ORIGINAL ARTICLE

Geochemistry and potential use of groundwaterin the Rocca Busambra area (Sicily, Italy)

M. Fontana Æ F. Grassa Æ G. Cusimano Æ R. Favara ÆS. Hauser Æ C. Scaletta

Received: 15 January 2008 / Accepted: 3 May 2008 / Published online: 20 June 2008

� Springer-Verlag 2008

Abstract In the Rocca Busambra area (mid-west Sicily,

Italy), from November 1999 to July 2002, 23 water points

including wells and springs were sampled and studied for

their chemical and isotopic compositions. Two rain gauges

were also installed at different altitudes, and rainwater was

collected monthly to determine the isotopic composition.

The obtained results revealed the Rocca Busambra car-

bonate complex as being the main recharge area on account

of its high permeability value. From a chemical view point,

two main groups of water can be distinguished: calcium–

magnesium–bicarbonate-type and calcium–magnesium–

chloride–sulphate-type waters. The first group reflects the

dissolution of the carbonate rocks; the second group

probably originates from circulation within flyschoid sed-

iments. Three water wells differ from the other samples

due to their relatively high Na and K content, which

probably is to be referred to a marked interaction with the

‘‘Calcareniti di Corleone’’ formation, which is rich in

glauconite [(K, Na)(Fe3+, Al, Mg)2(Si, Al)4O10(OH)2]. In

accordance with WHO guidelines for drinking water

(2004), almost all the samples collected can be considered

drinkable, with the exception of four of them, whose NO3-,

F- and Na+ contents exceed the limits. On the contrary, the

sampled groundwater studied is basically suitable for

irrigation.

Keywords Water quality � Environmental isotopes �Geochemistry � Italy

Introduction

Water is universally considered as being a blessing,

because its availability influences the quality of life of

every population. This concept is of particular importance

in Sicily, where there are often problems regarding water

supply. It should, however, be said that the water crises in

question are not always related to the arid climate, when

rainfall is not always sufficient to satisfy requirement, but

are often, instead, caused by insufficient planning and

management of the water resources. The new Italian reg-

ulations in the matter of water requires the study of all the

superficial water bodies and groundwater to monitor,

safeguard and manage these resources both from a quan-

titative and qualitative standpoint.

The Rocca Busambra area is a region extending for

about 140 km2 in the mid-west Sicily (Italy). It is charac-

terized by an important carbonate relief (Rocca Busambra)

arising in the middle of an extended outcrop of flysch. In

the past, the studied area was intensely investigated only

for its main structural, depositional and tectonic features.

The presence of several springs with a total annual flow

rate in the order of hundreds of liters per second sur-

rounding the carbonate massif provoked our interest to

investigate the circulation of groundwater in the most

important hydrological structures of the Rocca Busambra

area and to evaluate its potential use (for drinking or

M. Fontana (&) � F. Grassa � G. Cusimano � R. Favara �S. Hauser � C. Scaletta

Istituto Nazionale di Geofisica e Vulcanologia - Sezione di

Palermo, Via La Malfa 153, 90146 Palermo, Italy

e-mail: m.fontana@pa.ingv.it

G. Cusimano

Dipartimento di Geologia e Geodesia, Universita di Palermo,

Corso Tukory 131, 90134 Palermo, Italy

S. Hauser

Dipartimento di Chimica e Fisica della Terra,

Universita di Palermo, Via Archirafi 36, 90123 Palermo, Italy

123

Environ Geol (2009) 57:885–898

DOI 10.1007/s00254-008-1368-z

irrigation). Therefore, the water resource in the studied area

was evaluated through a preliminary water budget.

Water quality depends strongly on the water–rock

interaction processes and of course also on the anthropic

activities. Therefore, this study was focused mainly on the

hydrochemical characterization of groundwater flowing

within the Rocca Busambra, aimed to the distinction

between solutes deriving leaching of host rocks and those

produced by the effects of human pollution.

From November 1999 to July 2002, more than 20 water

samples periodically collected from the most representative

wells and springs were analyzed for their chemical and

isotope composition. During the same period, two rain

gauges were also installed to determine the isotope signa-

ture of the local meteoric recharge.

On the basis of the obtained results, a conceptual geo-

chemical model of groundwater circulation in the Rocca

Busambra area is here proposed. Finally, concentration of

major solutes allowed to define whether or not these waters

could be used for drinking purposes or for agricultural

irrigation.

The quality of the groundwater has been evaluated on

the basis of the concentration of major solutes. Interna-

tional standards for drinking water set by the World Health

Organization (2004) were used as references to evaluate

whether or not these waters could be used for drinking

purposes. On the other hand, to evaluate whether water is

suitable for agricultural purposes, all the collected samples

were plotted on the Wilcox diagram (Wilcox 1955).

Studied area

Geology

The study area, located in mid-west Sicily, extends for

approximately 140 km2 (Fig. 1). It consists of a carbonate

dorsal (Rocca Busambra) having a maximum height of

1,613 m above mean sea level (a.m.s.l.), and is surrounded

by flyshoid deposits. The outcropping rocks belong to three

different tectonic units (Catalano and D’Argenio 1982;

Roure et al. 1990; Lentini et al. 1994; Vitale 1995; Agate

et al. 1998), which originate from the deformation, in

Miocene age, of pre-existing paleo-geografic domains: (1)

a carbonatic unit that originated from the partial defor-

mation of the Imerese–Sicano domain, which mainly

emerges in the north-eastern portion of the study area

(Pizzo Chiarastella); (2) another prevailing carbonate unit

that originated from the deformation of the Trapanese

domain, which forms the Rocca Busambra dorsal almost

entirely and (3) the Numidian Flysch, which occupies most

of the studied territory. Late-orogenic terrains overlie the

abovementioned units.

Hydrogeology

On the basis of the lithology and geologic-structural aspects,

in the studied area, the presence of various hydrogeological

complexes has been recognized. Furthermore, from a point

of view of hydraulic conductivity (K), three main hydro-

geological complexes have been distinguished:

• High hydraulic conductivity (K [ 10-4 m s-1)

• Medium hydraulic conductivity (10-7 m s-1 \ K \10-4 m s-1)

• Poor hydraulic conductivity (K \ 10-7 m s-1)

The high hydraulic conductivity complex includes the

following:

Carbonate

complex (Rocca

Busambra and Pizzo

Chiarastella)

The carbonatic sequences of the

Imerese–Sicano (Late Triassic–

Eocene) and Trapanese domains

(Late Triassic–Paleocene) belong to

this complex. Both the intense

fracturing and the impressive

development of karst structures

confer a high secondary perme-

ability to this complex. The huge

extension coupled with high

permeability characteristics makes

this complex as the main potential

recharge area.

