Application of Persistent Scatterer Interferometry (PSI) in monitoring slope movements in Nainital,Uttarakhand Lesser Himalaya,India

Orogenic movements and sub-tropical climate have rendered the slopes of the Himalayan region intensely deformed and weathered. As a result, the incidences of slope failure are quite common all along the Himalayan region. The Lesser Himalayan terrane is particularly vulnerable to mass-movements owing to geological fragility, and many parts of it are bearing a high-risk of associated disaster owing to the high population density. An important step towards mitigation of such disasters is the monitoring of slope movement. Towards this, the Persistent Scatterer Interferometry (PSI) technique can be applied. In the present study, the PSI technique is employed in Lesser Himalayan town of Nainital in Uttarakhand state of India to decipher and monitor slope movements. A total of 15 multi-date ENVISAT ASAR satellite images, acquired during August 2008 to August 2010 period, were subjected to PSI, which revealed a continuous creep movement along the hillslopes located towards the eastern side of the Nainital lake. The higher reaches of the hill seem to be experiencing accelerated creep of \({\sim }21\) mm/year, which decreases downslope to \({\sim }5\) mm/year. Based on spatial pattern of varying PSI Mean LOS Velocity (MLV) values, high (H), moderate (M), low (L) and very low (S) creeping zones have been delineated in the hillslopes. Given the long history of mass movements and continuously increasing anthropogenic activities in Nainital, these results call for immediate measures to avert any future disaster in the town.     

Geochemistry and petrogenesis of the Palampur metavolcanics, Lesser Himachal Himalaya, India

Summary The Palampur metavolcanics (PV) in the northwest Himalaya are part of the Late Archaean (2.5 Ga) Rampur flood basalt province (RFBP) which represents one of the oldest manifestation of worldwide mafic magmatism. The volcanics occur as mafic lava flows with evidence of two phases of deformation. The first phase resulted in recrystallisation which almost completely obliterated the primary mineralogy, and the second phase was of weak cataclasis. Immobile trace element ratios as well as cation percent Al - (Fe - Ti) - Mg indicate that the volcanics are tholeiitic in composition. The chemical characteristics, such as the decoupling between HFS and LIL elements i.e., distinct negative Sr, Nb and Ti anomalies in the double normalisation ratios spiderdiagram together with low Ti/Y and Zr/Y ratios, testify the rocks as low-Ti continental flood basalts. The chemical variations in the volcanics can be related to varying extents of partial melting of the mantle source(s), followed by fractional crystallisation (predominantly olivine and clinopyroxene over plagioclase). Positive correlation between LREE and Fe abundances, Ce-Nd and Y/Nd-Zr/Y data preclude any significant role of crustal contamination in the evolution of their bulk chemistry. The REE data and [Mg]-[Fe] relations rather suggest that the parental magma of the PV derived from non-pyrolitic source(s) which was heterogeneous with respect to enrichment in Zr, LREE and Fe/Mg ratios. Mantle metasomatism appears to be the main process of such source enrichment, possibly caused by the addition of a volatilerich silicate melt phase.[/ p]

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Geochemie und Petrogenese der Palampur Metavulkanite, Lesser Himachal Himalaya, Indien

