. Several fragments weighing <2 kg and a single large fragment weighing ∼10 kg were recovered from the strewn field, which extended over several tens of square kilometers. Chemical, petrographic, and oxygen isotopic studies indicate it to be, in most aspects, a typical H5 chondrite, except the unusually low K content of ∼340 ppm. A cosmic ray exposure of 9.7 Ma is inferred from the cosmogenic noble gas records. Activities of eleven cosmogenic radionuclides were measured. 26 Al and 22 Na activities as well as the 22 Na/ 26 Al activity ratio are close to the values expected on the basis of solar modulation of galactic cosmic rays. The low 60 Co activity (<1 dpm/kg) is indicative of a small preatmospheric size of the meteorite. Cosmic ray heavy nuclei track densities in olivine grains range from ∼10 6 cm −2 in samples from the largest fragment to approximately (4-9) × 10 5 cm −2 in one of the smaller fragments. The combined track, radionuclide, and noble gas data suggest a preatmospheric radius of ∼20 cm for the Dergaon meteorite.
A comparative assessment of the hydrological quality of the shallow aquifers and surface water sources in the Jia Bharali River basin and adjoining areas of the Himalayan foothills has been made in this work. Six set of seasonal samples were analysed with respect to the common physicochemical parameters including major anions (carbonate-bicarbonate, chloride, sulphate, fluoride, nitrate and phosphate), and cations (calcium, magnesium, sodium, potassium). 74 % of the aquifers had higher TDS and 88 % had higher hardness in the wet seasons. The major cations were in the ranges of Ca: 7.1 -43.9 mg/L, Mg: 2.1 -25.9 mg/L, Na: 3.8 -40.8 mg/L, and K: 2.1 -22.7 mg/L. The total alkalinity was almost entirely due to the presence of bicarbonate. The aquifers are rich in chloride (5.6 -110.7 mg/L) and sulphate (3.1 -83.1 mg/L) with nitrate (BDL to 0.72 mg/L) and phosphate (BDL -1.27 mg/L), the latter being significantly high for some aquifers. In case of surface water sources, the major ions show wide variability (Ca: 1.56 -45.45 mg/L; Mg: 0.56 -14.56 mg/L; Na: 3.10 -14.30 mg/L; K: 1.0 -11.50 mg/L). The surface water rich in chloride (2.28 -38.45 mg/L) and sulphate (0.38 -29.45 mg/L), is also contains the nutrients, nitrate (BDL -1.45 mg/L) and phosphate (BDL -1.48 mg/L).
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