Influence of geology on arsenic concentrations in groundand surface water in central Lesvos, Greece

Maria Aloupi & Michael O. Angelidis &

Apostolos Μ. Gavriil & Michael Koulousaris &

Soterios P. Varnavas

Received: 8 October 2007 /Accepted: 3 March 2008 / Published online: 25 April 2008# Springer Science + Business Media B.V. 2008

Abstract The occurrence of As was studied in ground-water used for human consumption and irrigation, instream water and sediments and in water from thermalsprings in the drainage basin of Kalloni Gulf, island ofLesvos, Greece, in order to investigate the potentialinfluence of the geothermal field of Polichnitos–Lisvorion the ground and surface water systems of the area.Total dissolved As varied in the range <0.7–88.3 μg L−1

in groundwater, 41.1–90.7 μg L−1 in thermal springwater and 0.4–13.2 μg L−1 in stream water, whereasAs concentrations in stream sediments varied between2.0–21.9 mg kg−1. Four out of 31 groundwater samplesexceeded the EC standard of 10 μg L−1. The surveyrevealed an enrichment in both surface and groundwaterhydrological systems in the northern part of the area(average concentrations of As in groundwater, streamwater and stream sediment: 8.0 μg L−1, 8.8 μg L−1 and15.0 mg kg−1 respectively), in association with thevolcanic bedrocks, while lower As concentrations were

found in the eastern part (average concentrations ingroundwater, stream water and stream sediment:2.9 μg L−1, 1.7 μg L−1 and 5.9 mg kg−1 respectively),which is dominated by ophiolitic ultramafic forma-tions. The variation of As levels between the differentparts of the study area suggests that local geologyexerts a determinant influence on As geochemicalbehaviour. On the other hand, the geothermal activitymanifested in the area of Polichnitos–Lisvori does notaffect the presence of As in groundwater and streams.

Keywords Arsenic . Groundwater . Stream water .

Stream sediments . Lesvos

Introduction

Elevated As in groundwater intended for humanconsumption has been detected in several countriesall over the world, during the last decade, bringing outthe potential impact of As on public health forhundreds of millions of people (Nordstrom 2002;Smedley and Kinniburgh 2002; Mandal and Suzuki2002). The health risk resulting from As exposure hasrecently been reevaluated and there is now sufficientscientific evidence on the impact of As toxicity onhumans (Kapaj et al. 2006; Bhattacharya et al. 2007).In response to this knowledge, WHO (2001) andUSEPA (2001) have reduced the maximum Ascontaminant level (MCL) in drinking water from 50

Environ Monit Assess (2009) 151:383–396DOI 10.1007/s10661-008-0280-z

DO00280; No of Pages

M. Aloupi (*) :M. O. Angelidis :A. Μ. Gavriil :M. KoulousarisDepartment of Environment, University of the Aegean,81100 Mytilene, Greecee-mail: malou@env.aegean.gr

S. P. VarnavasDepartment of Geology, Laboratory of Applied Geochemistry,University of Patras,21100 Patras, Greece

to 10 μg L−1, an action that EC legislation hadalready taken since 1998 (EC 1998). The EC standardwas adopted by the Greek legislation in 2001 (O.G.G.2001).

Arsenic occurrence in natural waters is the result ofnatural or anthropogenic sources, natural sourcesbeing the major cause of environmental As problems(Smedley and Kinniburgh 2002). Naturally occurringAs in groundwater aquifers is a result of variousfactors, including groundwater physicochemical prop-erties along with regional climate and geologyconditions. Geothermal, mining and industrial activ-ities can also lead to high As levels (Smedley andKinniburgh 2002; Mandal and Suzuki 2002). Arsenicassociated with geothermal waters has been reportedin several parts of the world, including hot springs inUSA, Japan, New Zealand, Chile, Iceland, Russia(Kamchatka), France, Argentina and Dominica(Welch et al. 2000; Smedley and Kinniburgh 2002).On the other hand, a great number of recent studieshave linked the occurrence of the element in aquiferswith regional geology and hydrogeology, the mostserious contamination being in alluvial fluvial/deltaicor lacustrine plains and in intermediate to felsicvolcanic rocks (Welch et al. 1988; Armienta et al.1997; Welch et al. 2000; Acharyya 2002; Spencer2002; Ahmed et al. 2004; Bhattacharya et al. 2004;Bundschuh et al. 2004; Rodriguez et al. 2004; Kapajet al. 2006).

In Greece, high As concentrations have been foundmainly in the northern part of the country, leading tothe exposure of local population to As-contaminateddrinking water (up to 130 μg L−1 in some areas;Table 1).

High As concentrations in groundwater have beendetected in the industrial area and the suburbs ofThessaloniki (Fytianos and Christophoridis 2004;Katsoyiannis and Katsoyiannis 2006; Katsoyiannis etal. 2007), as well as in other places in the Prefecture ofThessaloniki (Fytianos and Christophoridis 2004), inthe Prefecture of Chalkidiki (Tyrovola et al. 2006;Katsoyiannis et al. 2007) and in eastern Thessaly(Kelepertsis et al. 2006). In most of these cases, theorigin of As was attributed to natural sources associatedwith the regional geological and hydrological back-ground such as the reducing character of the water, itslong residence time, the low water flow and a potentialimpact on the aquifers of the hydrothermal activitymanifested in an adjacent area.

In the island of Lesvos, the drainage basin of theKalloni Gulf has volcanic rock formations in its westernand northern part and geothermal springs activity inPolichnitos and Lisvori (southern and eastern part),suggesting possible As enrichment in groundwater,which is the only source of water supply for humanconsumption and irrigation in the area. Also, in the past,sparse groundwater samples revealed occasionallyenhanced As concentrations (Hellenic General StateLaboratory, unpublished data). In order to investigatethe potential impact of these natural As sources on thequality of groundwater resources in the area, a surveywas conducted to investigate As concentrations ingroundwater as well as in surface (stream) water andsediments in the drainage basin of Kalloni Gulf.

The study area

Kalloni Gulf is a semi-enclosed sea inlet in the centralpart of the island of Lesvos. It is the larger of twoshallow gulfs of the island whose formation andorientation are the result of regional tectonism (Novakand Soulakellis 2000). The drainage basin of the Gulfcovers nearly 11,000 ha, almost half the land surfaceof the island. The hydrologic network of the catch-ment of the Gulf is dense, consisting of a number ofbigger and smaller streams. Among these onlyVouvaris, Tsiknias and Mylopotamos maintain theirwater flow through the year while remaining streamshave a seasonally intermittent flow (Gavriil 2002).