Zusammenfassung Die Palampur Metavulkanite (PV), im nordwestlichen Himalaya, gehören zur spätarchaiischen (2.5 Ga) Rampur Plateau-Basalt-Provinz (RFBP), die einen der ältesten, weltweiten Phasen von mafischem Magmatismus manifestiert. Die Vulkanite treten als mafische Lavaströme auf und zeigen zwei Phasen von Deformation. Die erste resultierte in einer Rekristallisation, die nahezu den gesamten primären Mineralbestand überprägt hat. Die zweite Phase ist durch schwache Kataklase repräsentiert. Immobile Spurenelementverhältnisse, wie auch die Kationenprozent von Al- (Fe- (-Ti) -Mg, deuten eine tholeiitische Zusammensetzung der Vulkanite an. Die chemischen Charakteristika, die im unterschiedlichen Verhalten der HFS und LIL Elemente deutlich werden, deutlich negative Sr, Nb und Ti Anomalien in den zweifach normalisierten Spiderdiagrammen, niedrige Ti/Y und Zr/Y Verhältnisse, bezeugen, dass es sich um Ti-arme, kontinentale Plateaubasalte handelt. Die chemischen Unterschiede innerhalb der Vulkanite können auf unterschiedliche Grade von Aufschmelzung des (der) Mantelmaterials(e), gefolgt von fraktionierter Kristallisation (vor allem Olivin und Klinopyroxen, untergeordnet Plagioklas), zurückgeführt werden. Positive Korrelation der LREE mit Fe, wie auch die Ce-Nd und Y/Nd-Zr/Y Daten schließen eine signifikante Rolle von Krustenkontamination in der Evolution der Gesteinschemie aus. Die REE Daten und die /Mg/-/Fe/ Verhältnisse lassen eher vermuten, dass das Ausgangsmagma der PV von einem nicht-pyrolitischen Material stammt, welches bezüglich Anreicherung an Zr, LREE und Fe/Mg Verhältnis heterogen gewesen ist. Mantelmetasomatose scheint der Hauptprozeß für diese Anreicherng des Ausgangsmaterials gewesen zu sein, die möglicherweise durch Zufuhr einer silikatischen Schmelzphase, reich an flüchtigen Bestandteilen, hervorgerufen wurde.[/ p]

     

水化学—稳定同位素技术在岩溶水文地质研究中的应用

水化学—稳定同位素技术在岩溶水系统分析中得到了广泛的应用,尤其是在指示岩溶水文地球化学过程、识别岩溶水补给循环途径、溶质溯源及岩溶水污染监测防控等方面显示了独特的优势,产生了丰富的成果。本文着重阐述了环境稳定同位素δD、δ18O、87Sr/86Sr的工作原理,及水化学—稳定同位素技术在岩溶水文地质研究中的应用。此外,论文还以娘子关泉域和北京西山岩溶水系统为例,介绍了运用水化学—稳定同位素技术分析岩溶水系统补给的思路和方法,展望了该技术在岩溶水文地质和岩溶生态环境领域中的应用前景。     

Geothermal evolution of the evaporite-bearing sequences of the Lesser Himalaya, India

Neoproterozoic evaporites occurring in the western part of the Lesser Himalaya in India, coeval to Pakistan, Iran and Oman evaporites, were investigated in order to understand the degree of metamorphism in them and in associated carbonates. The evaporite-bearing succession occurs in association of phyllite, quartzite and carbonate near the Main boundary Thrust. In order to learn the details about the burial history of these evaporite rocks, the Kübler illite crystallinity index (KI) was measured from the illite peaks of the clay minerals separated from the evaporite rocks and it indicated that this section has reached a maximum temperature up to ~300°C. Microthermometric measurements on fluid inclusions present in the associated dolomite show range of homogenization temperatures (Th), from 220 to 280°C, well within the temperature range of anchizone metamorphism. Additionally, dolomite shows a highly negative δ¹⁸O signature (mean, −15.5‰_PDB), which is more likely related to diagenetic overprint from deep burial conditions rather than original precipitation from ¹⁸O-depleted seawater. The evaporites (sulfates and chloride) probably were transformed many times after their precipitation, but they have retained only the features developed during last one or two phases of alteration and deformation as they are continuously susceptible to minor changes in temperatures and stresses. The final temperature range of 42–78°C in sulfates and chloride gives thermal approximation estimate that is not in concordance with the thermal history of the basin and are likely related to conversion of anhydrite into gypsum and recrystallization of halite during exhumation. Highly negative oxygen isotopic composition, homogenization temperatures and KI values equivalent to a high anchizone metamorphism suggest a burial depth of ~10 km for these terminal Neoproterozoic evaporite-bearing sequences of the Lesser Himalaya.     

