Evaluating pollution potential of leachate from landﬁll

Environ Monit Assess (2010) 162:327–346DOI 10.1007/s10661-009-0799-7

Evaluating pollution potential of leachate from landfill site,from the Pune metropolitan city and its impact on shallowbasaltic aquifers

Sanjay S. Kale · Ajay K. Kadam · Suyash Kumar ·N. J. Pawar

Received: 29 October 2008 / Accepted: 27 January 2009 / Published online: 20 March 2009© The Author(s) 2009. This article is published with open access at Springerlink.com

Abstract Leachate produced by municipal solidwaste dumping site near the metropolitan city ofPune, India was examined for its pollution poten-tial and impact on surrounding shallow basalticaquifers. Twenty-eight physico-chemical parame-ters during post- and pre-monsoon seasons (Nov2006 and May 2007) were determined to as-sess the seasonal variation in the leachate pollu-tion index (LPI) as well as in the groundwaterquality. The leachate demonstrated higher LPIvalue during pre-monsoon, comparable to those atother metropolises outside India. Potentially toxicleachates derived from the dumping site havelargely influenced the adjoining basaltic aquifersthrough two different modes of transport. Despitehigh contents of heavy metals (Al, Cd, Cr, Cu,

S. S. Kale · A. K. KadamDepartment of Environmental Sciences,University of Pune, Pune 411 007, India

S. S. Kalee-mail: [email protected]

A. K. Kadame-mail: [email protected]

S. Kumar · N. J. Pawar (B)Department of Geology, University of Pune,Pune 411 007, Indiae-mail: [email protected]

S. Kumare-mail: [email protected]

Co, Fe, Mn, Ni, Pb and Zn) in the leachate, theaquifers in the close proximity of landfill site areleast polluted by metallic contaminants possiblydue to redox controls. Various geoenvironmen-tal features governing the dispersal of leachatecontaminants in the basaltic aquifers under semi-arid climatic regime have been identified and dis-cussed. Although a few remedial measures havebeen suggested to mitigate the impact of leachatepercolation and dispersion, the present study de-mands for a proper solid waste management inmetropolitan cities.

Keywords Leachate pollution index · Pune ·Landfill · Basaltic aquifers

Introduction

Leachate is a polluted liquid emanating from thebase of the landfill, which contains innumerableorganic and inorganic compounds (Papadopoulouet al. 2007). The improper collection, segregation,and disposal practices of municipal solid waste(MSW) produce highly concentrated leachates.Dispersal of leachates poses potential threats tolocal ecosystems especially to soils and ground-waters (Jorstad et al. 2004). The composition ofleachate depends upon the nature of solid wasteburied, chemical and biochemical processes re-sponsible for the decomposition of waste materi-als, and water content in total waste (Fatta et al.1999; Mor et al. 2006).

328 Environ Monit Assess (2010) 162:327–346

Leachates generated by the MSW in uncon-trolled landfills have become a major environmen-tal problem in million plus cities across the globe.Despite their hazardous impacts on environment,studies on the topic are sparse, particularly in hardrock landscapes. Groundwater contamination inhard rock terrains like basalts is an enduring sit-uation because of the slow and unstable flow ofwater through constricted passages. There is apredominance of the slower rate of water flowand higher residence times. Moreover, the watermigrates through the matrix of the host rock. Thismechanism, in most of the cases, is good enoughfor restricting the passage of contaminants fromsource to receptors. On the contrary, the pollu-tants are released slowly toward the areas of thesystem with higher permeability, thereby creatingconstant level of contamination and maintainingtheir toxicities. The dispersion of pollutants inthe surrounding aquifer media is therefore notgradual (with distance from source to receptors),inconsistent, and heterogeneous. This pronouncesa demand for evolving a model to envisage thedominance of geoenvironmental features on thecontaminant dispersal in hard rock backgrounds.For this intent, a MSW dumping site near Punemetropolitan city is selected with the objectivesto (1) evaluate the leachate pollution potential,(2) examine geochemical status of groundwaterin areas around the site, and (5) delineate thegeoenvironmental features controlling groundwa-ter pollution in a basaltic litho-environment.

Background study

Pune, in the western Indian state of Maharashtra,with an area of over 450 km2 and a vast pop-ulation of 3.5 million, is a city still developingand expanding. According to the latest availableestimates, it produces over 1,100 metric tons ofmunicipal and post-consumer solid waste on adaily basis (ESR 2006). The exponential growthin the Pune metropolis during the last decade(in terms of area, industry, population, and livingstandards) has put immense pressures on solidwaste management system of the local munici-pal body. As a common waste disposal practicein many metropolises (particularly in developingcountries), trucks from different parts of Pune

collect and bring solid wastes to the nearby siteand unload in an irregular fashion. These wastespredominantly contain domestic wastes (house-hold waste, street litter, municipal park sweep-ing waste, garden waste, commercial waste fromshops and trading centers, kitchen wastes, etc.).Further wastes from poultry and fish markets,slaughterhouses, dairy farms, and non-infectioushospital waste are also dumped without propersegregation, except by the rag pickers who rum-mage through the garbage and partially segregateit. They generally collect glass material, plastics,and metals to sell them at recycling units.

The site under review was previously an aban-doned stone quarry, which later (from 1993)served as a dumping site for MSW, with improperleachate collection system. Presently, it lookslike a hillock (of ∼15–25 m height) with ever-increasing heap of MSWs (Fig. 1a, b). The generalcomposition of waste is as follows: organic mat-ter, 65%; paper, 8%; plastic, rubber, leather, andsynthetic 7%; metal 6%; inert matter 10%; andglass 4% (ESR 2006), out of which organic matterproduces large amount of leachates. Consequently,the leachate production is high, organically com-plex in nature, and continuously growing. Theinstant effects of MSW decomposition are afoul and stinking smell felt from a distance andbreeding of houseflies, vermin, and pathogensbesides a very unpleasant sprawl. “Phursungi” and“Shewalewadi” are the two villages in this areaseverely affected due to leachate contaminationin soil and groundwater. Unhygienic drinking wa-ter and garbage-induced diseases, like dysentery,cholera and hepatitis, are frequently reported inthese villages during monsoon season. Therefore,the present work on the geochemistry of leachateas well as groundwaters from the study area wasconducted.