Arenaceous

complex

It is made up of calcarenites

(Aquitaniano–Langhiano), rich in

glauconite, of a gray-greenish

color, better known as ‘‘Calcareniti

di Corleone’’ (Trapanese domain)

and of quartz–arenites of the

Numidian Flysch (Late Oligocene–

Early Miocene). The permeability of

the first lithotype is strongly

dependent on the degree of

cementation, while the permeability

of the flyschoid deposits is to be

referred to the degree of fracturing

rather than to the porosity.

Evaporite

complex

It includes the evaporite deposits

(Messinian in age) belonging to the

late-orogene terrains. Although this

complex is highly permeable,

mainly due to the occurrence of

karst structures, it has a marginal

role in the groundwater circulation

of the study area because of its small

size.

The complexes belonging to the medium hydraulic

conductivity group are as follows:

886 Environ Geol (2009) 57:885–898

123

Marl-carbonate

complex

It has secondary hydraulic conductivity

due to fractures and karst structures.

This complex is mainly made up of

microcrystalline calcilutites, alternated

by marls, belonging to the Amerillo

Formation (Late Cretaceous–Eocene;

Trapanese domain) and Caltavuturo

Formation (Late Cretaceous–Eocene;

Imerese–Sicano domain).

Clay-sandy

complex

These are terrigenous deposits of

the Terravecchia formation (Upper

Tortonian–Lower Messinian). Sandy

and conglomeratic layers have moderate

hydraulic conductivity due to primary

porosity; this complex is almost

impermeable in correspondence with

the outcroppings of clay deposits.

The clay deposits, which represent the largest outcrop-

ping in the study area (about 90 km2), belong to the poor

hydraulic conductivity complex. It consists mainly of the

Mufara Formation (Carnico; Imerese–Sicano domain), the

‘‘Marne di S. Cipirrello’’ (Langhiano–Early Tortonian;

Trapanese domain) and Numidian Flysch (Upper Oligo-

cene–Lower Miocene).

Climate setting

In spite of its relatively high mean annual precipitation

(about 750 mm year-1), the Rocca Busambra area can be

considered as having a mainly semiarid climate. The cli-

matic characteristics of the study area are well known on

account of the temperature and rainfall data collected from

1921 to 1999 by eight stations belonging to the Hydrog-

raphical Service of the Sicilian Region network. In

particular, it has been possible to observe that the rainy

period occurs in winter, between November and February,

whereas the dry season is summertime, from June to

August. As regards temperatures, the lowest values (about

7�C) have been recorded in February, while August is the

hottest month with average temperatures of 27�C.

In Fig. 2, monthly precipitation data collected during the

observation period have been compared with those

regarding the long term observation period (1921–1999);

they have highlighted marked anomalies both in the

monthly and in the annual amounts of rainfall.

Water budget

In the framework of the aim of this study, the water

resource in the Rocca Busambra area was evaluated

Fig. 1 Hydrogeological map of the studied area. The location of the 23 water points and the two rain gauges collected are also reported

Environ Geol (2009) 57:885–898 887

123

through a preliminary water budget. For this, computation

was developed as a very simple model having as few

parameters as possible as suggested by Dooge (1977).

The starting point in evaluating water resource was to

determine the components of the water balance defined by

the following equation:

P ¼ Er þ I þ R

where P represents the amount of rainfall, Er is the effec-

tive amount of water lost during evapotranspiration, I is the

net infiltration and R is surface runoff.

Long term record of monthly precipitation and temper-

ature data (1921–1999) were available from eleven (P) and

seven (T) stations belonging to the Hydrographical Service

of the Sicilian Region network. To estimate the amount of

precipitation (P), the territory was divided into 11 subareas

following the method proposed by Thiessen (1911). Each

of the obtained areas represents the part of territory influ-

enced by the rain gauge station in it. The monthly amount

of rainfall (Pt) was computed as the monthly average value

weighted on the basis of the size of the subareas. The

annual precipitation (P), obtained by summing the twelve

monthly precipitation, resulted as being about 750 mm.

For computing the monthly effective evapotranspiration

(Ert), two main factors were used: (1) the monthly precipi-

tation (Pt) and (2) the monthly potential evapotranspiration

(Ept) as follows:

Ert ¼ min Pt; Ept

� �

The Ept factor was computed following the methods pro-

posed by Thornthwaite (1948) and Turc (1955).

Because Thornthwaite’s equation and Turc’s formula

generally produce Ept values, which tend to be underesti-

mated and overestimated respectively, to obtain a more

accurate calculation, an average value between those

computed applying the two methods described above was

taken into account. In Fig. 3, the temporal trends of the Ert,

Pt, Ept and Pe factors computed for the Rocca Busambra

region were plotted.

It can be noted that in the studied area from October to

March, the Ert is equal to Ept, since the monthly amount of

rainfall (Pt) is greater than the monthly potential evapo-

transpiration (Ept), whereas, in the remaining period of the

hydrologic year (from April to September), the Ept prevails

on the Pt and, therefore, the effective monthly evapo-

transpiration (Ert) is equal to Pt. As a result, during the

whole year, the total amount of water lost by evapotrans-

piration was estimated to be approximately 400 mm,

corresponding to 53% of the total annual precipitation.

By subtracting Er from P, the effective amount of pre-

cipitation (Pe), which represents the effective volume of

water available in the field (I + R) was obtained. To esti-

mate the parameter I for each of the outcropping

lithologies, the potential infiltration coefficient (p.i.c.) was

used (Celico 1986). This parameter expresses the per-

centage of infiltrating water in respect of effective

precipitation, as follows:

p.i.c. ¼ Pe

I

The I value, averaged on the relative extension of each

outcropping is around 85 mm (12% of the total precipita-

tion) and corresponds to an annual water availability of

about 2–3 9 107 m3 year-1. Nonetheless, the exact num-

ber of water points and consequently the total volume of

water discharged from the studied area is unknown; these

preliminary results seem to fit roughly the water discharge.

In fact, flow-rates of the spring nos. 9 and 10, two of the

most relevant water discharges in the Rocca Busambra

area, solely account for at least 10–15% of the total volume

of water.

Once P, Er, and I were computed, R was finally calcu-

lated as a difference. A value of 260 mm (about 35% of the

total annual precipitation) was obtained.

Fig. 2 Comparison between the monthly precipitation collected

during the year 2000 and those relative to long term observation

period (1921–1999)

Fig. 3 Temporal trends of Ert (dotted area), Pt (open diamonds), Ept

(closed squares) and Pe (dotted line) factors computed for the Rocca

Busambra region

888 Environ Geol (2009) 57:885–898

123

Field and analytical methods

Water temperature, pH, Eh and electrical conductivity (EC)

measurements were carried out directly at the sampling

points. Alkalinity determination was carried out in the

laboratory by means of HCl titration. Major dissolved

constituents were determined by ion-chromatography.

From December 1999 to November 2000, rain water

was collected monthly from two rain gauges located at

different elevations (i.e. PC at 800 m and PM at 530 m

a.m.s.l.). To prevent evaporation, 250 ml of liquid Vase-

line (CAS No. 8009-03-8) was introduced into the

collector.