基于水化学和氢氧同位素的峡口隧道涌水来源识别

峡口隧道是一条位于岩溶山区的深埋特长型隧道,遭遇了历时近两年来源不明的复杂涌水过程。为查明隧道的涌水来源和充水途径,通过解读隧道区的水文地质条件,分析对比不同涌水点的水化学及氢氧同位素组成差异,查明了隧道右洞北侧涌水主要来源于二叠—三叠系岩溶含水层,其他均来自于侏罗系裂隙含水层,二叠系灰岩与泥盆系石英砂岩接触部位发育的岩溶裂隙带为主要的充水途径。     

Deformation mechanisms in the frontal Lesser Himalayan Duplex in Sikkim Himalaya,India

Understanding deformation mechanisms in Himalayan rocks is a challenging proposition due to the complex nature of the deformed rocks and their genesis. Crustal deformation in the Himalayan thrust belt typically occurs in elastico-frictional (EF) or quasi-plastic (QP) regimes at depths controlled mainly by regional strain-rate and geothermal gradient. However, material property, grain-size and their progressive changes during deformation are also important controlling factors. We present evidence of EF deformation from Gondwana rocks developed during the emplacement of one of the frontal horses (Jorthang horse) in the Lesser Himalayan Duplex (LHD) structure associated with Lesser Himalayan rocks in the footwall of the Ramgarh thrust in the Rangit window near Jorthang in the Sikkim Himalaya. The rocks in the horse exhibit systematic changes in microand meso-structures from an undeformed protolith to cataclasite suggesting that it was emplaced under elastico-frictional conditions. Meso- to micro-scale shear fractures are seen developed in Gondwana sandstone and slate while intercalated fine-grained shale-coal-carbonates are deformed by cataclastic flow suggesting that material property and grain-size have played an important role in the deformation of the Jorthang horse. In contrast, the hanging wall schists and quartzites of the Ramgarh thrust exhibit quasi-plastic deformation structures. This suggests that the Jorthang horse was emplaced under shallower crustal conditions than the antiformally folded Ramgarh thrust sheet even though the Ramgarh sheet presently overlies the Jorthang horse.     

Normal faults in Panjal Thrust Zone in Lesser Himalaya and between the Higher Himalaya Crystallines and Chamba sequence in Kashmir Himalaya,India

Normal faults on mesoscopic scale are observed in the Panjal Thrust Zone in the Dalhousie area of western Htmachal. The boundary between the southern margin of the Higher Himalaya Crystalline (HHC) of Zanskar and the Chamba syncline sequence is also described as a normal fault, referred to as Bhadarwah Normal Fault in the Bhadarwah area of Doda district on the basis of field mapping and shear sense criteria using S-C fabric and porphyroblast rotation. The occurrence of these normal faults suggests that the extensional tectonic regime was not restricted only to the Zanskar shear zone area but that it also occurs south of the Higher Himalayan range. This suggests NE-directed subhorizontal extension and exhumation of deeper level rocks of Higher Himalaya Crystallines.     

Petrography,geochemistry and regional significance of crystalline klippen in the Garhwal Lesser Himalaya,India

Uphalda gneisses (UG) is a crystalline klippe located near Srinagar in Garhwal Himalaya. These gneisses are compared with Debguru porphyroids (DP) (≈Ramgarh group) of Garhwal–Kumaun Himalaya and Baragaon mylonitic gneisses (BMG) of Himachal Himalaya. Petrographic study reveals that the deformation of UG was initiated at higher temperature (above 350°C) and continued till lowering of temperature and deformation led to the mylonitization.     

