Phosphorus biogeochemistry in sediments of high altitudelakes, Kumaun Himalayas, India
P. Purushothaman & G. J. Chakrapani
Received: 5 February 2013 /Accepted: 11 December 2013# Saudi Society for Geosciences 2014
Abstract Kumaun Himalayan lakes, situated in the state ofUttarakhand, are one of the major tourist attractions in north-ern part of India. Present study is aimed to understand thebehavior of phosphorus in lake sediments and different chem-ical forms of phosphorus in sediments. The study was accom-plished by collection of core sediments from lakes. The coresamples were analyzed for major oxides, nutrients, and phos-phorus fractionation. The study shows that lake sediments arederived from catchment rocks. Total concentrations of nutri-ents (P, N, and S) in sediments varied differently and arederived from both natural and anthropogenic activities. Phos-phorus in sediments is sequestered more by calcium than ironand aluminum oxides, as carbonate flour apatite. Fractionationstudy shows that phosphorus as carbonate flour apatite and inexchangeable fraction. The dissolution of organic matter re-sults in release of phosphorus from sediments. The study alsoshows biogenic silica and sulfate act as major competitors ofphosphorus for sorption sites of iron oxides resulting in therelease of phosphorus from sediments.
Keywords Sediment geochemistry . Nutrients . Biogenicsilica . Sulfur . Phosphorus . Phosphorus fractionation .
KumaunHimalayas . Lakes
Phosphorus (P) concentrations in aquatic environments aremajor concerns due to the potential of P to cause eutrophica-tion. Sediment is a dominant P reservoir in many aquatic
ecosystems because suspended particulates in water columnseventually becomes bottom sediments possessing strong af-finity for dissolved P. Hence, phosphorus plays an importantrole in the eutrophication of the lake ecosystem (Kaiserli et al.2002; Ruttenberg 2004; Zhu et al. 2013). The phosphorus insediments is not directly available for aquatic organisms(Ramm and Scheps 1997; Zhou et al. 2001). However, minorvariations in physicochemical conditions release phosphorusfrom sediments to the overlying water (Khadka andRamanathan 2013). The main processes controllingaccumulation/release of phosphorus in sediments are adsorp-tion on to the Fe-oxy-hydroxides and precipitation with Caions (Golterman 1995). The influence of various factors inreleasing phosphorus from sediments has been studied bymany workers by both experimental and field studies, e.g.,Curtis (1989) and Caraco et al. (1993) (effect of sulfate ions),Gunnars and Blomqvist (1997), Hartikainen et al. (1996), Ishiiet al. (2010), Koski Vahala et al. (2001), Olila and Reddy(1997) (change in oxic state), Ringwood and Keppler (2002)(change in pH), Tuominen et al. (1998), Tallberg et al. (2008)(effect of Silicate ion), and Zan et al. (2010).
Kumaun Himalayan lakes in India, due to their picturesquenature, are one of the major tourist places in northern part ofthe country. Diversified nature of these lakes despite theirproximity has attracted many researchers. Different sourceslike soil erosion, illegal construction activities, automobileexhausts, and painting of boat in tourist season every yearpose serious problem of eutrophication and deterioration ofwater quality of these lakes (Singh and Gopal 2002;Choudhary et al. 2009; Purushothaman et al. 2008;Purushothaman et al. 2012; Purushothaman and Chakrapani2012). Eutrophication of lake Nainital is found to be increas-ing (Pant et al. 1980) due to its very high productivity (>8;Singh and Gopal 2002). Ali et al. (1999) observed thatNainital lake water is rich in nutrients and metals and foundthat macrophytes act as good removers of metals. However,there is no study reported from these lakes on bioavailabilityof phosphorus, the major limiting nutrient, which is present in
P. Purushothaman (*)Department of Civil Engineering, Saveetha School of Engineering,Saveetha University, Chennai, Tamil Nadu 602105, Indiae-mail: email@example.com
P. Purushothaman :G. J. ChakrapaniDepartment of Earth Sciences, Indian Institute of TechnologyRoorkee, Uttarakhand 247 667, India
Arab J GeosciDOI 10.1007/s12517-013-1234-5
sediment in different chemical forms. Hence, it becomesnecessary to know different form of phosphorus in sedi-ment, rather total concentration of phosphorus, as all theforms are not available for the organisms/released to theoverlying water column. Hence, it becomes imperative toknow different form of phosphorus in sediment, rathertotal concentration of phosphorus, as all the forms arenot available for organisms that are released to the over-lying water column. In the present study, different formsof phosphorus were studied along with other parametersin sediments and water to understand the phosphorusmobilization in four major lakes of Kumaun Himalaya,India.
