Geothermal arsenic: Occurrence, mobility andenvironmental implications

Jochen Bundschuh a,b,n, Jyoti Prakash Maity c

a Faculty of Health, Engineering and Sciences, University of Southern Queensland and National Centre for Engineering in Agriculture and International Centrefor Applied Climate Sciences, Weststreet, Toowoomba, Queensland 4350, Australiab Royal Institute of Technology (KTH), Teknikringen 76, SE-10044 Stockholm, Swedenc Department of Earth and Environmental Sciences, National Chung Cheng University, Ming-Shung, Chiayi County, Taiwan

a r t i c l e i n f o

Article history:Received 12 August 2013Received in revised form12 June 2014Accepted 28 October 2014

Keywords:Geothermal arsenicTerrestrial geothermal systemsSedimentary and volcanic geothermalreservoirsArsenic speciation and mobilityArsenic geomicrobiology

a b s t r a c t

Arsenic (As) contamination in geothermal systems has been identified in many areas of the world.Arsenic mobilization from rocks and mineral phases into geothermal fluids depends on available Assources, geochemical conditions and microbiological activity. In deep geothermal reservoirs Asmobilization is predominantly from As-bearing pyrite at temperatures of 150–250 1C, and at highertemperatures also from arsenopyrite. Highest As concentrations, mostly in the range of thousands totens of thousands of mg/L and in case of Los Humeros (Mexico) even of up to 162,000 mg/L are found involcanic geothermal systems whereas in low- and high-enthalpy sedimentary geothermal systems theyreach only about 2000 mg/L. At many sites, uprising geothermal waters contaminate shallow waterresources. From the geothermal springs, those with NaCl water type have the highest As concentrations;these waters correspond to original reservoir waters which were not significantly altered during itsascent. In the geothermal reservoir and deeper parts of hydrothermal system, As is predominantlypresent as neutral H3As(III)O3 (arsenius acid) and under sulfidic conditions also as thioarsenites; close tothe earth's surface oxidation through atmospheric oxygen to As(V) species may occur; however, this is aslow process. As(III) emerging in geothermal springs is oxidized quickly through microbial catalysis andoften most As is present as As(V), at a distance of few meters from the spring outlet. This reviewhighlights the occurrence and distribution of geothermal As worldwide, its sources and its mobilizationand the presence of different As species in geothermal fluids considering different geological settingsand processes involving geothermal fluids rising from deep geothermal reservoirs to the earth's surfacewhere it may mix with shallow groundwater or surface waters and contaminate these resources. Themicrobial diversity of hot spring environments which plays an important role to mobilize the As byoxidation and reduction process in the geothermal system is also addressed.

& 2014 Elsevier Ltd. All rights reserved.

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12152. Occurrence and distribution of geothermal arsenic as function of geological setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12153. Sources and mobilization of geothermal arsenic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12174. Arsenic species in geothermal fluids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12175. Microbiological activity related to geothermal fluids in surface-near environments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12186. Processes involving geothermal fluids rising from deep geothermal reservoirs to the earth´s surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12197. Mixing of deep geothermal fluids with shallow groundwater and surface water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12198. Summary and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1220

Contents lists available at ScienceDirect

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Renewable and Sustainable Energy Reviews

http://dx.doi.org/10.1016/j.rser.2014.10.0921364-0321/& 2014 Elsevier Ltd. All rights reserved.

n Corresponding author at: Faculty of Health, Engineering and Science, University of Southern Queensland, Toowoomba, Queensland 4350, Australia.Tel.: þ61 746312694; Fax: þ61 746312526.

E-mail addresses: jochen.bundschuh@usq.edu.au (J. Bundschuh), jyoti_maity@yahoo.com (J.P. Maity).

Renewable and Sustainable Energy Reviews 42 (2015) 1214–1222

Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1220References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1220

1. Introduction

Geothermal fluids and springs are found around the world.Arsenic (As) is a well-known toxic and carcinogenic metalloid thatis found in a wide variety of chemical species throughout theenvironment and can be readily transformed and mobilized bymicrobes, changes in geochemical conditions, and other environ-mental processes. The release of As from rocks into geothermalfluids occurs predominantly along active tectonic plate boundaries[1]. The As is found in geothermal reservoir fluids and surfacemanifestations (hot springs, fumaroles, solfataras) in many geolo-gical settings and may contaminate “cold” aquifers, vadose zone,and surface waters [2].

Naturally occurring As in groundwaters associated with terres-trial geothermal activity is recognized to be significant and has beenidentified in many areas of the world including Alaska, western USA,Mexico, Central America, northern Chile, Kamchatka, Japan, Taiwan,Philippines, Indonesia, Papua New Guinea, New Zealand, Iceland andFrance [2–5]. Arsenic concentrations in water from the El Tatio(North Chile), Copper River (USA), Yellowstone National Park (USA),Azores (Portugal) and Los Humeros (Mexico) are reported to be ashigh as 48,000 μg/L, 48,200 μg/L, 15,000 μg/L, 9500 μg/L and74,000 μg/L, respectively [6–11]. The As mobilization and concentra-tions in geothermal waters are highly variable depending on thereservoir rock composition, pressure, temperature, redox condition,pH, presence of gases and microbiological activity.

The contamination of surface and subsurface water by geother-mal waters with As may result in a severe environmental impact ofgeothermal systems; pollution can occur either naturally by mixingor during geothermal energy exploitation if residual waters are notadequately re-injected into the deep underground; consequencemay be the contamination of water resources used for drinking orirrigation purposes (ground and surface water) [12–16].

This paper reviews available data on As concentrations andspecies in terrestrial geothermal systems, chemical characteristics,surficial discharges and microbial activity, to identify processesthat determine the As concentrations in these waters, and themechanisms for immobilization or release of As into freshwaterbodies. It is not possible to describe and to evaluate all theworldwide existing geothermal sites; reason is that from most ofthem As data are not available, or they are classified and notaccessible. We address similarities and differences between Asconcentrations from geothermal systems of different geologicaland tectonic settings: (i) volcanic rocks at active plate boundaries,(ii) sedimentary rocks which derive their heat from deep igneousintrusions and (iii) aquifers with geothermal waters correspondingto shallow groundwater which is conductively heated or whichreceives heat by steam uprising from depth.

2. Occurrence and distribution of geothermal arsenicas function of geological setting

High As concentrations in geothermal waters have been describedover a century ago [17,18]. Since then, elevated As concentrations ingeothermal reservoir waters have been reported from all inhabitedcontinents. Common concentrations are in the range of thousands totens of thousands of mg/L [7,19–24]. A world-wide overview of Asconcentrations in fluids of geothermal wells and springs is given inTables 1 and 2, respectively. The fluids of geothermal reservoirs in

volcanic rocks along active plate boundaries have the highest Asconcentrations (typical range thousands to tens of thousands of mg/kg), but as high as 162,000 mg/kg at Los Humeros, Mexico [31,32].Exceptions are the geothermal reservoirs of Hawaii and Iceland(o0.1 mg/kg) despite that they are in volcanic rocks; these lowconcentrations may be explained by the presence of fresh basalticreservoir host rocks with low As content [2] or with lower residencetime compared to the other volcanic geothermal reservoirs (reducedtime for water–rock interactions). Compared to reservoirs in volcanicrocks, much lower As concentrations (o3–2010 mg/kg; Table 1) arefound in fluids of reservoirs in sedimentary rocks comprising bothhigh- (e.g. Cerro Prieto, Mexico: 250–500 mg/kg) and low-enthalpygeothermal reservoirs (SE Mexican oil fields: o3–2010 mg/kg,Table 1) [35–38,52].