Study area

Pune City restrains to the Deccan volcanicprovince (DVP) of Cretaceous–Eocene age(Krishnan 1982; Fig. 2). Despite the fact that cavi-ties, vesicles, flow contacts, lava pipes, and tun-nels can build up principal porosity in the basalt(Pawar and Shaikh 1995), the flows in the studyarea are relatively less porous. Conversely,

Environ Monit Assess (2010) 162:327–346 329

Fig. 1 a MSW dumpingsite showing leachatepond, Pune, India.b MSW dumping siteshowing heap of solidwaste, Pune, India

a

b

jointing and fracturing by way of interconnectivityhave conveyed localized secondary porosity andpermeability to form suitable groundwater reser-voirs at places (Pawar et al. 2008). Furthermore,the cooling features such as columnar jointsserve as hydrologic discontinuities, which in turnfunction as pathways for infiltration of rainwater.However, meager incidence of such primaryopenings in the exposed quarry sections nearbyMSW site indicates low porosity and permeabilityto basaltic flows in the area. The studied dumpingsite is about 20 km SE of Pune, on Pune-Saswadroad (Fig. 3). The study area around the dumping

site (73◦55′ to 74◦00′′ N and 18◦22′30′′ to E 18◦30′′)is situated at elevation ranging between 550and 660 m amsl with the MSW site located onthe eastern slopes of a small topographic high.Climate in the area is semi-arid with an averageannual rainfall of 550 mm. The year 2006 expe-rienced heavy rainfall (1266 mm; IMD 2007)much above the annual average of 550 mm. Juneto September is the period of rainy season withoccasional heavy rainfall events. This leads todispersion of leachates in the surrounding low-lying areas. A small natural stream, namely, KalaOdha, further carries the leachates downstream


Fig. 2 Location map ofMSW dumping site

(Fig. 3). A substantial part of leachates derivedfrom the municipal garbage gets naturally col-lected in a nearby small abandoned quarry (L7,Fig. 3) and acts as another point source. The totalarea available for MSW dumping site is about163 acre, and total study area under investigationis 96 km2.

Dug wells are the principle source of watersupply for drinking and other purposes in thestudy area. Groundwater withdrawal is confinedto vesicular, weathered, jointed, and fractured up-per basaltic crust, which is overlain by thin soilcover. Depleting groundwater levels are common,the condition being further aggravated by fre-quent drought like situations. Average groundwa-ter level during pre-monsoon is 5.7 m, whereasthe water tables are fairly shallower during post-monsoon with an average depth of 2.7 m. Theerratic nature of southwest monsoon is the con-trolling factor for groundwater fluctuations. Theeffect of leachate percolation is observed in manynearby dug wells in the form of brown taintedwaters with unpleasant foul smell.

The reddish brown soils rich in iron and ferricoxide content are present in higher regions ofthe study area (around the dumping site). Theseare medium textured silty soils. Moderately thickblack soils rich in organic matter and humus con-tent are observed in lower reaches. These arehighly fertile and are under intensive irrigation.

Sporadic patches of grayish soils are developedalong the gentle slopes. These are rich in CaCO3

and are described as calcareous soils.

Materials and methods

Sampling of leachate and groundwater

In order to observe the spatio-temporal variationsin the geochemistry of leachates and groundwa-ters, two undiluted representative leachate sam-ples (one from leachate collection pond ‘L7’ andanother from the base of solid waste heap ‘L5’)and 19 groundwater samples (17 dug well, onebore well, and one surface water) were collectedduring November 2006 (post-monsoon) and May2007 (pre-monsoon). A random sampling methodwas employed to collect the groundwater sam-ples with due consideration to represent land-usepatterns, topography, and areas close to dumpingsite. The samples were collected in pre-cleanedpolyethylene container of 1-l capacity. The pHand EC were recorded on site at the time ofsampling with digital pH meter and digital ECmeter, respectively. For the analysis of biologicaloxygen demand (BOD), 300 ml capacity BODbottles were used for the collection of samples,and dissolved oxygen was fixed onsite. For heavymetal analyses, samples were separately collected


L

L

Fig. 3 Location map of the study area


in pre-washed polyethylene containers of 100 mlcapacity and acidified onsite to avoid precipitationof metals. A Garmin global positioning systemwas used for recording spatial data.

Analytical methods

After sampling, the collected samples were im-mediately brought to the laboratory and kept inrefrigerator at temperature below 4◦C until an-alyzed (APHA 1995). The total hardness (TH),Ca, Mg, HCO−

3 , and Cl− were analyzed by titri-metric methods (APHA 1995). The Na and Kconcentrations were determined by flame photo-metric method while SO2−

4 , PO3−4 , and NO−

3 wereanalyzed by using UV-VIS spectrophotometer.The chemical oxygen demand (COD) was deter-mined by open reflux digestion method, and BODwas estimated by Azide modification of Win-kler method. Total organic carbon (TOC), F−,and CN− were determined by a nano-colorimeter(500D). The trace element concentrations (Fe,Zn, Cu, Ni, Cd, Pb, Cr, Mn, Al, and Co) were alsodetermined by using a nano-colorimeter (500D).

While the groundwater in DVP is of Ca +Mg–HCO3 type (Pawar et al. 1982), the mon-soon rainwater is charged with chloride, sulfate,nitrate, sodium, calcium, magnesium, and negli-gible amounts of bicarbonates (Das et al. 2004).The rainwater inputs to the groundwater were de-ducted from the geochemical data obtained, andcorrected records were used for the plots. Ana-lytical precision of the major ionic constituentswas measured by the normalized inorganic chargebalance (Huh and Edmond 1999). The resultingcation–anion charge balance errors in all ground-water samples are within ±5%, which is consid-ered to be acceptable (Berner-Kay and Berner1987; Edmond et al. 1995; Huh and Edmond1999).

Results

Geochemistry of “typical” groundwaterfrom basaltic aquifer

There is fairly a good amount of informationavailable on background chemistry of groundwa-

ter from uncontaminated basaltic aquifers (Pawarand Shaikh 1995; Pawar et al. 2008). How-ever, specifically, the studies on the chemistry ofgroundwater from Pune area are carried out byPawar et al. (1982). Their findings indicate thatwhile the wells piercing through basaltic, weath-ered basaltic, and doleritic dyke aquifers exhibitCa+Mg–HCO3 water type, the alluvial aquifersare dominantly characterized by Ca+Mg+Na–HCO3 type. The ionic load of the groundwateris dominantly derived from weathering of ferro-magnesian silicates (olivine and augite) and pla-gioclase feldspar, besides some contribution fromzeolites (Pawar et al. 2008). This information hasbeen used in comparing the characteristics ofgroundwater modified by mixing of leachatederived from MSW in the study area.

Leachate characterization

The leachate characterization was carried out fortwo consecutive seasons (post- and pre-monsoon).Leachate samples were analyzed for 18 generalparameters and ten heavy metals as discussedunder different heads. Average leachate compo-sition (of L5 and L7) and its seasonal variation areshown in Table 1.