The D/H ratios were determined via reduction with zinc

(Coleman et al. 1982) and the isotope measurements were

performed by a Delta Plus Finnigan IRMS. The 18O/16O

ratios were determined through CO2–H2O equilibration,

using an automatic preparation line, and the measurements

were carried out by an AP 2003 mass-spectrometer. The

results obtained have been reported in d per mil versus V-

SMOW international standard. The repeatability of the

isotope measurements is ±1% and ±0.1% for D/H and18O/16O, respectively.

Water classification

From November 1999 to July 2002, 23 water points such as

wells and springs were periodically sampled. Their physi-

cochemical parameters, as well as major and minor

dissolved constituents, are reported in Tables 1 and 2 as

mean, maximum and minimum values.

The Langelier–Ludwig diagram (Langelier and Ludwig

1942) in Fig. 4 shows that the samples are mainly con-

centrated in two groups: the first group (A) includes typical

calcium–magnesium–bicarbonate-type waters, whereas the

second one (B) straddles the field of calcium–magnesium–

chloride–sulphate-type and calcium–magnesium–bicar-

bonate-type waters.

Group A consists of ten water points, six of them (nos. 3,

4, 5, 6, 13 and 23) are located close to the dorsal while the

other four (nos. 9, 10, 21 and 22) are outflows that are

located along the western flank. These waters show annual

mean TDS values between 290 mg/l (no. 5) and 539 mg/l

(no. 4). The main chemical features of these waters

(Ca C Mg–HCO3-type) suggest an interaction between

meteoric waters and the carbonate rocks that form the

Rocca Busambra massif.

Table 1 Mean, minimum and maximum values of the physicochemical parameters of the waters collected

No. Temperature (�C) pH Eh (mV) EC (lS/cm) TDS (mg/l) n

Mean Min. Max. Mean Min. Max. Mean Min. Max. Mean Min. Max. Mean Min. Max.

1 11.8 8.8 14.5 7.3 6.7 7.6 28 -17 116 660 553 789 545 464 611 14

2 12.3 8.4 15.9 6.8 6.6 7.1 13 -15 34 417 326 495 315 300 332 4

3 11.3 6.5 17.1 7.9 7.2 8.2 123 86 178 399 318 538 347 302 438 14

4 11.0 8.9 12.7 7.3 6.9 7.8 149 110 236 516 300 691 539 436 717 9

5 13.9 8.2 17.7 7.5 6.9 8.0 119 60 285 332 236 408 290 248 328 15

6 13.9 7.0 16.7 7.4 6.8 7.7 106 48 208 379 302 507 340 275 395 14

7 18.5 13.0 25.0 7.5 7.2 7.7 185 -30 630 590 361 665 541 377 625 8

8 14.1 11.0 18.0 6.3 6.1 6.6 126 66 207 366 341 387 267 229 323 11

9 18.4 13.8 21.1 7.7 7.5 7.9 171 124 284 479 446 528 416 380 449 4

10 22.4 21.8 22.9 7.5 7.5 7.7 146 76 202 407 359 432 414 398 441 4

11 17.7 17.0 18.5 7.2 7.1 7.3 247 166 315 1,028 946 1,109 963 912 1,014 4

12 16.2 15.7 17.2 7.7 7.4 8.0 166 136 211 1,597 1,436 1,801 1,531 1,444 1,634 4

13 12.8 7.0 17.0 7.7 7.3 8.1 143 93 264 411 370 528 332 206 435 15

14 13.7 9.5 16.6 7.3 7.1 7.6 145 109 233 710 677 758 594 525 706 11

15 18.9 16.4 23.1 7.1 7.0 7.3 99 29 190 992 876 1,133 889 845 929 3

16 13.3 8.3 19.0 7.6 7.2 8.1 115 56 253 580 365 720 493 414 602 15

17 20.7 20.1 21.3 7.7 7.3 8.1 18 -115 142 577 529 661 520 474 578 4

18 17.9 17.8 17.9 7.8 7.6 7.9 108 70 146 1,084 957 1,210 968 905 1,032 2

19 16.7 16.0 17.4 7.2 7.2 7.3 158 145 171 1,055 1,005 1,105 949 876 1,022 2

20 19.9 18.0 21.7 7.4 7.3 7.6 168 149 187 919 900 937 746 691 801 2

21 19.8 19.5 20.0 7.4 7.2 7.5 161 158 164 415 413 416 355 342 367 2

22 18.0 18.0 18.0 7.3 7.2 7.3 164 155 173 426 422 430 363 353 373 2

23 15.4 13.0 19.6 7.5 7.1 8.1 200 130 285 282 219 321 285 263 304 3

EC electrical conductivity at 25�C, TDS total dissolved solids, n number of collected samples

Environ Geol (2009) 57:885–898 889

123

Tab

le2

Mea

n,

min

imum

and

max

imum

val

ues

of

the

maj

or

chem

ical

const

ituen

ts

No.

Na

KM

gC

aF

Cl

Br

NO

3S

O4

HC

O3

Mea

nM

in.

Max

.M

ean

Min

.M

ax.

Mea

nM

in.

Max

.M

ean

Min

.M

ax.

Mea

nM

in.

Max

.M

ean

Min

.M

ax.

Mea

nM

in.

Max

.M

ean

Min

.M

ax.

Mea

nM

in.

Max

.M

ean

Min

.M

ax.