The As concentrations in fluids of geothermal springs are shownin Table 2; they are either similar as in the reservoir if theycorrespond to reservoir water or are lower if they are altered bydilution or chemical reactions or if they correspond to conductively-heated or steam-heated shallow groundwater. Spring waters ofWairakei, Waiotapu and Ohaaki/Broadlands (New Zealand), Mt Apo(Philippines) and Tibet contain 230–3000, 710–6500, 1000, 3100–6200 and 5700 μg/L, respectively [26,42,53–55]. The spring watersemerging from the geothermal systems of El Tatio (North Chile), LosHumeros (Mexico), and Yellowstone National Park (USA) contain upto 47,000–50,000, 3900, and 15,000, respectively [6,7,9,10]. Maity

Table 1Arsenic concentration in geothermal wells

Geothermal field/area Arsenic (μg/L or mg/kg) Ref

Chile: El Tatio, Chile (VOL; H) 30,000–40,000 [25]45,000–50,000 [26]

Costa Rica: Miravalles (VOL; H) 11,900–29,100 [27]Rincón de la Vieja (VOL; H) 6000–13,000 [27]

Mexico: Cerro Prieto (SED; H) 250–1500 [28,29]Los Azufres (VOL; H) 5100–49,600 [30,31]Los Humeros (VOL; H) 500–162,000 [30,32]Cactus-Sitio Grande (SED; L) o3–47 [33–35]Luna-Sen (SED; L) o3–548 [36–38]Jujo-Tecominoacán (SED, L) o3–1900 [39]Pol-Chuc-Abkatún (SED, L) 90–2010 [39]

New Zealand: Broadlands (VOL; H) 5700–8900 [40]Kawerau (VOL; H) 539–4860 [41]Orakei Korako (VOL; H) 599–802 [26]Waiotapu (VOL; H) 2900–3100 [26]Wairakei (VOL; H) 4100–4800 [26]

1000–5200 [42]

Philippines: Tongonan (VOL; H) 20,000–34,000 [43]28,000 (mean) [44]

USA: Lassen Nat Park (VOL; H) 2000–19,000 [45]

Russia: Kamchatka (VOL; H) 2000–30,000 [46]Ebeko volcano, Kuril Is. (VOL) 190–28,000 [47]

Tibet: Yangbajing GTP (CC) 5700 [48]Japan: Hachoubaru GTP, Oita 3230 [49]Turkey: Kizildere GTP; wastewater 853 [50,51]

Geological characterization of geothermal system after Chandrasekharam andBundschuh [1]. VOL: volcanic rocks; CC: continental collision zone; L: lowtemperature reservoir, To150 1C; H: high temperature reservoir, T4150 1C; mix:mixed with shallow groundwater or surface water: GTP: geothermal power plant;Is.: island.

J. Bundschuh, J.P. Maity / Renewable and Sustainable Energy Reviews 42 (2015) 1214–1222 1215

Table 2Arsenic concentration in different geothermal springs.

Geothermal springs Arsenic (μg/L) References

BoliviaPoopó lake area 8–60 [114]Coipasa a Uyuni 34 [115]

ChileEl Tatio, Chile (VOL) 47,000 [25]

45,000–50000 [26]

EcuadorTambo river area (VOL) 1090–7850 [23,60]North-central Andean 2–969 (water) [116]

1600–717600 (Sediment)

Costa RicaMiravalles (VOL; H) 5–4650 [27]Rincón de la Vieja (VOL; H) 5–10,900 [27]

NicaraguaTipitapa (VOL) 262 [117]

MexicoLos Azufres (VOL; H) o3900 [24,52]

USASalton Sea (granite intrusion; H) 30–12,000 [118]Kilahuea, Hawaii (VOL) 60–105 [119]Soda Dam/Valles Caldera, (VOL; H) 1700 [120]

21–2400 [21]750–1400

Hot Creek, Eastern Sierra Nevada 157–15,000 [59]Yellowstone, WY (VOL; H) [20]

E1500 Nordstrom 2009, pers. communBath Spring, Y NP. 1500 [71,72]Hot Spring Ojo Caliente, YNP 2500 [71,72]Norris Geyser Basin, YNP [91]

RussiaKamchatka (VOL; L,H) 794–944 [121]Dominica (Lesser Antilles) (VOL) 7–90 [122]

Papua New Guinea 817–952 [123]Tutum Bay (VOL)

New Zealand 996Broadlands (VOL; H) 712–6470 [26]Waiotapu (VOL; H) 710–6500 [124]

307–382 [53]Orakei Korako (VOL; H) 3740–5110 [125]Wairakei (VOL; H) 230–3000 [126]

[42]

PhilippinesMt. Apo (VOL; H) 3100–6200 [54]

JapanTamagawa (VOL) 2300–2600 [127]Beppu hot spring (VOL) 210–1360 [49]Obaba hot spring (VOL) 550 [49]

RussiaKamchatka (VOL, H) 2000–3600 [128]

TaiwanKuan-Tzu-Ling 121–410 [5]Chung-Lun 91 [5]Bao-Lai 4.03 [5]Geothermal Spring Valley 1070–4210 [129]

ItalyPhlegraean Fields (VOL) 12–12,600 [130]

GreeceKalloni drainage basin, Lesvos (mix) 41.1–90.7 [131]Kalikratia, Chalkidiki (mix) 3.6–74.4 [132]Chalkidiki (mix) 3.0–68.8 [133]Aksios area (mix) 1–1843 [132]

ChinaRehai geothermal field, Yunnan Province 43.6–687 (91% as As(III)) [134]

TurkeyBalcova 163.5–1419.8 [112]

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et al. [5] reported As concentration in Kuan-Tzu-Ling and Chung-Lun hot spring (Taiwan) as 410 and 91 μg/L, respectively.

In the following we present some more details on selectedgeothermal systems, mostly from the Americas.

In the Yellowstone National Park (USA) the As concentrationsfound in geothermal waters are often 41000 μg/L [6,20] andreach 15,000 μg/L (Nordstrom pers. commun. 2009). The dischargeof geothermal spring water into the Firehole River which meets tothe Madison river results in As concentrations of 360, and 19 μg/Lin the Missouri river, 470 km downstream of the springs [56]. Thedischarging geothermal water is initially (in the deep geothermalreservoir) reducing (dominance of As(III)), but redox conditionschange fast to oxidizing when the geothermal water emerges inhot springs at the earth's surface (predominance of As(V)); [57].Geothermal waters are the primary As source in groundwater inseveral regions of USA, in particular in the western part [58,59].

At El Tatio (Chile), high As concentrations of up to 50,000 and30,000–40,000 μg/L have been reported in springs and wells,respectively (Chile) [25]. Ellis and Mahon [26] mention similarhigh As concentrations of 45,000–50,000 μg/L from these geother-mal waters related to a subduction zone with active volcanism.These geothermal discharges contribute to the As content of theLoa river [25].

The discharge of geothermal springs into surface waters wasstudied by in the Andes in Ecuador (Napo province) [60]. The springswater contains 1090–7852 μg/L of As. In water of two springs withlow redox potential (Eh: –112.2 and –103.8 mV, respectively), As(III)was dominant (74.4% and 61.2% of total As, 3152 and 6120 μg/L,respectively). Abundant Fe(III) precipitates around the spring outletsindicate fast oxidation of the water. In contrast, As(V) is predominantin other two springs with higher Eh (67.8% and 66.5% of their total Asconcentrations, amounting to 3555 and 7852 μg/L, respectively; Ehvalues are þ9.2 and þ7.3 mV, respectively).

At Rincón de la Vieja geothermal area (NW Costa Rica), most ofthe geothermal springs have low As concentrations; exceptions aretwo springs with NaCl-type water (Salitral Norte 1 and 2; As:10,600 and 10,900 μg/L, respectively) [27]. These high As concen-trations correspond to those found in the deep-seated andesiticgeothermal reservoir (As: 6000–13,000 μg/L); therefore water ofthese springs correspond to discharges from the geothermalreservoir. The other geothermal springs correspond to predomi-nantly conductively-heated or steam-heated shallow meteoricwaters [52] and As concentrations are consequently lower (5.2–132 μg/L) [27].

In Mexico As was studied in thermal fluids from geothermalreservoirs of three different types of geological settings: (i) high-enthalpy (4150 1C) system in volcanic rocks, related to volcanism, (ii)high-enthalpy, sited in sedimentary rocks, and (iii) low-enthalpy(o150 1C) geothermal systems in sedimentary rocks of petroleumreservoirs [52]. In the first group, water of the deep geothermalreservoirs contains As in wide concentration ranges of 500–162,000 μg/L at Los Humeros and 45–49,600 μg/L at the Los Azufressite. The As concentrations in the high- and low-enthalpy sedimen-tary geothermal reservoirs are of similar order. They are much lowerthan those of the geothermal reservoirs hosted in volcanic rocks.Values are 250–1500 μg/L for the high-enthalpy water of Cerro-Prieto.

The low-enthalpy oilfield waters in SE-Mexico contain o2000 μg/L ofAs at depths of 2900–6100m b.s.l. (Cactus-Sitio Grande: o3–47 μg/L;Luna-Seno3–548 μg/L; Jujo-Tecominoacáno3–1890 μg/L; Pol-Chuc-Abkatún: 90–2010 μg/L) [52].