The pH and EC The average pH varies from8.33 to 7.62 during post- and pre-monsoon sea-sons, respectively. The average values for EC areconsiderably high ranging between 99,510 and685,400 μS/cm during the two seasons, respec-tively. The extremely high values for EC are at-tributable to high levels of anions and cations.Feebly alkaline nature of leachate is an indicatorof the mature stage of the dumping site (Jorstadet al. 2004)

BOD, COD, and TOC The high values for BODand COD (Table 1) are indicative of high or-ganic matter in the wastes. The ratio for 5-dayBOD/COD for pre-monsoon is 0.75, and for post-monsoon, it is 0.6. This indicates that majority ofthe organic compounds is biodegradable (Fattaet al. 1999). The high values for TOC duringboth seasons are mainly due to decomposed andundecomposed product of organic wastes.


Table 1 Physico-chemical characteristics of leachate (av-erage of L5 and L7)

Constituents Post Pre Percent increasemonsoona monsoona or decrease inNov 2006 May 2007 concentration

pH 8.33 7.62 −9.32EC 99,510 685,400 85.48BOD5 4,122 6891 40.18COD 6,834 9200 25.72TOC 5,434 7000 22.37TN 262.5 312.5 16.00TH 2,200 1802 −22.09Na+ 2,550 2424 −5.20K+ 186.5 239.92 22.27Ca++ 340.5 439.79 22.58Mg++ 110.5 170.08 35.03Fe 78.75 125 37.00F− 21.37 29.25 26.94Cl− 4,485 4764 5.86CN− 0.19 0.27 29.63HCO−

3 2170 5,000 56.60SO2−

4 796 1024 22.27PO3−

4 188.6 312.5 39.65NO−

3 115 55 −109.09Cd 0.93 1.24 25.00Cr 2.87 5.22 45.02Cu 0.9 1.47 38.78Mn 4.15 6.84 39.33Co 0.258 0.339 23.89Ni 2.05 2.72 24.63Pb 0.84 0.8 −5.00Zn 1.63 1.91 14.66Al 7.46 11.12 32.91BOD5/COD 0.6 0.75 20.00aAll values are in mg/l, except pH, EC (in μS/cm) andBOD5/COD

Cations The possible sources of cations (Table 1)are domestic wastes. These values are higher thanthose mentioned for dumping sites operating formore than 10 years (Papadopoulou et al. 2007).Almost all cations show higher concentrationsduring pre-monsoon possibly due to higher evap-oration effect under semi-arid climatic setup.

Anions The high amount of chloride (Table 1) inleachate is due to mixing of domestic waste (Moret al. 2006). The possible anthropogenic sourcesof chloride are kitchen wastes from households,restaurants, and hotels. Elevated concentration ofdissolved organic materials, such as leachate and

ionically charged organic acids, could contributesignificantly to the total alkalinity (Jorstad et al.2004). Higher sulfate, nitrate, and fluoride concen-trations (Table 1) are primarily due to domesticwastes. The total nitrogen (TN) having values of262.5 mg/l (post-monsoon) and 312.5 mg/l (pre-monsoon) are toward the higher side becauseorganic matter decomposition processes producetremendous amount of ammonia. The cyanideconcentration in leachate is low for both the sea-sons because of the absence of industrial wastesin the constituents of MSW. The higher values ofphosphate (Table 1) also suggest a mature stage ofthe dumping site (Fatta et al. 1999).

Heavy metals The heavy metals analyzed are Al,Cd, Cr, Cu, Co, Fe, Mn, Ni, Pb, and Zn (Table 1).High concentration of Cd, Pb, Ni, and Zn suggestthat the wastes are mainly of municipal origin con-taining refused batteries, paint products, metallicitems, and fluorescents lamps. Concentrations ofCr reveal the presence of wood preservatives andpaint products in the waste, whereas high Mnconcentrations suggest a strong reducing environ-ment. The Al concentrations are a result of elec-tronic wastes and aluminum foils. The high rangeof iron (Table 1) is an indicative of the dumping ofmetal scrap and tin-based garbage at the dumpingsite. The dark brown color of the leachate is at-tributable to the oxidation of ferrous to ferric formand the formation of ferric hydroxide colloids andcomplexes with fulvic and humic substances (Chuand Cheung 1994).

Leachate pollution index

The leachate pollution index (LPI) provides anefficient method for evaluating the leachate con-tamination potential. It serves as a vital tool forpolicy makers and public about pollution threatfrom landfill. It is a quantitative and comparativemeasure for the leachate pollution potential. TheLPI is calculated using the equation (Kumar andAlappat 2005):

LPI =n∑

i=1

Wi pi (1)


where LPI = the weighted additive LPI, Wi = theweight for the ith pollutant variable, pi = the sub-index score of the ith leachate pollutant variable,n = number of leachate pollutant variables usedin calculating LPI

andn∑

i=1

Wi = 1

However, when the data for all the leachate pol-lutant variables included in LPI are not available,the LPI can be calculated using the concentrationof the available leachate pollutants. In that case,the LPI can be calculated by the equation:

LPI =

m∑i=1

Wi pi

m∑i=1

Wi

(2)

where m is the number of leachate pollutant pa-rameters for which data are available, but in that

case, m < 18 andm∑

i=1Wi < 1

The calculated LPI values at the site underreview (Table 2) are comparable to those at var-ious dumping sites in other metropolitan citiesacross the world (Kumar and Alappat 2005).Moreover, the present study takes into account

the seasonal variation in the pollution poten-tial of leachates. The lower LPI values for post-monsoon (19.04) than for pre-monsoon (24.67)suggest that the leachates have more pollutingpotential during pre-monsoon. This is evidencedin the highly deteriorated groundwater qualityduring pre-monsoon, as discussed in the next sec-tion. The high values of LPI during both the sea-sons demand that leachate generated from MSWdumping site should be treated, and site should bemonitored on a continuous basis.

Groundwater quality

The groundwater in study area is mainly used fordrinking and irrigation purpose. Tables 3 (post-monsoon 2006) and 4 (pre-monsoon 2007) depictthe seasonal variation in the different parametersof groundwater in the study area. It is evidentfrom the tables that the wells in the close vicinityof dumping site (8, 9, 13 14, 15, 16, 18, and 26)are the worst affected due to leachate percolationdespite a less permeable basaltic terrain.