152.6

47.8

58.9

2.6

1.7

3.1

17.3

16.3

19.4

76.4

66.9

83.6

0.4

0.2

1.0

81.4

70.9

97.8

0.4

0.1

0.9

1.9

0.0

3.8

29.2

25.0

40.3

283

235

302

228.1

26.2

29.7

2.3

1.7

3.1

11.6

11.1

12.2

44.9

42.7

48.6

0.2

0.2

0.2

56.0

54.9

56.4

0.2

0.2

0.2

1.6

0.0

4.3

20.5

19.5

22.1

149

143

156

316.8

14.9

19.1

0.5

0.0

1.2

3.3

2.9

3.6

71.3

60.7

89.0

0.2

0.1

0.4

28.2

23.0

32.3

0.1

0.0

0.2

0.7

0.0

3.8

15.3

11.5

19.7

211

189

268

418.7

12.9

27.6

1.0

0.0

3.4

5.8

4.5

8.3

117.0

99.8

153.3

0.1

0.0

0.2

25.8

21.6

34.0

0.1

0.0

0.2

2.0

0.0

5.0

43.2

28.3

64.4

326

268

421

510.5

8.5

14.4

0.9

0.0

1.6

3.2

1.8

6.8

59.7

52.3

65.5

0.3

0.1

0.6

17.4

15.6

19.1

0.1

0.0

0.2

4.7

3.0

7.5

8.8

7.7

11.0

184

159

201

69.7

7.1

13.8

0.7

0.0

1.6

2.8

1.6

4.0

74.9

65.7

83.2

0.3

0.2

0.6

16.9

13.8

27.7

0.1

0.0

0.2

4.1

2.4

9.5

8.4

6.7

11.0

222

177

244

731.8

21.2

36.1

2.3

2.0

2.7

13.0

9.7

14.6

95.2

69.7

108.2

0.4

0.2

0.6

37.8

33.7

40.1

0.2

0.0

0.6

1.4

0.0

2.5

55.3

33.1

65.3

303

207

354

828.6

26.0

32.2

2.3

1.4

2.7

9.2

7.3

12.0

34.4

31.3

38.9

0.5

0.2

1.0

43.9

38.3

48.2

0.4

0.1

0.9

2.3

0.6

5.7

30.7

26.4

40.8

114

98

140

920.0

19.3

21.4

1.9

0.2

2.7

19.3

18.1

21.1

64.0

59.5

67.8

1.0

1.0

1.1

30.0

25.9

34.6

0.1

0.1

0.1

4.8

2.6

7.7

26.6

25.0

30.3

249

229

262

10

16.4

14.0

17.7

2.4

2.1

3.0

29.5

27.8

31.7

48.7

46.5

51.7

2.2

2.1

2.3

20.5

18.7

24.5

0.5

0.1

1.6

2.9

1.2

5.4

24.7

23.4

25.6

266

262

278

11

69.6

53.6

78.4

2.0

0.7

3.8

26.8

25.0

29.0

161.9

156.3

168.5

0.5

0.3

0.7

83.4

80.5

86.1

0.5

0.4

0.7

35.7

32.8

39.7

126.1

123.0

127.9

457

439

479

12

376.9

354.3

420.4

12.2

10.6

13.5

25.0

20.7

31.3

35.2

30.6

40.3

1.2

0.1

1.9

124.9

109.2

143.0

0.6

0.4

0.7

3.4

0.0

8.1

196.6

192.1

200.0

755

726

775

13

10.9

8.6

12.4

1.1

0.6

1.6

3.1

2.3

4.5

70.8

38.3

91.0

0.3

0.0

0.6

18.9

16.7

26.8

0.2

0.0

1.6

1.7

0.6

4.8

6.7

4.8

10.8

219

134

281

14

38.1

32.4

48.5

3.0

2.1

4.3

22.9

21.4

24.1

94.4

85.2

107.6

0.5

0.0

0.8

43.1

35.5

56.7

0.3

0.1

0.6

2.6

0.0

5.2

170.9

156.6

226.2

218

192

232

15

105.3

91.0

117.5

4.2

3.4

5.2

26.2

24.6

28.7

104.9

100.8

107.4

0.2

0.0

0.3

42.1

40.4

43.8

0.2

0.2

0.2

3.0

0.0

5.3

197.0

188.3

202.4

406

397

418

16

43.6

33.1

53.6

2.5

0.8

4.1

14.5

13.0

16.8

74.4

68.1

85.8

0.4

0.0

0.6

42.9

32.3

52.8

1.2

0.0

9.3

3.8

0.0

7.9

102.0

83.6

127.3

208

183

244

17

92.6

82.1

113.3

4.0

2.9

6.1

14.0

11.5

20.4

32.3

19.0

40.5

1.0

0.9

1.1

36.5

32.4

46.1

0.2

0.1

0.3

5.5

4.0

6.9

36.6

34.6

41.3

297

287

302

18

190.6

186.2

195.1

25.3

23.3

27.4

20.1

18.0

22.1

43.6

39.5

47.7

0.5

0.3

0.7

45.3

42.2

48.4

0.1

0.0

0.2

12.9

10.7

15.0

268.5

255.0

281.9

362

330

394

19

59.4

55.2

63.5

10.8

10.3

11.3

17.2

16.5

17.9

176.7

169.1

184.3

0.2

0.2

0.2

111.5

104.1

118.9

0.1

0.0

0.3

64.4

60.6

68.2

174.0

157.4

190.7

334

302

366

20

64.2

62.0

66.3

21.0

20.1

21.8

12.3

11.2

13.3

119.1

108.5

129.7

0.2

0.2

0.2

106.4

105.7

107.0

0.2

0.0

0.4

174.0

143.5

204.6

80.9

75.4

86.4

168

165

171

21

14.5

14.3

14.7

1.3

1.3

1.4

22.5

22.0

22.9

46.5

46.1

47.0

1.4

1.4

1.5

18.8

18.4

19.1

0.0

0.0

0.0

4.0

3.8

4.1

21.2

21.0

21.5

224

214

235

22

17.7

17.5

17.9

3.3

2.6

4.0

22.7

22.5

22.9

46.3

45.8

46.8

1.3

1.3

1.4

18.5

18.4

18.6

0.0

0.0

0.0

2.8

2.8

2.9

22.9

22.6

23.2

227

220

235

23

9.5

8.5

10.1

0.8

0.8

0.8

4.1

4.0

4.4

59.3

55.9

65.9

0.1

0.1

0.2

17.8

17.0

18.4

0.0

0.0

0.1

3.8

1.9

5.7

10.6

9.6

12.0

179

165

186

All

the

conce

ntr

atio

ns

are

expre

ssed

inm

g/l

890 Environ Geol (2009) 57:885–898

123

Group B includes 10 water points: two of them (nos. 1

and 2) are located on the northern part of Rocca Busambra,

whereas nos. 7, 8, 14, 15 and 16 are outflows to the north of

the dorsal at the flyschoid deposits; spring nos. 19 and 20

issue from the western zone, at the boundary between the

Numidian Flysch and the marls of the ‘‘Marne di S. Cip-

irrello’’ formation, and finally water point no. 11 lies in

proximity of Pizzo Chiarastella (north-eastern sector).

The mean TDS value ranges between 267 mg/l (no. 8)

and 963 mg/l (no. 11). Such a wide range in the TDS

values suggests the presence of hydrogeological circuits

having different lengths and/or residence times.

The average chemical composition (Ca [ Na–HCO3 C

SO4 and Ca [ Na–HCO3 C Cl types) of the latter group of

samples highlights two main components: a Ca–HCO3

component and an additional Na–SO4–Cl component.

While it seems unquestionable that the Na–SO4–Cl

component mainly reflects the interaction with the Numi-

dian Flysch deposits (Favara et al. 2000) as they outflow

from the quartz–arenites, it is not clear about the origin of

the Ca–HCO3 component. There are two possibilities: cal-

cium and bicarbonate might originate from the dissolution

of the limestone forming the dorsal or from the calcite

cement within the quartz–arenites. The former process is

evident in sample no. 7 (TDS = 541 mg/l), the chemical

signature of which leans towards A group composition, and

probably indicates a mixing between group A and group B

waters. On the contrary, very low TDS value (267 mg/l) in

sample no. 8 suggests that it exclusively drains the quartz–

arenites and consequently the carbonate component derives

from the dissolution of carbonate cement.