3. Sources and mobilization of geothermal arsenic

Arsenic is released from the host rocks of the geothermalreservoir. Significant quantities of As are leached from non-mineralized andesite during hot water–rock leaching experimentswith As concentrations up to 1300 μg/kg in the leachate [9,26]. Thehigh residence time of the fluids in the reservoir, high temperatureand pressure, and the reducing conditions (prevalence of As(III)and thioarsenites), which have higher mobility than As(V) andthioarsenates, together with under saturation of most reservoirfluids regarding to arsenopyrite and other As minerals favordissolution of As [2]. This leaching occurs together with otherelements, such as boron (B), fluoride (F), chromium (Cr), strontium(Sr), barium (Ba), antimony (Sb), lithium (Li), selenium (Se),thallium (Tl), mercury (Hg), and hydrogen sulfide (H2S) [2,5,61].Together with As, this element assembly provides a good finger-print to identify geothermal water components in mixtures, e.g.when geothermal water mixes with shallow cold groundwater orsurface water. In deep geothermal reservoirs, As is mainly allo-cated in pyrite whereas arsenopyrite (FeAsS) is rare [2]. Arsenic isfound mostly as As-bearing pyrite (up to 3.7 wt% As) at tempera-ture 150–250 1C, [40,62], or it is found associated with Fe oxides[63]. At 4250 1C, As is predominantly present as arsenopyrite(FeAsS), As-bearing pyrite (FeS2), and other arsenides such aslollingite (FeAs2) [64–66]. However, the exact chemical form ofhow As is included in the pyrite is still unknown [67,68] and atemperature-dependent solid-solution reaction between pyriteand arsenopyrite was postulated [65].

After dissolution, depending on the environmental and ther-modynamic conditions of the geothermal fluid, As can remain inthe liquid phase or it may partition into the vapor/gas phase [69].The As partitioned into the vapor/gas phase can rise along faults tothe earth's surface where it emerges in fumaroles and steamfields; whereas the liquid phase emerges in geothermal springs ormixes close to the earth's surface with cold shallow groundwater[27,69,70].

4. Arsenic species in geothermal fluids

In geothermal fluids, dissolved As is generally present ininorganic forms either as As oxyanions or as neutral species orin sulfidic environments as thioarsenates/thioarsenites; however,methylated As compounds may be formed under anoxic condi-tions by microbiological processes [71,72]. In deep geothermalreservoirs, mainly As(III) is released [59] by dissolution from thehost rock [2]. Due to reducing conditions in the deep geothermalreservoir, As is present in trivalent form. Arsenic is transported asH3As(III)O3 (arsenious acid) in most hydrothermal waters; H3AsO3

is considered as product of both As oxide (As4O6) and orpiment

Table 2 (continued )

Geothermal springs Arsenic (μg/L) References

Heybeli 1249 [14]Balcova-Narlidera 1400 [112]Hamambogazi 6936 [135]

Geological characterization of geothermal system after Chandrasekharam and Bundschuh [1]. VOL: volcanic rocks; CC: Continental collosion zone; L: low temperaturereservoir, To150 1C; H: high temperature reservoir, T4150 1C; mix: mixed with shallow groundwater or surface water; YNP: Yellowstone National Park.

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(As2S3) dissolution in reduced fluids which occurs over a widetemperature range and acid to neutral pH conditions [62]. Duringthe ascent of geothermal fluids, either as liquid or as gases/vapor,As(III) is oxidized to As(V) when it comes into contact withatmospheric oxygen. Due to the slow oxidation kinetics, As(III)can still be present in the water under oxidizing conditions closeto the discharge zone. However, oxidation can be accelerated bythe presence of microbes attached to submerged macrophytes as itdescribed in stream water of the Eastern Sierra Nevada where arapid decrease in As(III) with distance from the geothermal springvent was observed together with an increase in As(V) [59]. In suchoxidized systems, the mobility of As is a function of the transfor-mation of the As(ΙΙΙ) to the oxidized As(V) species. Depending onpH and availability of adequate sorption sites of minerals such asoxide minerals, i.e., amorphous Al-, Mn- and Fe oxides andhydroxides, the As(V) species is then sorbed. However, if thecontact time along the flow path (close to earth's surface outlet)of water and solid phase is short, redox transformations are ratherincomplete and As(ΙΙΙ) species may be present. In addition, the Asmobility in reduced systems is governed by dissolution of Fe- andMn-oxyhydroxides in the aquifer sediments due to microbialmediated biogeochemical interactions [73]. Further, sulfate redu-cing bacteria play an important role in the transformation of As(V) to As(III) in geothermal systems with temperatures below70 1C [5].

In strongly sulfidic environments and reducing conditions, Ascan form sulfide complexes; thereby As thioanions (arsenic-sulfidespecies) replace arsenates and arsenites in the water [53,72,74–79].Intense discussions about the stoichiometric compositions, oxida-tion states and thermodynamic stabilities of the As thioanions havebeen going on in the last decades [80]. Under the condition of nearsaturation with respect to orpiment (As2S3), the As thioanions,probably with the generic formula HxAsðIIIÞ3Sx–36 (x¼1–3) can beformed [53,74,81,89]. In waters with lower sulfide content, stronglyreducing conditions and high undersaturation with respect to As2S3,monomeric thioanions, HxAsðIIIÞSn–33 and HxAsðIIIÞOS�3

2n , are likely toform [82,83]. However, newer investigations found that at least sixthiolated As species can coexist in sulfidic waters; there S/As ratiosapproximating 0, 1, 2, 3 and 4 [72,76,78,84]. These findings questionthe earlier results and contradictory views about As thioanionscontinue to exist [80]. A key problem is that the earlier thermo-dynamic data on the stabilities of As thioanions are uncertain andincomplete; to overcome this problem Helz and Tossell [80] appliedcomputational and empirical information to construct a provisionalequilibriummodel for As thioanion distributions in sulfidic water. Incontrast to previous authors who postulated that As(III) or As(V) redox species do not coexist, these researchers found that bothare important and can coexist under commonly encountered pHand S-II conditions.

Arsenic forms volatile species at elevated temperatures [62,85–87].On world-wide scale, very little research has been performed on Asand its speciation in geothermal gases. The analysis of fumarolic gasesfrom Yellowstone National Park found the inorganic species AsH3 and(in decreasing order of occurrence) the organic species (CH3)2AsCl,(CH3)3As, (CH3)2AsSCH3 and CH3AsCl2 [71].

5. Microbiological activity related to geothermal fluidsin surface-near environments

The biodiversity of geothermal environments and elementalmobilization is considerably more complex in comparison to low-temperature surface or groundwater environments. The complexmicrobial community plays an important role to mobilize As in thegeothermal system. Arsenic is metabolized by bacterial assimila-tion, methylation, detoxification, and anaerobic respiration [88].

Arsenic mobilization from solid to liquid phase occurs in thepresence of microbes through oxidation/reduction. Bacterial isolatessuch as Clostridium sulfidigenes and Desulfovibrio psychrotolerans areable to reduce both sulfate and arsenate, implying the release ofAs(III) into the hot spring fluids under reducing conditions [5].Hamamura et al. [89] reported that due to arsenite-oxidation insulfate-chloride springs, arsenate concentration in fluid increasedwith the increase of the O2 concentration while dissolved sulfidedecreased at the same time. As a result active deposition of As(V)–Fe(III)-oxides occurred in the hot spring. In addition, microbialactivity played an impotent role in As transformation at the springoutlet. Along the detoxification/metabolism pathway of microor-ganism, As(III) is transformed into As(V). Thereby reduced sulfurcompounds or As(III) can serve as electron donor. The thermophilicbacterial community changes the oxidation state of arsenic [As(III)to As (V)] in geothermal systems [90,91]. The As(V) is reduced to As(III) in the presence of H2S and thiosulfate (S2O3) [5,92–95], hencegeothermal waters containing sulfide or thiosulfate preserve As asAs(III), until the reduced sulfur is oxidized or volatilized [96].Hirayama et al. [97] reported that T. subterraneous is a sulfur/thiosulfate-oxidizing bacterium and that this bacterium was iso-lated from subsurface geothermal aquifer water (�70 1C) in theHishikari gold mine, Japan. The microbial growths occur chemo-lithoautotrophically with reduced sulfur compounds as electrondonors and with oxygen as an electron acceptor using CO2 as acarbon source. Sulfurovum lithotrophicum, a novel mesophilic sulfur-and thiosulfate-oxidizing bacterium survives chemolithoautotro-phically with elemental sulfur or thiosulfate as a sole electrondonor and oxygen (optimum 5% in gas phase) or nitrate as electronacceptor in the gas-bubbling sediment at the Iheya North hydro-thermal system in the mid-Okinawa Trough, Japan [98]. The Asoxidation occurred biotically in the high As acid–chloride–sulfategeothermal spring system at Yellowstone National Park [99,100],Mono Lake, California [101] and California [102]. Inskeep et al. [103]studied five geothermal microbial communities in YellowstoneNational Park (e.g., Crater Hills, Norris Geyser Basin; Joseph's CoatHot Springs, Mammoth Hot Springs and Calcite Springs) andreported that all sites contained evidence of arsB genes of bacteria.The high As concentrations associated with Yellowstone's geother-mal ecosystem may postulate that these microorganisms are cap-able of efficient arsenite efflux (aqueous As levels: 10–130 mM). ThearsC gene, which is often found together with arsB on the arsoperon [88] and codes for an arsenate reductase associated withdetoxification, was only found in the bacterial-dominated sitesMammoth Hot Springs and Calcite Springs, and these sequenceswere affiliated with microorganisms like Thermus and Sulfurihydro-genibium [90]. Gihring et al. [90] found Thermus aquaticus andThermus thermophilus in a hot spring in Yellowstone National Parkthat effectively oxidize As(III) at about the same rate as in acid hotsprings. Gihring and Banfield [104] isolated a thermophilic strain,Thermus (strain HR 13) from an As-rich hot spring where As(III)oxidized under aerobic conditions by a detoxification process andthis Thermus strain HR 13 can grow using As(V) as its electronacceptor under anaerobic conditions. The nonphotosynthetic bac-terium, Ectothiorhodospira grew under anaerobic conditions usingAs(III) as its electron donor in Mono Lake and also grew as anautotroph with sulfide or hydrogen gas in place of As(III) [105,106].The biomineralization of As-rich hydrous ferric oxides occurs in thepresence of microbial mat (Acidimicrobium, Thiomonas, Metallo-sphaera and Marinithermus) [107]. Kulp et al. [101] reported thatthe oxidation of As(III) to As(V) occurs under anoxic conditionsin the presence of Ectothiorhodospira-like purple bacteria orOscillatoria-like cyanobacteria. It is also reported that the As(III)oxidation occurred by bacterial mat along geochemical gradients oftemperature (69.5–78.2 1C) and pH (6.76–7.06) [108]. Langner et al.[91] reported that at the outlet point of a geothermal spring, total

