10th Asian Regional Conference of IAEG (2015)

Chemical Characterization of Acid Tunnel Drainage
Toshiyuki KURAHASHI(1), Shuichi TAMOTO(1) and Yoshinori YAJIMA(1)(1) Civil Engineering Research Institute for Cold Region, Public Works Research Institute, Japan
E-mail:kurahashi-t@ceri.go.jp
Abstract
Acid tunnel drainage of groundwater seepage through pervious rocks and joints has
been released without care to public water bodies during maintenance immediately aftertunnel excavation. The drainage water and seepage water are suspected of chemicallycorroding the tunnels and of being toxic to organisms in the natural environment.
This paper describes the results of water quality measurements, ICP spectrochemical
analysis and ion chromatography to characterize the chemical variation of the drainage
water and the seepage water. We collected 18 samples of drainage water and seepage waterfrom five tunnels during maintenance in eastern Japan and determined the quantities of four
elements (Ca2+, Fe, Cl- and SO42-) by either ICP spectrochemical analysis or ion
chromatography. The samples were found to contain both hydrochloric and sulfuric acids.
The Cl-/SO42- ratios were as high as those of hot springs around Quaternary volcanoes. In
addition, concentrations of both Ca2+ and Fe were found to be proportional to those ofhydrogen ion. It is suggested that acid drainage and seepage readily dissolved both Ca2+ andFe from the concrete, steel supports and rocks.
Keywords: acid tunnel drainage, ICP spectrochemical analysis, ion chromatography

1.

during maintenance in eastern Japan.

Introduction

Contamination of surface drainage systems byacid drainage water has become an environmental
problem issues (Blowes et al., 2003). The flow ofacid mine drainage water into surface streams, rivers
and lakes has sometimes caused those water bodies tohave low pH (pH 2 to pH4). In addition, the highconcentrations of sulfate and metals contained in suchacidic water are toxic to many organisms in thenatural environment. Acid tunnel drainage water ofgroundwater seepage through pervious rocks andjoints has been released without care to public water
bodies during the tunnel maintenance stage just after
excavation, too (Photo. 1). Acid drainage waterfrom tunnels is also suspected of causing thisproblem.
High acidity gives water a greater capacity todissolve minerals and metals from rocks andmaterials. Strongly acid groundwater seepage led tochemical attack on the lining concrete of the Mikuni
Tunnel (Suzuki and Suwa, 1971).
This paper describes the results of water quality
measurements and the quantification of four elements(Ca2+, Fe, Cl- and SO42-) by either ICP
spectrochemical analysis or ion chromatography, tocharacterize the chemical variation of acid tunnel
drainage water and seepage water from five tunnels

Photo. 1 Acid drainage water from a tunnel
2.

Method

2.1 Water quality measurement in situ
We measured temperature, potential hydrogen(pH),electricalconductivity(EC)andoxidation-reduction potential (Eh) with a combination
probe at 18 spots of seepage or drainage from fivetunnels during maintenance in eastern Japan (Fig. 1).
We measured for at least 5 minutes at each spot, until
the readings stabilized (Photo. 2).