The three remaining water points (wells nos. 12, 17 and

18), which are not included either in group A or in group B,

show singular chemical characteristics. In the Langelier–

Ludwig diagram, they fall in the fields of sodium–potas-

sium–bicarbonate (wells nos. 12 and 17) and sodium–

potassium–chloride–sulphate (no. 18) type waters, and

differ from the other samples because of their relatively

high content in Na and K. The enrichment in the alkaline

elements at wells 17 and 18 could be caused by the dis-

solution of glauconite as suggested by the presence of

significant thicknesses of the ‘‘Calcareniti di Corleone’’

formation emerging in the vicinity of the wells.

At well no. 12, located to the north-east of Rocca Bu-

sambra, the alkaline elements prevail over the earth-

alkaline metals, probably as a result of cation exchange

processes between clay minerals and water, in accordance

with the following reaction:

Na - Clay + 1/2Caþþ + 1/2Mgþþ

¼ 2Naþ + CaMg - Clay

Moreover, this well has the highest TDS value (1,531 mg/l)

suggesting a longer residence time in the aquifer. High

alkalinity content (755 mg/l) points to the dissolution of an

external source of CO2 into the water.

The cation ternary diagram (Fig. 5a) highlights that

some samples belonging to group A and located to the west

of the dorsal are progressively enriched in magnesium.

Moreover, these waters show a positive correlation

between Mg2+ and F- contents (Fig. 6) suggesting that the

magnesium and fluoride in these waters have the same

origin. This enrichment could derive from the dissolution

of hydrothermal fluorite, which has often been found in the

Triassic dolostone belonging to the Trapanese domain

(Bellanca et al. 1990).

In the HCO3–SO4–Cl ternary diagram (Fig. 5b), the

waters belonging to group A fall very close to the HCO3

vertex, whereas B group waters are aligned along two

evolution trends: towards the Cl vertex and towards the

sulphate corner. This differentiation could be the result of a

mineralogical complexity of the flyschoid deposits (Alaimo

and Ferla 1975), where sulphur-rich minerals (sulphides

and sulphates) and Cl-bearing compounds have been

found.

Chemical equilibrium

During flow, groundwater tends to dissolve the rocks

forming the aquifer in which it circulates, as long as

chemical equilibrium is attained. The saturation index (SI)

is a parameter that describes whether a solution is saturated

(SI = 0), oversaturated (SI [ 0) or undersaturated (SI \ 0)

in respect of the mineral in question. It is defined as the

Fig. 4 Langelier–Ludwig classification diagram

Environ Geol (2009) 57:885–898 891

123

logarithm of the ratio between the ion activity product

(I.A.P.) for a given mineralogical phase and the equilib-

rium constant of its solubility product (Ksp) as follows:

SI ¼ log I.A.P.�

Ksp

� �:

The saturation state with respect to the main carbonate

minerals was applied successfully to distinguish between

prevailing limestone aquifers and dolostone aquifers. For

this reason, the PHREEQC computer program (Parkhurst

and Appelo 1999) was used to evaluate the saturation

indexes of the group A water points in respect of pure

calcite (SIc), dolomite (SId) and fluorite (SIf) (Table 3).

The arrangement of the water points in the SIc–SId

diagram (Fig. 7) provides us with two important insights.

All the waters taken into consideration are nearly saturated

with respect to calcite (-0.3 \ SIc \ 0.4), thus confirming

that the dissolution of limestone is the main water–rock

interaction process. The samples show a wider range of

saturation with respect to dolomite. Springs nos. 6, 5 and

23, located on the south-east flank of Rocca Busambra, are

strongly undersaturated (SId \ -1), suggesting that they

prevalently drain through Mesozoic limestone. The

remaining water points (nos. 3, 4, 9, 10, 13, 21 and 22) are

nearly saturated or saturated with respect to dolomite, thus

suggesting that the Mg contents is probably controlled

mainly by the dissolution of the Mg-rich limestone and/or

dolostone (Trias–Lias in age), which characterise the bot-

tom part of the carbonate sequence.

The hypothesis that these springs are fed by deeper

hydrogeological circuits also seems to be confirmed by the

arrangement of the samples in the SId–SIf diagram (Fig. 8).

As fluorite is a very common hydrothermal mineral in the

Triassic dolostone of the Trapanese domain (Bellanca et al.

1990), all the samples are undersaturated with respect to

fluorite, except for samples nos. 9, 10, 21 and 22, which are

nearly saturated.

Fig. 5 Triangular plots: a Ca–Na + K–Mg; b SO4–HCO3–Cl

Fig. 6 Mg versus F contents in the group A samples

Table 3 Saturation indexes with respect to pure calcite (SIc), dolo-

mite (SId) and fluorite (SIf), calculated only for group A samples

Number SI Calcite SI Dolomite SI Fluorite

3 0.4 -0.4 -2.1

4 0.2 -0.7 -2.3

5 0.0 -1.1 -1.9

6 0.0 -1.3 -1.9

9 0.4 0.5 -1.0

10 0.2 0.4 -0.5

13 0.3 -0.6 -1.9

21 -0.2 -0.4 -0.8

22 -0.3 -0.6 -0.8

23 0.0 -1.0 -2.7

892 Environ Geol (2009) 57:885–898

123

Isotope composition

Precipitation

The isotopic composition of precipitation in the Rocca

Busambra area is reported in Table 4 together with the

weighted average values. The dD and d18O values range

from -60% to -16% and from -9.2% to -2.7%,

respectively, at the PC rain gauge, and between -70% and

-13% and between -10.9% and -2.6%, respectively, at

the PM station. According to the temperature-dependent

isotope fractionations occurring during water evaporation/

droplet condensation processes (the so-called ‘‘seasonal

effect’’), rainwater shows more negative isotope values

during the cold months than during the warm season, when

precipitation is enriched in heavy isotopes, although there

are some exceptions.

The samples collected in March and October at both

stations show more positive dD and d18O values than those

expected, given the seasonal trend; this coincides with

monthly amounts lower than the general trend. On the

contrary, the rainwater isotope composition of the sample

collected in April at PC station shows the most negative

value. This anomalous value is most probably related to a

precipitation event that occurred under peculiar environ-

mental conditions (i.e., condensation temperature lower

than average monthly ones).

The stable isotope composition of the precipitation was

plotted on the dD–d18O diagram (Fig. 9). The meteoric

water line (MWL), as defined by Craig (1961), and the

MMWL regarding Mediterranean precipitations (Gat and

Carmi 1970) are also reported on the same diagram. Most

of the samples collected monthly fall within these two

reference lines. The best fit line for these points is as

follows:

dD ¼ 6:4� d18Oþ 5:5

which represents the local MWL (LMWL).

Fig. 8 SIf versus SId plot. Samples belonging to the group A are

reported. The dotted lines represent the range of saturation (±0.5)

Table 4 Isotopic composition of precipitation in the Rocca Busam-

bra area, collected by two rain gauges: PC (800 m a.m.s.l.) and PM

(530 m a.m.s.l.)