Physico-chemical properties of groundwater

The pH values (Table 3, physico-chemical data)for all groundwater samples are within the range

Table 2 LPI for pre-monsoon (Nov 2006) and post monsoon (May 2007) seasons

S. no Leachate Mean value Individual pollution Weight Wi Overall pollutionconstituent rating pi rating piwi

Post Pre Post Pre Post Pre Post Premonsoon monsoon monsoon monsoon monsoon monsoon monsoon monsoon

1 pH 8.33 7.62 5 5 0.055 0.055 0.275 0.2752 TDS 11,800 16,700 26 42 0.05 0.05 1.3 2.13 BOD5 4,122 6,891.5 48 55 0.061 0.061 2.928 3.3554 COD 6,834 9,200 65 74 0.062 0.062 4.03 4.5885 TKN 262.5 312.5 7 8 0.053 0.053 0.371 0.4246 Total iron 78.75 125 8 11 0.045 0.045 0.36 0.4957 Copper 0.9 1.47 6 7 0.05 0.05 0.3 0.358 Nickel 2.05 2.72 7 10 0.052 0.052 0.364 0.529 Zinc 1.63 1.91 6 6 0.056 0.056 0.336 0.33610 Lead 0.84 0.8 7 7 0.063 0.063 0.441 0.44111 Total chromium 2.87 5.22 13 36 0.064 0.064 0.832 2.30412 Chloride 4485.23 4764.2 38 46 0.048 0.048 1.824 2.20813 Cyanide 0.19 0.27 5 5 0.058 0.058 0.29 0.29

Total 0.717 0.717 13.651 17.686Final LPI value by dividing Total Overall pollution rating by total Wi 19.04 24.67


Tab

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Phy

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for

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EC

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HC

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SAR

CB

E%

BO

DC

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Phy

sico

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mic

alda

taD

W1

7.91

823

464

99.1

1.32

87.1

59.8

1.35

83.4

600

27.9

1.1

512

0.06

4.6

12.8

DW

47.

871,

192

180

320.

10.

9214

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030

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433.

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57,0

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635

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2.82

300.

960

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5.6

1,08

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953

4.83

4.92

167.

331

2D

W9

7.78

13,8

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669

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4268

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0394

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044

.91.

844

1.64

2.72

15.2

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W10

7.73

740

403

55.1

0.82

79.1

49.8

0.89

72.1

500

26.9

1.8

521.

19−0

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6.2

9.2

DW

117.

7795

130

021

9.1

0.82

64.6

33.8

0.92

80.6

800

28.9

4.6

255.

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10.4

DW

127.

6984

637

552

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2.9

28.8

0.95

83.4

540

27.9

2.4

221.

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DW

137.

941,

329

405

248.

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718

8.5

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125.

362.

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7.53

100

800

399.

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8.9

85.8

1.02

696.

986

044

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546

6.14

−2.9

612

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W15

7.67

2,50

058

928

9.1

0.92

110.

975

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9649

5.2

500

46.9

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905.

18−0

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28D

W16

7.81

4,30

055

640

9.1

1.02

110.

967

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8452

0.8

740

40.9

2.3

257.

551.

55.

27.

2D

W18

7.78

1,09

638

121

9.1

0.82

90.3

37.8

0.87

126

680

35.9

2.3

754.

881.

5115

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DW

197.

9799

816

733

9.1

0.72

3121

.81.

3566

.488

023

.92.

513

11.4

23.

152.

34.

8D

W21

8.21

980

191

148.

10.

9247

17.8

0.62

103.

338

027

.92.

23

4.67

2.5

13.4

20SW

226.

8359

521

663

.115

.935

.830

.82.

166

.432

019

.917

.829

1.87

−3.4

314

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W23

7.76

132

225

32.1

0.72

32.6

34.8

0.65

12.4

340

4.9

1.6

40.

93−1

.57

4.6

24D

W26

7.87

489

426

53.1

0.92

5511

9.8

0.64

3850

016

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342

1.12

2.55

3.2

10.4

DW

277.

781,

194

234

12.1

0.92

69.4

14.8

0.51

40.7

180

32.9

2.2

220.

341.

042.

28.

8D

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7.43

121

109

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0.92

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8.9

0.95

120

150

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74.

134.

260.

41.

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764,

694

387

182.

91.

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130

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4833

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226

0.91

616

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30.7

Min

6.83

100

109

12.1

0.72

14.9

8.9

0.51

12.4

150

0.9

1.1

30.

34−3

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0.4

1.6

Max

8.21

57,0

0099

640

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15.9

300.

911

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331

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0.29

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627

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0.35

198.

425

5.9

13.5

6.03

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3.16

62.

387

36.9

768

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Tab

le3

(con

tinu

ed)

Sam

ple

noF

eM

nC

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IC

uZ

nN

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rC

dP

b

Tra

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0.05

0.01

0.01

20.

64B

DL

0.23

0.02

BD

L0.

010.

15D

W4

0.03

0.02

0.02

80.

160.

080.

160.

040.

050.

004

0.18

DW

80.

12.

280.

096

1.34

0.64

1.12

0.28

0.6

0.00

80.

15D

W9

1.8

0.08

0.06

21.

760.

40.

820.

240.

210.

007

0.15

DW

102.

5B

DL

BD

L0.

09B

DL

0.02

0.1

0.04

0.00

30.

16D

W11

0.03

0.02

0.00

40.

560.

010.

140.

040.

060.

004

0.17

DW

122

0.01

0.00

20.

640.

010.

060.

020.

080.

004

0.18

DW

130.

70.

020.

044

0.72

0.01

0.09

0.04

0.16

0.00

20.

15D

W14

0.03

0.24

0.04

60.

760.

650.

880.

240.

240.

004

0.16

BW

150.

20.

010.

009

1.6

BD

L0.

6B

DL

0.6

0.00

30.

18D

W16

0.2

0.01

0.00

50.

5B

DL

0.7

0.01

BD

L0.

003

0.16

DW

180.

050.

020.

024

0.56

0.01

0.26

0.04

0.2

0.00

20.

18D

W19

BD

L0.

010.

016

0.56

0.01

0.08

0.02

0.48

BD

L0.

16D

W21

BD

L0.

020.

020.

8B

DL

BD

LB

DL

BD

L0.

002

0.14

SW22

0.17

0.08

0.02

81.

120.

240.

720.

120.

160.

003

0.17

DW

230.

80.

01B

DL

BD

LB

DL

0.09

BD

LB

DL

0.00

20.

15D

W26

0.1

BD

LB

DL

0.7

BD

LB

DL

0.01

0.5

0.00

30.

15D

W27

BD

LB

DL

BD

LB

DL

BD

LB

DL

BD

LB

DL

0.00

10.

15D

W28

0.3

0.01

0.00

80.

460.

010.

090.

020.

06B

DL

0.18

Avg

0.56

60.