1

10th Asian Regional Conference of IAEG (2015)reference electrode. Readings of electricalconductivity (EC) were also standardized to the
conductivity of a substance at 25°C.
Determination of groundwater origin is an
important aspect of hydrological investigations. An
Eh-pH diagram can be used as a first approximation
to characterize natural waters after Baas Becking et al.
(1960). They collected more than 6,200 pairs of Ehand pH values, and charted the distributions of Ehand pH of natural water bodies in an Eh-pH diagram(Fig. 2). The diagram showed two distribution sets ofnatural acid waters.
One is geothermal water. Its distribution set wasdelineated in both ranges from 1.2 to 9.5 in the pH
values and from +0.7 to -0.185 V in the Eh values inthe Eh-pH diagram of Baas Becking et al. (1960).
Using a database of groundwater geochemistry,
Asamori et al. (2002) reported that acid groundwaterwith pH of < 4.8 mainly occurs in currently active
volcanic regions and is distributed from several
kilometers to about 20 km from Quaternary
volcanoes. Groundwater is contaminated withvolcanic gases such as hydrogen chloride or sulfur
dioxide. Hydrogen chloride is highly soluble in waterand is emitted as hydrochloric acid (HCl), a verystrong acid.
The other is oxidized mine water. Its distribution
set was shown in both ranges from 2 to 9 and from
+0.8 to around +0.17 V in the Eh values in the Eh-pH
diagram of Baas Becking et al. (1960) (Fig. 2). This
peculiarity is directly attributable to the presence of
pyrite (FeS2). Acid drainage can occur whereverrocks containing sulfide minerals are exposed to theatmosphere. The net reaction for the oxidation of
pyrite which may be written as

LegendSample Location

#W
#J
#G

#AK

#AD

Fig. 1 Tunnel locations for groundwater samplingin eastern Japan

4FeS2+15O2+14H2O→4Fe(OH)3+8SO42-+16H+
The greater the amount of pyrite oxidized, the lower
is the pH of the water. Similar reactions can be
written for other common sulfide minerals, such as
chalcopyrite (Cu2S), pyrrhotite (Fe1-xS), sphalerite(ZnS) and galena (PbS). Acid waters may containgreat amounts of heavy metal elements such as As,
Pb and Se, which are toxic to many organisms.
We compared our results with those of two
distribution sets of acid waters bodies in the Eh-pH
diagram of Baas Becking et al. (1960) and attempted
to characterize their origins in the inorganic aqueous
environments.

Photo. 2 A water quality measurement device(temperature, pH, EC, Eh)
As readings are dependent on solution
composition, water temperature and the type of
sensor used, they needed to be normalized for mutualcomparison.
TheEhsensorusesasilver/silver-chloride reference electrode in place ofthe standard hydrogen electrode. Readings from the
Eh channel displayed in Volts were normalized to thestandard hydrogen electrode values as a standard

2.2 Sampling
We collected 18 groundwater samples at seepage
or drainage sites from five tunnels between
November 2012 and December 2013 to determine thequantities of four elements (Ca2+, Fe, Cl- and SO42-)
by either ICP spectrochemical analysis or ion
chromatography. The samples were filtered using

2

10th Asian Regional Conference of IAEG (2015)
3.

filter paper with 1-micrometer pores to remove any
solid substances. Two 500-ml polypropylene bottles
that had been rinsed with concentrated nitric acid,tap water and pure water were filled with the sampled
water. To one of the two bottles, we added 1-mlconcentrated nitric acid per 100-ml water, to keep themetals dissolved for ICP spectrochemical analyses.

Results and Discussion

3.1 Results of water quality measurements
The results of temperature, potential hydrogen(pH),electricalconductivity(EC)andoxidation-reduction potential (Eh) are given in Table
1. The pH values range from 3.3 to 5.6. The specificconductivity ranges from 68 to 413 micro-S/cm. The
Eh values range from 0.448 to 0.740 V. The pH
values of the acid drainage water are below 5.8, avalue that is specified by The Water Pollution
Prevention Law of Japan as the minimum allowable
pH value for drainage in terms of protecting humanlife from water pollution in public water bodies.
Fig. 2 shows an Eh-pH diagram modified from
Bass Becking et al. (1960). An attempt was made to
distinguish between the water that had leached fromthe oxidized pyrite and that which had contaminatedthe geothermal environment.

2.3 Ion chromatography
Chemically suppressed ion chromatography usinga Dionex DX-320J, Ion Pac AS14 and AERS-500
system was used for the analysis of sulfate (SO42-)
and chloride (Cl-) in 11 groundwater samples fromthree tunnels.
We divided the samples into sulfuric acid orhydrochloric acid by a graph with both Cl-/SO42- ratio
and Cl-+SO42- concentration to differentiate the waterby origin. The sample with the high ratio wassuggestive of containing a large amount ofhydrochloric acid that originated in geothermal
environments. Hydrochloric acid is known to be morechemically corrosive to concrete materials thansulfuric acid is (Makita and Sakamoto, 1973).