J. Bundschuh, J.P. Maity / Renewable and Sustainable Energy Reviews 42 (2015) 1214–12221218

soluble As was predominantly As(III) and oxidation of As(III) wasnot detected over the first 2.7 m downstream, corresponding to anarea dominated by a yellow filamentous SO-rich microbial mat.However, rapid oxidation of As(III) to As(V) was observed between2.7 and 5.6 m distance from the spring outlet, corresponding to thezone where the SO-rich mats terminate, and where concentrationsof dissolved sulfide decrease and a brown Fe/As-rich mat startsto occur.

6. Processes involving geothermal fluids rising from deepgeothermal reservoirs to the earth´s surface

Hydrothermal waters change their physical and chemicalnature during their rise from the deep geothermal reservoir toor near to the earth's surface due to physical, chemical andbiological processes. It is of particular interest whether the ascentoccurs under adiabatic or non-adiabatic conditions [1]. Geother-mal fluids ascending without or with marginal loss of heat byconductive cooling, appear as NaCl-type water with near neutralpH, high silica content and a Cl–/SO2–

4 ratio of 41; arsenic andchloride are positively correlated in these waters. The NaCl-typewaters generally show the highest As concentrations since theycorrespond to original reservoir waters as the previously pre-sented examples from Costa Rica have shown. The major gasphases in these waters are magmatic CO2 and H2S. Uprisinggeothermal waters, which mix with shallow HCO–

3 rich ground-water, become HCO3-type waters. Geothermal waters with highH2S gas content, which condense near to the earth's surface, formpools with waters rich in SO2�

4 and low in Cl� . Such pools give riseto low pH and high SO2�

4 water at the surface, due to oxidation.Acidic SO4Cl water develops through oxidation of volcanic H2S thatis sometimes contained in high concentrations in NaCl waters.During sub-surface boiling and phase separation As and Cl�

remain in the fluid phase [2]. Consequently, many geothermalwaters show a positive correlation between As and Cl� . However,such a correlation alone does not prove a common source of Asand Cl� . Reason is that despite that the As is derived predomi-nantly from the leaching of the reservoir host rocks, there aredifferent potential Cl� sources: (i) reservoir host rock leaching, (ii)seawater component and (iii) gaseous HCl from magmaticcomponents.

The pH of geothermal water increases due to CO2 loss duringadiabatic cooling of uprising thermal water and precipitate basemetals [2]. However, As together with Au, Sb and Hg remainsdissolved under higher pH conditions and precipitates later in thezone closer to the earth's surface. Recent geothermal systems areanalogous examples for fossil epithermal ore deposits, whichmakes the linkage between As release into the environment dueto the mining of epithermal gold deposits evident [2]. The As-bearing minerals encountered in epithermal deposits are orpi-ment, realgar, and elemental As. The deposition of these mineralstakes place according to acid reactions in metal-bearing thermalwaters (e.g., hot springs with acid–sulfate waters). At the earth'ssurface, this results in fast oxidation of As(III) to As(V) (due toexposure of O2), and precipitation of different mineral phases[109], which removes As from the fluid [2]. However, the oxidationdoes not occur in high sulfide content geothermal waters [19,91].

The Fe-oxyhydroxides are primary As sequestration agents. At hotspring deposits, they are an important As source for re-mobilizationunder therefore favorable geochemical conditions. Arsenic sorption onFe-oxyhydroxides and correlation between As and Fe-oxyhydroxidesin geothermal systems is essential to understand mobility of geother-mal As. Arsenic sorption on Fe oxyhydroxides controls solid-phase Asspeciation in geothermal systems (presence of Fe), which are eitherabout neutral NaCl waters or acidic sulfate- and chloride-rich waters

[109]. Microbes in geothermal systems may catalyze fast oxidation ofAs(III) [91,107,108], but not much is known how microbial catalysisand/or biomineralization control formation of Fe-oxyhydroxides.

7. Mixing of deep geothermal fluids with shallow groundwaterand surface water

The uprising geothermal waters may either discharge at theearth's surface as hot springs, or mix with shallow groundwater.The concentration of As dissolved in the groundwater mixdepends on (i) As concentration of the geothermal water compo-nent, (ii) pH/Eh conditions of the geothermal water, (iii) coldwater/solid aquifer matrix components, (iv) mixture ratio betweenboth waters and (iv) availability of mineral phases that may act assuitable sorption sites for dissolved As.

The contamination of surface and subsurface waters with Asfrom hydrothermal waters can constitute a severe environmentalimpact [14,16]. Several references report mixing of As-richgeothermal waters with groundwater of cold aquifers or surfacewater, limiting their use for water supply as shown in Table 3[12,14–16,110,111]. In the example of Balcova, Turkey, geothermalwater mixes with cold regional groundwater resources within afractured zone due to the natural upward movement of geother-mal fluid along the fault line [112]. At the Los Angeles CaliforniaAqueduct water (average As: 20.2 μg/L), the As contents have beenattributed to geothermal activity in the Long Valley area (MonoCounty) [59]. At Tatio geothermal springs (Chile) (Table 3),geothermal As-rich (47,000 μg/L; Table 3) water discharges intoLoa River which supplies water for over half a million of people[25]. In Ecuador, geothermal water (1090–7850 μg/L) dischargesinto Tambo river and Papalacta Lake, which is used for watersupply [60]. The mixing of As-rich (11.4–1660 μg/L) geothermalwater with shallow groundwater is also reported from Burruyacúbasin (NW Argentina) [113].

Table 3Geothermal fluids mix with shallow groundwater or surface water.

Geothermal field/area Arsenic (μg/L) References

ChileEl Tatio, Chile (VOL) 47,000 [25]

45,000–50000 [26]Ecuador

Tambo river area (VOL) 1090–7850 [23.60]

ArgentinaChaco-Pampean plain 11.4–1660 [113]

GreeceKalloni drainage basin, Lesvos (mix) 41.1–90.7 [131]Kalikratia, Chalkidiki (mix) 3.6–74.4 [132]Chalkidiki (mix) 3.0–68.8 [133]Aksios area (mix) 1–1843 [132]

ChinaRehai geothermal field, YunnanProvince

43.6–687 (91% as As(III))

[134]

TurkeyBalcova (L) 163.5–1419.8 [112]Balcova (Mix) 0.7–170.1 [112]Tuzla Geothermal Field 136 [136]

Geological characterization of geothermal system after Chandrasekharam andBundschuh [1]. VOL: volcanic rocks; CC: continental collosion zone; L: lowtemperature reservoir, To150 1C; H: high temperature reservoir, T4150 1C; mix:mixed with shallow groundwater or surface water.

