relationships of heavy metals in natural lake waters with physicochemical characteristics of waters...

Relationships of Heavy Metals in Natural Lake Waterswith Physico-chemical Characteristics of Watersand Different Chemical Fractions of Metals in Sediments

Ajay P. Singh & Prakash C. Srivastava &

Prashant Srivastava

Received: 25 June 2007 /Accepted: 1 October 2007 / Published online: 16 November 2007# Springer Science + Business Media B.V. 2007

Abstract The relationships between heavy metalconcentrations and physico-chemical properties ofnatural lake waters and also with chemical fractionsof these metals in lake sediments were investigated inseven natural lakes of Kumaun region of UttarakhandProvince of India during 2003–2004 and 2004–2005.The concentrations of Cr, Mn, Fe, Ni, Cu, Zn, Cdand Pb in waters of different lakes ranged from 0.29–2.39, 10.3–38.3, 431–1407, 1.0–6.6, 5.3–12.1, 12.6–166.3, 0.7–2.7 and 3.9–27.1 μg l−1 and in sediments14.3–21.5, 90.1–197.5, 5,265–6,428, 17.7–45.9,13.4–32.0, 40.0–149.2, 11.1–14.6 and 88.9–167.4 μg g−1, respectively. The concentrations ofall metals except Fe in waters were found well belowthe notified toxic limits. The concentrations of Cr,Mn, Ni, Cu, Zn, Cd and Pb were positivelycorrelated with pH, electrical conductivity, biologicaloxygen demand, chemical oxygen demand andalkalinity of waters, but negatively correlated withdissolved oxygen. The concentrations of Cr, Ni, Zn,

Cd and Pb in waters were positively correlated withwater soluble + exchangeable fraction of these metalsin lake sediments. The concentrations of Zn, Cd andPb in waters were positively correlated with carbon-ate bound fraction of these metals in lake sediments.Except for Ni, Zn and Cd, the concentrations of restof the heavy metals in waters were positivelycorrelated with organically bound fraction of thesemetals in lake sediments. The concentrations of Cr,Mn, Ni, Cu and Zn in waters were positivelycorrelated with reducible fraction of these metals inlake sediments. Except for Cd, the concentrations ofrest of the metals in waters were positively correlatedwith residual fraction and total content of theseheavy metals in lake sediments.

Keywords Chemical fractions . Heavymetals . Lakes .

Sediments .Water

1 Introduction

Toxic levels of heavy metals in waters and sedimentsmay impose serious threat to aquatic species as wellas humans. The concentrations of heavy metals innatural water bodies are often elevated due toanthropogenic interferences. Investigations on heavymetals in natural waters have received considerableattention as they provide a coded history of lake’senvironment (Riggey et al. 1982; Pennington 1982;

Water Air Soil Pollut (2008) 188:181–193DOI 10.1007/s11270-007-9534-6

A. P. Singh : P. C. Srivastava : P. SrivastavaDepartment of Soil Science,G. B. Pant University of Agriculture and Technology,Pantnagar, UA 263145, India

P. Srivastava (*)Savannah River Ecology Laboratory,The University of Georgia,P.O. Drawer E,Aiken, SC 29802, USAe-mail: [email protected]

Forstner 1976; Forstner and Wittamann 1981; Siva-kumar et al. 2000). It has also been established thatthe damage to aquatic ecosystem owing to heavymetals is mainly a function of bio-available metalfraction rather than the total amount of metal presentin waters or in sediments (Chester and Voutsinou1981; Waldichuk 1985). Hence, to assess the extent ofpollution hazard and to understand the dynamics ofheavy metals in natural water bodies, the intensities ofdifferent chemical fractions of heavy metals in sedi-ments have to be looked into besides the total amountof metals in waters and sediments.

