Renuka Lake ecosystem and wetland protection, Lesser Himalaya ...

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other land uses. It even absorbs sediment,chemical nutrients and other substances innon-point source run off. Riparian zones areinstrumental in water quality improvementfor both surface and water flowing intowater bodies through sub-surface or groundwater flow. The wetland riparian zonesshows a particularly high rate of removal ofnitrate entering a stream and thus has aplace in eutrophication management.Because of there prominent role insupporting a diversity of species, riparianzones wetland are often the subject ofnational protection in a Biodiversity ActionPlan.Renuka Lake having a riparian courseand a wetland shows water quality control,soil conservation, their biodiversity andinfluence on aquatic ecosystem. Toestablish these characters a comprehensivestudy of water quality, lake and wetlandsediment geochemistry, isotope chemistryto determine rate of sedimentation, andsurvey of flora and fauna distribution havebeen carried out. The lake is unique inlesser Himalaya and is under RamsarConvention Environment Act.2. MethodologyThe water samples were collected in prewashed1L polythelene bottles filling it tothe capacity. Within 5-6 hours of collectionpH, E.C, D.O, TDS etc. were measuredusing portable field kit. The samples werefiltered using 0.45 µm Millipore filtermembranes. A part of this was used formeasurement of carbonate and bi-carbonateby acid titration, choride by AgNO 3titration, sulphate by Ba(ClO 4 ) 2 titrationafter passing the samples through cationexchange resin, phosphate by an ascorbicacid spectrophotometry, silicate bymolybdenum blue spectrometry. Na, K byflame photometer and Ca and Mg by AAS2100(Perkin Elmer Atomic AbsorptionSpectrophotometer).The sediment samples carefully selectedwere collected from lake and wetland, driedand processed. The samples were ground to-200 mesh size in agate mortar and wereused for making pellets. These pellets weresubjected to X-ray fluorescencespectrophotometer (energy dispersive,Phillips EXAM-6 system) and major andtrace elements were estimated. Theaccuracy was checked by running USGSsediment standards SDO1, SCO1, GSD9and SO1. The major element accuracy is~2.5%. The REE’s were measured on ICP-MS using G2 and SDO1 standards in theUniversity of Kiel, Germany. As the REE.sare present in minor quantities in the matrixelements, therefore, elements have to beseparated as a group so that the spectralinterference from the matrix elements canbe avoided. The precision of data is betterthan 5% except for Ce and Nd, which haveprecision of about 10% and for REE(
The average rain fall in the region isbetween 150-199.9 cm per annum (Joshi,1984) 1 . The Renuka Lake is 10.50m inlength and 204m in breadth with amaximum depth of ~13m and catchmentarea is ~254.3ha.The catchment rocks of Renuka are darkcarbonaceous shales and slates, closelyinterbedded with thin slaty quartzitebelonging to Infra Krol Group. The slatyquartzites, or clay slates are frequentlycalcareous and consists of quartz, carbonate,sericite and pyrite and in some caseschlorite. The green-gray calcareous shaleand argillaceous limestone with variablegradation are of Krol A Group. The purpleredshales with intercalation of green-shalesand thin dolomitic cherty limestone belongto Krol B Group. The well bedded grayishwhitelimestone with shale represents KrolC. The rock formation belongs to neo-Proterozoic – Proterozoic age. (Auden,1934) 2 . The soil composition of the regionalso show a heterogeneous mixture ofcarbonate rocks, sandstones, shales,siltstone in various proportion (Srikantiaand Bhargava,1998) 3 . The soil cover is thindue to weathering-limited conditions(Stallard and Edmond, 1987) 4 as physicalerosion has been stronger due to upliftingHimalaya.4. Water quality of Renuka LakeThe lake water is alkaline, pH rangesbetween 8.21 to 8.55 in the month ofMarch-April. The carbonate alkalinity is2.45 meq/l average. Ca 2+ and Mg 2+ are themajor cations and contribute 38.57 to48.93% and 44.71 to 54.16% of the totalcation budget, respectively. The HCO - 3 andSO 2_4 are the major anions contributing36.97b to 51.90 and 43.25 to 51.91% to theanion budget, respectively. The high Ca 2+ +Mg 2+ -and HCO 3 in water indicatedissolution of limestone in the lake basinwhich is supported by (Ca 2+ +Mg 2+ -):HCO 3equivalent ratio of ±2.55.The high SO 2_ 4 inthe lake is derived from black carbonaceousshale and gypsum in the lithology. Duringweathering process rocks exposed to theatmosphere come in contact with dissolvedO 2 (rain water) that reacts with pyriteresulting in oxidative decompositionproducing H 2 SO 4 by the followingreactions:4FeS 2 +15O 2 + 8H 2 O→2Fe 2 O 3 + 8H 2 SO 4H 2 SO 4 →2H + SO 2_ 4 (Berner and Berner,1987) 5 ……………………(1)As water draining rocks where sulphideoxidation is taking place, the presence ofcarbonate minerals neutralizes acid andhence the pH of lake water remains alkaline(Das and Parkash, 2001) 6 . The contributionof Na and K is between 4 and 7% of themajor ion budget of the lake. The low+(Na+K)/T Z ratio (0.058) indicates thatthere is no significant contribution ofcations to the lake water from thedegradation of alumino-silicates. Thedepletion in K compared to Na may be dueto its resistance to weathering and that K + isutilized in the formation of clay mineralillite. As the hardness of water exceeds theprescribed safe limit hence unfit fordrinking, domestic and agriculture use. Thevariation in chemistry of water is related toanthropogenic activity and riparian wetlandzone. It is observed that PO 2_ 4 and in somecases SO 2_4 in water samples in contactwith wetland are depleted (1.5 to 3.5µg/land 120 to 135 mg/l, respectively) where asthere concentration is enhanced in samplestaken from wetland (12.0 to 13.5 µg/l and150 to 160 mg/l, respectively).The variationshows that these nutrients are adsorbed invegetation/soil thus protecting the lakewater from further pollution. The traceelement content of Renuka water showhigher concentration of Fe and Pb in3
Page 1: Renuka Lake ecosystem and wetland p
Page 5 and 6: 2008) 10 .In addition grazing and r
Page 7: Table 2. Rare Earth Elements( REE)

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