The total population in the area is 15,000 inhab-itants, residing in small towns and villages. The mainhuman activity is agriculture (non intense cultivationof olive trees, limited livestock farming). The use offertilizers is restricted to rather small quantities ofnitrogenous products, while there is a mild manufac-turing activity related to food processing (Gavriil andAngelidis 2005).

The sole source of water for human consumptionand irrigation is groundwater, supplied either bymunicipal and private tube wells, or, more rarely, bynatural springs. In the alluvial plain of Kalloni thealternation of layers of impermeable clay materialswith layers of permeable sand and gravel depositsfavours the formation of repeated aquifers up to adepth of 100 m. On the contrary, in the eastern partunconsolidated conglomerates and alluvial deposits of

384 Environ Monit Assess (2009) 151:383–396

Tab

le1

Phy

sicochem

ical

parametersandtotaldissolvedAsin

variou

stypesof

naturalwaters(m

eanvalueandrang

ein

parentheses)

Sam

ples

pHCon

ductivity

(μScm

−1)

Hardn

ess

(mgCaC

O3L−1)

Total

dissolvedAs

(μgL−1)

Reference

Groun

dwater

Kalloni

drainage

basin,

Lesvo

s31

7.49

(6.80–8.63

)77

2(304–2

,940

)22

3(17–57

0)5.3a

(<0.7–

88.3)

1Prefectureof

Thessalon

iki

527.6(7.0–8

.3)

846(447–1

,732

)31

8(120–5

07)

2.9(nd–23

.7)

2Indu

strial

area

ofThessalon

iki

117.6(7.3–8

.0)

1,08

2(440–2

,480

)25

0(126–7

10)

46(4–130

)3

Aksiosarea,near

Thessalon

iki

107.9(7.5–8

.1)

1,05

3(490–2

,360

)23

5(117–4

00)

29(3–68.8)

4Kalikratia,Chalkidiki

117.15

(6.75–7.45

)1,18

4(813–1

,780

)46

3(371–6

47)

28(3.6–74.6)

4Triglia,Chalkidiki,drinking

water

Upto

305

Triglia,Chalkidiki,irrigatio

nwater

60–7

005

Eastern

Thessaly

266.4(6.0–6

.6)

12(1–125

)6

Typ

ical

backgrou

ndnaturalconcentrations

<1–10

7,8

ECandGreek

standard

6.5–9.5

2,50

010

Geothermal

water

Kalloni

drainage

basin,

Lesvo

s2

6.56

(6.33–6.79

)18

,865

(17,83

0–19

,900

)1,68

0(1,602–1

,758

)65

.92(41.14

–90.70

)1

Kalikratia,Chalkidiki

26.73

(6.65–6.8)

1,64

0(1,580–1

,700

)67

2(653–6

90)

20.0

(4.2–35.8)

4Worldwide

<10–5

0,00

07,

9,10

,11,12

Stream/river

water

Kalloni

drainage

basin,

Lesvo

s9

8.02

(6.99–8.72

)70

2a(462–1

4,10

0)25

0a(170–1

,840

)5.62

(0.35–13

.24)

1Europ

eanandNorth

American

rivers

1.42

13Pristinerivers,worldwide

0.8

14Pollutedrivers,worldwide

Upto

21,800

7

1Thissurvey,2Fytiano

sandChristoph

oridis(200

4),3KatsoyiannisandKatsoyiannis(200

6),4Katsoyiannisetal.(200

7),5Tyrov

olaetal.(200

6),6Kelepertsisetal.(200

6),7

SmedleyandKinnibu

rgh(200

2),8MandalandSuzuk

i(200

2),9Ballantyn

eandMoo

re(198

8),10

Welch

etal.(198

8),11

Mitrakas

(200

1),12

Planer-Friedrich

etal.(200

6),13

And

reae

etal.(198

3),14

Froelichet

al.(198

5)aAfter

theexclusionof

1extrem

evalue

Environ Monit Assess (2009) 151:383–396 385

small thickness allow the formation of shallow andrestricted aquifers (Mandilas and Kardakari 1998).

The geology of the study area is complex (Fig. 1). Thebasement of the island consists mainly of Palaeozoicand Mesozoic schists and phyllites with intercalationsof carbonate rocks, outcropping near Polichnitos. At theeastern part of the study area this crystalline series isassociated with ophiolitic ultramafic rocks (peridotitesand pyroxeno-peridotites with various degrees ofserpentinisation) which are considered part of theNeothythian basement. The northern and western partis covered by neogenic volcanic formations (pyroclasticlayers, lavas originating from early (Miocene) and late(Lower Pliocene) volcanic activity, 100 m thick. Anignimbrite deposition originating from Miocene volca-nism forms a wide zone between the metamorphicrocks and the volcanic masses in the northern part,spreads towards the south, up to Polichnitos, where itoverlies the ophiolites. A layer of neogenic lacustrineand fluvial deposits, with a thickness ranging from a

few to 100 m, intercalated with pyroclastic rocks,locally overlies the ignimbrites. Quaternary alluvialplains form on the coast, the most extensive field beingin the north, in the area of Kalloni (Hecht 1971–1974;Kelepertsis and Chatsidimitriadis 1983; Katsikatsoset al. 1986; Fytikas et al. 1989; Michelot et al. 1993;Serelis 1995; Novac and Soulakellis 2000; Mountrakiset al. 2001; Lamera et al. 2001).

The Polichnitos–Lisvori area has one of the mostimportant geothermal fields of Lesvos and the onlyone within the limits of the study area. Surfacemanifestations of this geothermal field appear nearPolichnitos and near Lisvori and their waters arewidely used for hydrotherapy. The thermal field isformed within the layer of ignimbrites, whosepermeability is increased by tectonic fractures andfaults (Aggelopoulos 2003).

The Polichnitos and Lisvori thermal springs are ofthe alkaline chloride type. Isotopic data and Br−/Cl−

and Na+/Cl− ratios have indicated that the origin of

Fig. 1 Geology of the studyarea

386 Environ Monit Assess (2009) 151:383–396

thermal fluids is both meteoric and sea water, the seawater contribution being nearly 30%, whereas geo-thermometry has led to an estimation of geochemicaltemperature in the range of 120–150°C attained at adepth of 1.5 km (Fytikas et al. 1989; Michelot et al.1993; Lambrakis and Kallergis 2005).

Materials and methods

A total of 31 samples of groundwater, twowater samplesfrom thermal springs, nine streamwater and nine bottomstream sediment samples were collected in June of 2005from the drainage basin of the Kalloni Gulf (Fig. 2). Theaim of the sampling scheme was the investigation ofthe potential influence of the Polichnitos–Lisvorigeothermal field on As occurrence in ground andsurface water and the detection of potential sources ofthe element, through the assessment of the spatialvariability of As in the water systems of the study area.