178

0.02

690.

763

0.18

80.

379

0.08

30.

246

0.00

380.

162

Min

0.03

0.01

0.00

20.

090.

010.

020.

010.

040.

001

0.14

Max

2.5

2.28

0.09

61.

760.

651.

120.

280.

60.

010.

18SD

0.80

50.

564

0.02

590.

454

0.25

80.

363

0.09

40.

209

0.00

240.

013

For

the

phys

ico-

chem

ical

data

,all

valu

esar

ein

mg/

l,ex

cept

pHan

dE

Cis

inμ

S/cm

.For

the

trac

eel

emen

tda

ta,a

llva

lues

are

inm

g/l.

Tra

ceel

emen

tlo

wer

dete

ctio

nlim

itfo

rN

anoc

olor

500D

:For

Fe,

Mn,

Al,

Ni,

Cu,

and

Cr,

0.01

mg/

l;C

o,0.

002

mg/

l;Z

n,0.

02m

g/l;

Cd,

0.00

2m

g/l;

Pb,

0.00

5m

g/l

DW

dug

wel

l,B

Wbo

rew

ell,

SWsu

rfac

ew

ater

,SA

Rso

dium

abso

rpti

onra

tio,

CB

E%

perc

entc

harg

eba

lanc

eer

ror,

BO

Dbi

oche

mic

alox

ygen

dem

and,

CO

Dch

emic

alox

ygen

dem

and,

BD

Lbe

low

dete

ctio

nlim

it


Tab

le4

Phy

sico

-che

mic

alan

dtr

ace

elem

entd

ata

for

the

grou

ndw

ater

arou

ndM

SWdu

mpi

ngsi

te,P

une,

Indi

a—pr

e-m

onso

on(M

ay20

07)

Sam

ple

nopH

EC

TH

Na+

K+

Ca+

+M

g++

F−

Cl−

HC

O− 3

SO2− 4

PO

3− 4N

O− 3

SAR

CB

E%

BO

DC

OD

Phy

sico

-che

mic

alda

taD

W1

7.64

643

208

74.1

0.72

48.9

20.8

1.65

97.6

200

25.9

1.3

122.

244.

421.

48

DW

47.

4597

918

290

.11.

3223

.929

.81.

1811

519

033

.92

192.

91.

490.

610

DW

86.

8871

,700

3,80

11,

899

44.9

800.

543

7.7

1.49

4,40

02,

000

674

175

1813

.41

−3.4

828

0.4

336

DW

97.

4615

,400

784

400.

12.

1219

8.9

69.8

1.15

1,01

510

057

.92.

515

6.22

2.16

5.7

56D

W10

7.44

854

302

69.1

0.72

3850

.41.

112

625

024

.40.

85

1.73

4.75

232

DW

117.

531,

026

318

99.1

0.42

28.9

59.8

1.03

157

330

36.4

1.3

92.

42−0

.29

0.6

32D

W12

7.27

846

245

79.1

0.72

48.9

29.8

0.87

115

220

33.9

145

2.2

0.4

0.2

32D

W13

7.49

1,96

925

320

0.1

3.12

43.9

34.8

0.67

313

310

49.4

217

5.48

−4.7

52.

232

DW

147.

4511

,600

509

450.

18.

2288

.969

.81.

0674

245

053

.92.

827

8.68

0.17

4.5

80B

W15

7.06

1,60

020

735

0.1

0.82

33.9

29.8

1.14

470

290

56.4

2.3

410

.58

0.36

5.3

56D

W16

7.44

8,60

018

228

0.1

2.52

23.9

29.8

1.04

376

260

43.9

2.5

19.

030.

292

40D

W18

7.55

977

108

55.1

0.22

18.9

14.8

0.87

57.9

150

22.9

21

2.3

0.27

230

DW

197.

3796

790

374.

10.

3211

.714

.81.

3138

046

033

.42

3217

.14

−3.7

0.6

8D

W21

7.13

768

365

89.1

0.52

35.8

66.9

0.92

80.6

420

29.9

1.3

242.

034.

735.

225

SW22

7.68

322

269

79.1

8.02

43.8

38.7

2.6

89.1

320

23.4

26.3

122.

13.

294.

948

DW

237.

3511

,100

133

55.1

0.72

28.9

14.8

0.85

43.7

230

11.4

3.5

72.

08−2

.74.

956

DW

267.

051,

089

302

489.

10.

8238

.949

.81.

2373

726

052

.91.

339

12.2

40.

985.

572

DW

277.

351,

311

453

70.1

0.92

66.3

60.8

0.89

112

410

39.9

1.3

161.

491.

881.

416

DW

287.

131,

300

303

120.

12.

5263

.934

.81.

0421

432

047

.915

.31

3−4

.04

1.8

18A

vg7.

357,

003

474

280.

24.

1988

.78

60.9

31.

1650

7.4

377.

471

.113

165.

646

0.32

817

.43

51.9

Min

6.88

322

9055

.10.

2211

.714

.80.

6743

.710

011

.40.

81

1.49

−4.7

50.

28

Max

7.68

71,7

003,

801

1,89

944

.980

0.5

437.

72.

64,

400

2,00

067

417

545

17.1

44.

7528

0.4

336

Std.

dev

0.21

16,3

2282

141

9.8

10.1

177.

193

.13

0.42

981.

840

5.1

147

39.7

12.8

4.78

32.

955

63.7

171

.9


Tab

le4

(con

tinu

ed)

Sam

ple

noF

eM

nC

oA

lC

uZ

nN

iC

rC

dP

b

Tra

ceel

emen

tdat

aD

W1

0.1

BD

L0.

011.

280.

010.

320.

040.

05B

DL

0.18

DW

40.

050.

040.

021.

360.

240.

340.

040.

07B

DL

0.16

DW

80.

154.

280.

122.

560.

761.

120.

640.

8B

DL

0.15

DW

93.

30.

840.

094.

160.

520.

930.

540.

36B

DL

0.15

DW

105

0.01

BD

L0.

06B

DL

BD

LB

DL

0.09

BD

L0.

17D

W11

0.05

0.04

0.01

0.72

0.06

0.16

0.06

0.1

BD

L0.

2D

W12

40.

02B

DL

0.68

0.12

0.08

0.04

0.2

BD

L0.

2D

W13

0.05

0.04

0.06

20.

060.

080.

120.

28B

DL

0.18

DW

140.

50.

360.

18.

80.

881.

360.

41.

72B

DL

0.19

BW

150.

5B

DL

BD

L0.

8B

DL

2.6

0.01

0.9

BD

L0.

22D

W16

0.05

BD

LB

DL

1.4

BD

L0.

