Rikunomizu（Limnology in Tokai Region of Japan）60 : 15 - 19（2013）

ArticleThe origin of sulfur in the lake Fukami-ike, Japan
Mayuko NAKAGAWA 1), Yuichiro UENO 2), Akiko YOKOYAMA 3), Akihiko YAGI 4)
and Naohiro YOSHIDA 5)

Abstract
Fukami-ike, a eutrophic lake in Japan, has a relatively high sulfate concentration (585 ± 56 μmol L-1) over the entire
surface. In order to determine the origin of sulfur in this lake, flow rates and sulfate concentration of five inflows and an
outflow were measured and analyzed. The water flux of precipitation in the catchment area is similar to that of surface
outflow. Approximately 90 % of precipitation enters to the lake as groundwater inflow. Approximately 20 % of surface sulfur
outflux is supplied by surface sulfur influx and the remaining is supplied by groundwater inflow, regardless of the amountof precipitation. The sulfate concentration of groundwater and surface inflow channels on the west side (approximately 400 μmol L-1) was much lower than on north side (approximately 1400 μmol L-1) of the lake. Such a difference would be causedby the degree of sulfur content in the sedimentary rocks. The sulfate concentration and sulfur content of precipitation andfertilizers contributed little to the sulfur source of the lake, which was also supported by their large sulfur isotopic ratios(+6.1 ‰ to +8.3 ‰). Thus, the weathered sedimentary rocks surrounding the lake (-28.3 ‰ to +9.1 ‰) are the main sourceof sulfur in the lake. Furthermore, the sulfur in the coarse-grained sandstone from Oshimojo Formation is estimated tocontribute more than 70 % of the sulfur in the lake.
Key words: origin of sulfate, sulfur isotope, fertilizers, sedimentary rocks, lake Fukami-ike(Received: 1 November 2012, Accepted: 2 March 2013)
reported (Cook and Kelly, 1992; Robinson, 1997). The sulfur

Introduction

isotopic ratios can be used to identify the sources such as natural

Fukami-ike is a monomictic lake located 484 m above sea level

and anthropogenic S contribution.

in the mountainous area of southern Nagano Prefecture. The lake is

The objectives of this study were to gain a better understanding

stratified from April to November, and hydrogen sulfide producedof the sulfur cycle and to clarify the source of sulfur in the lake. We

by sulfate-reducing bacteria can be detected in the hypolimnion.

investigated the origin of sulfur in the lake by performing chemical

During the stratification period, photosynthetic bacteria growand isotopic analyses of inflows, an outflow, lake water, fertilizers,

vigorously in the upper layer of the H2S zone (Yagi et al., 1983).

and the sedimentary rocks surrounding the lake.

One previous study showed the sulfate and sulfide concentrationsin the anoxic layer of the lake play an important role in the relative

Methods

activity of sulfate reduction and anoxygenic photosynthesis(Nakagawa et al., 2012). The sulfur in lakes generally originatedFor determining water and sulfur fluxes, inflow rates and sulfate

from the weathering of sulfur containing rocks in the catchment

concentrations of channels a-e (Fig. 1) were measured monthly

area. However, some fraction of sulfur from agricultural andfrom June to November in 2011 by a volumetric method. Outflow

industrial origin such as fertilizers and industrial effluents is also

rates at channel f were also measured with an electromagnetic

1)

Academy for Co-creative Education of Environment and Energy Science, Tokyo Institute of Technology, 4259 Nagatsutacho, Midori-ku, Yokohama,226-8502, Japan2)
Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8551, Japan
3)
Water agency INC., 3-25 Higashigokencho, Shinjuku-ku, Tokyo,162-0813,
4)
Environmental Engineering Course, Aichi Institute of Technology, 1247 Yachigusa, Yakusacho, Toyota, Aichi, 470-0392, Japan
5)
Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, 4259 Nagatsutacho, Midori-ku, Yokohama, 226-8502, Japan15