2 Materials and Methods

The present investigation was undertaken in Nainitallake region in Uttarakhand province of India (Fig. 1),which comprises seven important natural lakes andlies between 29°18′–29°22′N latitudes and 79°31′–79°36′E longitudes between the altitude range of1,270 to 1,935 m above mean sea level (msl). Waterand sediment samples were collected from Bhimtal(altitude: 1,346 m above msl), Naukuchiatal (altitude:1,300 m above msl), Punatal (also known asGaruntal; altitude: 1,270 m above msl), Sattalcomprising Sitatal, Ramtal and Hanumantal (altitude:1,280 m above msl) and Nainital (altitude: 1,935 mabove msl) of Nainital district. Water samples were

collected in air-tight plastic cans following standardprocedure (APHA 1998) in four seasons, viz.,summer (June), autumn (September), winter (Decem-ber) and spring (March) during 2003–2004 and2004–2005. Sediment samples were collected insummer season at a distance of 5–7 m from the shoreat 1–1.25 m depth using core samplers with closedend. After collection, the sediment samples wereimmediately transferred in thick plastic bags and carewas taken not to allow direct contact with theatmospheric air.

Water samples were transported to the laboratorylocated at an elevation of 243.8 m above msl andanalysed for pH, electrical conductivity (EC), dis-solved oxygen (DO), biological oxygen demand(BOD), chemical oxygen demand (COD) and alka-linity HCO�

3

� �by using standard methods (APHA

1998). Sediment samples were passed through a2 mm sieve. Mechanical analysis of sediments wasdone by Bouyoucos hydrometer method (Bouyoucos1927). Sediment pH and EC were measured in 1:2sediment water suspension (Jackson 1973) using pHmeter and EC meter, respectively. The EC of sedi-ments was expressed in dS m−1 at 25°C. Total carbonin lake sediments was analysed by adopting themethod outlined by Page et al. (1982). Readilyoxidized C content was determined following modi-fied Walkley and Black’s method as described byJackson (1973). Carbonate in sediment samples was

Fig. 1 Location of natural lakes (shown as white dots) in Nainital district of Uttarakhand province of India

182 Water Air Soil Pollut (2008) 188:181–193

measured by acid neutralization method as describedby Schollenberger (1945).

For analysis of different chemical fractions ofheavy metals, 3 g fresh sediment portions were placedinto 50 ml polycarbonate centrifuge tubes. Anequivalent amount of sediment was oven dried at105°C for 48 h to express the content of heavy metalson dry weight basis. Wet sediment sample placed incentrifuge tube was sequentially extracted as per thescheme given by Ahnstrom and Parker (1999) toobtain the following five operationally defined frac-tions of heavy metals:

F1 (soluble + exchangeable form): Two extrac-tions with 0.1 M Sr(NO3)2F2 (specifically sorbed and carbonate boundform): One extraction with 1 M NaOAc (pH 5.0)F3 (organically bound or oxidisable fraction):Three extractions with 5% NaOCl (pH 8.5) at 9–95°CF4 (reducible form): Three extractions with 0.2 Moxalic acid + 0.2 M ammonium oxalate + 0.1 Mascorbic acid (pH 3.0)F5 (residual fraction): Dissolution of remainingamount of metals in sample through HF–HClO4

digestion

The concentrations of heavy metals (Cr, Mn, Fe,Ni, Cu, Zn, Cd and Pb) in waters and differentsediment extracts were analysed by using atomicadsorption spectrophotometry (GBC: Avanta-M) asper the procedure described by APHA (1998).

3 Results and Discussion

3.1 Physicochemical Properties of Waters

Seasonal variations were noted in the physico-chem-ical properties of waters (Fig. 2). Different propertieslike pH, EC, HCO�

3 , BOD and COD showedmaximum values during summer, while minimumvalues were recorded during autumn season. Theobserved trend could be attributed to the evaporationof water from lakes during summer and subsequentdilution due to precipitation and run-off from thecatchment area during rainy season (Bhatt et al. 1999;Radhika et al. 2004). High pH of waters duringsummer could be ascribed to increased photosynthet-ic assimilation of dissolved inorganic carbon by

planktons (Farrell et al. 1979; Goldman 1972; King1970). A similar effect could also be produced bywater evaporation through the loss of half bound CO2

and precipitation of mono-carbonate (Khan andChowdhary 1994).

The alkaline pH and high alkalinity of lake watersmight be due to the use of detergents by neighbouringpopulation for washing of clothes, vehicles andutensils. A wash off from area having calcite anddolomite minerals could also partly contribute toalkalinity (Paka and Rao 1997a, b). Higher alkalinityindicated the potential susceptibility of these waterbodies for eutrophication. Water body with alkalinityvalues above 100 mg l−1 is considered nutritionally rich(Spence 1967) and on the basis of this observationmost of lakes of Nainital district could be consideredprone to eutrophication problem.