环境同位素在水循环研究中的应用

环境同位素广泛存在于自然界水体中,在降水、地表水、地下水、土壤水和植物体内相互转化的水循环过程中,同位素的分馏效应导致不同水体具有不同的同位素含量。利用不同水体同位素含量之间的差异,可研究它们之间的相互转化方式及转化量。介绍了环境同位素在大气降水和降水-地表水-地下水“三水”之间转化中的研究进展,并阐述了其在水循环应用中存在的问题及应用前景。     

Modification of fold geometry in Almora Crystalline Shear Zone,Lesser Himalaya,India

The folds generally initiate at several discrete points along a layer or multilayer undergoing compressional forces. These compressional forces often lead to rotation of fold segments and in all such regimes, folds are strongly asymmetrical and are in complete agreement with the direction in which the force is applied and also with the related thrust sheet movement. This paper illustrates the progressive change in fold geometry with increasing compression and ductile shearing using natural example as studied in the Almora Crystalline Zone (ACZ).     

Environmental pollution impact on water and sediments of Kumaun lakes, Lesser Himalaya, India: a comparative study

A study of the water and sediment chemistry of the Nainital, Bhimtal, Naukuchiyatal and Sattal Lakes of Kumaun, has shown that the water of these lakes are alkaline and that electrical conductivity, total dissolved solid and bicarbonate HCO ₃ ⁻ are much higher in Nainital than in the other three lakes. The weathering of limestone lithology and anthropogenic pollution, the latter due to the very high density of population in the Nainital valley, are the primary sources of enhanced parameters. The low pH of Nainital Lake water is due to low photosynthesis and enhanced respiration, increasing CO₂ in the water and the consequent enhancement of Ca²⁺ and HCO ₃ ⁻ . The dissolved oxygen in Nainital Lake is less compared to other lakes, indicating anoxic conditions developing at the mud–water interface at depth. The PO ₄ ³⁻ content in Nainital is higher (124 μg/l), showing an increasing trend over time leading to eutrophic conditions. The trace metals (Cu, Co, Zn, Ni, Mn, and Sr) are present in greater amounts in the water of Nainital Lake than in the other three lakes, though Fe and Cr are high in Bhimtal and Fe in Naukuchiyatal. The higher abundance is derived from the leaching of Fe–Mg from metavolcanic and metabasic rocks. Most of the heavy metals (Cr, Ni, Cu, Mn, Fe, Sr, and Zn) significantly enrich the suspended sediments of the lakes compared to the bed sediments which due to their adsorption on finer particles and owing to multiple hydroxide coating and organic content, except for Fe, which is enriched in the bed sediments. The high rate of sedimentation, 11.5 mm/year in Nainital, compared to Bhimtal with 4.70 mm/year, Naukuchiyatal with 3.72 mm/year, and Sattal with 2.99 mm/year, has resulted in shorter residence time, poor sorting of grains, and lesser adsorption of heavy metals, leading consequently, their depletion in the bed sediments of Nainital Lake.     

Structure and petrology of mylonite and related rocks from the Lesser Himalaya,Garhwal, India

In the Lesser Himalayan region of Garhwal, an elongate, NW-SE trending zone of mylonitic rocks is developed along the Singuni Thrust within the metasedimentary formation of the Deoban-Tejam Belt. Detailed petrography of various mylonitic rocks indicates that a quartz and felspar porphyry was emplaced along the Singuni Thrust. This was initially metamorphosed in the almandine-amphibolite facies before profound ruptural or cataclastic and crystalloblastic deformation evolved mylonitic rocks in the green schist facies. Southwesterly dipping foliation and an equally prominent mica lineation plunging in the same direction are developed in these mylonitic rocks. The quartzite is also intensely cataclastically deformed in the green schist facies and is highly schistose with a prominent mica lineation normal to the trace of Singuni Thrust, Uttarkashi Thrust and Main Central Thrust in the ‘a’ direction of tectonic transport. In quartzite and mylonitic rocks, a probable contemporaneous development of the metamorphic and structural elements has been postulated along the Singuni Thrust during large scale tectonic movements. Normally exposed Gamri Quartzite is more metamorphosed near its base along the Singuni Thrust and Uttarkashi Thrust while the intensity of deformation increases near the top of normally exposed quartzite along the Main Central Thrust and, thus, signifying the role of thrusting in cataclastically deforming the rocks and contributing to the phenomenon of widespread reversal of metamorphism in the Lesser Himalaya.     