Groundwater samples were obtained directly fromcontinuously operating public and private tube wells(n=22) and from springs (n=9). A single sample wascollected from each sampling point.

At sample collection pH and conductivity of watersamples were measured by means of a portableCONSORT C932 electrochemical analyzer, equippedwith a SP10T pH and a SK10T conductivity elec-trode. Water total hardness was determined by theEDTA titration method (Greenberg et al. 1985).

All chemicals used in the determinations were ofanalytical reagent grade and all water used was from aMilli-Q water purification system (18.2 MΩ cm).Sample handling in the laboratory was carried out in aNUAIRE (NU 154-524E) laminar flow hood.

The water samples for As determination werecollected directly into dark polyethylene vials. Avolume of 500 mL was vacuum filtered through a pre-cleaned Nuclepore 0.4 μm polycarbonate membranefilter; the filtrate was adjusted to pH≤2 with HCl and

Fig. 2 Sampling stations

Environ Monit Assess (2009) 151:383–396 387

stored in dark polyethylene containers at 4°C(McCleskey et al. 2004). Total dissolved As wasdetermined by hydride generation atomic absorptionspectrometry (HG-AAS) on a Perkin-Elmer 5100 PCAtomic Absorption Spectrometer, equipped with anAs hollow cathode lamp, an electrically heated quartzcell with a 15 cm path length, and a Perkin-ElmerFIAS 100 flow injection analysis system. Theanalytical procedure was based on the methoddescribed by Shraim et al. (1999) but the analyticalparameters were subjected to in-house optimizationbecause of equipment differences. In this study, theinstrument was set at a wavelength of 193.7 nm, with0.7 nm for the monochromator spectral bandpass. Thequartz cell was heated to 900°C. The carrier andreductant solutions were 0.03 M HCl and 0.5%ΒΗ4Νa in 0.05% NaOH, respectively, and their flowrates were adjusted to 2 and 4 mL min−1 respectively.The sample loop was 250 μL. Before the analysis, thewater samples were mixed with L-cysteine to a finalconcentration of 2 g L-cysteine/100 mL of filtrate anda contact time <10 min was allowed prior todetermination. As a Certified Reference Material fordissolved As in fresh water was not available, thetrueness of measurements was assessed throughrecovery of additions of known amounts of As in asample (International Organization for Standardization1993). The calculated recovery was 103.5%.

Microwave acid digestion was performed for thedetermination of As in particulate matter. TheNuclepore filters were digested in Savillex Teflonbombs with 1 mL aqua regia and 1 mL HF 40% v/v.Digests were diluted to 25 mL in pre-cleaned polypro-pylene volumetric flasks containing 0.5 g boric acid(Loring and Rantala 1992). Arsenic was determined byGFAAS using the same analytical parameters as for Asdetermination in sediments (see below). Analyticalperformance was assessed by analysis of appropriateamounts (∼10 mg) of the BCSS-1 (marine sediment)Reference Material certified by NRCC (Table 2).

The limits of detection, calculated as three standarddeviations of nine successive replicates of the reagentblank, for dissolved and particulate As in watersamples were 0.7 and 0.1 μg L−1 respectively.

Stream sediment samples were collected with aplastic scoop, stored in plastic containers and kept at4°C until analysis. Grain size distribution wasmeasured by wet sieving according to the methoddescribed by Loring and Rantala (1992). The following

fractions were determined: silt + clay (<63 μm), sand(63 μm<x<2 mm) and gravel (>2 mm). Arsenic, Feand Li in sediment samples was determined in the<2 mm fraction after microwave assisted wet digestionwith aqua regia and HF, in Teflon bombs (Loring andRantala 1992). The determinations were performed in aPerkin-Elmer 5100 PC-ZL Atomic Absorption Spec-trometer, by the FAAS technique for Fe and Li and theGFAAS technique for As. Hollow cathode lamps wereused as the light source and the selected wavelengthswere 248.3 nm (0.2 nm) for Fe, 670.8 nm (1.4 nm)for Li and 193.7 nm (0.7 nm) for As (slit inbrackets). Deuterium arc (for Fe) and tungsten halide(for Li) continuous source lamps were used forbackground correction in FAAS. Zeeman backgroundcorrection was used in GFAAS. In As determinationthe pyrolysis was performed at 1,400°C assisted by5 μL of 10.0±0.2 g Pd /L as chemical modifier and theatomization was achieved at 2,200°C. The injectedvolume of the sample was 10 μL. The quality of theanalytical results was controlled with the use of theBCSS-1 (Table 2). Because BCSS-1 is not certified forLi, analytical trueness was checked by comparison tothe value provided by Rantala and Loring (1990).

Statistical analysis was performed with the SPSS12.0 software. For the calculation of the regressionmodels between As and metal concentrations in streamsediments, the initial regression models were examinedfor influential points through the analysis of theresiduals, the calculation of Cook’s distance, which isa measure of how much the residuals of all cases wouldchange if a particular case were excluded from the

Table 2 Certified/indicative and measured values of As, Fe (asFe2O3) and Li in the Reference Material BCSS-1 and calculatedtrueness % (trueness % = 100×(Certified value−Measured value)/Certified value; International Organization for Standardization1993)

As (mg kg−1) Fe2O3 (%) Li (mg kg−1)

Certified value 11.1±1.4 4.70±0.14 46.5±1.0a

Particulate matterMeasured value(n=6)

11.1±1.5 – –

Trueness % 0 – –SedimentsMeasured value(n=6)

10.6±1.2 4.90±0.06 45.3±2.1

Trueness % −4.5 4.3 −2.6

a Indicative value (Rantala and Loring 1990)

388 Environ Monit Assess (2009) 151:383–396

calculation of the regression coefficients, and throughthe calculation of DfBeta for the slope, which shows thechange in the slope that results from the exclusion of aparticular case. When one or more influential pointswere detected, then the regression was carried out again,after the exclusion of these points. This procedure wasnot feasible for the regression of As to Li which was notstatistically significant for the initial data, but when thetwo obviously outlying points noticed in the scatter plotwere removed it turned out to be strong.

Results and discussion

The conductivity, pH, total hardness and total Asconcentrations, in groundwater for human consump-tion and thermal springs are shown in Table 3.