Low dissolved oxygen during summer might alsobe due to anticipated higher microbial activities.Decomposition of organic matter might be an impor-tant factor in consumption of dissolved oxygen, asmore vigorous deposition could be likely during warmweather, which also witnessed increased inflow oftourists in the region (Bagde and Verma 1985). The re-oxygenation of waters during monsoon might beoccurring due to circulation and mixing by inflowafter monsoon rains (Hannan 1978).

3.2 Heavy Metal Concentrations in Waters

Seasonal variations in different heavy metal concen-trations in water from different lakes are presented inFig. 3. The concentrations of heavy metals in water ofnatural lakes remained well below the toxic limits(WHO 1988). A remarkably high concentration of Fein the water of these lakes indicated that this metalwas abundant in soil and rocks of the catchment areafrom where the water reaches to these lakes. Asregards the effect of season on heavy metalconcentration in the water of different lakes, con-centrations of metals like Cd, Cr, Cu, Fe, Mn, Ni,Pb and Zn were maximum during summer, whileminimum concentrations were observed during au-tumn season. This trend could be attributed to theevaporation of water from lakes during summer andsubsequent dilution due to precipitation and run-offfrom the catchment area during rainy season (Jainand Salman 1995; Paka and Rao 1997a, b; Patil et al.2004).

Water Air Soil Pollut (2008) 188:181–193 183

Fig. 2 Some physicochemical properties of water of different lakes


Fig. 3 Seasonal variation in different heavy metal concentrations in water of different lakes


3.3 Physicochemical Properties of Sediments

The averaged data of 2 years on physicochemicalproperties of sediments from different lakes arepresented in Table 1. The values averaged over yearsfor different lakes indicated that the highest claycontent was found in Nainital (24.5%) followed byRamtal (23.7%), Punatal (23.0%), Hanumantal(21.07%), Sitatal (20.7%), Bhimtal (16.2%) andNaukuchiatal (9.3%).

The silt content values averaged over years fordifferent lakes revealed that the silt content variedfrom 2.2 (Nainital) to 5.5% (Bhimtal), whereas siltcontent in Naukuchiatal, Sitatal, Punatal, Ramtal andHanumantal were found to be 3.5, 3.3, 2.7, 2.7 and2.5%, respectively.

Yearly averaged values of sand content fromdifferent lakes (Table 1) indicated that the highestsand content was found in Naukuchiatal (87.2%)followed by Bhimtal (78.3%), Punatal (74.3%),Hanumantal (76.5%), Sitatal (76.0%), Ramtal(73.7%) and Nainital (73.3%).

The values averaged over years for different lakesindicated that the highest CaCO3 equivalent wasfound in Nainital (37.55%) followed by Bhimtal(14.89%), Ramtal (11.56%), Hanumantal (9.90%),Sitatal (9.83), Punatal (4.25%) and Naukuchiatal(2.65%). The carbonate content of lake sedimentsindicated the dominance of carbonate minerals in thecatchment area, from where eroded material andrunoff bring mineral solids and a possible generationof insoluble carbonates in aquatic environment rich inalkaline earth metals.

Yearly averaged pH values for different lakesindicated that the highest pH was found in Nainital(8.89) followed by Bhimtal (8.81), Ramtal (8.11),Hanumantal (8.10), Sitatal (8.09), Punatal (7.98) and

Naukuchiatal (7.85). In general, the pH of the sedi-ments of these lakes was alkaline. Relatively higherpH in sediments of Nainital and Bhimtal might be dueto high CaCO3 content.

The EC values of the sediments (Table 1) showedthat Nainital had the highest EC (0.229 mS cm−1)followed by Bhimtal (0.189 mS cm−1), Hanumantal(0.148 mS cm−1), Sitatal (0.143 mS cm−1), Ramtal(0.139 mS cm−1), Naukuchiatal (0.122 mS cm−1) andPunatal (0.093 mS cm−1).