Mayuko NAKAGAWA et al.
extracted from ~10-g samples using a Kiba method (Kiba et al.,1955). Then, acid volatile sulfur (AVS) and pyrite sulfur wereextracted by 6N HCl and CrCl3 (Canfield et al., 1986). These
treatments extracted sulfur compounds as H2S, which is thenconverted to Ag2S. The detection limit of the sulfur contents was 5.5
× 10-5 mg S g-1.
Sulfate concentrations in water samples were measured by ion
chromatography (IC; Dionex Qic) equipped with IonPAC AS11HC column (Dionex). After the sulfur compounds were converted
into Ag2S, sulfur isotopic ratios were measured by fluorination
and a multiple gas chromatographic (GC) technique. The isotopic
composition of SF6 was determined using Thermo-Fishier
MAT253 mass spectrometers, both equipped with a dual inlet
system. Sulfur isotopic compositions are reported relative to theFig. 1 Bathymetrical map and sampling stations of Lake Fukamiike. The sampling stations are for (a-e) inflows, (f) outflow,(g) lake water at the deepest point, (h) groundwater well,(i) spring water, and (r1-r7) sediment rocks.

Fig. 1

Vienna Canion Diavro Troilite (VCDT) standard according to()

R sample
δ34S = ln ─── × 1000 [‰]R standard(3)

where R denotes the isotope ratios (34S / 32S) of samples andstandards. The analytical reproducibility of the δ34S value,current meter (model ACM210-D; Alec Electronic, Kobe). The

as demonstrated by the replicate analyses of several working

detailed measurement procedures for flow rates and sulfur isotopic

standards, is better than 0.6 ‰ .

ratios are described elsewhere (Nakagawa et al., 2012). The
relative standard deviation (RSD) of each inflow rate measurement

Results

was approximately 12 %. The RSD of the current meter used foroutflow measurements was 2 %. Annual fluxes were estimated

The 2011 annual water fluxes of evaporation, precipitation,15

by multiplying flow rate by time. Outflow and inflow water

surface inflow, and surface outflow to and from the lake aresamples were collected in polyethylene bottles to measure theshown in Table 1. Addition to the water fluxes in 2011, three-34

concentrations and δ S values of sulfate. Meteorological data

year observation from 2008 to 2010 reported in previous study(rainfall at Anan-cho, air temperature and duration of sunshine(Nakagawa et al., 2012) were averaged to show the range of eachat Iida-shi) were obtained from the Automated Meteorologicalwater flux (Table 1). The water fluxes in 2011 showed a similar

Data Acquisition System (AMeDAS) monitored by the Japan

trend to the hydrological mass balance model suggested in the

Meteorological Agency (http://www.jma.go.jp/jma/indexe.html).

previous study. Approximately 10 % of the precipitation water

Sulfate concentrations in precipitation were obtained from theflux in the catchment area is surface inflow into the lake, and the

Limnology Committee of Shimoina Kyoiku-kai (2009).

remaining would be potential groundwater inflow into the lake.

Lake water was sampled to determine the distribution of sulfate

This estimated water flux of groundwater inflow into the lake isconcentration in the surface water of the lake.

almost the same value to the imbalance between the water flux of

For determining the origin of sulfate in the lake, the sedimentarysurface input and output into and from the lake.

rocks in the catchment area of the lake and fertilizers BBC-284

The mean sulfate concentrations and annual sulfur fluxes of lakeand NKC-201 (JA Agriyell-Nagano) used in paddy fields were

surface water, groundwater, inflows, and outflow are listed in Table

sampled. The rocks were sampled from both the Oshimojo (r1-r4)

2. Measured sulfate concentrations of inflow channels a, b, c, d,and Arakida formations (r5-r7) (Fig. 1).

and e varied from 360 to 1550 μmol L-1. The annual mean sulfate

Rock samples were first cut into slabs about 10 cm across using

concentrations of channels a and b were lower (337-556 μmol

a diamond-tipped saw to remove weathered surfaces. Thereafter,L-1) than those of channels c, d, and e (945-1633 μmol L-1). The~10-g slabs were crushed into small chips about 2 mm across using

total surface sulfate influx was 63 kmol yr-1, which was calculated

a stainless steel mortar and pestle. The small chips were pickedby multiplying the sulfate concentration and monthly water fluxand crushed using an agate mortar and pestle. The fertilizers wereof each channel (Table 1). The sulfate concentration of outflow

crushed using a porcelain mortar and pestle. Total sulfur waschannel f was almost equal to that of the lake surface water ( ① - ⑩ ;16

The origin of sulfur in the lake Fukami-ike, Japan
Table 2. Sulfate concentration, sulfur fluxes and δ34S values forseveral inputs and outputs of the Lake Fukami-ike in 2011.