6B

DL

0.05

BD

L0.

18D

W18

0.05

0.04

0.06

1.36

0.24

0.34

0.12

0.36

BD

L0.

19D

W19

0.5

0.02

0.02

0.84

0.01

0.18

0.06

0.21

BD

L0.

18D

W21

0.01

BD

LB

DL

0.56

BD

LB

DL

0.04

0.6

BD

L0.

17SW

220.

20.

280.

031.

920.

620.

980.

080.

24B

DL

0.19

DW

234.

50.

01B

DL

BD

LB

DL

0.15

0.01

BD

LB

DL

0.18

DW

261.

15B

DL

BD

LB

DL

BD

L0.

1B

DL

BD

LB

DL

0.22

DW

27B

DL

BD

LB

DL

0.74

BD

LB

DL

0.01

0.2

BD

L0.

18D

W28

0.5

0.04

0.02

5.6

0.06

0.14

0.02

0.1

BD

L0.

19A

vg1.

148

0.46

30.

0491

2.04

90.

298

0.59

30.

139

0.37

2B

DL

0.18

3M

in0.

010.

010.

010.

060.

010.

080.

010.

05B

DL

0.15

Max

54.

280.

128.

80.

882.

60.

641.

72B

DL

0.22

Std.

dev

1.72

91.

171

0.03

942.

228

0.31

30.

678

0.2

0.43

1B

DL

0.01

9

For

the

phys

ico-

chem

ical

data

,all

valu

esar

ein

mg/

l,ex

cept

pHan

dE

Cis

inμ

S/cm

.For

the

trac

eel

emen

tda

ta,a

llva

lues

are

inm

g/l.

Tra

ceel

emen

tlo

wer

dete

ctio

nlim

itfo

rN

anoc

olor

500D

:For

Fe,

Mn,

Al,

Ni,

Cu,

and

Cr,

0.01

mg/

l;C

o,0.

002

mg/

l;Z

n,0.

02m

g/l;

Cd,

0.00

2m

g/l;

Pb,

0.00

5m

g/l

DW

dug

wel

l,B

Wbo

rew

ell,

SWsu

rfac

ew

ater

,SA

Rso

dium

abso

rpti

onra

tio,

CB

E%

perc

entc

harg

eba

lanc

eer

ror,

BO

Dbi

oche

mic

alox

ygen

dem

and,

CO

Dch

emic

alox

ygen

dem

and,

BD

Lbe

low

dete

ctio

nlim

it


of WHO (2002) standards. EC is the indicator ofdissolved inorganic ions in groundwater; the wellshaving highest values (DW8, DW9, and DW16)during both the seasons are in the close vicinity ofdumping site demonstrating the effect of leachateon groundwater. Higher EC values during pre-monsoon possibly show the effect of evaporationas well as the impact of leachate. The BOD andCOD values are relatively low for both seasons;

yet, the wells around dumping sites have highervalues (Table 3, physico-chemical data; highestvalues in DW 8 close to dumping site). The sameis true for TH values.

Major cations in groundwater

Similar to physicochemical parameters discussedabove, all wells around the dumping site exhibit

Fig. 4 a Scatter plotCa+Na vs HCO3.b Scatter plot Mg vsHCO3. c Scatter plotCa+Mg vs HCO3

R2 = 0.0056

R2 = 0.6035

0

5

10

15

20

25

30

0 2 4 6 8 10 12 14 16

HCO3 (epm)

0 2 4 6 8 10 12 14 16

HCO3 (epm)

0 2 4 6 8 10 12 14 16

HCO3 (epm)

Ca+

Na

(ep

m)

Post-monsoon

Pre-monsoon

a

R2 = 0.0011

R2 = 0.1485

0

2

4

6

8

10

12

14

16

18

Ca+

Mg

(ep

m)

Post-monsoon

Pre-monsoon

c

R2 = 0.0807

R2 = 0.0989

0

2

4

6

8

10

12

Mg

(ep

m)

Post-monsoon

Pre-monsoon

b


exceedingly higher values for major cations ana-lyzed (Table 3, physico-chemical data), with DW8showing highest values. The high concentrationfor sodium around the landfill indicates impactof leachate. The other cations also depict similarpatterns. The high concentration of Na+ may posea risk to persons suffering from cardiac, renal, andcirculatory diseases (Mor et al. 2006). Despite fewinputs from agricultural activities, the high con-centration of K+ has been reported to be an indi-cation of the leachate effect (Eillas 1980). Besidesdomestic wastes, the silicate minerals (plagioclase,feldspar, and augite) could also have contributedtoward sources of sodium, calcium, and magne-sium in basaltic host rock (Hem 1985).

Major anions in groundwater

An excess of chloride in water is usually takenas an index of pollution and considered as tracerfor groundwater contamination (Loizidou andKapetanios 1993). Higher concentrations of chlo-rides are observed in wells close to dumping site(DW8, DW9, DW14, and DW16) during both sea-sons. The concentration is considerably high in thewell DW8; values ranged from 435.6 mg/l for post-monsoon to 4,400 mg/l for pre-monsoon. The highchloride content in groundwater is from pollutionsources such as domestic effluents, fertilizers, sep-tic tanks, and leachates (Mor et al. 2006). Increasein chloride level is injurious to people sufferingfrom diseases of heart and kidney (WHO 2002).The high alkalinity imparts water an unpleasanttaste and may be deleterious to human healthalong with the high pH, TDS, and TH. Enhancedrock water interaction during post-monsoon couldalso contribute (to a limited extent) toward theincreased values for HCO−

3 (Pawar 1993).Agricultural fertilizers and leachate are the

main source of sulfate in groundwaters. The SO2−4

concentration in groundwater is within WHOstandard (2002) for both seasons. Still, the valuesare considerably high in DW8. The concentra-tions have reduced during post-monsoon possiblydue to sulfate reduction. The agricultural fer-tilizers are also the main source of phosphatein groundwater. High concentration reduces thebiotic component of groundwater. The highestconcentrations are at DW8 during both the sea-sons, indicating the effect of leachate on ground-water. In general, the major sources for nitratein groundwater include domestic sewage, runofffrom agricultural fields, and leachate from landfillsites (Pawar and Shaikh 1995; Lee et al. 2003;Jalali 2005). Similar to other anions, the valuesfor nitrate are higher in all the wells surroundingthe dumping site. The decreasing hierarchy ofdominant cations and anions in the groundwa-ters around the dumping site is Na+ > Ca++ >

Mg++ > K+ and HCO−3 > Cl− > SO2−

4 > NO−3 .

Except for few wells, the sodium absorption ratiovalues are low and have improved during post-monsoon season.