Yearly averaged values for different lakes indicatedthat the highest total carbon (TC) percentage wasfound in Naukuchiatal (2.37%) followed by Bhimtal(1.11%), Nainital (1.00%), Hanumantal (0.68%),Punatal (0.63%), Sitatal (0.60%) and Ramtal(0.55%). The values of readily oxidisable carbon(ROC) averaged over years for different lakesindicated that the highest readily oxidisable carbonwas found in Naukuchiatal (1.027%) followed byNainital (0.68%), Bhimtal (0.54%), Punatal andHanumantal (0.22%) and Sitatal and Ramtal(0.20%). Highest contents of readily oxidisable carbonand total carbon in Naukuchiatal could be attributed toa lotus pond attached to main water body and also toleaf fall from the surrounding dense vegetation.Higher contents of readily oxidisable carbon and totalcarbon in Bhimtal and Nainital could be partlyattributed to a big flock of ducks inhabiting theselakes and to increased anthropogenic interferences dueto large tourist inflow to these recreation spots.

In lake sediments, the contents of total Cr, Mn, Fe,Ni, Cu, Zn, Cd and Pb ranged from 14.3–21.5, 90.1–197.5, 5265–6428, 17.7–45.9, 13.4–32.0, 40.0–149.2,11.1–14.6 and 88.9–167.4 μg g−1, respectively (Datanot shown). Except for Fe, the total content of heavymetals in sediments was highest for Nainital andNaukuchiatal and lowest for Ramtal and Sitatal.

Lake Clay(%)

Silt(%)

Sand(%)

pH(2:1)

EC (2:1)(mS cm−1)

ROC(%)

TC(%)

CaCO3

equivalent (%)

Bhimtal 16.2 5.5 78.3 8.81 0.189 0.54 1.11 14.89Naukuchiatal 9.3 3.5 87.2 7.85 0.122 1.02 2.37 2.65Punatal 23.0 2.7 74.3 7.98 0.094 0.22 0.63 4.25Sitatal 207 3.3 76.0 8.09 0.144 0.20 0.60 9.83Ramtal 23.7 2.7 73.7 8.11 0.139 0.20 0.55 11.56Hanumantal 21.0 2.5 76.5 8.10 0.148 0.22 0.68 9.90Nainital 24.5 2.2 73.3 8.89 0.229 0.68 1.00 37.55CD (p=0.05) 1.0 0.7 1.3 0.15 0.003 0.04 0.13 0.72

Table 1 Physicochemicalproperties of sediments


3.4 Chemical Fractions of Heavy Metals in Sedimentsof Different Lakes

Chemical fractions of heavy metals viz. water solubleand exchangeable (F1), NaOAc extractable (F2),organically bound (oxidisable) (F3), Fe and Mn oxidebound (reducible) (F4) and residual (F5) in sedimentsof different lakes are presented in Fig. 4. The residual(Cr–F5) fraction was the most dominant fraction of Crin the sediments of all lakes. Lindau and Hossner(1982) noted about 87% of total Cr to be associatedwith alkaline and silicate minerals. Iron and Mn-oxidebound (Cr–F4) fraction represented the second mostdominant fraction in lake sediments. A close associ-ation of Cr content with Fe-oxide has been reportedby Zachara et al. (1989). On an average, carbonatebound (Cr–F2) fraction was the third dominantfraction of Cr in lake sediments. Interestingly, thehighest content of this fraction was recorded inNainital, which also had the highest CaCO3% andthis indicated affinity of reduced form of Cr3+ withcarbonates.

Both water soluble + exchangeable (Cr–F1) andorganically bound (Cr–F3) fractions represented al-most similar dominance. Under anoxic conditionsprevailing in lakes, higher solubility of Cr due toreduction appeared to be the case in lake sediments.On an average, only 2.75% of total Cr was found tobe associated with organic matter.

Like Cr, residual (Mn–F5) fraction represented themost dominant fraction of Mn in lake sediments. Thiswas expected as the lakes received most of Mn supplythrough suspended particulates coming along withrunoff. Lindau and Hossner (1982) noted that innatural marshes 53% of Mn was locked in residualfraction. Manganese–F2 fraction represented the secondmost dominant fraction of Mn in lake sediments. Thehighest content of Mn–F2 was recorded in Nainital,which also had the highest CaCO3 content in sedi-ments. Manganese is one of the micronutrient cations,which has been reported to get fixed on the surface ofCaCO3 particulates (Lindau and Hossner 1982).