Conductivity values ranged between 304 and2,940 μS cm−1, with values higher than 1,000 μScm−1 found in samples collected from some low-lyingcoastal sites. These values are probably due toseawater intrusion in the aquifer. Nonetheless, theindicator quality standard of 2,500 μS cm−1 proposedby the EC and Greek legislation for conductivity indrinking water (EC 1998; O.G.G. 2001) is exceededin only one sample. As a general trend, higherconductivity values were measured in samples fromthe eastern part of the study area (13 out of 14samples had conductivity greater than 700 μS cm−1),whereas in 11 out of 13 samples from the northernpart conductivity values were less than 700 μS cm−1.The average values of conductivity, when the outlyingvalues are excluded, are 732, 526 and 500 μS cm−1

for eastern, northern and western sites respectively.The range of pH values was between 6.80 and 8.63,

with none of the values exceeding the limits (6.5–9.5)proposed by the Greek legislation for drinking water(O.G.G. 2001). Values of pH in the range 6.0–8.5 aretypical for groundwater in the absence of iron sulphideminerals from the bedrock, with which groundwaterinteracts (Fisher 2002). Like conductivity, pH variedamong the different parts of the study area. Values ofpH greater than 8.00 were measured only in samplesfrom the area of Polichnitos–Lisvori, in the east, whilepH diminishes on average towards the north and thewest (average values: 7.78, 7.34 and 6.97 for eastern,northern and western sites respectively).

Groundwater samples from the drainage basin ofthe Kalloni Gulf were mostly hard. Over 40% of the

samples were characterized as “very hard” andanother 42% as “hard” according to the classificationby the U.S. Geological Survey (U.S. Department ofthe Interior, U.S. Geological Survey, Maintainer: OfficeofWater Quality (n.d.)). The highest hardness was foundin the sample with the highest conductivity. Although apronounced pattern of geographical distribution was notdetected for hardness, soft and moderately hard watersamples were more frequent among the eastern stations,whereas very hard water was more frequent in the north.

Table 3 Conductivity (in μS cm−1), pH, total hardness (in mgL−1) and total dissolved As (in μg L−1) in groundwater—drinking and thermal springs—from the Kalloni Gulf drainagebasin

SampleID

Conductivity pH Totalhardness

Total dissolvedAs

Drinking groundwaterL1 701 8.07 431 <0.7L3 741 7.77 358 1.3L4 778 7.27 142 6.6L5 790 7.14 144 5.4L6 854 8.60 38 <0.7L7 871 8.56 5 <0.7L8 890 8.63 5 <0.7L10 1,315 7.46 176 6.4L11 1,288 7.44 177 6.8L12 463 7.60 147 2.9L13 454 7.73 150 2.9L14 469 7.06 259 3.6L15 510 7.24 245 5.1L16 2,940 7.19 570 6.6L17 613 7.71 216 4.8L18 552 7.59 202 9.7L19 568 7.55 183 9.1L20 541 7.57 179 11.1L21 304 7.02 119 14.0L23 570 7.44 222 9.3L24 736 6.91 169 12.5L25 579 7.90 422 1.8L26 858 7.69 112 <0.7L27 800 7.05 298 4.4L37 1,161 6.80 397 5.9L38 1,133 6.92 438 4.4L39 495 7.23 176 7.9L40 509 6.92 170 5.5L41 519 7.96 171 88.3L42 471 7.23 170 5.0L43 457 6.90 142 5.2Thermal springsL2 19,900 6.79 1,758 90.7L9 17,830 6.33 1,602 41.1

Environ Monit Assess (2009) 151:383–396 389

On the other hand it is worth noticing that both the higherand the lower hardness values were recorded in twoadjacent areas, in the east. Specifically, total hardness aslow as less than 40 mg CaCO3 L

−1 was found in watersamples from the village of Lisvori while very highvalues, in the range of 350–450 mg L−1, were found inthe village of Polichnitos a few kilometers to the south.

As far as total dissolved As is concerned, the ECMCL of 10 μg L−1 was exceeded in only foursamples. However, it must be noted that even inthese cases As was below 15 μg L−1 in all but onesample, from Skala Kallonis, which had a much higherAs level, reaching 88.3 μg L−1 (the correspondingwater supply had been banned for drinking purposes).The geographical variability of dissolved As shows aclear difference between the different parts of the studyarea; average values (ranges in parentheses) in the east,north and west are 2.9 (0.4–6.8), 8.0 (3.6–14.0) and 5.9(4.4–7.9) μg L−1 respectively (the extreme value of88.3 μg L−1 is not included in calculations). Arsenicconcentrations >9 μg L−1 were determined only insamples from the area between the villages of Ag.Paraskevi and Napi, in the north, while low As(<3 μg L−1) occurred only in the eastern part.Intermediate concentrations were found in samplesscattered throughout the drainage basin.

Although baseline As concentrations in groundwaterquoted in literature vary widely, in the range of fourorders of magnitude, typical background naturalconcentrations from different countries are between <1and 10μg L−1 (Smedley and Kinniburgh 2002; Mandaland Suzuki 2002). Arsenic levels in groundwater fromthe study area are within the range of or occasionallyslightly exceed these values, with the exception of thesingle sample with a substantially high concentration.

The human activities within the limits of the studyarea are considered to pose limited stress on theenvironment. The absence of big cities, large scaleindustry, mining activities and intensive agriculturesuggest that anthropogenic sources are highly unlikelythe cause of As contamination of aquifers. Thus, as inmany other cases in Greece and all over the world, theorigin of As is probably attributed to natural sources.Although according to Johannesson et al. (1996) and toSmedley and Kinniburgh (2002), a clear-cut relationshipbetween high As in groundwater and the composition ofthe source rocks and aquifer materials was notestablished, a great number of more recent studies haveassociated the occurrence of the element in the aquifers

with regional geology and hydrogeology, the heaviestcontamination being in alluvial fluvial/deltaic or lacus-trine plains and in intermediate to felsic volcanic rocks(Welch et al. 1988; Armienta et al. 1997; Welch et al.2000; Acharyya 2002; Spencer 2002; Ahmed et al.2004; Bhattacharya et al. 2004, Bundschuh et al. 2004,Rodriguez et al. 2004; Kapaj et al. 2006).

Geothermal activity is another well documentedsource of As in groundwater (Ballantyne and Moore1988; Welch et al. 1988; Mitrakas 2001; Smedley andKinniburgh 2002; Planer-Friedrich et al. 2006). Sucha case for example occurs in the area of Triglia,Chalkidiki (Tyrovola et al. 2006).

On the contrary, the findings of the present studysuggest that As contamination of the groundwateraquifer is not affected by the geothermal field ofPolichnitos–Lisvori, as the majority of the drinkinggroundwater samples from this area (L1–L8, L25,Fig. 2) have As concentration <2 μg L−1, and onlytwo samples from the adjacent village of Vassilikahave slightly higher values (5.5–6.5 μg L−1). It seemsthat the groundwater aquifer does not undergo anysubstantial mixing with the ascending geothermalfluids. Another reason is the potential incorporationof As occurring in geothermal fluids onto iron oxides/hydroxides in a well oxygenated environment, result-ing in the depletion of As in the liquid phase. This issupported by the geochemical behaviour of As in theSantorini and the Yali hydrothermal fields, HellenicVolcanic Arc. At both fields As in sedimentsincreased seawards, with increasing distance fromthe hydrothermal fields (Varnavas and Cronan 1988,1991, 2005; Cronan et al. 2000).

