, sewage sludge and sludge amended soils, road dust and run off, waste and miscellaneous materials along with other approaches of sequential extraction methods are being presented. A discussion on the application of chemometric methods in sequential extraction analysis is also being given. The study of single and sequential extraction methods for various reference materials are also being looked into. The review covers several aspects of the single and sequential extraction methodologies. The use of each reagents involved in these schemes are also discussed briefly. Finally the present upto date information by different workers in various fields of environmental geochemistry along with the possible future developments are also being outlined.

Genetic Evidence on the Origins of Indian Caste Populations

Abstract: The origins and affinities of the ∼1 billion people living on the subcontinent of India have long been contested. This is owing, in part, to the many different waves of immigrants that have influenced the genetic structure of India. In the most recent of these waves, Indo-European-speaking people from West Eurasia entered India from the Northwest and diffused throughout the subcontinent. They purportedly admixed with or displaced indigenous Dravidic-speaking populations. Subsequently they may have established the Hindu caste system and placed themselves primarily in castes of higher rank. To explore the impact of West Eurasians on contemporary Indian caste populations, we compared mtDNA (400 bp of hypervariable region 1 and 14 restriction site polymorphisms) and Y-chromosome (20 biallelic polymorphisms and 5 short tandem repeats) variation in ∼265 males from eight castes of different rank to ∼750 Africans, Asians, Europeans, and other Indians. For maternally inherited mtDNA, each caste is most similar to Asians. However, 20%–30% of Indian mtDNA haplotypes belong to West Eurasian haplogroups, and the frequency of these haplotypes is proportional to caste rank, the highest frequency of West Eurasian haplotypes being found in the upper castes. In contrast, for paternally inherited Y-chromosome variation each caste is more similar to Europeans than to Asians. Moreover, the affinity to Europeans is proportionate to caste rank, the upper castes being most similar to Europeans, particularly East Europeans. These findings are consistent with greater West Eurasian male admixture with castes of higher rank. Nevertheless, the mitochondrial genome and the Y chromosome each represents only a single haploid locus and is more susceptible to large stochastic variation, bottlenecks, and selective sweeps. Thus, to increase the power of our analysis, we assayed 40 independent, biparentally inherited autosomal loci (1 LINE-1 and 39 Alu elements) in all of the caste and continental populations (∼600 individuals). Analysis of these data demonstrated that the upper castes have a higher affinity to Europeans than to Asians, and the upper castes are significantly more similar to Europeans than are the lower castes. Collectively, all five datasets show a trend toward upper castes being more similar to Europeans, whereas lower castes are more similar to Asians. We conclude that Indian castes are most likely to be of proto-Asian origin with West Eurasian admixture resulting in rank-related and sex-specific differences in the genetic affinities of castes to Asians and Europeans.

Arsenic toxicity of groundwater in parts of the Bengal basin in India and Bangladesh: the role of Quaternary stratigraphy and Holocene sea-level fluctuation

Abstract: Arsenic toxicity in groundwater in the Ganges delta and some low-lying areas in the Bengal basin is confined to middle Holocene sediments. Dissected terraces and highlands of Pleistocene and early Holocene deposits are free of such problems. Arsenic-rich pyrite or other arsenic minerals are rare or absent in the affected sediments. Arsenic appears to occur adsorbed on iron hydroxide-coated sand grains and clay minerals and is transported in soluble form and co-precipitated with, or is scavenged by, Fe(III) and Mn(IV) in the sediments. It became preferentially entrapped in fine-grained and organic-rich sediments during mid-Holocene sea-level rises in deltaic and some low-lying areas of the Bengal basin. It was liberated subsequently under reducing conditions and mediated further by microbial action. Intensive extraction of groundwater for irrigation and application of phosphate fertilizer possibly triggered the recent release of arsenic to groundwater. This practice has induced groundwater flow, mobilizing phosphate derived from fertilizer, as well as from decayed organic matter, which has promoted the growth of sediment biota and aided the further release of arsenic. However, the environment is not sufficiently reducing to mobilize iron and arsenic in groundwater in the Ganges floodplains upstream of Rajmahal. Thus, arsenic toxicity in the groundwater of the Bengal basin is caused by its natural setting, but also appears to be triggered by recent anthropogenic activities.