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8. Summary and conclusions

Arsenic is a ubiquitous component of active geothermal sys-tems where it can be released by leaching in significant amountsfrom the host rocks of the deep-seated geothermal reservoirs. Inreservoir rocks, the uprising geothermal fluids may contaminateshallow water resources making them unsuitable for water supply.However, these systems are complex and, often it remains unclearwhether As comes from geothermal or other geogenic of anthro-pogenic As sources.

The release, propagation through the subsurface towards thezone close or at the earh's surface is controlled by different factorscomprising:

� As occurs predominantly as As-bearing pyrite (FeS2) at tempera-tures of 150–250 1C, and as arsenopyrite (FeAsS) at 4250 1C.

� The highest As concentrations in geothermal reservoir fluidsoccur along active plate boundaries hosted in volcanic rocks;typical As concentrations are 500–162,000 μg/L. Fluids ofgeothermal reservoirs in sedimentary basins have lower Asconcentrations (up to 2010 μg/L), independently whether theyare of low (o150 1C) or high- (4150 1C) enthalpy type.

� From the geothermal springs, those with NaCl water type have thehighest As concentrations; these waters correspond to originalreservoir waters which were not significantly altered during itsascent. These NaCl waters can significantly contaminate freshwateraquifers and surface environments when discharging as geother-mal springs. In contrast, shallow warm freshwater aquifers orgeothermal springs which receive their elevated heat contentthrough conduction or which are steam-heated have much lowerAs concentration and therefore pose a lower hazard for freshwaterresources and surface environments.

� When the pH of geothermal water increases due to CO2 lossduring adiabatic cooling along the ascend, base metals areprecipitated whereas As keeps in solution.

� At geothermal springs, Fe-oxyhydroxides are primary Assequestration agents and form an important source for futureAs re-mobilization if geochemical conditions change and favorthis process.

� Under reducing reservoir conditions, As is present in trivalentform, as arsenius acid (H3As(III)O3) in most hydrothermalwaters (pHo9.2) and if sulfidic conditions are present addi-tionally as thioarsenites. During ascend to the earth's surface,e.g. along faults, the trivalent As is oxidized when coming intocontact with atmospheric oxygen, i.e. in shallow aquifers,vadose zone or at the earth's surface itself when it emergesin springs, fumaroles or steam fields.

� The rapid decrease in As(III) with distance from the geothermalspring vent (and increase of As(V)) is often fast (within fewmeters from the vent) is probably catalyzed by microbes.Where microbial processes are absent or limited, As(III) canstill be present in the water under oxidizing conditions.Determination of specific inorganic or microbiological assem-blages (footprints) to identify geothermal As in these waters istherefore crucial. New information in this area is necessaryto understand the role geothermal As plays in the genesis ofAs-rich ground- and surface water resources, which are usedfor human consumption.

Acknowledgment

JB thanks the National Science Council Taiwan (NSC) forfinancial support. JPM thanks NSC for postdoctoral research posi-tion (NSC 100-2811-M-194-008).

References

[1] Chandrasekharam D, Bundschuh J. Low-enthalpy geothermal resources forpower generation. 1st ed. The Netherlands: CRC Press/Balkema; 2008(Francis & Taylor).

[2] Webster JG, Nordstrom DK. Geothermal arsenic. In: Welch AH, StollenwerkKG, editors. Arsenic in ground water: geochemistry and occurrence. NewYork: Springer; 2003. p. 101–25.

[3] Smedley PL, Kinniburgh DG. A review of the source, behaviour and distribu-tion of arsenic in natural waters. Appl Geochem 2002;17:517–68.

[4] Leal-Acosta ML, Shumilin E, Mirlean N, Sapozhnikov D, Gordeev V. Arsenicand mercury contamination of sediments of geothermal springs, mangrovelagoon and the Santispac bight, Bahía Concepción, Baja California peninsula.Bull Environ Contam Toxicol 2010;85:609–13.

[5] Maity JP, Liu CC, Nath B, Bundschuh J, Kar S, Jean J-S, Bhattacharya P, Liu J-H,Atla SB, Chen C-Y. Biogeochemical characteristics of Kuan-Tzu-Ling, Chung-Lun and Bao-Lai hot springs in southern Taiwan. J Environ Sci Health, Part A2011;46:1207–17.

[6] Ball JW, Nordstrom DK, Jenne EA, Vivit DV. Chemical analysis of hot springs,pools, geysers, and surface waters from Yellowstone National Park, Wyomingand its vicinity. USGS open-file report 98-182, 1998.

[7] Romero L, Alonso H, Campano P, Fanfani L, Cidu R, Dadea C, et al. Arsenicenrichment in waters and sediments of the Rio Loa (Second region, Chile).Appl Geochem 2003;18:1399–416.

[8] Motyka RJ, Poreda RJ, Jeffrey AWA. Geochemistry, isotopic composition, andorigin of fluids emanating from mud volcanoes in the Copper River basin,Alaska. Geochim Cosmochim Acta 1989;53:3302–9.

[9] Ellis AJ, Mahon WAJ. Natural hydrothermal systems and experimental hotwater/rock interactions (Part II). Geochim Cosmochim Acta 1967;31:519–38.

[10] Gonzalez-Partida E, Hinojosa ET, Verma MP. Interracción agua geothermica-manantiales en el campo geotermico de Los Humeros, Mexico. IngenieriaHidraulica en Mexico 2001;XVI:185–94.

[11] Henke K. Arsenic: environmental chemistry, health threats and wastetreatment. Hoboken, New Jersey: John Wiley & Sons; 2009; 94–5.

[12] Demirel Z, Yildirim N. Boron pollution due to geothermal wastewaterdischarge into the Buyuk Menderes River, Turkey. Int J Environ Pollut2002;18:602–8.

[13] Gemici U, Tarcan G. Distribution of boron in thermal waters of westernAnatolia, Turkey, and examples of their environmental impacts. Environ Geol2002;43:87–98.

[14] Gemici U, Tarcan G. Hydrogeological and hydrochemical feature of theHeybeli Spa, Afyon Turkey: arsenic and the other contaminants in thethermal waters. Bull Environ Contam Toxicol 2004;72:1107–14.

[15] Dogdu MS, Bayari CS. Environmental impact of geothermal fluids on surfacewater, groundwater and streambed sediments in the Akarcay Basin, Turkey.Environ Geol 2005;47:325–40.

[16] Baba A, Ármannsson H. Environmental Impact of the utilization of ageothermal area in Turkey. Energy Source Part B 2006;1:267–78.

[17] Clarke FW. Data of geochemistry; U.S. Geological Survey Bulletin 330; USGS:Reston, VA; 1908.

[18] Gooch FA, Whitfield JE. Analyses of waters of the Yellowstone National Park,with an account of the methods of analysis employed. US Geol Surv Bull1888:47.

[19] Stauffer RE, Jenne EA, Ball JW. Chemical studies of selected trace elements inhot-spring drainages of Yellowstone National Park. US Geological SurveyProfessional Paper 1044-F; 1980.

[20] Stauffer RE, Thompson JM. Arsenic and antimony in geothermal waters ofYellowstone National Park, Wyoming, USA. Geochim Cosmochim Acta1984;48:2547–61.

[21] Criaud A, Fouillac C. The distribution of arsenic (III) and arsenic (V) ingeothermal waters: Examples from the Massif Central of France, the Island ofDominica in the Leeward Islands of the Caribbean, the Valles Caldera of NewMexico, U.S.A. and southwest Bulgaria. Chem Geol 1989;76:259–69.

[22] Welch AH, Westjohn DB, Helsel DR, Wanty RB. Arsenic in ground water ofthe United States: occurrence and geochemistry. Ground Water2000;38:589–604.

[23] Bundschuh J, Armienta MA, Birkle P, Bhattacharya P, Matschullat J, Mukher-jee AB. Natural arsenic in groundwater of Latin America. (Francis & Taylor).In: Bundschuh J, Bhattacharya P, editors. Arsenic in the environment. 1st ed.The Netherlands: CRC Press/Balkema; 2009.

[24] Birkle P, Bundschuh J, Sracek O. Mechanisms of arsenic enrichment ingeothermal and petroleum reservoirs fluids in Mexico. Water Res2010;44:5605–17.

[25] Cusicanqui H, Mahon WAJ, Ellis AJ. The geochemistry of the El Tatiogeothermal field, northern Chile. In: 2nd United Nations GeothermalSymposium Proceedings, Lawrence Berkeley Laboratory, University of Cali-fornia. Berkeley, CA; 1976.