The waters from the thermal springs of Polichnitos(L2) and Lisvori (L9) were slightly acidic and hadhigh conductivity and hardness. The temperature ofthe water was 87°C and 65°C respectively and itsdissolved As content varied between the two sam-pling sites with concentration at the Polichnitossprings around 90 μg L−1, more than twice as highas the concentration in Lisvori. According to theliterature, As in geothermal waters shows a bigvariability, ranging from <10 μg L−1 to tens ofmilligrams/liter (Ballantyne and Moore 1988; Mitrakas2001; Smedley and Kinniburgh 2002; Planer-Friedrichet al. 2006; Tyrovola et al. 2006). Compared to theupper limit of this range, the concentration of theelement in the thermal springs of Polichnitos andLisvori is relatively low.

390 Environ Monit Assess (2009) 151:383–396

When the geographical distribution of As levels inthe groundwaters of the study area is examined inrelation to the geological background, a relationshipbetween them becomes evident. The results of thissurvey show that high and low As containing ground-waters are discriminated in aquifers developed indifferent bedrock materials, as high As concentrationswere determined only in samples from the north,where neogenic volcanic rocks (mainly pyroclasticmaterial and lavas) prevail. Low As concentrations(<3 μg L−1) occurred only in the eastern part, wherethe bedrock material comprises the formation ofignimbrites underlain by ophiolotic peridotites. Asmentioned above, volcanic felsic and intermediaterocks, and sediments derived from them, are associ-ated with elevated As levels in groundwater, probablynot because they contain more As than other types ofrocks, but because the As is more readily mobilizedfrom them (Welch et al. 1988; Welch et al. 2000;Spencer 2002). Furthermore, the only noticeably highAs concentration in groundwater (88.3 μg L−1) wasfound at a coastal site (Skala Kallonis), in the north ofthe gulf, located in an extensive alluvial plain. This isin accordance to the general argument set by theliterature that As contaminated aquifers develop inalluvial deposits, in many places all over the world(Welch et al. 1988; Ahmed et al. 2004).

In order to further examine the suggestion ofassociation between As occurrence in groundwaterand geology, As has been determined in both waterand bottom sediments of a number of streams withinthe study area. Iron and Li were also determined instream sediments because they are considered to

represent the main lithological units covering thestudy area. In particular, studies on the geochemistryof Li have shown that it varies proportionately withincreasing silica in volcanic rocks and that itsconcentrations in these rocks are in the order of 10–30 mg kg−1 at 60% SiO2 though occasionally they canexceed 65 mg kg−1 (Coradossi and Martini 1981;Ryan and Langmuir 1987). On the contrary, Li has amuch lower abundance in peridotites, with concen-trations in the range of 1–3 mg kg−1 due to itsincompatibility during partial melting and fractionalcrystallisation (Ryan and Langmuir 1987; Seitz andWoodland 2000). On the other hand, Fe abundancegenerally increases from felsic to mafic and ultramaficrocks, with world average contents of 2.7%, 8.6% and9.9% respectively (Krauskopf and Bird 1995). Chemicalanalyses of the ultramafic rocks of Lesvos were foundto contain an average of 8.8% of Fe2O3 (Serelis 1995),corresponding to 6.2% of Fe. Consequently, anyrelationship between As and Li and/or Fe variationcould be an indication of the bedrock type that releaseAs in the hydrological systems of the study area.

Arsenic in stream waters from the drainage basinof the Kalloni Gulf, along with conductivity, pH andhardness are shown in Table 4. The same table showsAs, Fe and Li in sediments of the respective streams.

The very high conductivity (14,100 μS cm−1),matching a correspondingly high hardness, wasrecorded at station L32, collected near the mouth ofa small stream was presumably due to mixing withseawater. This probably happens in the adjacentstation L33 as well though to a considerably lesserdegree. As for the rest of the samples, conductivity

Table 4 Conductivity (in μS cm−1), pH, total hardness (in mg L−1) and dissolved (dAs) and particulate (pAs) As (in μg L−1) in streamwaters along with As (in mg kg−1), Fe (%) and Li (in mg kg−1) in stream sediments from the drainage basin of the Kalloni Gulf

Sample ID Water Sediments

Conductivity pH Total hardness dAs pAs As Fe Li

L22 495 7.96 183 12.4 <0.1 18.8 3.3 12.4L28 822 6.99 298 5.0 1.0 7.2 2.6 15.0L29 701 8.62 492 1.0 <0.1 11.0 4.9 7.3L30 784 8.45 531 <0.7 <0.1 3.4 7.8 4.9L31 462 7.85 330 <0.7 <0.1 2.0 9.7 6.0L32 14,100 8.38 1,840 6.8 0.7 9.3 4.4 15.3L33 1,050 8.72 544 4.0 <0.1 7.7 0.2 1.5L34 806 7.22 238 8.4 1.2 17.5 3.3 10.8L35 479 8.11 170 11.6 <0.1 21.9 3.4 12.8

Environ Monit Assess (2009) 151:383–396 391

and hardness ranges were 462–822 μS cm−1 and 170–531 mg L−1, respectively. Stream waters werealkaline, with pH between 6.99 and 8.72.

Total dissolved As varied from <0.7–13.2 μg L−1.The concentrations measured in the streams of thestudy area are high, compared to the average values inEuropean and North American rivers (1.42 μg L−1,Andreae et al. 1983) or in pristine rivers (0.8 μg L−1,Froelich et al. 1985). Much higher concentrationshave been found in rivers polluted either by waste-water discharges or by mining activities (Smedley andKinniburgh 2002). However, as mentioned above, thehigh values observed in the stream waters of theKalloni Gulf drainage basin could not be attributed tosuch human related sources. The geographical patternof the variation of total dissolved As in streamsresembled that of groundwater. The highest valueswere encountered in both of the two samples from thestream Tsiknias and a single sample from its tributary,in the north. This stream (with its tributaries) is thebiggest amongst those flowing into the Kalloni Gulf.The stream runs through the neogene igneous rocks(upper and lower lava units, vitrophyric lava) ofnorthern part of the study area (Hecht 1971–1974;Kelepertsis and Chatsidimitriadis 1983). On the otherhand, As level below 1 μg L−1 was found in rivers fromthe eastern part. As with groundwater, geothermalactivity often affects As concentrations in river waters(Smedley and Kinniburgh 2002). This process could notbe supported for the Kalloni Gulf drainage basin, sincethe highest As values and the geothermal field do notcoincide spatially. In any case, the As concentrationsmeasured in stream waters must have been affected byevaporation, since the flow rates are very diminishedduring the summer. A similar process has been noticedfor trace metals in a previous study (Gavriil 2002). Aseasonal survey would confirm this hypothesis andascertain the As levels through the year.