Iron and Mn-oxide (Mn–F4) fraction representedthe third most dominant fraction of Mn in lakesediments. Lindau and Hossner (1982) also notedthat 11% of Mn in natural marshes existed as easilyreducible fraction and attributed it to gradual trans-formation of Mn(OH)2 associated with suspendedmatter into residual phase. The next dominant fraction

of Mn in lake sediment was organically bound (Mn–F3) fraction. Manganese is known to be complexedwith water soluble and insoluble fractions of organicmatter. The insoluble fraction, especially underalkaline pH conditions binds Mn irreversibly, whilewater soluble fraction is known to enhance thesolubility of Mn (Page 1962). Water soluble +exchangeable (Mn–F1) fraction represented the small-est fraction of Mn in lake sediments and it wasanticipated owing to alkaline pH of lake sediments.The solubility of Mn is reported to decrease 100-foldfor each unit increase in pH (Lindsay 1972).

As regards the distribution of Fe in differentchemical fractions in lake sediments, residual (Fe–F5) fraction was the most dominant fraction, as itrepresented 88.18 to 93.42% of total Fe. Chester andHughes (1969) noted that about 85% of the sedimentFe was fixed in residual phase of deep sea sediments.Iron associated with reducible fraction (Fe–F4) repre-sented the second most dominant fraction accountingfor only 5.56 to 10.66% of total Fe in lake sediments.Lindau and Hossner (1982) also observed similarbehaviour and attributed the same to transformation ofFe oxides associated with suspended materials andgradual incorporation in other chemical fractions.

Organically bound (Fe–F3) fraction represented onan average the third most abundant fraction in lakesediments. Organic matter is known to form com-plexes with Fe. Overall, low values of this fractionindicated that it possibly existed as insoluble staticfraction. Carbonate bound (Fe–F2) fraction repre-sented 0.10 to 2.33% of total Fe and the highest valuewas recorded in Nainital, which also had the highestCaCO3 equivalent percent. Water soluble and ex-changeable (Fe–F1) fraction represented the smallestfraction (0.03 to 0.06% of total Fe) in lake sediments.Such behaviour was anticipated in view of alkaline pHof lake sediments. Lindsay (1984) reported minimumsolubility of Fe in the pH range of 7.4 to 8.5.

The relative distribution of Ni in different chemicalfractions in lake sediments indicated that the residual(Ni–F5) fraction represented the most dominantfraction as it accounted for 33.98 to 63.66% of totalNi in lake sediments. Lindau and Hossner (1982)found that about 53% of total Ni in sediments wasfixed in the residual fraction. Next to residual fraction,the second most dominant fraction was organicallybound (Ni–F3) fraction, which represented 12.52 to25.55% of total Ni. These findings were in concor-


Fig. 4 Chemical fractions of different heavy metals


dance to those of Lindau and Hossner (1982).Carbonate bound (Ni–F2) fraction was the third mostdominant fraction of Ni (representing 13.94 to29.64% of total Ni). The carbonate fraction wasrelatively higher in Bhimtal, although highest CaCO3

equivalent percent was observed in Nainital. Thisindicated that the nature of carbonates might also playa possible role in trapping this heavy metal. Iron andmanganese oxide bound (Ni–F4) fraction accountedfor 7.28 to 11.49% total Ni. Sesquioxides, especiallyMn oxides are known to retain Ni in sediments(Lindau and Hossner 1982). Water soluble + ex-changeable (Ni–F1) fraction represented the leastdominant fraction of Ni and accounted for on anaverage 4.81% of total Ni.

