Bhishm Kumar

Determination of recent sedimentation rates and pattern in Lake Naini, India by 210Pb and 137Cs dating techniques

Abstract Environmental 210 Pb (natural) and 137 Cs (anthropogenic) dating techniques were applied to determine recent sedimentation rates and pattern in Lake Naini, Uttar Pradesh, India. Core samples from different locations in the lake were collected and analysed for 210 Pb and 137 Cs. From the analysis it appears that the lake is not reducing in depth at a rate reported by earlier investigations. Recent sedimentation rate, estimated by the 210 Pb dating technique, has been found to be fairly constant at one location (the mean dry mass sedimentation rate being 0.112±0.010 g cm −2 a −1 ) but varying at other locations in the lake (the dry mass sedimentation rates ranging from 0.026±0.010 to 0.421±0.050 g cm −2 a −1 ). At all locations the short-term rates (for the last three decades) derived from 137 Cs, a fall-out nuclide, have been observed to be marginally higher compared to long-term (last 120–150 yr) rates deduced from 210 Pb. The spatial and depthwise distribution of 137 Cs and 210 Pb and spatial variation of surface 210 Pb/ 137 Cs in the obtained sediment cores of the lake, along with their textural properties (like porosity and water content), provide preliminary information on the existence of different depositional zones throughout the lake and on the physico-chemical nature of the sedimentation process in the lake (i.e., bioturbation, slumping, sediment focusing, land erosion/land slide etc).

Estimation of subsurface components in the water balance of Lake Nainital (Kumaun Himalaya, India) using environmental isotopes

Abstract Lake Nainital, located in the Kumaun Himalayan region in northern India, is a major drinking water source to the people living in and around the lake basin. The water balance of the lake has been computed for the first time. The subsurface outflow components are estimated by indirect methods and then the subsurface inflow calculated by means of the water balance equation. The results are verified using the environmental isotope mass balance method. Further, the chloride mass balance method is also employed for comparison of the results with two other methods. The slope of the δ18O-δD water line of the lake (7.1) is very close to that of the local meteoric water line (7.5) indicating that the effect of evaporation in the lake is not manifested in the isotope characteristics of the lake. The mass balance results indicate that the groundwater contribution is about 50% of the total annual inflow to the lake. The subsurface outflow is about 55% of the total annual outflow from the lake. This shows that the lake is a “flow-through” type with substantial groundwater inflow and lake seepage. The results of both chloride and isotope mass balance methods corroborate the results of the water balance method. The water retention time for Lake Nainital, estimated by isotopic mass balance, chloride mass balance and conventional water balance methods, is about 1.93, 1.77 and 1.92 years, respectively.

Sedimentation rate and pattern of a Himalayan foothill lake using 137Cs and 210Pb

Abstract An attempt has been made to determine the sedimentation rate and pattern of Mansar Lake, a natural lake located in the Himalayan Foothills of Jammu and Kashmir, India. Five core samples were collected from different locations in the lake and analysed for 137Cs and 210Pb. The results show that the rate of sedimentation in the lake varies between 1.4 and 3.7 mm year−1 with the mean rate of 2.3 ± 0.02 mm year−1. The spatial variation of sedimentation rate provides evidence on the existence of three depositional zones in the lake. The higher sedimentation rates at two sites located near the periphery of the lake show the effects of human activities in the catchment area, such as agriculture and construction. The sediment accumulation rate of Mansar Lake is compared with that of four Lesser Himalayan lakes and it is found that Mansar Lake is receiving sediment at the rate of 892.8 m3 km−2 year−1, which is higher than for all the Lesser Himalayan lakes. This higher rate reveals that the Siwalik terrain of the Himalayan Foothills, consisting of sandstone, mudstone, siltstone and clay, is eroding out at a faster rate than the Lesser Himalaya terrain.

A compact tritium enrichment unit for large sample volumes with automated re-filling and higher enrichment factor

Tritium (3H) in natural waters is a powerful tracer of hydrological processes, but its low concentrations require electrolytic enrichment before precise measurements can be made with a liquid scintillation counter. Here, we describe a newly developed, compact tritium enrichment unit which can be used to enrich up to 2L of a water sample. This allows a high enrichment factor (>100) for measuring low 3H contents of <0.05TU. The TEU uses a small cell (250mL) with automated re-filling and a CO2 bubbling technique to neutralize the high alkalinity of enriched samples. The enriched residual sample is retrieved from the cell under vacuum by cryogenic distillation at -20°C and the tritium enrichment factor for each sample is accurately determined by measuring pre- and post- enrichment 2H concentrations with laser spectrometry.

Studying Dynamics of the South West Monsoon in Indian Sub-Continent through Geospatial Correlation of Isotopes in Air Moisture

The isotopic data of atmospheric air moisture collected from Kakinada in coastal region (Andhra Pradesh), Sagar in Central India (Madhya Pradesh), Kanpur in Indo-Gangetic plains (Uttar Pradesh), Roorkee in foot hills of Shiwalik (Uttarakhand), Jammu in Sub-Himalayan region (Jammu & Kashmir) and Manali in Himalayan region (Himachal Pradesh) measured in Isotope Laboratory of NIH, Roorkee and has been analysed using Matlab to find out the local/ regional component of atmospheric moisture. The isotopic analysis confirms the continental and altitude effects which were earlier deciphered by the precipitation. Further, the isotopic data analysis validates the impact of local moisture on rainfall and help in resolving the moisture sources in different seasons. This analysis further concludes that the isotopic composition of air moisture can be applied for finding the onset of monsoon.

Isotopic Observations from Two Stations of North India to Investigate Geographical Effects on Seasonal Air Moisture

Air moisture samples were collected from 2 stations of north India for the years 2012 and 2013: one located in high Himalayas inMarhi, Manali, Himachal Pradesh and second in Indo-gangetic plains of Roorkee, Uttarakhand using condensation method for studying seasonal variations in isotopic composition. In high Himalayas, the air moisture was found isotopically more enriched (δD) as compared to the moisture collected in Indo-gangetic plains. But due to the arrival of oceanic vaporduring the monsoon season, the isotopic values start getting depleted whichopens up the possibility to use isotopic composition of air moisture for seasonal studies.

Understanding the Seasonal Dynamics of the Groundwater Hydrogeochemistry in National Capital Territory (NCT) of India Through Geochemical Modelling

A geochemical assessment of seasonal dynamics in the groundwater chemistry of the National Capital Territory (NCT), Delhi, was attempted through geochemical modelling, mineral precipitation sequences with rainfall and water evaporation cycle. Saturation indices calculated using PHREEQC indicated that the degree of water–rock equilibrium changes significantly from pre-monsoon to post-monsoon. The schematic model of SI change with water table fluctuation showed that during monsoon, as rainwater percolates through the soil, partial pressure of CO2 becomes higher than that of the atmospheric value and led to the formation of more carbonic acid that react with the carbonate minerals to produce

A New Technique for the Calibration of Neutron-Moisture Probe

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