Particulate As in most of the cases was <0.1 μg L−1

and never exceeded 2 μg L−1. The comparisonbetween dissolved and particulate concentrationsshows that dissolved As accounts on average for 92%of the total load, indicating that the transport of theelement by stream waters into the Kalloni Gulf takesplace mainly in the dissolved phase. This finding is inaccordance to the literature (Barringer et al. 2007).

Regarding stream sediments, As and metals contentsshowed a great variability, in the range of 2.0–21.9 mgkg−1 for As, 0.2–9.7% for Fe and 1.5–15.3 mg kg−1 for

Li. Minimum Fe and Li values were found in sedimentfrom sample site L33. However, this sample consistedmainly of visible fine-grained plant debris and for thisreason it has not been included in the following dataanalysis. The rest of sediments were coarse grained,with a silt + clay content between 0% and 12%. Thecoarse fraction consisted of sand in the range 29–85%and gravel in the range 3–71%.

A strong association exists between As concen-trations in bottom material and water (Fig. 3), whichcorresponds to a correlation coefficient, R, of 0.89,significant at the 0.003 level (for the calculation of R,concentrations below the analytical limit of detectionwere replaced by the half of this value). A similarrelationship between As levels in stream water andsediment has been recognized in previous studies(Aston et al. 1975; Wilson and Hawkins 1978).

As a general remark, it could be said that there is apositive co-variation between As and Li in streamsediments and a negative co-variation between bothAs and Li with Fe (Fig. 4a, b, c). These relationshipscould provide useful information on the origin of Asin the stream sediments, so they were furtherinvestigated by regression analysis.

The strong negative relationship between Fe and Li(Fig. 4a) reflects the difference in rock types that formthe watersheds of the streams under investigation. Inaccordance to the literature, the highest Fe and lowest

0

5

10

15

0 5 10 15 20 25

As in stream sediments (mg Kg-1)

As

in s

trea

m w

ater

s (µ

g L-1

) R = 0.89

Fig. 3 Relationship between As concentrations in water andbottom sediments in various streams from the drainage basin ofthe Kalloni Gulf

392 Environ Monit Assess (2009) 151:383–396

Li levels are found in the sediments of the streamsVouvaris and Rema (L31 and L30 respectively) whichflow on the peridotites of the western coast of theKalloni Gulf, whereas high Li and low Fe content

characterize the sediments of Tsiknias in the north,where intermediate to felsic tertiary volcanic rocksdominate. The positive co-variation of As with Li(Fig. 4b), combined with the reverse co-variation withFe (Fig. 4c), indicates that the As occurrence instream sediments is associated to the presence offelsic and intermediate volcanic rocks and/or alluvialdeposits derived from volcanic rocks in their catch-ment areas. Although several studies have not beenable to show any significant difference in average Ascontent among the different types of igneous rocks,except possibly a slight enrichment in volcanicglasses (Onishi and Sandell 1955; Smedley andKinniburgh 2002; Mandal and Suzuki 2002), athorough survey on geochemical background ofstream sediments from Campania region, Italy, proveda strong dependence of As on the underlyingvolcanoclastic lithologies (Albanese et al. 2007).The same study assumed that As baseline (i.e. notanthropogenically influenced) values in stream sedi-ments from pyroclastic deposits were in the range of10–29 mg kg−1, as opposed to much lower values(between 3.7 and 10.2 mg kg−1) assigned to silici-clastic and carbonate deposits. The As concentrationsin the Tsiknias sediments determined in this surveyare within the range of values associated withvolcanic lithology.

Conclusions

The survey of As levels in groundwater, stream waterand stream sediments from the drainage basin of theKalloni Gulf revealed an enrichment in both surfaceand groundwater hydrological systems in the northernpart of the area. This enrichment is probably due tonatural lithogenic sources since there is no evidenceof anthropogenic origin of the element. The variationof As levels between the different parts of the studyarea, combined with geochemical substantiation,shows a consistent association of elevated As withthe volcanic bedrocks of the area, suggesting thatlocal geology exerts a determinant influence on Asgeochemical behaviour. On the other hand, the geother-mal activity manifested in the area of Polichnitos–Lisvoridoes not affect the presence of As in groundwater andstreams.

Although contamination of groundwater resourceswith As was found to be no more than 1.5 above the

L31

L32

y = -0.47x + 9.14R2 = 0.87

0.0

4.0

8.0

12.0

0.0 5.0 10.0 15.0 20.0

Li (mg kg-1)

Fe

(%)

L28

L32

y = 2.37x - 9.01R2 = 0.94

0.0

10.0

20.0

30.0

0.0 5.0 10.0 15.0 20.0

Li (mg kg-1)

As

(mg

kg-1

)

L28

y = -2.79x + 26.61R2 = 0.83

0.0

10.0

20.0

30.0

0.0 2.0 4.0 6.0 8.0 10.0 12.0

Fe (%)

As

(mg

kg-1

)

a

b

c

Fig. 4 Scatterplots and regression models of Fe:Li (a), As:Fe(b) and As:Li (c) in various stream sediments from the drainagebasin of the Kalloni Gulf

Environ Monit Assess (2009) 151:383–396 393

EC and Greek quality standards (with one exception)there is indication that part of the population of thecentral part of the island of Lesvos is locally exposedto health risks because of the long-lasting consump-tion of As contaminated drinking water. Arseniccontamination of underground and/or surface watercould occur in other parts of the island, a hypothesisthat should be tested in the future.

Acknowledgments This Project was co-funded by theEuropean Social Fund and National Resources-(EPEAEK-II)“PYTHAGORAS”.

References

Acharyya, S. K. (2002). Arsenic contamination in groundwateraffecting major parts of southern West Bengal and parts ofwestern Chhattisgarh: Source and mobilization process.Current Science, 82(6), 740–744.

Aggelopoulos, C. (2003). Hydrogeologic study of the thermalsprings of Polichnitos and Lisvori in Lesvos p. 35.Thessaloniki: Hellenic Thermalistic Society S.A. (inGreek).

Ahmed, K. M., Bhattacharya, P., Hasan, M. A., Akhter, S. H.,Alam, S. M. M., Bhuyian, H. M., et al. (2004). Arsenicenrichment in groundwater of the alluvial aquifers inBangladesh: An overview. Applied Geochemistry, 19(2),181–200.

Albanese, S., De Vivo, B., Lima, A., & Cicchella, D. (2007).Geochemical background and baseline values of toxicelements in stream sediments of Campania region (Italy).Journal of Geochemical Exploration, 93, 21–34.