The distribution of Cu among different chemicalfractions in lake sediments indicated that the residual(Ni–F5) fraction was the most dominant fraction(representing 25.32 to 60.40% of total Cu) followedby the reducible (Cu–F4) fraction wherein Cu isoccluded by Fe and Mn oxides. Lindau and Hossner(1982) reported that especially Mn oxides have agreater effect on occlusion of Cu and Ni as comparedto Fe-oxides. Carbonate bound (Cu–F2) fraction wasthe third most dominant fraction, which represented3.59 to 29.59% of total Cu in lake sediments. Dudleyet al. (1988) reported that Cu being adsorbed by fineparticles of CaCO3 gets precipitated as Cu(OH)2 andCu(OH)CO3. The fraction of Cu associated withorganic matter (Cu–F3) represented 2.73 to 8.53% oftotal Cu. Copper is known to form complexes withboth soluble and insoluble organic matter. In general,the lesser proportion of Cu associated with organicmatter could be attributed to its uptake by planktonsand/or leaching over years (Lindau and Hossner 1982).

Water soluble + exchangeable (Cu–F1) fraction ofCu represented only 1.04 to 2.82% of total Cu.Lindau and Hossner (1982) worked on experimentaland natural marshes and noted that on an average<2% Cu and Ni was associated with this fraction.

The relative distribution of different chemicalfractions of Zn in lake sediments indicated that theresidual (Zn–F5) fraction was the most dominantfraction as it accounted for 57.85 to 78.24% of totalZn. This behaviour could be attributed to bothlithophile and chalcophile nature of Zn. Gupta andChen (1975) reported that 23 to 42% of Zn waslocked as residual phase in Los Angeles Harboursediments.

Zinc associated with reducible (Zn–F4) fractionrepresented the second largest fraction, whichaccounted for 6.80 to 28.48% of total Zn. In thispool, Zn is likely to exist in occluded form in Fe–Mnoxides. Carbonate bound (Zn–F2) fraction appeared tobe the third most dominant fraction, which represents4.52 to 9.74% of total Zn in lake sediments. Thehighest accumulation of this fraction was noted inNainital, which also had the highest accumulation ofCaCO3. Like Cu, Zn is also precipitated on thesurface of carbonate as hydroxide and/or hydroxidecarbonate.

Organically bound (Zn–F3) fraction represented2.42 to 15.13% of total Zn in lake sediments. Such awide variation in this fraction might possibly berelated to the variations in the organic matteraccumulated in the sediments of different lakes. Watersoluble and exchangeable (Zn–F1) fraction repre-sented only 1.52 to 3.53% of total Zn. Lindau andHossner (1982) noted that about 4% of total Znexisted as water soluble and exchangeable fraction inthe Pepper Grove and Jamaica Beach substratesamples.

The relative distribution of different chemicalfractions of Cd in lake sediments indicated that theresidual (Cd–F5) fraction was the most dominantfraction as it accounted for 69.22 to 78.10% of totalCd and the same could be attributed to chalcophilenature of Cd, especially under aquatic ecosystem.Carbonate bound (Cd–F2) fraction was the secondmost dominant fraction and represented 11.95 to18.25% of total Cd. The highest value of this fractionwas recorded in Nainital, which also had the highestcontent of CaCO3.

Water soluble + exchangeable (Cd–F1) fractionrepresented the third most dominant fraction of Cd inlake sediments. Relatively higher amount of Cd inthis chemical fraction possibly indicated the solubili-sation of Cd by soluble organic matter present inwater in alkaline pH range. Organically bound (Cd–F3) fraction represented 2.76 to 6.17% of total Cd andthe highest proportion of this fraction was noted inNaukuchiatal, which also had the highest readilyoxidisable carbon and total carbon. Interestingly,reducible (Cd–F4) fraction represented only 2.18 to4.98% of total Cd in lake sediments and this might beattributed to greater affinity of Cd to carbonates ratherthan sesquioxides in mixed mineral matrix of lakesediments.


The relative distribution of different chemicalfractions of Pb in lake sediments revealed that theresidual (Pb–F5) fraction was the most dominantfraction as it accounted for 72.92 to 85.42% of totalPb. This behaviour could be attributed to bothlithophile and chalcophile nature of Pb. Like Cd,carbonate bound (Pb–F2) fraction was the secondmost dominant fraction, which accounted for 3.96 to10.75% of total Pb in lake sediments.