Stratigraphy and provenance of Late Palaeozoic diamictites in parts of Garhwal Lesser Himalaya,India

The Garhwal Lesser Himalayan Krol Belt contains two well developed diamictite horizons in the Late Palaeozoic Blaini Formation. Structureless and massive diamictites contain clasts of different shape, roundness and lithologies comprising mainly shale, slate, phyllite, quartzite, vein quartz and limestone dispersed in fine sandy argillaceous and calcareous matrix.Clast composition and petrography of the diamictites and other lithologies of the Blaini Formation reveal the presence of sedimentary and low grade metamorphic rocks in the provenance of the Blaini. The provenance seems to be the Lesser Himalayan terrain of the Simla Slate, Jaunsar and Shali-Deoban carbonates which had probably undergone structural deformation prior to the Late Palaeozoic. Two glacier advances deposited the diamictites near the shoreline of the Krol Basin during Late Palaeozoic.

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Zusammenfassung Im Krol Belt des Kleinen Himalaya sind in der jungpaläozoischen Blaini-Formation zwei Horizonte mit sedimentären Diamictiten enthalten. Die strukturlosen und massiven Diamictite enthalten Klastika verschiedener Form, Rundung und Lithologie. So findet man Schiefer, Phyllite, Quarzite, Gangquarze und Kalke in einer feinsandigen, tonigen Matrix mit Karbonatanteilen. Die Zusammensetzung der Klaste und die Petrographie der Diamictite sowie der übrigen Gesteine der Blaini-Formation zeigen die Anwesenheit von Sedimentgesteinen und schwach metamorphisierten Gesteinen im Einzugsbereich der Blaini-Formation. Dieser Bereich kann die Simla-Schiefer und die Jaunsar- und Shali-Deoban-Karbonate des Kleinen Himalaya mit umfassen, die vermutlich vorjungpaläozoisch metamorphisiert wurden. Während zweier Gletschervorstöße sind die Diamictite randlich im Krol-Becken während des Jungpaläozoikums abgelagert worden.

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Résumé Dans la ceinture de Krol de l'Himalaya mineur, la Formation de Blaini, d'âge Paléozoique supérieur, renferme deux horizons à diamictites sédimentaires. Celles-ci, massives et sans structure interne, contiennent des éléments clastiques de forme arrondi et lithologie différents; ce sont des schistes métamorphiques, des phyllites, des quartzites, du quartz-filonien et des calcaires disposés dans une matrice fine, argilosableuse avec participation carbonatée. La composition des éléments clastiques et la pétrographie des diamictites, comme celles des autres roches de la Formation de Blaini, montrent la présence de roches sédimentaires et de roches faiblement métamorphiques de même provenance que la formation de Blaini; cette provenance peut comprendre les schistes de Simla et les roches carbonatées de Jaunsar et de Shali-Deoban qui furent métamorphisées probablement avant le Paléozoique supérieur. C'est au cours de deux avancées glaciaires que les diamictites ont été déposées en bordure du bassin de Krol pendant le Paléozoique supérieur.