Andreae, M. O., Byrd, T. J., & Froelich, O. N. (1983). Arsenic,antimony, germanium and tin in the Tejo estuary, Portugal:Modelling of a polluted estuary. Environmental Science &Technology, 17, 731–737.

Armienta, M. A., Rodriques, R., Aguayo, A., Ceniceros, N.,Villasenor, G., & Cruz, O. (1997). Arsenic contaminationof groundwater in Zimapan, Mexico. HydrogeologyJournal, 5, 39–46.

Aston, S. R., Thornton, I., Webb, J. S., Milford, B. L., &Purves, J. B. (1975). Arsenic in stream sediments andwaters of South West England. Science of the TotalEnvironment, 4(4), 347–358.

Ballantyne, J. M., & Moore, J. N. (1988). Arsenic geochemistryin geothermal systems. Geochimica et CosmochimicaActa, 52, 475–483.

Barringer, J. L., Bonin, J. L., Deluca, M. J., Romagna, T.,Cenno, K., Alebus, M., et al. (2007). Sources and temporaldynamics of arsenic in a New Jersey watershed, USA.Science of the Total Environment, 379(1), 56–74.

Bhattacharya, P., Welch, A. H., Ahmed, K. M., Jacks, G., &Naidu, R. (2004). Arsenic in groundwater of sedimentaryaquifers. Applied Geochemistry, 19(2), 163–167.

Bhattacharya, P., Welch, A. H., Stollenwerk, K. G., McLaugh-lin, M. J., Bundschuh, J., & Panaullah, G. (2007). Arsenicin the environment: Biology and Chemistry. Science of theTotal Environment, 379, 109–120.

Bundschuh, J., Farias, B., Martin, R., Storniolo, A., Bhatta-charya, P., Cortes, J., et al. (2004). Groundwater arsenic inthe Chaco-Pampean Plain, Argentina: Case study fromRobles county, Santiago del Estero Province. AppliedGeochemistry, 19, 231–243.

Coradossi, N., & Martini, M. (1981). Fluorine, chlorine andlithium distribution in igneous rocks of Lipari and Vulcano(Aeolian Islands, Italy). Bulletin of Volcanology, 44(3),565–571.

Cronan, D. S., Varnavas, S. P., & Hodkinson, R. (2000).Hydrothermal mineralizing processes and associated sed-imentation in the Santorini hydrothermal embayments.Marine Georesources and Geotechnology, 18, 77–118.

EC. Council Directive (98/83/EC) of 3 November 1998 on thequality of water intended for human consumption. OfficialJournal of the European Communities 1998; L 330: 32–54.

Fisher, R. S. (2002). Groundwater quality in Kentucky: pH.Kentucky Geological Survey. Information Circular 6,Series XII, 4 pp.

Froelich, P. N., Kaul, L. W., Byrd, J. T., Andreae, M. O., &Roe, K. K. (1985). Arsenic, barium, germanium, tin,dimethylsufide and nutrient biogeochemistry in CharlotteHarbor, Florida, a phosphorus-enriched estuary. Estuarine,Coastal and Shelf Science, 20, 239–264.

Fytianos, K., & Christophoridis, C. (2004). Nitrate, arsenic andchloride pollution of drinking water in northern Greece.Elaboration by applying GIS. Environmental Monitoringand Assessment, 93, 55–67.

Fytikas, M., Kavouridis, T., Leonis, C., & Marini, L. (1989).Geochemical exploration of the three most significantgeothermal areas of Lesbos island, Greece. Geothermics,18(3), 465–475.

Gavriil, A. M. (2002). Study of mechanisms of metal transportand early diagenesis In the semi-enclosed and shallowmarine system of Kalloni Bay, Lesvos, Greece. Disserta-tion, University of the Aegean, (in Greek)

Gavriil, A. M., & Angelidis, M. O. (2005). Metal and organiccarbon distribution in water column of a shallow enclosedBay at the Aegean Sea Archipelago: Kalloni Bay, island ofLesvos, Greece. Estuarine, Coastal and Shelf Science, 64(2–3), 200–210.

Greenberg, A. E., Trussell, R. R. & Clesceri, L. S. (Eds.)(1985). Standard methods for the examination of waterand waste waters, 16th ed. (pp. 1268). Washington:American Public Heath Association, American WaterWorks Association, Water Environment Federation.

Hecht, J. (1971–1974). Geologic map of Lesvos Island (5sheets). Athens: (Hellenic) National Institute of Geologicaland Mining Research (IGME).

International Organization for Standardization (1993). ISO3534-1:1993 Statistics—Vocabulary and symbols—Part1: Probability and general statistical terms, 47 pp.

Johannesson, K. H., Stetzenbach, K. J., Kreamer, D. K., &Hodge, V. F. (1996). Multivariate statistical analysis ofarsenic and selenium concentrations in groundwaters from

394 Environ Monit Assess (2009) 151:383–396

south-central Nevada and Death Valley, California. Jour-nal of Hydrology, 178, 181–204.

Kapaj, S., Peterson, H., Liber, K., & Bhattacharya, P. (2006).Human health effects from chronic arsenic poisoning—areview. Journal of Environmental Science and Health—Part A Toxic/Hazardous Substances and EnvironmentalEngineering, 41(10), 2399–2428.

Katsikatsos, G., Migiros, G., Triantaphyllis, M., & Mettos, A.(1986). Geological structure of the internal Hellines (eastThessaly—southwest Macedonia, Euboea–Attica–northernCyclades islands and Lesvos.) Geology and GeophysicalResearch, Special Volume, 191–212.

Katsoyiannis, I. A., Hug, S. J., Ammann, A., Zikoudi, A., &Hatziliontos, C. (2007). Arsenic speciation and uraniumconcentrations in drinking water supply wells in NorthernGreece: Correlations with redox indicative parameters andimplications for groundwater treatment. Science of theTotal Environment, 383, 128–140.

Katsoyiannis, I. A., & Katsoyiannis, A. A. (2006). Arsenic andother metal contamination of groundwaters in the indus-trial area of Thessaloniki, Northern Greece. EnvironmentalMonitoring and Assessment, 123, 393–406.

Kelepertsis, A., Alexakis, D., & Skordas, K. (2006). Arsenic,antimony and other toxic elements in the drinking water ofEastern Thessaly in Greece and its possible effects onhuman health. Environmental Geology, 50, 76–84.

Kelepertsis, A. E., & Chatsidimitriadis, E. (1983). Factorscontrolling the mineralogy and geochemistry of the recentsurface sediments of the Kalloni Gulf, Lesvos Island,Greece. Geologische Rundschau, 72(1), 167–190.