Month PC PM

dD d18O mm dD d18O mm

December 2000 -48 -8.9 111 -36 -7.1 48

January 2001 -34 -6.3 121 -70 -10.9 46

February 2001 ND ND ND -42 -7.6 40

March 2001 -23 -5.3 33 -13 -2.9 16

April 2001 -60 -9.2 58 -43 -6.8 40

May 2001 -16 -2.7 65 -15 -2.8 42

June 2001 ND ND ND -15 -2.6 19

July 2001 -17 -3.5 9 -17 -4.2 3

August 2001 -45 -8.5 44 ND ND ND

September 2001 -39 -7.5 48 -40 -6.7 74

October 2001 -33 -6.1 48 -22 -4.6 44

November 2001 -48 -8.5 127 -44 -7.1 82

Weighted average -40 -7.2 -38 -6.5

Fig. 7 SIc versus SId plot. Samples belonging to the group A are

reported. The dotted lines represent the range of saturation (±0.5)

Environ Geol (2009) 57:885–898 893

123

Because rainfall is not uniformly distributed throughout

the year, volume-weighted mean values were computed as

follows:

dwm ¼X12

i¼1

qi � di � q�1tot

where qi represents the amount of rainfall collected during

the i-esime month, d is the isotopic composition (both

hydrogen and oxygen) and qtot is the annual rainfall.

The weighted mean isotope values computed show a

progressive negativization as altitude increases (Fig. 10).

The linear regression through these data points provides the

vertical isotopic gradient for this area, which quantifies the

so-called ‘‘altitude effect’’ on the isotopic composition of

rain. The obtained value is about 0.26%/100 m, which is

slightly higher than that previously determined for north-

west Sicily (0.2%/100 m; Hauser et al. 1980).

Groundwater

The maximum, minimum and mean values of the isotopic

composition of the water collected from the springs and

wells are reported in Table 5. The mean d18O value ranges

from -8.0% (sample no. 4) to -6.4% (samples nos. 12

and 19), whereas the dD values range from -45% (sam-

ples nos. 5, 6 and 8) to -39% (sample no. 12).

In the dD–d18O diagram (Fig. 11), the groundwater

samples have been plotted together with the LMWL and

the weighted mean isotope values of precipitation at both

stations. Almost all the samples collected lie along the

Fig. 10 d18O values of groundwater versus their respective elevation

expressed in m a.m.s.l

Table 5 Isotopic composition of groundwater samples

Number dD d18O Altitude

(m a.m.s.l.)Mean Min. Max. Mean Min. Max.

1 -43 -45 -40 -7.9 -8.2 -7.7 835

2 -43 -44 -42 -7.8 -7.9 -7.7 940

3 -43 -45 -40 -7.9 -8.1 -7.7 1,010

4 -44 -47 -41 -8.0 -8.3 -7.5 910

5 -45 -48 -41 -7.9 -8.2 -7.6 850

6 -45 -48 -41 -7.8 -8.0 -7.7 960

7 -44 -46 -41 -7.8 -8.0 -7.6 750

8 -45 -48 -42 -7.7 -7.9 -7.5 595

9 -42 -44 -40 -7.6 -7.7 -7.3 385

10 -44 -45 -42 -7.8 -7.8 -7.7 370

11 -41 -43 -39 -6.8 -7.0 -6.7 520

12 -39 -43 -37 -6.4 -6.5 -6.3 580

13 -44 -47 -42 -7.7 -8.0 -7.5 980

14 -44 -47 -39 -7.8 -7.9 -7.6 740

15 -43 -45 -42 -7.7 -7.8 -7.7 775

16 -43 -47 -39 -7.7 -7.8 -7.5 640

17 -41 -42 -41 -7.6 -7.7 -7.5 570

18 -42 -43 -40 -7.1 -7.1 -7.1 585

19 ND ND ND -6.4 -6.8 -6.1 570

20 ND ND ND -6.5 -6.6 -6.3 540

21 ND ND ND -7.8 -7.9 -7.8 380

22 ND ND ND -7.9 -8.0 -7.9 375

23 -44 -44 -44 -7.9 -8.0 -7.7 860

Mean, minimum and maximum dD and d18O values are expressed in

d values

Fig. 9 dD–d18O diagram of the rain waters monthly collected in the

Rocca Busambra area

894 Environ Geol (2009) 57:885–898

123

LMWL line, which underlines the fact that groundwater is

meteoric in origin and not affected by secondary postfor-

mation processes. All the samples show more negative dD

and d18O values than those of weighted mean rainwater and

fall within a narrow range (d18O = - 7.8%o ± 0.2;

dD = - 43%o ± 2), but only three samples (nos. 11, 12

and 18) showing values in the same range of those

regarding weighted mean precipitation.

Given that the isotopic composition of rainwater

becomes more negative as elevation increases, groundwa-

ter with d18O values lower than those of weighted mean

rainwater could be related to recharge areas located at

higher elevations. By solving the vertical isotopic gradient

in respect of elevation (Q), the following equation was

obtained:

Q = � 385� d18O � 1977

This relationship allows us to estimate the mean elevation

of the main recharge areas when the isotopic composition

of groundwater is known.

In Fig. 10, the d18O values of groundwater are reported

against their respective elevation. It is possible to observe

that almost all the water discharges have an d18O value of

-7.8% ± 0.2, which corresponds to a recharge area at an

elevation of 1,025 ± 75 m a.m.s.l. As far as the remaining

samples are concerned (nos. 11, 12, 18, 19 and 20), the

d18O values that fall between -7.2% and -6.4% corre-

spond to a feeding area from 500 to 800 m a.m.s.l.

Almost all the samples show isotope values that are

fairly constant over time as they have a limited d18O annual

variability (D18Od18Omin–d18Omax \ 0.5 d%) lower than

that of rainwater (D18O & 4 d%) during the period of

effective meteoric (i.e., from October to March). The

annual variability in the composition of groundwater iso-

topes allowed to distinguish between limited and huge

aquifers hosted in the Rocca Busambra area.

Isotope values fairly constant over time imply that vol-

umetrically extended aquifers do exist and that they are

capable of modulating the variations in the isotopic com-

positions induced by local meteoric recharge. On the

contrary, springs showing a d18O annual variability[0.5%seem to be the result of the limited volume of their

respective aquifers. In fact, the flow rate of these springs

changes drastically throughout the year until the springs

themselves actually disappear, as is the case of spring no. 4.

Model of groundwater circulation

Based on the chemical and isotopic compositions of the

waters collected, a circulation model for the groundwater

in the Rocca Busambra area is proposed here. Two main

recharge zones have been inferred on the basis of the stable

isotope signature. The first one is located between 500 and

800 m a.m.s.l., whereas the second one has an average

elevation of about 1,025 ± 75 m a.m.s.l. The first recharge

area corresponds to the main outcroppings of the quartz–

arenites of the Numidian Flysch and the terrigenous

deposits (sands and conglomerates) of the Terravecchia

Formation surrounding the carbonate dorsal.