Water soluble + exchangeable (Pb–F1) fractionwas the third most dominant fraction, whichaccounted for 3.74 to 6.35% of total Pb in lakesediments. Reducible (Pb–F4) fraction represented3.01 to 8.39% of total Pb in lake sediments. Thus,similar to Cd, Pb also exhibited higher preference tocarbonate minerals rather than Fe–Mn oxides in lakesediments. Organically bound (Pb–F3) fraction repre-sented 0.80 to 2.24% of total Pb. Lead is known toform insoluble and stable chelates with organicmatter. However, under submerged conditions thepresence of organic matter possibly solubilized Pband thus, the fraction reported in this study indicatedonly insoluble and stable fraction of Pb associatedwith organic matter.

3.5 Relationship between Physico-chemicalProperties of Waters and Concentration of HeavyMetals in Waters

Simple correlation coefficients (r) computed betweenphysico-chemical properties and concentrations ofdifferent heavy metals in water from different lakesare presented in Table 2. The concentrations of Cd,Cr, Cu, Mn, Ni, Pb and Zn were significantly andpositively correlated with pH, EC, BOD, COD andalkalinity of waters at p=0.01. The concentrations ofCd, Cr, Cu, Mn, Ni, Pb and Zn were significantly and

negatively correlated with DO at p=0.01. Theconcentration of Fe in waters was statistically notcorrelated with any physico-chemical properties ofwaters considered here.

3.6 Relationship between Metal Concentrations inWaters with their Different Chemical Fractions inSediments

Simple correlation coefficients (r) computed betweenthe concentrations of metal in waters and theirdifferent chemical fractions in sediments of differentlakes are presented in Table 3. The concentration ofCr in the water of different lakes was significantly andpositively correlated with water soluble + exchange-able (Cr–F1), organically bound (Cr–F3) and residual(Cr–F5) fractions and total Cr content of the sedi-ments at p=0.01 and with Fe–Mn oxide boundfraction (Cr–F4) at p=0.05, respectively.

The concentration of Mn in the water of differentlakes was significantly and positively correlated withorganically bound (Mn–F3), Fe–Mn oxide bound(Mn–F4) and residual (Mn–F5) fractions and totalMn content of the sediments at p=0.01.

The concentration of Fe in the water of differentlakes was significantly and positively correlated withresidual (Fe–F5) fraction of the sediments at p=0.01and with organically bound fraction (Fe–F3) and totaliron content at p=0.05, respectively.

The concentration of Ni in the water of differentlakes was significantly and positively correlated withwater soluble + exchangeable fraction (Ni–F1) andtotal Ni content of the sediments at p=0.01 and withFe–Mn oxide bound (Ni–F4) and residual (Ni–F5)fractions at p=0.05, respectively.

The concentration of Cu in the water of differentlakes was significantly and positively correlated with

Table 2 Relationship between physico-chemical properties of waters and concentration of heavy metals in waters from different lakes

Cr Mn Fe Ni Cu Zn Cd Pb

pH 0.389** 0.555** 0.009 0.842** 0.381** 0.890** 0.569** 0.709**EC 0.385** 0.648** −0.053 0.879** 0.224 0.910** 0.562** 0.815**DO −0.267* −0.588** 0.024 −0.872** −0.264* −0.907** −0.518** −0.732**BOD 0.515** 0.743** 0.099 0.757** 0.601** 0.897** 0.549** 0.774**COD 0.339** 0.641** 0.020 0.876** 0.348** 0.922** 0.553** 0.791**Alkalinity 0.441** 0.733** 0.102 0.817** 0.398** 0.900** 0.659** 0.826**

*Significant at p=0.05

**Significant at p=0.01


organically bound (Cu–F3), Fe–Mn oxide bound (Cu–F4) and residual (Cu–F5) fractions and total Cucontent of the sediments at p=0.01.

The concentration of Zn in the water of differentlakes was significantly and positively correlated withwater soluble + exchangeable (Zn–F1), CaCO3 bound(Zn–F2), Fe–Mn oxide bound (Zn–F4) and residual(Zn–F5) fractions and total zinc content of the sedi-ments at p=0.01.

The concentration of Cd in the water of differentlakes was significantly and positively correlated withwater soluble + exchangeable fraction (Cd–F1) at p=0.01 and CaCO3 bound (Cd–F2) fractions of thesediments at p=0.05, respectively.