1

Oxidizedmine water

0.8

T=25 ℃
P=1 atm

0.6

2.4 ICP spectrochemical analysis
Calcium (Ca2+) and iron (Fe) were analyzed bydirect aspiration of ground water samples into an
Inductively Coupled Plasma atomic emission
spectrometry device (ICP-AES). Two different linear
concentration standards were prepared: from 0.01 to
0.50 mg/L for iron, and from 0.10 to 5 mg/L for
calcium. We compared the results of theseconcentrations with maximum concentrations
determined by the equation that expresses therelationship between hydrogen ion and iron andbetween hydrogen ion and calcium hydroxide toestimate the amount of both iron and calcium ionsdissolved chemically from lining concrete or steel
supports of tunnel.

0.4
Geothermal
environment

0.2
Eh (V)

Primary
mine water

0
-0.2
-0.4
-0.6
0

2

4

6
pH

8

10

12

Fig. 2. An Eh-pH diagram modified from Baas
Becking et al. (1960)

Table 1 Results of water quality measurement, ICP spectrochemical analysis and ion chromatography
RY; Rhyolite, DA; Dacite, ND; Neogene deposits
Sample Tunnel Geology
#1
#2
#3
#4
#5
#6
#7
#8
#9
#10
#11
#12
#13
#14
#15
#16
#17
#18

#AD
#AD
#AD
#AD
#AD
#AD
#AD
#AD
#AD
#AD
#AD
#AD
#AD
#AK
#G
#G
#J
#W

Date

ND
2012/11/5
ND
2012/11/5
ND
2013/1/13
ND
2013/1/13
ND
2013/1/13
ND
2013/12/17
ND
2013/12/17
ND
2013/12/17
ND
2013/12/17
ND
2013/12/17
ND
2013/12/17
ND
2013/12/18
ND
2013/12/18
ND
2012/11/8
ND
2013/12/3
ND
2013/12/3
RY
2013/11/22
DA, RY 2012/8/28

Occurrence
drainagedrainageseepageseepageseepageseepageseepageseepageseepageseepageseepagedrainagedrainageseepagedrainagedrainagedrainagedrainage

Temp.
(℃)
9.7
10.3
6.9
5.9
7.7
6.3
4.4
6.0
6.4
7.5
6.8
6.8
6.6
10.8
9.8
7.6
5.0
28.2

pH
3.5
3.6
4.0
4.3
3.3
4.2
4.3
4.7
5.2
3.2
4.4
3.7
3.5
5.2
3.3
3.3
5.2
5.6

Eh
(V)
0.698
0.698
0.550
0.501
0.670
0.626
0.590
0.480
0.448
0.623
0.502
0.683
0.718
0.457
0.681
0.740
0.640
0.470

EC
(uS/cm)
208
182
126
127
413
136
121
107
96
360
181
235
321
82
393
412
68
127

3

H+
(mol/L)
3.55E-04
2.82E-04
1.12E-04
5.13E-05
5.01E-04
6.17E-05
5.25E-05
2.14E-05
6.61E-06
6.03E-04
4.27E-05
2.14E-04
3.31E-04
6.76E-06
4.79E-04
5.13E-04
6.61E-06
2.34E-06

Fe
Ca2+
Cl(mol/L) (mol/L) (mol/L)
1.43E-04 4.96E-05
1.14E-04 2.67E-05
2.80E-05 8.57E-07
6.40E-05 1.64E-05
7.38E-05 3.22E-05
4.91E-05 3.16E-06 3.25E-05
7.26E-05 2.37E-05 3.16E-05
1.68E-04 1.66E-05 3.77E-05
1.44E-04 8.32E-06 3.04E-05
7.17E-05 1.71E-05 3.54E-05
4.08E-05 3.99E-05 3.66E-05
1.04E-04 2.38E-05 3.20E-04
1.13E-04 4.06E-05 5.83E-04
1.24E-04 1.46E-06
1.76E-04 4.03E-05 4.55E-04
1.90E-04 2.38E-05 2.71E-04
1.86E-04 1.96E-07 7.49E-05
1.68E-04-

