Search

Surface sediments in the Vembanad wetland system, southwest India were analyzed for metals. Assessing the extent of metal contamination in Vembanad wetland surface sediments using individual and combined metal pollution indices shows high heterogeneity of sediment characteristics, sources, sedimentary dynamics and geochemical processes and deciphering natural to anthropogenic contribution. The metal distributions varied greatly in the northern and southern stations suggesting sediment heterogeneity. Sediment concentrations of Cd, As, Pb and Zn were high and exceeded the standard value. Enrichment factor, geoaccumulation index, modified degree of contamination and pollution load index showed that the sediments are moderate to extremely polluted in most of the northern sites. It suggests that Cd and As fell under the extreme amount of metal contamination followed by Pb and Zn which comes under strongly contaminated level. The close relationship of sedimentological and geochemical parameters could be due to the intrinsic relationship of the physico-chemical condition and provenance to the Vembanad wetland system. The main contaminated metal contribution appears to be the anthropogenic input and a small amount from the weathered rocks and sediments present in the course of the rivers. The extent of metal pollution in the Vembanad wetland system implies that the condition may impact the biota and also human health in the vicinity of the wetland.

Tropical semi-arid grasslands are a widespread and ecologically and economically important terrestrial biome. Here, we use paleoecology to understand woodland–grassland transitions across the mid- to late-Holocene period in the Banni grassland, western India. Multi proxy analyses involving palynology, phytoliths and elemental geochemistry were carried out on two sediment cores retrieved from wetlands (Chachi and Luna), to understand temporal fluctuations in vegetation, moisture availability and other environmental parameters. Based on the results, the Chachi core was divided into two major climatic phases. Phase 1 (4600–2500 cal. yr BP) was characterised by high precipitation and abundance of pollen types and phytolith morphotypes that indicate the presence of woody savanna, and mesic herbaceous taxa. Phase 2 (2500 cal. yr BP to the present) was characterised by lower precipitation, lower abundance of mesic taxa and an increase in grass phytolith abundance. However, the period from ~1000 cal. yr BP to the present was characterised by the increased abundance of leguminous taxa, dryland herbs/shrubs and a decline in grass phytolith abundance. The Luna core (~1000 cal. yr BP to the present) also showed results matching with the Chachi core for this latter period. Overall, moisture availability in the ecosystem appears to have declined since 4600 cal. yr BP, and the vegetation has responded to this. Although the balance between tree, shrub and grass elements has fluctuated, overall, the region has remained as an open ‘grass and shrub savanna’ with sparse woody vegetation throughout this period. Our study provides insights into the vegetation dynamics and environmental settings in a poorly understood tropical arid-grassland ecosystem from Asia during the mid-late-Holocene.

Trace elements and grain size parameters of a sediment core collected from Vagamon Lake, situated at the edge of Western Ghats, were analyzed. The ascending order of average concentration of metals is showing the following order - Al > Fe > Ti > Mg > Mn > Cr > Zn > Ni > Pb > Cu > Co > As > U> Cd. The metals are not showing a good correlation with the textural parameters, which indicates the grain size is not controlling the metal distribution in the study area. The enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (CF), modified degree of contamination (mCd), and pollution load index (PLI) calculated to assess anthropogenic contamination. Results showed moderately-strongly As contamination in the region. Statistical analysis, such as Principal Component Analysis and Cluster Dendrogram analysis carried out to determine possible interrelationships between the different metals and textural parameters in the Vagamon sediment core. The results indicated that As could be attributed to anthropogenic sources and may be predominantly affected by human activities. Also, the moderate pollution of the elements like Zn, Ni, Cr and Pb may be associated with both natural and anthropogenic sources. The gradual increase of this As contamination is a threat to the plants, human beings and the other biota. Present-day tourism activities, increasing constructions and usage of fertilizers-pesticides-insecticides at the Vagamon area contribute to this alarming situation.

Asymmetric ventriculomegaly, interhemispheric cyst and dysgenesis of the corpus callosum (AVID) constitutes a rare imaging triad. Additional findings include subcortical and subependymal heterotopia, polymicrogyria, fused thalami, deficient falx, and hydrocephalus. The knowledge of this triad helps us to diagnose prenatally by sonography and fetal MRI. In this case report authors present MRI Imaging findings in a case of AVID syndrome in a 6year old male child presenting with history of seizures and delayed milestones.

Ice rafted debris (IRD) records were studied in two sediment cores (SK200/22a and SK200/27) from the sub-Antarctic and Polar frontal regime of the Indian sector of Southern Ocean for their distribution and provenance during the last 22,000 years. The IRD fraction consists of quartz and lithic grains, with the lithic grains dominated by volcaniclastic materials. IRD content was high at marine isotope stage 2 but decreased dramatically to near absence at the Termination 1 and the Holocene. The concentration of IRD at glacial section of the core SK200/27 was nearly twice that of SK200/22a. Moreover, IRD were more abundant at the last glacial maxima (LGM) in SK200/27 with its peak abundance proceeding by nearly two millennia than at SK200/22a. It appears that an intensification of Antarctic glaciation combined with a northward migration of the Polar Front during LGM promoted high IRD flux at SK200/27 and subsequent deglacial warming have influenced the IRD supply at SK200/22a. Quartz and lithic grains may have derived from two different sources, the former transported from the Antarctic mainland, while the latter from the islands of volcanic origin from Southern Ocean. Sea-ice, influenced by the Antarctic Circumpolar Current is suggested to be a dominant mechanism for the distribution of lithic IRD in the region.