Hydrochemical and Multivariate Statistical Evaluation of Heavy Metals in Shallow Alluvial Aquifers of North Brahmaputra Plain,India

The aim of this study was to display distribution and relationships of heavy elements in the unconfined, shallow alluvial aquifers of the lower Jia Bharali catchment and adjoining areas in central part of North Brahmaputra Plain (NBP), India using hydrochemical as well as multivariate statistical techniques such as principal component analysis (PCA) and cluster analysis. The original matrix was made up of 10 trace elements (As, Cd, Cu, Co, Cr, Fe, Mn, Pb, Ni and Zn) estimated from 50 shallow alluvial dug wells in both the wet and the dry season for a duration of 3 hydrological years (2008–2011). Except As, Cu and Zn all the other toxic metals in the shallow aquifers were found exceeding the WHO maximum permissible limits for drinking water. PCA extracted five varimax factors as geogenic, agricultural and anthropogenic explaining about 71.2% of the total variance in the wet season and 69.3% total variance in the dry season. Hierarchical cluster analysis classified the dug wells into two groups in the wet season and three groups in the dry season with respect to the heavy elements. The results emphasized the need for routine monitoring and management in order to avoid contamination of groundwater sources in the NBP with respect to the dissolved trace elements.     

Solid state 13C-NMR spectroscopy of some oligocene coals of Assam and Nagaland

Five representative sub-bituminous coals from NE part of India have been analyzed with respect to their distribution of carbon functional groups through ¹³C solid state NMR experiments. The ¹³C Cross Polarised/Magic Angle Spinning NMR spectra of the coal samples were recorded at temperatures of 23°C, 50°C and 70°C respectively and the changes on their structures were interpreted. The NMR spectra of low rank coals were found to exhibit varying degrees of fine structures. The aromaticities of the coal were also determined from the C/H ratios of coal. Some changes in the peak positions along with the formation of simple aromatic units were observed on mild heating.     

Seasonal variation in the biochemical composition of red seaweed (<Emphasis Type="Italic">Catenella repens</Emphasis>) from Gangetic delta,northeast coast of India

The biochemical composition of red seaweeds, Catenella repens was investigated in this present study along with subsequent analysis of relevant physico-chemical variables. In this study, the relationship between the nutritive components of this species and the ambient environmental parameters was established. Protein content varied from 2.78 ± 0.30% of dry weight (stn.3) to 16.03 ± 0.96% of dry weight (stn.1) with highest values during monsoon. The protein levels were positively correlated with dissolved nitrate content and negatively correlated with water temperature (except stn.3) and salinity. Carbohydrate content of this species varied significantly (p < 0.05) during pre-monsoon between stations and the values showed positive relationship with salinity and surface water temperature. In contrast to carbohydrate, lipid concentration was lowest in values and varied very slightly between seasons and stations. Astaxanthin content of the seaweed species was greater in pre-monsoon than monsoon and post-monsoon in all the selected stations. Compared with the three seasons, samples of red seaweed collected in pre-monsoon has high carbohydrate-astaxanthin in contrast to protein-lipid which showed high values during monsoon. Statistical analysis computed among the environmental and biochemical parameters suggests the potential role played by the abiotic parameters on biosynthetic pathways of seaweed. This paper also highlights the influence of the nutritional quality of water that can be used for mass cultivation of Catenella repens.     

Dissolved trace metals in the shallow aquifers of the Jia Bharali River Basin, North Brahmaputra Plain

The lower Jia Bharali catchment and adjoining areas in central part of North Brahmaputra Plain (NBP) is characterized by more than 800m thick Older and Younger Alluvium deposited by the west flowing Brahmaputra river and the south flowing trans Himalayan rivers. Unconfined, shallow alluvial aquifers of the area with a general southward flow are largely tapped for domestic use through numerous dug well attached with almost every household. Monitoring of 180 dug wells for two hydrological years show strong seasonal fluctuation of the groundwater table linked to the summer monsoon that brings more than 1500mm precipitation in the area between June-September. This study has presents the first ever systematic database on toxic trace elements viz., As, Cr, Fe, Mn, Ni, Pb and Zn from the shallow aquifers in north Brahmaputra plain based on water samples from 50 monitoring wells collected in both dry and wet seasons. The data was analysed with respect to WHO standards for drinking water and significantly, 2 % of the measurements show As in excess of the WHO limit while 60% of the samples in the wet season and as much as 90 % of the same in dry season have Cr content more than the WHO permissible limit. Pb concentration is above permissible limit of 0.05 mg/L in most of the dry season samples although 88 % of the rainy season samples show Pb concentration exceeding this limit. 34 % of the samples in the wet seasons and 86 % of the samples in the dry seasons have Mn above the permissible limit of 0.1 mg/L while in case of Ni, 56 % of the aquifers in the wet season and 72 % of the aquifers in the dry season show Ni content above the permissible limit of 0.02 mg/L. Zn contents of the aquifers are however very low throughout the year.     

Toxic Trace Metals in the Surface Water Sources of Jia–Bharali river basin,North Brahmaputra Plain,India—A Hydrochemical Elucidation

Water Resources - Surface water samples from thirty five sources in the Jia Bharali river basin in north Brahmaputra plain, North East India were analyzed for ten toxic trace elements namely As,...