Krauskopf, K. B., & Bird, D. K. (1995). Introduction toGeochemistry (3rd ed.) McGraw Hill, pp. 647.

Lambrakis, N., & Kallergis, G. (2005). Contribution to thestudy of Greek thermal springs: Hydrogeological andhydrochemical characteristics and origin of thermalwaters. Hydrogeology Journal, 13(3), 506–521.

Lamera, S., Seymour, K. S., Vamvourakis, C., Kouli, M.,Paraskevas, E., & Pe-Piper, G. (2001). The Polychnitosignimbrite of Lesvos island. Bulletin of the GeologicalSociety of Greece, 34(3), 917–921.

Loring, D. H., & Rantala, R. T. T. (1992). Manual for thegeochemical analysis of marine sediments and suspendedparticulate matter. Earth-Science Reviews, 32, 235–283.

Mandal, B. K., & Suzuki, K. T. (2002). Arsenic around theworld: A review. Talanta, 58, 201–235.

Mandilas, C., & Kardakari, N. (1998). Conservation andpromotion of the wetland of the Kalloni Gulf, Lesvos.Special Environmental Assessment. Hellenic Ministry ofEnvironment, Physical Planning and Public Works, Mytilini(in Greek).

McCleskey, R. B., Nordstrom, D. K., & Maest, A. S. (2004).Preservation of water samples for arsenic(III/V) determi-nations: An evaluation of the literature and new analyticalresults. Applied Geochemistry, 19(7), 995–1009.

Michelot, J.-L., Dotsika, E., & Fytikas, M. (1993). Ahydrothermal and isotopic study of thermal waters onLesbos island (Greece). Geothermics, 22(2), 91–99.

Mitrakas, M. (2001). A survey of arsenic levels in tapunderground and thermal mineral waters of Greece.Fresenius Environmental Bulletin, 10, 717–721.

Mountrakis, D., Thomaidou, E., Zouros, N., & Kilias, A.(2001). Kinematic analysis and tertiary evolution of theLesvos ophiolites and metamorphic sole (Aegean Sea,Greece). Bulletin of the Geological Society of Greece, 34(1), 267–274.

Nordstrom, D. K. (2002). Worldwide occurrences of arsenic inground water. Science, 296, 2143–2145.

Novak, I. D., & Soulakellis, N. (2000). Identifying geomorphicfeatures using LANDSAT-5rTM data processing techniqueson Lesvos, Greece. Geomorphology, 34, 101–109.

Official Government Gazette of the Hellenic Republic (O.G.G.),Issue B’, No 892. Quality of water intended for humanconsumption, in compliance to the Council Directive 98/83/EC of 3 November 1998 (Common Ministerial Order Υ2/2600/2001).

Onishi, H., & Sandell, E. B. (1955). Geochemistry of arsenic.Geochimica et Cosmochimica Acta, 7, 1–33.

Planer-Friedrich, B., Lehr, C., Matschullat, J., Merkel, B. J.,Nordstrom, D. K., & Sandstrom, M. W. (2006). Speciationof volatile arsenic at geothermal features in YellowstoneNational Park. Geochimica et Cosmochimica Acta, 70(10),2480–2491.

Rantala, R. T. T., & Loring, D. H. (1990). Determination ofLithium in the NRCC Marine Sediments: MESS-1, BCSS-1, PACS-1 and the NIST River Sediment: SRM 2704.Geostandards and Geoanalytical Research, 14(3), 475–476.

Rodriguez, R., Ramos, J. A., & Armienta, A. (2004).Groundwater arsenic variations: The role of local geologyand rainfall. Applied Geochemistry, 19(2), 245–250.

Ryan, J. G., & Langmuir, C. H. (1987). The systematics oflithium abundances in young volcanic rocks. Geochimicaet Cosmochimica Acta, 51, 1727–1741.

Seitz, H.-M., & Woodland, A. B. (2000). The distribution oflithium in peridotitic and pyroxenitic mantle lithologies—An indicator of magmatic and metasomatic processes.Chemical Geology, 166(1–2), 47–64.

Serelis, K. G. (1995). A research of the ophiolites of Lesvos.Dissertation, Agricultural University of Athens, (in Greek).

Shraim, A., Chiswell, B., & Olszowy, H. (1999). Speciation ofarsenic by hydride generation-atomic absorption spectrom-etry (HG-AAS) in hydrochloric acid reaction medium.Talanta, 50, 1109–1127.

Smedley, P. L., & Kinniburgh, D. G. (2002). A review of thesource, behaviour and distribution of arsenic in naturalwaters. Applied Geochemistry, 17, 517–568.

Spencer, J. (2002). Natural occurrence of arsenic in southwestground water. Southwest Hydrology, 1(1), 14–15.

Tyrovola, K., Nikolaidis, N. P., Veranis, N., Kallithrakas-Kontos, N., & Koulouridakis, P. E. (2006). Arsenicremoval from geothermal waters with zero-valent iron—Effect of temperature, phosphate and nitrate. WaterResearch, 40(12), 2375–2386.

U.S. Department of the Interior, U.S. Geological Survey,Maintainer: Office of Water Quality (n.d.). Retrieved July9, 2007, from http://water.usgs.gov/owq/Explanation.html.

USEPA (2001). The arsenic and clarifications to complianceand new source contaminants monitoring, 66 FR 6976.

Varnavas, S. P., & Cronan, D. S. (1988). Arsenic, antimony andbismuth in sediments and waters from the Santorini hydro-thermal field, Greece. Chemical Geology, 67, 295–305.

Environ Monit Assess (2009) 151:383–396 395

Varnavas, S. P., & Cronan, D. S. (1991). Hydrothermal metal-logenic processes off the islands of Nisiros and Kos in theHellenic Volcanic Arc. Chemical Geology, 99, 109–133.

Varnavas, S. P., & Cronan, D. S. (2005). Submarine hydro-thermal activity off Santorini and Milos in the CentralHellenic Volcanic Arc: A synthesis. Chemical Geology,224, 40–54.

Welch, A. H., Lico, M. S., & Hughes, J. L. (1988). Arsenic inground water of the western United States. Ground Water,26(3), 333–347.

Welch, A. H., Westjohn, D. B., Helsel, D. R., & Wanty, R. B.(2000). Arsenic in ground water of the United States:Occurrence and geochemistry. Ground Water, 38(4),589–604.

WHO (2001). Environmental health criteria 224, arsenic andarsenic compounds. Inter-organization programme for thesound management of chemicals. Geneva.

Wilson, F. H., & Hawkins, D. B. (1978). Arsenic in streams,stream sediments, and ground water, Fairbanks area,Alaska. Environmental Geology, 2(4), 195–202.

396 Environ Monit Assess (2009) 151:383–396