Kumaun Himalayan lakes, Nainital, Bhimtal, Sattal, andNaukuchiatal, are located (2924 N and 7928 E, 2920N;7936E, 2921N; 7932E and 2919N; and 7935E, re-spectively) in Nainital district of Uttarakhand state, India.The tectonically formed crescent shaped Nainital Lakelies at an altitude of 1,938 m has two different subba-sins, Mallital and Tallital, divided in the middle with aridge. The lake receives water from two springs,paradhara and siphadara. The other lakes Bhimtal,Sattal, and Naukuchiatal are at an altitude 1,331,1,370, and 1,320 m, respectively. The formation ofBhimtalNaukuchiatal lake system was related to aWNW-ESE trending strike-slip fault traversing the area.The formation of Sattal Lake is believed to be due to theblockade of ravines due to debris flow. The drainage patternof lakes is trellis type and is structurally controlled by faultsand fractures (Purushothaman 2009).
Among these lakes, Nainital is highly populated with al-most 40,000 inhabitants. The other lakes are sparsely popu-lated with Bhimtal facing an increasing population due tonewly formed industrial area. The lithology of lakes in Nainihills ranges from paleoproterozoic to terminal proterozoic.The detailed description of the study area is discussed else-where (Valdiya 1988; Valdiya 1980; Das et al. l995;Nachiappan et al. 2000; Chakrapani 2002; Das 2005;Purushothaman 2009). The rocks in Nainital Lake catchmentconsists mainly of carbonate rocks such as limestone, dolo-mite, gypsum, calcareous slates, ferruginous shales, andgreywackes. The northwestern part is made exclusively ofargillaceous limestone and marlites, whereas southwesternpart comprises dolomite with limestone and black carbona-ceous slates (Valdiya 1988). Bhimtal and Naukuchiatal consistof Bhimtal Volcanics (amygdaloidal, vesicular basalt, andchlorite schist) and Bhowali Quartzite. Sattal catchment rocksinclude Jantwaliagaon Limestone along with Bhimtal volca-nic and Bhowali Quartzite (Valdiya 1988).
Sample collection and analysis
Sediment cores were collected from deepest part of lakes(Fig. 1) using a gravity corer during Jan. 2006. The collectedcores were segmented into subsamples of 2 cm thickness eachin the field immediately. The samples were stored in refriger-ated condition in clean and air-tight polythene bags. In the lab,core sediment samples were air dried and powdered. Majoroxides were determined by XRF (Siemens SRS 3000 sequen-tial X-Ray Spectrometer) at Wadia Institute of HimalayanGeology, Dehradun, India. The rock standard SDO-1 wasused for XRF study with errors not exceeding 5 %. Themineralisable nitrogen was analyzed using Kjeldahl instru-ment (JaguarGeneric name). The biogenic silica was deter-mined after digesting the sediment samples with 1MNaOH at150 C (Hartikainen et al. 1996) and analyzed using UVVisspectrophotometer. Organic matter in sediments was removedby treatment with H2O2 and digested using triacid (HCl+HNO3+HF) method and were analyzed for total sulfur usingDRC 3000 Elan, Perkin Elmer ICP-MS at Institute Instrumen-tation Centre, I.I.T Roorkee. The USGS standard SCO-1 wasused to calibrate the instrument for total sulfur analysis.