SO42- Cl-+SO42Cl-/SO42(mol/L) (mol/L)
3.92E-04 4.25E-04 0.083
3.72E-04 4.04E-04 0.085
3.53E-04 3.90E-04 0.107
3.03E-04 3.33E-04 0.101
8.60E-04 8.96E-04 0.041
6.51E-04 6.88E-04 0.056
5.40E-04 8.60E-04 0.593
5.98E-04 1.18E-03 0.974
1.20E-03 1.65E-03 0.379
1.19E-03 1.46E-03 0.229
3.51E-04 4.26E-04 0.213-

10th Asian Regional Conference of IAEG (2015)
All pairs of pH and Eh values were plotted in anoxidation range. A negative correlation wasrecognized between pH and Eh. However, anoxidized mine water area is wholly overlaid on ageothermal environment water one in the pH range
from 2 to 9. The result of the attempt is that no
samples of the geologically distinct environments
could be differentiated by their Eh-pH characteristics.

However, the ratios of seepage or drainage ateight spots from Tunnel #AD have a wide variety ofacids in acidity and components. The pH values arefrom 3.3 to 5.2. The sample with the highest pH hasroughly triple the chloride and sulfate (Cl-+SO42-)
concentration of the sample with the lowest pH.
However, the components are considered to be mixed
acids of hydrochloric and sulfuric acids. The highest
Cl- concentration is 20 times the lowest one. The
degree of chemical corrosion to the tunnel is assumed
to be different at each spot.

3.2 Results of ion chromatography
We determined chloride (Cl-) and sulfate (SO42-)
concentrations of 11 samples by ion chromatography
to characterize their sources in the inorganic aqueous
environments.
In 11 samples, the separation between peaks ofchloride (Cl-), and sulfate (SO42-) showed goodresolution. As seen in Table 1, the chloride
concentrations range from 3.04×10-5 to 5.83×10-4
mol/L. The sulfate concentrations range from 3.03×
10-4 to 1.65×10-3 mol/L.
Both concentrations show that the concentrationsof chloride plus sulfate (Cl-+SO42-) concentrations
range from 3.33×10-4 to 1.65×10-3 mol/L, and theCl-/SO42- ratios vary from 0.083 to 0.974. The
concentrations of Cl-+SO42- are approximately
proportional to those of hydrogen ion (H+) (Fig. 3).

Cl-+SO42(mol/l)
0.010

#AD
This report#G#J
Tokumitsu and Matsushita(1979)

0.008

0.006

Myoban hot spring

0.004

Azuma River

Kirishima river

0.002

Kirishima hot spring
0.000

Cl-+SO42(mol/L)

0.0

1.0E-02

0.2

0.4

0.6

0.8
1.0
Cl-/SO42-

Fig. 4. Relationship between Cl-/SO42- ratios and
Cl-+SO42- concentrations

1.0E-03

3.3 Results of ICP spectrochemical analysis
We determined the dissolved Fe and Ca2+
concentrations of 18 samples from five tunnels by
ICP atomic emission spectrometry (ICP-AES) toestimate the effect of chemical attack resulting fromthe seepage and drainage of acidic water.
As seen in Table 1, the dissolved Feconcentrations range from 1.96×10-7 to 4.96×10-5
mol/L. The concentrations of Fe increased with thoseof hydrogen ion along a maximum dissolved Fe line,
a line that was based on the reaction between iron andhydrogen ion (Fig. 5a). Consequently, the Fe isconsidered to have readily dissolved from steel
supports or rocks by the acid.
The dissolved Ca2+ concentrations range from
2.80×10-5 to 1.90×10-4 mol/L. The concentrationsof Ca2+ are roughly proportional to those of hydrogen
ion along the maximum dissolved Ca line, which isbased on the reaction between calcium hydroxide(Ca(OH)2) and hydrogen ion (Fig. 5b). Calcium
hydroxide is a major component of lining concrete.
The calcium is considered to be readily leachable
from the lining concrete. Many cracks and dissolution
and pop-out were observed in the lining concrete ofone of the tunnels (Photo. 3).