The highest recharge zone perfectly coincides with the

topographic and hydrogeologic setting of the Rocca Bu-

sambra carbonate massif. In accordance with the

sedimentary sequence, three main flow-paths have been

recognized within this carbonate relief (Fig. 12).

Along the south-eastern orographic side of Rocca Bu-

sambra, groundwater circulation occurs in short circuits

predominantly hosted within the Triassic limestone. The

springs that outflow in this area (nos. 5, 6 and 23) show

very low salinity values, high Ca/Mg ratios and the

achievement of a saturation state with respect to calcite

while they are undersaturated with respect to dolomite.

Along the north and north-eastern flanks of the dorsal,

springs are mainly fed by hydrogeological circuits hosted

within that portion of the carbonate succession where Mg-

rich limestone is dominant. Carbonate waters (nos. 3, 4 and

13) that drain from this flank show intermediate Ca/Mg

ratios, which result as being close to saturation state with

respect to both calcite and dolomite. Seven water points

belonging to group B issue from this flank. The discharges,

which outflow from the quartz–arenites, are typical contact

springs that drain from the carbonate rocks overlying the

Numidian Flysch.

Water points 9, 10, 21 and 22, which drain from the

western flank, are chemically different from the other waters

of group A, thus reflecting a different hydrogeological set-

ting. These springs show a progressive increase in their

magnesium and fluoride contents as they flow westward.

This leads to low Ca/Mg ratios (close to 1 at spring 10) and

Fig. 11 dD–d18O diagram of the groundwater samples

Environ Geol (2009) 57:885–898 895

123

saturation with respect to both calcite and dolomite and also

to almost complete saturation with respect to fluorite (spring

no. 10). The circulation of these waters is thought to be deep

enough to reach the Triassic dolostone at the bottom of the

Trapanese domain, where deposits of hydrothermal fluorite

have been found (Bellanca et al., 1990). These findings seem

to be indicative of hydraulic communication between the

central part of Rocca Busambra and the buried carbonate

structures, emerging in limited outcroppings on the western

portion of the study area.

Such a chemical evolution could also be explained by

considering other relieves as being alternative recharge

areas. These relieves, situated in the neighborhood of the

study area, should have similar topographic and geological

characteristics to those of the Rocca Busambra dorsal. For

instance, M. Kumeta (1,233 m a.m.s.l.), the nearest car-

bonate relief that extends for about 20 km2, consists mainly

of the same carbonate succession of the Rocca Busambra

dorsal (Fig. 12).

The chemical features and isotope signatures of the

meteoric water infiltrating through M. Kumeta and flowing

southwards within the carbonate structures, buried below

the impermeable cover, should be comparable to the waters

infiltrating into the Rocca Busambra dorsal area and

flowing westwards at depth. Moreover, it is reasonable to

presume that both the Rocca Busambra and the M. Kumeta

carbonate reliefs contribute to the feeding of these springs.

Quality of the waters and their potential use

The quality of the groundwater and, consequently, its

potential use either as drinking water or irrigation water has

been evaluated on the basis of chemical analyses. To

evaluate whether or not these waters could be used for

drinking purposes, the chemical data was compared with

the maximum permissible concentrations indicated in the

WHO guidelines (World Health Organization 2004) and

reported in Table 6). Nearly all of the analyzed samples

fall within the range of drinkable waters, with the excep-

tion of a few whose NO3- (nos. 19 and 20), F- (no. 10) and

Na+ (no. 12) contents were too high.

While the excess of F- and Na+ can probably be

referred to natural water–rock interaction processes, high

nitrate contents have to be related to anthropic pollution. In

fact, when fertilizers are used in agriculture, often a part of

the nitrogen is not assimilated by the plants; so, it goes into

the aquifers thereby lowering the quality of the water.

To evaluate whether water is suitable for agricultural

purposes, some quality requirements must be satisfied. The

parameters that were taken into consideration are as fol-

lows: (1) Salinity: reported in terms of electrical

conductivity (EC); (2) Sodium adsorption ratio (SAR):

related to the soil’s ability to adsorb sodium; (3) Residual

sodium carbonate (RSC): it indicates the degree of

Fig. 12 Sketch map of

groundwater circulation

in the studied area

Table 6 Limit values for drinking water, extracted by WHO guide-

lines (World Health Organization 2004)

Parameter Limit values (mg/l)

Clorides 250.0

Sulphates 500.0

Sodium 200.0

Nitrates 50.0

Fluoride 1.5

896 Environ Geol (2009) 57:885–898

123

precipitation of calcium and magnesium in the soils. The

latter parameter is calculated as the difference between the

concentrations of the carbonate species (CO3 + HCO3)

and the concentration of earth alkaline elements

(Ca + Mg).

The classification diagram (Fig. 13), proposed by Wil-

cox (1955), couples both the conductivity (CE) and the

SAR values. Almost all the waters collected were sub-

stantially suitable for irrigation, as they fall within the

C2S1 and C3S1 fields. Both these fields indicate low

hazard of soil alkalinization and medium–high hazard of

accumulation of salt in the soil. In particular, the carbonate

groundwater (group A) was of good quality, as it falls

solely in the C2S1 field. On the contrary, the group B

waters plot along a trend from C2S1 to C3S1 fields, thereby

highlighting a progressive worsening in the quality of the

water as the length of the circuits and/or the residence

times increased.

The other water points, which are not included in groups A

and B, plot into three fields (C2S1, C3S2 and C3S3). Based

on the Wilcox diagram, sample no. 12 is harmful for irriga-

tion and agricultural activity. Moreover, it is the only sample

that exceeds the maximum RSC values (2.5 mequiv./l;

Mckee and Wolf 1963).

Conclusions

The groundwater circulating in and around the Rocca Bu-

sambra carbonate dorsal was arranged in two main groups:

• Ca C Mg–HCO3 (group A)

• Ca [ Na–HCO3 C SO4 and Ca [ Na–HCO3 C Cl

(group B)

The first one reflects the dissolution of the limestone and

dolostone forming the Rocca Busambra relief. The second

group highlights two main components: a prevailing Ca–

HCO3 component originating from the dissolution of car-

bonate minerals and an additional Na–SO4 or Na–Cl

component that reflects interaction with the Numidian

Flysch deposits (Favara et al. 2000).

Three waters (samples nos. 12, 17 and 18) showed

peculiar chemical features and therefore they are not

included either in the group A or in the group B waters.

These samples differ from the group A and group B waters

because of their relatively high content in Na and K. The

enrichment in alkaline elements seems to be due to the

dissolution of glauconite and/or to the cation exchange

processes between clay minerals and water.