Leachate as a source of ions in groundwaters

Lithogenic inputs from rock–water interactions(dissolution of primary silicates) are the mainsources of ions in groundwaters under naturalconditions. The principal lithologic unit in thestudy area is basalt, which is distinguished byolivine (2–3%), pyroxene (augite; 24–47%), andplagioclase feldspar (labradorite; 40–65%) (Beanet al. 1986; Subbarao et al. 1994). Incongruentdissolution of these primary silicate minerals inthe groundwater can be given as follows (Pawaret al. 2008):

Mg2SiO4 (s)+4 H2CO3 =2Mg+4HCO3+H4SiO4

Olivine[mMg/mHCO3=1:2

]

(1)

4 Ca0.5Na0.5Al2Si2O8 (s)+6CO2+9H2O=3Al2Si2O5 (OH)4+2Na+2Ca+6HCO3+4 SiO2

Plagioclase[mHCO3/mSiO2=3:2 and mNa/mCa=1:1

] (2)


CaMgFeAl2Si3O12 (s)+6CO2+5 H2O=Al2Si2O5 (OH)4+Ca+Mg+Fe+6HCO3+SiO2

Augite[mHCO3/mSiO2=6:1 and mCa/mMg=1:1

] (3)

Rainwater charged by CO2 in the atmospherepermeates through soil zone and stimulates thebasaltic aquifers in the area, which is the source ofprotons in the above reactions. The above rock–water interaction processes liberate base cations(especially Ca, Mg, and Na) and bicarbonate alongwith concurrent increase in pH (Rabemanana et al.2005). Considering Eq. 2, plagioclase feldspar(labradorite) is a solid solution series betweenanorthite (An) and albite (Ab) in the basalt, whichsets Na/Ca ratio in the groundwater from 0.5 to1.0 (Garrels 1967; Drever 1982). The attributesfor Na/Ca ratio (post-monsoon, 0.17–21.45, aver-age 3.38; pre-monsoon, 1.06–31.86, average 5.51)in groundwaters from the study area are farbeyond this range, signifying dominant influenceof leachates on groundwaters. The values haveimproved during post-monsoon due to enhancedrock–water interactions as well as dilution ofleachates. The increase in the values of Na/Cain some wells could also be due to the precipita-tion of secondary CaCO3 minerals in unsaturatedzone. Field observations support this inference, assecondary carbonates are observed in the dug wellsections of weathered basaltic aquifers. However,very low values of Na/Ca (0.17) are observed inonly one well (DW 27) far away from the land-fill as well as the leachate carrying stream (KalaOdha).

The scatter plot Na+Ca vs HCO3 (Fig. 4a)shows weak positive correlation both in post- andpre-monsoon seasons. This supports the meagerinput of these ions from plagioclase dissolution.The cross-plots of Mg vs HCO3 and Ca+Mg vsHCO3 also depict poor correlation (Fig. 4b, c),suggesting scant contribution from olivine andpyroxene weathering (Ca+Mg–HCO3). This im-plies that the major part of the ionic load inthe groundwaters is dominantly derived fromleachates. All correlations have slightly improved

Table 5 Groundwater samples exceeding permissible lim-its for trace elements (WHO 2002)

Element WHO permissible Post-monsoon Pre-monsoonlimit (mg/l) (%) (%)

Fe 0.3 31.58 47.37Mn 0.5 5.26 10.53AI 0.2 78.95 84.21Cu 1.0 0.00 0.00Zn 5.0 0.00 0.00Ni 0.02 68.42 68.42Cr 0.05 68.42 89.47Cd 0.003 63.15 0.00Pb 0.001 100 100

during post-monsoon due to dilution of leachatesand enhanced rock–water interactions. Availabil-ity of larger surface area during post-monsoonprovides favorable conditions for the above geo-chemical reactions.

Trace elements in groundwater

Despite high concentration of almost all heavymetals analyzed in the leachates (Table 1), thegroundwaters (Tables 3 and 4, trace element data)in the study area are least affected by the metalpollution except well numbers DW1 and DW11,where Pb and Zn values are elevated possibly dueto localized sources of pollution such as agricul-ture. However (barring a few exceptions), heavymetal concentrations (except Cu and Zn) in ma-jority of groundwater samples are above permissi-ble limits (WHO 2002; Table 5).

Discussion

The present results demonstrate the impact ofleachate on deteriorating groundwater quality in a


basaltic terrain. The leachates having moderatelyhigh pollution potential (LPI = 19.04 and 24.65 inpost- and pre-monsoon, respectively) have largelymodified the groundwater quality in terms ofits physicochemical parameters. The wells in theclose vicinity of the dumping site are the worstaffected despite a hard, compact, and less per-meable basaltic lithology. Various controlling fac-tors for the leachate contamination are outlinedbelow.

Rainfall parameter The rainfall pattern in thesemi-arid regions of DVP is erratic. Long droughtyears and occasional heavy wet spells lead toaccelerated dispersion of leachate in the sur-rounding areas causing surface and subsurfacecontamination. It is to be noticed that the year2006 experienced heavy rainfall (more than twotimes of the annual average). The groundwaterquality as well as leachate pollution potential isimproved during post-monsoon plausibly due toheavy rainwater recharge.

Leachate transportation mode Two leachate-receiving modes in the aquifers of the area areidentified. As the Kala Odha (Fig. 5b) originatesnear MSW site, it receives leachates directly fromthe base of dumping site that perennially flowsthrough it. The width of this leachate-carryingchannel is quite limited (2–5 ft); still, it acts asa linear source of pollution. On the contrary,the surface water flowing in Farshicha Odha isrelatively unpolluted, and the channel is dry formost of the times. It is interesting to note that thewells situated along the Farshicha Odha are highlypolluted (wells 9 and 13). This implies towardanother mode of leachate movement through soil–hard rock interface and also through weathered,fractured, jointed, and vesicular upper basalticcrust along the gentle slopes. This second modeis more dominant, as lateral recharge from pol-luted channels in hard rock is restricted. This isevidenced by the low pollution levels in wells 22and 28 located at the banks of Kala Odha.

Topography Basaltic terrains exhibit undulatoryand rugged topography. The location of dumpingsite near the top of a topographic high (rechargezone) has induced the permeation of leachate in

the groundwater system along the slopes. Thewells (DW1, DW10, DW11, and DW12) are prac-tically unaffected by the leachate contaminationbecause these wells lie on the opposite (western)slope of the topographic high (Fig. 3).