1.0E-04

1.0E-05

1.0E-06
1.0E-06

1.0E-05#AD

1.0E-04#G#J

1.0E-03

1.0E-02
H+ (mol/L)

Fig. 3. Correlation between Cl-+SO42- and hydrogenion concentrations
The positive correlation between theseconcentrations suggests that most of the Cl-+SO42might come from hydrochloric or sulfuric acids. As
the samples contained appreciable hydrochloric acid,they might be groundwater contaminated withvolcanic gas in a geothermal environment. It was also
proven that some of the ratios were as high as thoseof hot springs in geothermal environments
determined by Tokumitsu and Matsushita (1979) (Fig.
4).

4

10th Asian Regional Conference of IAEG (2015)
Some Ca2+ concentrations are above the maximum
dissolved Ca line when hydrogen ion concentrations
were less than 1.0 × 10-4 mol/L. The calcium isconsidered to be added by solution of gypsum(CaSO4・H20).
We concluded that the acid drainage water or
seepage water from the tunnel caused chemicalcorrosion and readily dissolved Ca2+ and Fe from thetunnel materials.

a)
Fe (mol/L)
1.E-03

1.E-04

4.

Conclusions

1.E-05

1.E-06
1.E-06

1.E-05#AD#AK

1.E-04#G#J

In this paper, we used iron chromatography todetermine that acid tunnel drainage water andseepage groundwater contain both hydrochloric andsulfuric acids. The Cl-/SO42- ratios were as high as
those of hot springs around Quaternary volcanoes.
Our ICP spectrochemical analyses revealed that theconcentrations of both Ca2+ and Fe were proportional
to those of hydrogen ion and that calcium and iron
had been readily dissolved from lining concrete, steel
supports and rocks.

1.E-03
H+ (mol/L)b)
Ca2+ (mol/L)
1.E-03

References
1.E-04

Asamori, K., Ishimaru, T. and Iwatsuki, T.(2002):
Distribution of acidic groundwater around
Quaternary volcanoes in Japan, JNC Technical
Review, vol.15, pp.103-111.
Baas Becking, L. G. M., Kaplan, I. R. and Moore D.
(1960): Limits of the natural environment in termsof pH and oxidation-reduction potentials, Geology,
Vol. 68, pp.243-284.
Blowes, D. W., Patacek, C. J., Jambor, J. L. andWeisener, C. G. (2003): The chemistry of acid minedrainage, Treatise on Geochemistry, Vol.9,
Elsevier-Pergamon, pp.149-204.
Makita, M. and Sakamoto, H. (1973): Acid proof ofconcrete, 27th Annual Research Meeting of Ministryof Construction, pp.115-121.
Suzuki, M. and Suwa, Y. (1971): Chemical attack andthe prevention to acid groundwater seepage at
Mikuni Tunnel, Roads and Concrete, Vol.13, No.1,
pp.5-22.
Tokumitsu, Y. and Matsushita, H. (1979): Concrete
in hot spring regions, Concrete Journal, Vol.17,
No.11, pp.31-35.

1.E-05

1.E-06
1.E-06#AD

1.E-05#AK #G

1.E-04#J #W

1.E-03
H+ (mol/L)

Fig. 5 Correlations of both Ca2+ andconcentrations with hydrogen ion onesFe

Photo. 3 Dissolution of borehole core drilled atlining concrete5