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Stability assessment of slide zones in Lesser Himalayan part of Yamunotri pilgrimage route,Uttarakhand, India

The present study deals with the slope stability analysis and geotechnical assessment of a part of pilgrimage route to one of the holy shrines of India, i.e. Yamunotri. The route also embraces a proposed site for 204 m high concrete gravity dam across River Yamuna near Lakhwar village with the aim of generation of 300 MW power. Several slide zones were identified and based on the discontinuity orientation, structural features and debris materials, they are recognised as planar, wedge or circular failure types. The morphological dimensions, structural data, orientations and geotechnical parameters of circular failure slides within weathered quartzites, phyllites and shales were evaluated by extensive field work and by laboratory tests for their stability analysis. Internal mechanisms, cohesion and angle of internal friction that resist shear stress in slope materials, obtained from direct shear test are showing minor variation due to relatively consistent grain size distribution and mineralogical composition. General slope is about 40°–43° with sparse vegetation. Materials in and around slide zones are sands with appreciable amount of fines falling in SP–SM category as per Unified Soil Classification System (USCS), except Niste B slide which has clean sands lying in SP group. Factor of safety, computed by requisite parameters of strength, soil and slope properties in circular failure charts, varies from 1.02 to 1.23 in dry conditions while it reduces below unity with increasing saturation, representing stable conditions in dry conditions but with seepage and saturation along the cracks and discontinuities during rainfall make them unstable. Presence of steep slopes, proximity to stream channels and significant weathered and jointed area are causative factors in the route with rainfall and road widening as major triggers initiating the failure.     

U-Pb zircon ages and Sm-Nd isotopic characteristics of the Lesser and Great Himalayan sequences,Uttarakhand Himalaya,and their regional tectonic implications

Detrital zircons (DZ) and Nd isotopic characteristics constraint maximum depositional ages of two distinct Paleoproterozoic and Neoproterozoic terranes across the Main Central Thrust zone (Munsiari Group) in the Himalaya. New DZ ages and Nd isotopic characters are reported from the Inner Lesser Himalaya (iLH) sedimentary belt (Berinag Group quartzite) and the Munsiari Group through the Great Himalayan Sequence (GHS–Vaikrita Group) across the MCT to the lower parts of the Tethyan Himalayan Sequence (THS) along the Alaknanda–Dhauli Ganga valleys, Uttarakhand Himalaya. The iLH Berinag Group quartzite yielded nearly unimodal DZ U-Pb ages between 2.05 and 1.80 Ga with ε_Nd(0) values of −17 and −23, while the overthrust Munsiari Group, bounded by the Munsiari Thrust at the base and the Vaikrita Thrust (MCT) at the top, represents the Proterozoic magmatic arc with ∼1.95 and 1.89 Ga U-Pb zircon age population with an average of −25 ε_Nd(0) value; the arc developed during the Columbia Supercontinent assembly. In contrast, overthrust Great Himalayan Sequence (GHS–Vaikrita Group) above the MCT is characterized by entirely new Neoproterozoic 1.05–0.85 Ga zircon population, which appears for the first time in this sequence, and has higher ε_Nd(0) values (average −16). Tectonically overlying the GHS, the Tethyan Himalayan Sequence (THS) has first appearance of the Early Paleozoic detrital zircons, with its ε_Nd(0) values like the GHS. Broadly, these characters persist throughout the Himalayan belt from Himachal to NE Himalaya. The iLH sediments were possibly derived from northernly ∼1.9 Ga magmatic arc, and southern the Archean–Proterozoic Aravalli–Bundelkhand nuclei of the Indian craton. Potential sources for the GHS sediments may be a northerly ‘destroyed’ Neoproterozoic magmatic arc whose remnants exists within the Himalaya as the Neoproterozoic granitoids, and possibly be the iLH sedimentary belt, an ‘In-board’ Aravalli–Delhi Fold Belt (ADFB)–Central Indian Tectonic Zone (CITZ) in the south.     