Phosphorus fractionation in sediment samples were carried outfollowing SEDEX method (Table 1, Ruttenberg 1992). Themajor fractions determined were exchangeable; iron bound;authigenic apatite, calcium carbonate, and biogenic apatitebound; and detrital apatite bound and organic matter bound.
The dried sediment samples were homogenously grinded,from which 0.5 g of the sample was used for phosphorus frac-tionation. A rotary shaker was used for shaking the samples. Allexperiments were carried out at room temperature. The sampleswere washed with specific reagents and millipore water afterevery step and were added to the previously extracted fraction.
Major oxides and nutrients
The major oxide composition of sediments is presented inTable 2. Silica (SiO2) is the dominant oxide in lakes (3762%), followed byAl2O3 andCaO in theNainital Lake,whereasother lakes show high Fe2O3 (T). Other oxides, K2O and Na2O,are almost constant throughout the core (13 %) in the lakes.
Phosphorus concentration (Table 2) is high inNainital and Sattal lake sediments (>0.3 %) comparedto other two lakes (
of Nainital Lake is higher (1,7603,000 mg/kg) compared toother three lakes shows increasing up core trend. Other threelakes have comparatively low sulfur content with concentra-tion varying between 5991,762 mg/kg (Bhimtal), 1,7002,100 mg/kg (Sattal) and 8991,466 mg/kg (Naukuchiatal),respectively. The biogenic silica (Table 3) shows an oppositetrend with Nainital Lake shows lesser concentration (3001,200 mg/kg) compared to other three lakes (>300 mg/kg).
Biogenic apatite+calcium carbonate bound fraction(Fig. 2ad) contains most of the phosphorus (>90 %) andshows a decreasing trend up core. Exchangeable fraction isthe next dominant fraction in Nainital and Bhimtal, followed
by organic fraction. In Sattal Lake, phosphorus is predominant-ly associated with reducible fraction followed by organic frac-tion, whereas in Naukuchiatal Lake, phosphorus is associatedwith biogenic apatite+calcium carbonate bound fraction.
The major oxide chemistry of lakes shows similar trend to thecatchment lithology. High concentration of CaO and MgO inNainital Lake (Table 2) may be due to presence of calcareousrocks such as limestone, dolomite, and calcareous shales in thecatchment area. The major oxide chemistry of other threelakes are similar to that of Bhimtal formation and BhowaliQuartzites (Raina and Dungrakoti 1975; Bhat and Ahmad1987) and metabasites of Bhimtal and Bhowali area(Varadarajan 1974) indicating major influence of catchmentlithology in sediment compositions. The high silica concen-tration in lakes may be due to partial dissolution of silica inamygdules of basalts and quartzites.
Sulfur concentration in lakes shows that Nainital Lake(Table 3) is enriched in sulfur compared to other lakes. This
Table 1 Brief outline of SEDEX extraction procedure (Ruttenberg 1992)
Fraction Reagent Reaction time (h)
Exchangeable andloosely bound P
1 M MgCl2 (pH=8.0) 2
Fe bound P Sodium (0.3 M) citrate,(1 M) bicarbonate,and 1.25 g dithionite(pH=7.6)
Authigenic apatite,CaCO3 bound P,and biogenic apatite
1 M sodium acetate buffer(pH=4.0 with acetic acid)
Detrital P 1 M HCl 16
Organic P Ash (@ 550 C)+1 M HCl 16
Fig. 1 Geological and location map of the study area (modified after, Valdiya 1988); inset Geology of the Naukuchiatal (modified after Bartarya 1993)
Arab J Geosci
may be due to the presence rocks of Krol B formation whichconsists of minerals like pyrite and gypsum, in the catchmentarea (Nautiyal 1955). The domestic effluent discharge in toNainital Lake may also add significant amount of sulfur. Lowconcentration/absence of sulfur bearing minerals might be re-sponsible for low concentration of sulfur in other three lakes.