[26] Ellis AJ, Mahon WAJ. Chemistry and geothermal systems. New York:Academic Press; 1977.

[27] Hammarlund L, Piñones J. Arsenic in geothermal waters of Costa Rica—aminor field study. TRITA-LWR [MSc thesis]. LWR-EX-09-02, Department ofLand and Wayer Resources Engineering, KTH. Stockholm, Sweden; 2009.

[28] Lippmann MJ, Truesdell AH, Frye G. The Cerro Prieto and Salton Seageothermal fields—are they really alike? In: Proceedings of the 24th

J. Bundschuh, J.P. Maity / Renewable and Sustainable Energy Reviews 42 (2015) 1214–12221220

workshop on geothermal reservoir engineering, Stanford University, SGP-TR-162; 1999.

[29] Mercado S, Bermejo F, Hurtado R, Terrazas B, Hernández L. Scale incidenceon production pipes of Cerro Prieto geothermal wells. Geothermics1989;18:225–32.

[30] Birkle P. Herkunft und Umweltauswirkungen der Geothermalwässer von LosAzufres. Wiss. Mitt. 6, Institute for Geology, Technical University Freiberg.Germany; 1998.

[31] González-Partida E, Birkle P, Torres-Alvarado I. Evolution of the hydrother-mal system at the geothermal field of Los Azufres, Mexico, based on fluidinclusion, isotopic and petrologic data. J Volcanol Geotherm Res2000;104:277–96.

[32] Arellano VM, García A, Barragán RM, Izquierdo G, Aragón A, Nieva D. Anupdated conceptual model of the Los Humeros geothermal reservoir(Mexico). J Volcanol Geotherm Res 2003;124:67–88.

[33] Birkle P., Portugal E., Caracterización química e isotópica de los acuíferosprofundos de los campos petroleros Cactus, Níspero, Río Nuevo y Sitiogrande en Chiapas: origen y dinámica de la migración. Report 11-11840,Instituto de Investigaciones Eléctricas, Cuernavaca, Mexico; 2001.

[34] Birkle P, Angulo M. Conceptual hydrochemical model of Late Pleistoceneaquifers at the Samaria-Sitio-Grande petroleum reservoir, Gulf of Mexico,Mexico. Appl Geochem 2005;20:1077–98.

[35] Birkle P, Portugal E, Rosillo JJ, Fong JL. Evolution and origin of deep reservoirwater at the Activo Luna oil field, Gulf of Mexico, Mexico. AAPG Bull2002;86:457–84.

[36] Birkle P. Caracterización química e isotópica de los acuíferos profundos delcampo Jujo-Tecominoacán. Final report, Instituto de Investigaciones Eléctri-cas. Cuernavaca, Mexico, IIE/11/2473/F; 2004.

[37] Birkle P, Martínez-García B, Milland-Padrón CM. Origin and evolution offormation water at the Jujo-Tecominoacán oil reservoir, Gulf of Mexico. Part1: Chemical evolution and water–rock interaction. Appl Geochem2009;24:543–54.

[38] Birkle P, Martínez-García B, Milland Padrón CM, Eglington BM. Origin andevolution of formation water at the Jujo-Tecominoacán oil reservoir, Gulf ofMexico. Part 2: Isotopic and field-production evidence for fluid connectivity.Appl Geochem 2009;24:555–73.

[39] Birkle P. Estudio isotópico y químico para la definición del origen de losacuíferos profundos del Activo Pol-Chuc. Final report, Instituto de Investi-gaciones Eléctricas. Cuernavaca, Mexico, IIE/11/12093/I02/F; 2003.

[40] Ewers GR, Keays RR. Volatile and precious metal zoning in the Broadlandsgeothermal field, New Zealand. Econ Geol 1977;72:1337–54.

[41] Brown KL, Simmons SF. Precious metals in high-temperature geothermalsystems in New Zealand. Geothermics 2003;32:619–25.

[42] Ritchie JA. Arsenic and antimony in some New Zealand thermal waters. N Z JSci 1961;4:218–29.

[43] Kingston R. The Tongonan geothermal field Leyte Philippines: report onexploration and development. Report, Kingston Reynolds Thom and Allar-dice Ltd. Auckland, New Zealand; 1979.

[44] Darby d'EC. Arsenic and boron in the Tongonan environment. Conference:geothermal resource council annual meeting, vol. 4. Salt Lake City, UT, USA;1980.

[45] Thompson JM. Chemistry of thermal and nonthermal springs in the vicinityof Lassen Volcanic National Park. J Volcanol Geotherm Res 1985;25:81–104.

[46] Goleva GA. Metal content of hydrotherms in areas of active volcanism. In:Naboko SI, editor. Hydrothermal mineral-forming solutions in the areas ofactive volcanism. New Delhi, India: Nauka; 1974.p. 113–5 (Novosibirisk. Translated in 1982 for US Dept. Interior and NationalScience Foundation by Amerind Publishing Co.).

[47] Khramova GC. Effects of intensified activity of the Ebeko Volcano on thecomposition of the water of Goryachoe Lake. In: Naboko SI, editor. Hydro-thermal mineral-forming solutions in the areas of active volcanism. NewDelhi, India: Nauka; 1974. p. 88–94 (Novosibirisk. Translated in 1982 forUS Dept. Interior and National Science Foundation by Amerind PublishingCo).

[48] Guo Q, Wang Y, Liu WB. As, and F contamination of river water due towastewater discharge of the Yangbajing geothermal power plant, Tibet,China. Environ Geol 2008;56:197–205.

[49] Yoshizuka K, Nishihama S, Sato H. Analytical survey of arsenic in geothermalwater in Kyushu Island, Japan and arsenic removal with magnetite. J EnvironGeochem Health 2010;32:297–302.

[50] Kabay N, Yilmaz I, Yamac S, Samatya S, Yuksel M, Yuksel U, et al. Removaland recovery of boron from geothermal wastewater by selective ionexchange resins. I. Laboratory tests. React Funct Polym 2004;60:163–70.

[51] Kabay N, Yilmaz I, Yamac S, Yuksel M, Yuksel U, Yildirim N, et al. Removaland recovery of boron from geothermal wastewater by selective ionexchange resins. II. Field studies. Desalination 2004;167:427–38.

[52] Birkle P, Bundschuh J. The abundance of natural arsenic in deep thermalfluids of geothermal and petroleum reservoirs in Mexico. In: Bundschuh J,Armienta MA, Birkle P, Bhattacharya P, Matschullat J, Mukherjee AB, editors.Geogenic arsenic in groundwater of Latin America. CRC Press/BalkemaPublisher; 2009. p. 145–53.

[53] Webster JG. The solubility of As2S3 and sulphide-bearing fluids at 25 and90 1C. Geochim Cosmochim Acta 1990;54:1009–17.

[54] Webster JG. The source of arsenic (and other elements) in the Marbel –

Matingo river catchment, Mindanao, Philippines. Geothermics1999;28:95–111.

[55] Guo H-M, Yang S-Z, Tang X-H, Li Y, Shen Z-L. Groundwater geochemistry andits implications for arsenic mobilization in shallow aquifers of the Hetaobasin, Inner Mongolia. Sci Total Environ 2007;393:131–44.

[56] Nimick DA, Moore JN, Dalby CE, Savka MW. The fate of geothermal arsenic inthe Madison and Missouri rivers, Montana and Wyoming. Water Resour Res1998;34:3051–67.

[57] Nordstrom DK, Ball JW, McCleskey RB. Ground water to surface water:chemistry of thermal outflows in Yellowstone National Park. In: Inskeep W,McDermott TT, editors. Geothermal biology and geochemistry in Yellow-stone National Park. Bozeman, MT: Thermal Biology Institute, Montana StateUniversity; 2005. p. 73–94.

[58] Eccles LA. Sources of arsenic in streams tributary to Lake Crowley California.USGS Water resources investigation report 76-36. 1976.

[59] Wilkie JA, Hering JG. Rapid oxidation of geothermal arsenic(III) insteamwaters of the eastern Sierra Nevada. Environ Sci Technol 1998;32:657–62.

[60] Cumbal L, Bundschuh J, Aguirre V, Murgueitio E, Tipán I, Chavez C. The originof arsenic in waters and sediments from Papallacta lake in Ecuador. In:Bundschuh J, Armienta MA, Birkle P, Bhattacharya P, Matschullat J, Mukher-jee AB, editors. Natural arsenic in groundwater of Latin America. 1st ed.. TheNetherlands: CRC Press/Balkema; 2009. p. 81–90 (Francis & Taylor).

[61] Ellis AJ, Mahon WAJ. Natural hydrothermal systems and experimental hot-water/rock interactions. Geochim Cosmochim Acta 1964;28:1323–57.