The concentration of Pb in the water of differentlakes was significantly and positively correlated withwater soluble + exchangeable (Pb–F1) fraction andtotal Pb content at p=0.01 and CaCO3 bound (Pb–F2),organically bound (Pb–F3) and residual (Pb–F5)fractions of the sediments at p=0.05, respectively.

The relationships between the concentrations ofdifferent metals in waters and the intensity of differentchemical fractions of respective metals indicated thestate of dynamic equilibrium through which thesechemicals fractions contribute directly or indirectly toambient water in the aquatic ecosystem.

Water soluble + exchangeable fraction of metals insediments indicates the chemical fraction in readyequilibrium with ambient water. A significant andpositive correlation between concentrations of Cd, Cr,Ni, Pb and Zn with this chemical pool indicated theeasy establishment of equilibrium in respect of thesemetals. The concentrations of Cd, Pb and Zn in watersshowed significant and positive correlation withcarbonate bound fractions of these metals in sedi-

ments. This kind of behaviour is attributed to theaffinity of these elements to form sparingly solublecarbonate salts, which might release these metalsunder aquatic environment.

The concentrations of Cr, Cu, Fe, Mn and Pb inwaters had significant and positive correlation withorganically bound fraction of these metals. Thesemetals are known to form organo-metallic complexeswith organic matter, which might release these metalsdepending upon their stability constants and prevail-ing physico-chemical conditions.

The concentrations of Cr, Cu, Mn, Ni and Zn inwaters had significant and positive correlation withFe–Mn oxide bound fraction. Iron and Mn-oxide areknown sinks of metals, especially heavy metals inaquatic system. These oxides are amphoteric in natureand develop charges depending upon the prevailingpH of the system. Since the pH of waters wasalkaline, the oxides would have negative chargesand could be expected to hold cations partly in non-specifically bound form.

The concentrations of all cations except Cd inwaters had significant and positive correlation withresidual fraction of these metals. The residual fractionis likely to hold these metals either as a structuralconstituent of their mineral lattice structure or asdiscrete precipitate of insoluble sulphides etc. Underanaerobic conditions, some part of residual fraction islikely to release metals.

The concentrations of all metals except Cd showeda significant and positive correlation with the totalcontent of respective metals in sediments. This kindof behaviour is not common in agricultural soils, butcould be expected in aquatic ecosystem where anoxicenvironment prevails.

Water soluble andexchangeable (F1)

Carbonatebound (F2)

Organicallybound (F3)

Fe–Mn oxidebound (F4)

Residual(F5)

Totalcontent

Ca 0.755** 0.754** 0.852** 0.741** 0.760** 0.768**Mg 0.395 0.795** 0.799** 0.784** 0.366 0.582*Cr 0.988** 0.518 0.769** 0.614* 0.786** 0.896**Mn 0.337 0.489 0.767** 0.692** 0.935** 0.953**Fe −0.342 −0.234 0.557* −0.455 0.675** 0.621*Ni 0.989** 0.531 0.139 0.635* 0.958** 0.958**Cu 0.119 0.099 0.931** 0.805** 0.655* 0.785**Zn 0.880** 0.803** 0.034 0.787** 0.866** 0.872**Cd 0.733** 0.594* 0.255 −0.029 0.227 0.388Pb 0.715** 0.570* 0.547* 0.041 0.919** 0.947**

Table 3 Relationship be-tween metal concentrationsin waters with differentchemical fractions of metalsin sediments of differentlakes

*Significant at p=0.05

**Significant at p=0.01


4 Conclusions

The concentrations of heavy metals and other waterquality parameters undergo seasonal changes and thevalues are generally higher during summer. Theproblem of heavy metal contamination was notserious in the water of these natural lakes. Theconcentrations of heavy metals in waters are relatedto different physico-chemical properties of waters.The concentrations of Cd, Cr, Ni, Pb and Zn in watersare closely related to water soluble + exchangeablefraction of these heavy metals in lake sediments.However, the bio-availability of metal fractions boundto carbonates, oxides and hydrous-oxides, organicmatter and residual fractions depends upon the natureof metal.

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relationships of heavy metals in natural lake waters with physicochemical characteristics of waters...

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