It has been shown that bacteria, algae, and high plants usesilica for their growth. Silica is deposited as thin (100 nm)amorphous and often granular crusts which coat the wall(Coradin and Lopez 2003). Silica present in the cells oforganisms is termed as biogenic silica. Diatoms frustules arethe dominant organisms possessing silica and hence are con-sidered to be the source of major part of the biogenic silica,and thus, concentration of biogenic silica is directly propor-tional to amount of diatoms in sediments. Diatoms frustulessettle faster from water column, and their slow rate of disso-lution causes high concentration of biogenic silica in
sediments. The low concentration of biogenic silica inNainital Lake (Table 3) might be due to absence of abundantdiatoms in the lake (Pant et al. 1980). Increasing concentrationof biogenic silica with depth is due to the presence of diatomsand consequently lesser dissolution rate of the diatoms(Teodoru et al. 2006).
Phosphorus in lake sediments is obtained from lithology andthrough domestic wastes and agricultural runoff (Ruttenberg2004). Total phosphorus concentration in Nainital and Sattallakes is similar to that of total phosphorus of major moderatelyeutrophic to hyper eutrophic lakes around the world (Table 4).Total phosphorus concentrations in lakes differ widely irre-spective of their trophic status. The concentration of totalphosphorus in lakes Vesijarivi (Hartikainen et al. 1996), On-ondaga (Penn and Auer 1997), Apopka, and Okeechobe (Olilaand Reddy 1997) is much higher compared to the KumaunHimalayan lakes which may be due to the increased urbani-zation and pollution in lakes. The lake Erken (Rydin 2000),
Table 2 Major oxides in sediments at different depths (in %)
Depth (cm) CaO MgO Na2O K2O Al2O3 P2O5 Fe2O3 (T)
02 12.6 3.5 0.3 2.6 10.1 0.4 4.7
46 6.1 3.2 0.3 2.5 9.7 0.4 3.7
1012 5.4 3.5 0.3 2.6 10.2 0.4 3.8
1618 3.1 3.9 0.4 2.8 11.3 0.3 4.3
2224 2.5 3.9 0.4 2.9 11.4 0.3 4.5
2830 3.0 4.2 0.4 2.8 11.3 0.3 4.4
02 1.4 7.5 0.5 1.5 11.6 0.2 13.3
46 1.2 8.1 0.5 1.5 11.8 0.2 13.9
1012 1.0 7.8 0.6 1.5 12.0 0.2 13.7
1618 1.0 7.7 0.6 1.5 11.7 0.2 13.4
2224 1.0 8.8 0.7 1.5 12.2 0.2 14.8
2830 1.1 8.6 0.9 1.5 12.4 0.2 12.3
3436 1.0 9.6 0.7 1.5 12.9 0.2 15.5
04 0.6 2.4 0.3 2.5 10.4 0.4 7.6
46 0.5 2.3 0.3 2.5 11.4 0.4 7.4
1012 0.5 2.4 0.3 2.7 12.2 0.3 7.3
1618 0.6 2.5 0.3 3.3 12.9 0.2 7.6
2224 0.7 2.3 0.3 2.9 12.0 0.5 7.7
2628 0.5 2.5 0.3 3.8 15.3 0.3 8.6
04 1.2 2.9 0.5 1.5 9.0 0.2 7.2
46 1.2 3.1 0.6 1.7 10.0 0.1 7.3
1012 1.2 0.0 0.6 1.7 9.6 0.1 7.2
1618 1.2 2.8 0.6 1.6 8.2 0.1 6.7
2224 1.2 2.9 0.6 1.7 8.6 0.1 7.1
Table 3 Total sulfur, nitrogen, and biogenic silica in sediments of dif-ferent depths in the lakes
Depth (cm) Total sulfur (mg/kg) Biogenic silica (mg/kg)
05 2872.3 429.7
510 3014.2 297.2
1015 2716.0 491.3
1520 1323.8 235.6
2025 2717.1 415.8
2530 2891.9 1217.0
3035 1770.1 2507.0
05 1762.4 4,366.0
510 1243.6 4,130.0
1015 1318.1 4,204.0
1520 1028.0 3,845.0
2025 599.7 3,533.0
05 1700.1 3,282.0
510 1547.6 3,157.0
1015 1771.0 3,256.0...