The water isotope signature indicated that the ground-

water is of meteoric origin and is not affected by secondary

postformation processes. Based on the 18-Oxygen vertical

isotope gradient (0.26 d%/100 m) computed from the

isotope composition of the rainwater collected at two rain

gauges, two main recharge zones were inferred. The first

one has an average elevation of about 1,025 ± 75 m

a.m.s.l., which coincides with the topographic setting of the

Rocca Busambra carbonate massif. The second one, loca-

ted between 500 and 800 m a.m.s.l., corresponds to the

main outcroppings of the Numidian Flysch deposits and the

Terravecchia Formation.

The water resource in the studied area, evaluated

through a preliminary water budget, was inferred to be in

the order of about 2–3 9 107 m3 year-1. As expected, the

Rocca Busambra massif is the main infiltration area of the

aquifers feeding all the water points belonging to group A

(Ca C Mg–HCO3-type) and almost all those belonging to

group B.

Three main flow-paths were recognized on the basis of

the sedimentary sequence within this carbonate relief:

• Along the south-eastern side where limestone prevails

(very low salinity, high Ca/Mg ratios, SIc = 0 and

SId \ 0)

• Along the north and north-eastern flank of the dorsal,

where Mg-rich limestone are dominant (carbonate

waters had intermediate Ca/Mg ratios, SIc = 0,

SId = 0). This flow-path also involves seven group B

springs, which are typical contact springs that drain

from the carbonate rocks overlying the Numidian

Flysch

• Along the western flank where Triassic dolostone and

hydrothermal fluorite deposits were inferred to be

found at depths beneath the covering deposits. Along

this flow-path, groundwater shows a progressiveFig. 13 Wilcox classification diagram

Environ Geol (2009) 57:885–898 897

123

increase in Mg and F, the lowest Ca/Mg ratios, SIc = 0,

SId = 0 and SIf ? 0. A chemical evolution of this kind

could also be explained by considering other relieves

having similar topographic and geological characteris-

tics to those of the Rocca Busambra dorsal as being

alternative recharge areas.

A comparison with the WHO guidelines for drinking

waters highlighted that nearly all the samples are suitable

for drinking use, with the exception of four samples in

which the NO3-, F- and Na+ contents exceeded the limits.

High NO3- contents have to be probably referred to the use

of fertilizers, while high F- and Na+ contents exceeding

the WHO limits result from water–rock interaction pro-

cesses. Almost all the waters collected had a low hazard

risk of soil alkalinization and a medium–high hazard risk of

salt accumulation in the soil, and are therefore suitable for

irrigation with the only exception of sample no. 12.

References

Agate M, Basilone L, Catalano R, Franchino A, Merlini S, Sulli A

(1998) Ipotesi sulla condizione strutturale della Rocca Busambra

(Hypothesis on the structural setting of Rocca Busambra dorsal).

In: Proceedings of the 79th National Congress of the ‘‘Societa

Geologica Italiana,’’ Palermo, Italy, 21–23 September 1998, pp

71–78

Alaimo R, Ferla P (1975) Natrojarosite e thenardite, solfati idroter-

mali ricchi in sodio, nelle argille variegate con dickite di

Scillato–Caltavuturo (Sicilia) [Natrojarosite and thenardite, Na-

rich sulphate hydrothermal minerals embedded within the dickite

clay of Scillato–Caltavututro (Sicily)]. Period Mineral 44:227–

243

Bellanca A, Dongarra G, Neri R, Parello F (1990) Geochemistry of

ground waters in carbonate rocks hosting fluorite mineraliza-

tions, northwestern Sicily. Acque Sotterranee IV:47–53

Catalano R, D’Argenio B (1982) Schema geologico della Sicilia

(Geological scheme of Sicily). In: Catalano R, D’Argenio B

(eds) Guida alla geologia della Sicilia occidentale. Societa

Geologica Italiana, Palermo, pp 126–135

Celico P (1986) Valutazione delle risorse e delle riserve idriche

sotterranee. In: Prospezioni idrogeologiche (Evaluation of

groundwater resources and reserves), Cap. VIII, vol 2. Liguori

Editore, Napoli, pp 13–185

Coleman ML, Sheppard TJ, Duhrham JJ, Rouse JE, Moore GR (1982)

Reduction of water with zinc for hydrogen isotopic analysis.

Anal Chem 54:993–995

Craig H (1961) Isotopic variations in meteoric waters. Science

133:1702–1703

Dooge JCI (1977) Problems and methods of rainfall-runoff modelling.

In: Ciriani TA, Maione U, Wallis JR (eds) Mathematical models

for surface water hydrology. Wiley, New York, pp 71–108

Favara R, Grassa F, Valenza M (2000) Hydrochemical evolution and

environmental features of Salso River catchment, central Sicily

(Italy). Environ Geol 39:1205–1215

Gat JK, Carmi I (1970) Evolution of isotopic composition of

atmospheric waters in the Mediterranean Sea area. J Geophys

Res 75:3039–3040

Langelier WF, Ludwig HF (1942) Graphical methods for indicating

the mineral character of natural waters. J Am Water Works

Assoc 34:335–352

Hauser S, Dongarra G, Favara R, Longinelli A (1980) Composizione

isotopica delle piogge in Sicilia. Riferimenti di base per studi

idrogeologici e relazioni con altre aree mediterranee (Rainwater

isotope composition of Sicily. A reference for hydrogeological

studies and relationships with other Mediterranean areas). Rend

Soc Ital Mineral Petrol 36(2):671–680

Lentini F, Carbone S, Catalano S (1994) Main structural domains of

the Central Mediterranean Region and their Neogene tectonic

evolution. Boll Geof Teor Appl 36:103–125

Mckee JE, Wolf HW (1963) Water quality criteria. California State

Water Quality Control Board, Sacramento, 548 pp

Parkhurst DL, Appelo CAJ (1999) User’s guide to PHREEQC—a

computer program for speciation, batch-reaction, 1D-transport

and inverse geochemical calculation. US Geological Survey

Water-Resources Investigation Report 99-4259, 312 pp

Roure F, Howell DG, Muller C, Moretti I (1990) Late Cenozoic

subduction complex of Sicily. J Struct Geol 12(2):259–266

Thiessen AH (1911) Precipitation average for large areas. Mon

Weather Rev 39:1082–1089

Thornthwaite CW (1948) An approach towards a rational classifica-

tion of climate. Geogr Rev 38:55–94

Turc L (1955) Le bilan d’eau des sols. Relations entre les

precipitations, l’evaporation et l’ecoulement (Soil water bal-

ances: relation between precipitation, evaporation and runoff).

Ann Agron 5:491–596

Vitale FP (1995) Il segmento sicano della catena sud-tirrenica: bacini

neogenici e deformazione attiva (The ‘‘sicano’’ segment of the

south-tyrrhenian chain: neogenic basins and active deforma-

tions). Stud Geol Camerti Spec Vol (2):491–507

World Health Organization (2004) Guidelines for drinking-water

quality, vol 1: recommendations, 3rd edn. WHO, Geneva

Wilcox LV (1955) Classification and use of irrigation waters. US

Department of Agriculture Circular No. 969, 19 pp

898 Environ Geol (2009) 57:885–898

123