Chemodynamics of trace metal fractions in surface sediments of the Pandoh Lake,Lesser Himalaya,India

The seasonal variation in the trace metals’ concentrations (Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn) were investigated in surface sediments of the Pandoh Lake. The horizontal distribution of TC, TN, and TP reflects spatial and temporal differences in sedimentary organic production. The chemical sequential extraction of heavy metals was carried out by seven-step fractionation scheme (Leleyter and Probst in Int J Environ Chem 73:109–128, 1999). The significant concentrations of Ni and Cd were associated with “water soluble (Eua)” fraction in the monsoon and winter, respectively, while “exchangeable (Exch)” and “carbonate-bound (Carb)” fractions for Ni and Cd were abundant in winter and summer. The Cd, Cu, and Pb associated with “Exch” fraction in the summer season support their availability on exchange sites due to oxidized nature of surface sediments. Enrichment of Co, Fe, Mn, and Zn in “AFeO” fraction showed poor bioavailability, while Cd, Cu, and Mn in the monsoon, Co in the winter and summer, and Zn in the winter season showed significant “organically bound (Org)” fraction. The ANOVA was significant for chemical fractions of trace elements except “Carb” fraction of Pb and Zn and “CFeO” fraction of Pb. Factor analysis revealed that the “Eua”, “Exch”, and “Carb” fractions together control the metal enrichment of “MnO”, “AFeO”, and “CFeO” fractions in the summer season.     

Ionic sources and water quality assessment around a reservoir in Tehri, Uttarakhand, Garhwal Himalaya

The paper discusses the ionic sources and chemical quality of the waters (surface and groundwater) around the Tehri reservoir in Uttarakhand, Garhwal, Himalaya, for drinking and irrigation purposes. The main Bhagirathi river, tributary streams and springs and groundwater are the main sources of water for the reservoir and inhabitant living around it. Fifty-two water samples were collected from springs, handpumps (borewell) and streams and were analysed for major ions. The pH is varying from 6.8 to 8.6 and EC from 28 to 820 μS/cm. The chemical composition of water is dominated by Ca, Mg and HCO₃. The high ratio of Ca + Mg/Na + K and low ratio of Na + K/TZ indicate dominance of carbonate dissolution as the main solute acquisition process in this part of Lesser Himalaya. The trilinear and X–Y plots suggest less contribution from silicate weathering and anthropogenic activities. The excess of Na over Cl indicating much of the alkalis in the waters of Tehri area have source other than precipitation possibly from silicate weathering. Recharged by meteoric water, the quality of water in the study area is controlled essentially by chemical processes occurring between water and lithology and locally altered by human activities. Among the trace metals the concentration of Fe at few locations has marginally exceeded the WHO and BIS standards of drinking water. The analytical result computed from various water quality indices indicate fairly good quality of water for both drinking and irrigation purposes. The factor analysis performed on the major ion data indicate two factors are the most important affecting the water quality of the area.     

Phosphorus fractionation in surficial sediments of Pandoh Lake,Lesser Himalaya,Himachal Pradesh,India

The fractionation of P in Pandoh Lake surface sediments has been investigated for the first time in order to understand its environmental availability and sources, and the eutrophication status of this lake. Inorganic-P is present mainly as authigenic-P (step-III). The authigenic P concentration is higher in winter relative to the summer and monsoon seasons and ranged from 35.9 to 46.9 μg/g. The loosely sorbed or exchangeable-P (step-I), Fe(III)-bound-P (step-II) and detrital inorganic-P (step-IV) were higher in the monsoon season and varied from 3.70 to 11.1 μg/g, 16.9 to 32.0 μg/g and 9.89 to 17.0 μg/g, respectively. Organic-P reached a maximum in the summer season and ranged from 8.00 to 14.9 μg/g. Authigenic-P and detrital inorganic-P show seasonal changes, as pH influences the interaction between P and CaCO₃ in the water column. In the winter season, phosphate is precipitated out of the water column and fixed in the sediments as a result of an increase in pH. Calcite-bound-P in the sediments may be redissolved by decreasing pH in the summer season. Relatively high rates of mineralization during the monsoon results in the seasonal pattern of organic-P fractionation to sediment as follows: monsoon = winter < summer. Iron, Ca, organic matter and silt and clay contents seem to play a significant role in regulating the seasonal P budget. Principal component analysis (PCA) was used to identify the factors which influence sedimentary P in the different seasons.