Redox controls Despite high concentration ofheavy metals in the leachate, the groundwatersexhibit feeble geochemical signatures in termsof heavy metal contents. Even the wells in theclose vicinities of dumping site are least affectedby the high-level presence of heavy metals inthe leachates. This implies toward redox con-trols over occurrence and movement of traceelements. A reductive ambient subsurface envi-ronment is favorable for the concentration ofheavy metals (particularly Fe, Mn, Cu, Pb, andZn) in the groundwater system (Edmunds et al.2002; Pawar and Nikumbh 1999). It is to be notedthat in basaltic terrains, the groundwater is con-fined to fractured, fissured, jointed, and weatheredzones/pockets. Water table fluctuation in sucha litho-environment is diminutive and heteroge-neous. As a result, highly reducing conditions aregenerally not reached particularly under slopingconditions. Moreover, the heavy metals remainin the waste or at the waste–rock interface as aresult of redox-controlled precipitation reactions(Yanful et al. 1988). The metal mobility is alsocontrolled by physical sorptive mechanisms, andlandfills have an inherent in situ capacity for min-imizing the mobility of heavy metals (Pohlandet al. 1993). These conditions have moderatelyretarded the permeation of heavy metals into thegroundwater system.

Influence of unlined irrigation canal An unlinedNW–SE running canal flows across the regionalslopes and groundwater flow in the area. This hasmoderately retarded the permeation of contam-inants in areas down-slope side of the canal, asevidenced by low contamination levels in wellsDW19, DW21, SW22, DW23, DW27, and DW28.

Age of MSW dumping site The dumping sitehas been receiving solid wastes without propersegregation and pretreatment since 1993. Millionsof tons of solid wastes have already been dumpedat the site. Age of the landfill dominantly governs


a

b

Fig. 5 a Conceptual model depicting dispersion of leachate contaminants in the groundwaters. b Model depicting mode oftransport of leachate contaminants in the groundwaters

the leachate characteristics and hence influencesthe LPI values. High LPI values indicate that theleachates generated from the dumping site are notstabilized. This has resulted in high concentrationsof heavy metals in leachate.

Induced fracturing The dumping site was previ-ously an abandoned stone quarry before 1993. Thebuilding stone excavations in the region generallygo up to a depth of 40 m. Quarrying of hard

and compact basaltic materials needs a large-scaleblasting that generates induced fracturing in thesurrounding host rocks. These induced fracturesin the country rocks at the dumping site have ac-celerated the subsurface permeation of leachatesto the surrounding wells.

Surface and subsurface flow dynamics The oc-casional, short-spelled, and heavy rains generateintense sheet flows along the gentle slopes in the


region. As the location of dumping site is on theeastern slopes of the topographic high, heavy rainscause huge amount of leachate dispersal overthe entire area toward NE of dumping site. Thisrunoff water (sheet flow) looks dark black in colorbecause of occasional burning (five to six times ina year) of solid wastes. It spreads over large areasincluding soil horizons eventually contaminatingthe open wells and natural streams.

Along the groundwater flow direction (towardsNE), the leachate contaminants travel throughsubsurface fractured and fissured upper basalticcrust to low-lying areas. The subsurface flow in-creases during post-monsoon season, though theleachates are diluted. The unlined canal cutsacross the general slope and groundwater flowlines thereby reducing the dispersal of leachatecontaminants in the down-slope areas.

A conceptual model depicting mechanisms ofleachate contamination in the area is shown inFig. 5a and b. The model is expected to be helpfulin deciphering conducive and non-conducive ar-eas for leachate migration and contamination.

Remedial measures

The 3-R principle (reduce, reuse, and recycle)is an appropriate methodology for solid wastemanagement and also for abatement of leachate-induced groundwater pollution. Adopting decen-tralized dumping sites in million plus cities likePune may reduce the amount of leachate gen-eration and its pollution potential. Reduction ofsolid waste generation at source may be achievedby various awareness campaigns in residential so-cieties. Proper segregation of biodegradable andnon-biodegradable wastes at the source should bepracticed with composting the daily solid wastegenerated at the vicinity of residential complexes(e.g., vermicomposting) and reuse–recycle of thenon-biodegradable waste.

Construction of lined dumping site andleachate collection ponds positively helps avoidtransport of leachate to subsurface aquatic envi-ronment. The proper physico-chemical treatments(coagulation, precipitation, ammonia stripping,activated carbon adsorption, ion exchange, andreverse osmosis) could be applied to reduce the

organic, inorganic, and heavy metal load throughleachate (Chttaranjan and Chan 1986). Further-more, biological treatment (aerobic/anaerobic)would be economical with methane gas generationand utilization.

Conclusion

The lateral and vertical flow of water in hard rockterrains like basalt is slow and unstable due toconstricted passages. This, to a certain extent, re-stricts the migration of contaminants from sourceto receptors. However, a negative consequenceof the mechanism is that the pollutants maintaina constant level of contamination and their tox-icities. This is evidenced by the higher level ofpollution in the wells adjoining the dumping siteduring both seasons despite rainwater rechargeduring monsoon.

The leachate derived from the Pune munic-ipal waste dumping site demonstrates exceed-ingly high values for almost all physico-chemicalparameters analyzed, including potentially toxicheavy metals. The influence of leachate percola-tion (through two different modes) is evident onthe surrounding wells. Besides meager lithogenicinputs from rock–water interactions in basalticlitho-environment, the leachates are the primesource of all ions in the groundwater. High LPIvalues indicate that the leachates generated fromdumping site are not stabilized, resulting in highconcentrations of heavy metals in leachate. De-spite their high concentrations, the groundwatersare least affected in terms of heavy metal contents,plausibly due to redox controls. Various geoen-vironmental features like topography, relief, andflow dynamics have largely controlled the perme-ation of leachate to the groundwater system in thebasaltic terrain under semi-arid climatic regime.Erratic rainfall patterns and induced fracturingin the country rocks have accelerated the conta-minant movement and infiltration. Although theintensity of pollution in the groundwaters can bemitigated by the remedial measures discussed, thepresent study warrants for a proper solid wastemanagement as a long-term policy in metropolitancities.


Acknowledgements Authors would like to thank Prof. V.S. Ghole, Head, Department of Environmental Sciences,and Head, Department of Geology University of Pune, forproviding necessary facilities. Thanks are due to Prof. P.G.Saptarshi, (Department of Environmental Sciences) forcontinuous encouragement and support. Help in fieldworkand analyses of samples by Mr. S. K. Gaikwad and Mr. S.D. Kodre is thankfully acknowledged.

Open Access This article is distributed under the termsof the Creative Commons Attribution Noncommercial Li-cense which permits any noncommercial use, distribution,and reproduction in any medium, provided the originalauthor(s) and source are credited.

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