[62] Ballantyne JM, Moore JN. Arsenic geochemistry in geothermal systems.Geochim Cosmochim Acta 1988;52:475–83.

[63] Christensen OD, Capuano RA, Moore JN. Trace-element distribution in anactive hydrothermal system, Roosevelt hot springs thermal area, Utah.J Volcanol Geotherm Res 1983;16:99–129.

[64] Heinrich CA, Eadington PJ. Thermodynamic predictions of the hydrothermalchemistry of arsenic, and their significance for the paragenetic sequence ofsome cassiterite–arsenopyrite-base metal sulfide deposits. Econ Geol1986;81:511–29.

[65] Pokrovski GS, Kara S, Roux J. Stability and solubility of arsenopyrite, FeAsS, incrustal fluids. Geochim Cosmochim Acta 2002;66:2361–78.

[66] Scott SD. Chemical behaviour of sphalerite and arsenopyrite in hydrothermaland metamorphic environments. Miner Mag 1983;47:427–35.

[67] Kolker A, Nordstrom DK. Occurrence and micro-distribution of arsenic inpyrite. USGS workshop on arsenic in the environment. Denver, USA;February 21–22, 2001.

[68] Simon G, Huang H, Penner-Hahn JE, Kesler SE, Kao LS. Oxidation state ofgold and arsenic in gold-bearing arsenian pyrite. Am Mineral.1999;84:1071–9.

[69] Giroud N. A chemical study of arsenic, boron and gases in high-temperaturegeothermal fluids in Iceland [PhD thesis]. University of Iceland; 2008.

[70] Smith CL, Ficklin WH, Thompson JM. Concentrations of arsenic, antimony,and boron in steam and steam condensate at The Geysers, California.J Volcanol Geotherm Res 1987;32:329–41.

[71] Planer-Friedrich B, Lehr C, Matschullat J, Merkel BJ, Nordstrom DK, Sand-strom MW. Speciation of volatile arsenic at geothermal features in Yellow-stone National Park. Geochim Cosmochim Acta 2006;70:2480–91.

[72] Planer-Friedrich B, London J, McCleskey RB, Nordstrom DK, Wallschläger D.Thioarsenates in geothermal waters of Yellowstone National Park: determi-nation, preservation and geochemical importance. Environ Sci Technol2007;41:5245–51.

[73] Bhattacharya P, Jacks G, Ahmed KM, Routh J, Khan AA. Arsenic in ground-water of the Bengal Delta Plain aquifers in Bangladesh. Bull Environ ContamToxicol 2002;69:538–45.

[74] Eary LE. The solubility of amorphous As2S3 from 25 to 90 1C. GeochimCosmochim Acta 1992;56:2267–80.

[75] Wood SA, Tait CD, Janecky DR. A Raman spectroscopy study of arsenite andthioarsenite species in aqueous solutions at 25 1C. Geochem Trans2002;3:31–9.

[76] Wilkin RT, Wallschläger D, Ford RG. Speciation of arsenic in sulfidic waters.Geochem Trans 2003;4:1–7.

[77] Bostick BC, Fendorf S, Brown Jr GE. In situ analysis of thioarsenite complexesin neutral to alkaline sulphide solutions. Mineral Mag 2005;69:781–95.

[78] Hollibaugh JT, Carini S, Gürleyük H, Jellison R, Joye SB, LeCleir G, et al.Arsenic speciation in Mono Lake, California: response to seasonal stratifica-tion and anoxia. Geochim Cosmochim Acta 2005;69:1925–37.

[79] Beak DG, Wilkin RT, Ford RG, Kelly SD. Examination of arsenic speciation insulfidic solutions using X-ray absorption spectroscopy. Environ Sci Technol2008;42:1643–50.

[80] Helz GR, Tossell JA. Thermodynamic model for arsenic speciation in sulfidicwaters: a novel use of ab initio computations. Geochim Cosmochim Acta2008;72:4457–68.

[81] Spycher NF, Reed MH. As(III) and Sb(III) sulfide complexes: an evaluation ofstoichiometry and stability from existing experimental data. GeochimCosmochim Acta 1989;53:2185–94.

[82] Helz GR, Tossell JA, Charnock JM, Pattrick RAD, Vaughan DJ, Garner CD.Oligomerization in As(III) sulfide solutions: theoretical constraints andspectroscopic evidence. Geochim Cosmochim Acta 1995;59:4591–604.

[83] Clarke MB, Helz GR. Metal–thiometalate transport of biologically active traceelements in sulfidic environments. 1. Experimental evidence for copperthioarsenite complexing. Environ Sci Technol 2000;34:1477–82.

[84] Stauder S, Raue B, Sacher F. Thioarsenates in sulfidic waters. Environ SciTechnol 2005;39:5933–9.

J. Bundschuh, J.P. Maity / Renewable and Sustainable Energy Reviews 42 (2015) 1214–1222 1221

[85] Cengiz K. Effects on environment and agriculture of geothermal wastewaterand boron pollution in Great Menderes Basin. Environ Monit Assess2007;125:377–88.

[86] Kuritani T, Nakamura E. Elemental fractionation in lavas during post-eruptive degassing: evidence from trachytic lavas, Rishiri Volcano, Japan.J Volcanol Geotherm Res 2006;149:124–38.

[87] Glover R. Boron distribution between liquid and vapour in geothermal fluids.In: New Zealand geothermal workshop, Proceedings; 1988. p. 223–7.

[88] Stolz JF, Basu P, Santini JM, Oremland RS. Arsenic and selenium in microbialmetabolism. Annu Rev Microbiol 2006;60:107–30.

[89] Hamamura N, Macur RE, Korf S, Ackerman G, Taylor WP, Kozuba M, et al.Linking microbial oxidation of arsenic with detection and phylogeneticanalysis of arsenite oxidase genes in diverse geothermal environments.Environ Microbiol 2009;11:421–31.

[90] Gihring TM, Druschel GK, McCleskey RB, Hamers RJ, Banfield JF. Rapidarsenite oxidation by Thermus aquaticus and Thermus thermophilus: field andlaboratory investigation. Environ Sci Technol 2001;35:3857–62.

[91] Langner HW, Jackson CR, McDermott TR, Inskee WP. Rapid oxidation ofarsenite in a hot spring ecosystem, Yellowstone National Park. Environ SciTechnol 2001;35:3302–9.

[92] Cherry JA, Shaikh AU, Tallman DE, Nicholson RV. Arsenic species as anindicator of redox conditions in groundwater. J Hydrol 1979;43:373–92.

[93] DeKonnick LL. The precipitation of arsenic with hydrogen sulphide. Bull SocBelg Chim 1909;23:88–94.

[94] Forbes GS, Estil HW, Walker OJ. Induction periods in reactions betweenthiosulfate and arsenite or arsenate: a useful clock reaction. J Am Chem Soc1922;44:97–102.

[95] Rochette EA, Bostick BC, Li G, Fendorf S. Kinetics of arsenate reduction bydissolved sulfide. Environ Sci Technol 2000;34:4714–20.

[96] Nordstrom D.K., Ball J.W., McCleskey R.B. Processes governing arsenicconcentrations in thermal waters of Yellowstone National Park: in U.S.Geological Survey Workshop on Arsenic in the Environment; 2001.

[97] Hirayama H, Takai K, Inagaki F, Nealson KH, Horikoshi K. Thiobactersubterraneus gen. nov., sp. nov., an obligately chemolithoautotrophic, ther-mophilic, sulfur-oxidizing bacterium from a subsurface hot aquifer. Int J SystEvol Microbiol 2005;55:467–72.

[98] Inagaki F, Takai K, Nealson KH, Horikoshi K. Sulfurovum lithotrophicum gen.nov., sp. nov., a novel sulfur-oxidizing chemolithoautotroph within the ε-Proteobacteria isolated from Okinawa Trough hydrothermal sediments. Int JSyst Evol Microbiol 2004;54:1477–82.

[99] Jackson CR, Langner HW, Donahoe-Christiansen J, Inskeep WP, McDermottTR. Molecular analysis of microbial community structure in an arsenite-oxidizing acidic thermal spring. Environ Microbiol 2001;3:532–42.

[100] Donahoe-Christiansen J, D'Imperio S, Jackson CR, Inskeep WP, McDermottTR. Arsenite-oxidizing hydrogenobaculum strain isolated from an acid-sulfate-chloride geothermal spring in Yellowstone National Park. ApplEnviron Microbiol 2004;70:1865–8.

[101] Kulp TR, Hoeft SE, Asao M, Madigan MT, Hollibaugh JT, Fisher JC, et al.Arsenic (III) fuels anoxygenic photosynthesis in hot spring biofilms fromMono Lake, California. Science 2008;321:967–70.

[102] Salmassi TM, Walker JJ, Newman DK, Leadbetter JR, Pace NR, Hering JG.Community and cultivation analysis of arsenite oxidizing biofilms at HotCreek. Environ Microbiol 2006;8:50–9.

[103] Inskeep WP, Rusch DB, Jay ZJ, Herrgard MJ, Kozubal MA, Richardson TH, et al.Metagenomes from high-temperature chemotrophic systems reveal geo-chemical controls on microbial community structure and function. PLoSOne 2010;5(e9773):1–15.

[104] Gihring TM, Banfield JF. Arsenite oxidation and arsenate respiration by a newThermus isolate. FEMS Microbiol Lett 2001;204:335–40.

[105] Oremland RS, Hoeft SE, Santini JM, Bano N, Hollibaugh RA, Hollibaugh JT.Anaerobic oxidation of arsenite in Mono Lake water and by a facultative,arsenite-oxidizing chemoautotroph, strain MLHE-1. Appl Environ Microbiol2002;68:4795–802.

[106] Oremland RS, Stolz JF. The ecology of arsenic. Science 2003;300:939–42.[107] Inskeep WP, Macur RE, Harrison G, Bostick BC, Fendorf S. Biomineralization

of As(V)-hydrous ferric oxyhydroxide in microbial mats of an acid–sulfate–chloride geothermal spring, Yellowstone National Park. Geochim CosmochimActa 2004;68:3141–55.

[108] Connon SA, Koski AK, Neal AL, Wood SA, Magnuson TS. Ecophysiology andgeochemistry of microbial arsenic oxidation within a high arsenic, circum-neutral hot spring system of the Alvord Desert. FEMS Microbiol Ecol2008;64:117–28.

[109] Alsina M, Saratovsky I, Gaillard J-F, Pasten PA. Arsenic speciation in solidphases of geothermal fields. In: Barnett MO, Kent DB, editors. Adsorption ofmetals by geomedia II: variables, mechanisms, and model applications.Amsterdam: Elsevier; 2007. p. 17–440.

[110] Celik MY, Sabah E. The geological and technical characterization of Ömer–Gecek geothermal area and the environmental impact assessment ofgeothermal heating system in Afyon, Turkey. Environ Geol 2002;41:942–53.

[111] Tarcan G, Gemici U. Effects of the contaminants from Turgutlu–Urganlıthermomineral waters on cold ground and surface waters. Bull EnvironContam Toxicol 2005;74:485–92.

[112] Aksoy N, Şimşek C, Gunduz O. Groundwater contamination mechanism in ageothermal field: a case study of Balcova, Turkey. J Contam Hydrol2009;103:13–28.

[113] Nicolli HB, Bundschuh J, García JW, Falcón CM, Jean J-S. Sources and controlsfor the mobility of arsenic in oxidizing groundwaters from loess-typesediments in arid/semi-arid dry climates – evidence from the Chaco–Pampean plain (Argentina). Water Res 2010;44:5589–604.

[114] Ormachea M, Ramos O, Quintanilla J, García M, Bhattacharya P, Thunvik R,et al. Arsenic occurrence in thermal springs of the central Bolivian Altiplano.In: Jean J-S, Bundschuh J, Bhattacharya P, editors. Arsenic in geosphere andhuman diseases. London: Taylor & Francis Group; 2010. p. 520–2.

[115] Banks D, Markland H, Smith PV, Mendez C, Rodriguez J, Huerta A, et al.Distribution, salinity and pH dependence of elements in surface waters of thecatchment areas of the Salars of Coipasa and Uyuni, Bolivian Altiplano.J Geochem Explor 2004;84:141–66.

[116] Cumbal L, Vallejo P, Rodriguez B, Lopez D. Arsenic in geothermal sources atthe north-central Andean region of Ecuador: concentrations and mechanismsof mobility. Environ Earth Sci 2010;61:299–310.

[117] Lacayo ML, Cruz A, Calero S, Lacayo J, Fomsgaard I. Total arsenic in water, fish,and sediments from Lake Xolotlan, Managua, Nicaragua. Bull Environ ContamToxicol 1992;49:463–70.

[118] White DE. Environments of generation of some base-metal ore deposits. EconGeol 1968;63:301–35.

[119] De Carlo EH, Thomas DM. Recovery of arsenic from spent geothermal brineby flotation with colloidal ferric hydroxide and long chain alkyl surfactants.Environ Sci Technol 1985;19:538–44.

[120] Reid KD, Goff F, Counce DA. Arsenic concentration and mass flow rate innatural waters of the Valles caldera and Jemez Mountains region, NewMexico. New Mexico Geol 2003;25:75–82.

[121] Belkova NL, Zakharova JR, Tazaki K, Okrugin VM, Parfenova VV. Fe–Sibiominerals in the Vilyuchinskie hot springs, Kamchatka Peninsula, Russia.Int Microbiol 2004;7:193–8.

[122] McCarthy KT, Pichler T, Price RE. Geochemistry of Champagne hot springsshallow hydrothermal vent field and associated sediments, Dominica, LesserAntilles. Chem Geol 2005;224:55–68.

[123] Pichler T, Veizer J. Precipitation of Fe(III) oxyhydroxide deposits fromshallow-water hydrothermal fluids in Tutum Bay, Ambitle Island, PapuaNew Guinea. Chem Geol 1999;162:15–31.

[124] Jones B, Renaut RW, Rosen MR. Biogenicity of gold- and silver-bearingsiliceous sinters forming in hot (75 1C) anaerobic spring-waters of Cham-pagne Pool, Waiotapu, North Island, New Zealand. J Geol Soc2001;158:895–911.

[125] Papke RT, Ramsing NB, Bateson MM, Ward DM. Geographical isolation in hotspring cyanobacteria. Environ Microbiol 2003;5:650–9.

[126] McKenzie EJ, Brown KL, Cady SL, Campbell KA. Trace metal chemistry andsilicification of microorganisms in geothermal sinter, Taupo volcanic zone,New Zealand. Geothermics 2001;30:483–502.

[127] Noguchi K, Nakagawa R. Arsenic and arsenic-lead sulfide sediments fromTamagawa Hot Springs, Akita Prefecture. Proc Japan Acad 1969;45:45–50.

[128] Karpov GA, Naboko SI. Metal contents of recent thermal waters, mineralprecipitates and hydrothermal alteration in active geothermal fluids, Kam-chatka. J Geochem Explor 1990;36:57–71.

[129] Jean J-S, Bundschuh J, Chen CJ, Guo H-R, Liu C-W, Lin T-F, et al. The Taiwancrisis: a showcase of the global arsenic problem. Arsenic in the environment,vol. 3. Leiden, The Netherlands: CRC Press/Balkema Publisher; 2010; 1–201.

[130] Celico P, Dall'Aglio M, Ghiara MR, Stanzione D, Brondi M, Prosperi M.Geochemical monitoring of the thermal fluids in the phlegraean fields from1970 to 1990. Bull Soc Geol 1990;111:409–22.

[131] Aloupi M, Angelidis MO, Gavriil AM, Koulousaris M, Varnavas SP. Influence ofgeology on arsenic concentrations in ground and surface water in centralLesvos, Greece. Environ Monit Assess 2009;151(1–4):383–96.

[132] Katsoyiannis IA, Hug SJ, Ammann A, Zikoudi A, Hatziliontos C. Arsenicspeciation and uranium concentrations in drinking water supply wells inNorthern Greece: correlations with redox indicative parameters and implica-tions for groundwater treatment. Sci Total Environ 2007;383:128–40.

[133] Kouras A, Katsoyiannis I, Voutsa D. Distribution of arsenic in groundwater inthe area of Chalkidiki, Northern Greece. J Hazard Mater 2007;147:890–9.

[134] Zhang G, Liu C-Q, Liu H, Jin Z, Han G, Li L. Geochemistry of the Rehai andRuidian geothermal waters, Yunnan Province, China. Geothermics2008;37:73–83.

[135] Davraz A. Hydrogeochemical and hydrogeological investigations of thermalwaters in the Usak Area (Turkey). Chem Geol 2008;54:615–28.

[136] Baba A, Yuce G, Deniz O, Ugurluoglu DY. Hydrochemical and isotopiccomposition of Tuzla geothermal field (Canakkale-Turkey) and its environ-mental impacts. Environ Forensics 2009;10:144–61.

J. Bundschuh, J.P. Maity / Renewable and Sustainable Energy Reviews 42 (2015) 1214–12221222