Table 1. Annual water fluxes of precipitation in the catchment area,
into and out from the Lake Fukami-ike.
Sampling point

four-year averaged
annual flow* ± SD †Annual flowin 2011 ± SD ††(106 L yr-1)(106 L yr-1)

InputsSampling point (n)[SO4] ± SD(μmol L-1)

Flux ± SD †(kmol yr -1)

δ34S ± SD ††
(‰ )

a (6)

360 ± 174.1 ± 0.2

– 15.8Catchment area

precipitation

423 ± 117

590

b (6)

468 ± 73

2.3 ± 0.4

– 15.3 ± 0.9

Lake inflowa11.3 ± 4.1

11.5 ± 0.6c (6)1550 ± 144

13.4 ± 1.3– 17.3 ± 3.6b

3.5 ± 1.0

0.5 ± 0.2d (6)1334 ± 238

17.6 ± 3.2– 18.7 ± 0.5c7.4 ± 2.1

8.7 ± 0.2e (6)1372 ± 211

25.3 ± 4.0– 18.3 ± 0.5

d14.1 ± 4.7

13.5 ± 0.4

total surface inflow*

1112 ± 92

62.8 ± 5.3– 18.1 ± 1.5

0.6 ± 0.1**

e19.2 ± 7.7

19.1 ± 1.6

precipitation

10 ± 5

total inflow

55.6 ± 10.2

57.8 ± 1.8

groundwater h (3)417 ± 33

– 15.0 ± 0.7

Lake outflow

f443 ± 132592 ± 12spring water i (1)1369

n. d. ‡

Lake surface

precipitation

41.3 ± 11.4**

57.6

evaporation***

15.0 ± 1.5

14.8 ± 1.4

Lake surface ① - ⑩

outflux-influx

361 ± 132492 ± 7†

Net flux of lake

Outputs

outflow f (6)558 ± 52

14.0 ± 1.7

309 ± 30

– 12.6 ± 0.7
n. d. ‡

585 ± 56

The SD represent propagated error from calculation (flux = [SO4]× annual flow in 2011).
††
The δ34S values are obtained from Nakagawa et al. 2012.
*
The sulfate concentration and the δ34S value were weighted
according to each annual inflows (a-e). The sulfate flux was
the sum of all inflow sulfate fluxes.
**
Data around Nagano prefecture (Akata et al., 2002)‡
The‘n.d.’represent the data not determined†

The SD represents annual variability for each flux and error
propagation of calculation.
††
The SD represent measurement errors and error propagation of
calculation.
*
Data showed four-year averaged values from 2008-2011(2008-2010; Nakagawa et al., 2012, 2011; this study)**
Data obtained from the Automated Meteorological Data
Acquisition System (AMeDAS).
***
Data calculated by Makkink method (Nagai et al., 1993).

Table 3. Sulfur contents and isotopic values of sediment rocks andfertilizer samples.
Sample nameFormation

Stone group

Table 2). The annual sulfur surface outflux was approximately five-1

S content

δ34S[mg S g-1][‰]

times greater than the surface sulfur influx (309 kmol yr ). The

Rock sample

sulfur flux difference between the surface influx and outflux intor1

Oshimojo

Coarse-graind sandstone

5.7 × 10-5

9.1

r2

Oshimojo

Coarse-graind sandstone

3.0 × 10-4

-26.1

Sulfur contents and δ34S values of sedimentary rocks andr3

Oshimojo

Coarse-graind sandstone

2.1 × 10-4

-28.3

fertilizers are summarized in Table 3. The sulfide compounds

r4

Oshimojo

Coarse-graind sandstone

4.4 × 10-4

-16.9

-1

and from the lake was calculated to be 245 kmol yr .

r5

(AVS, and pyrite sulfur) in rock samples were below the detection

r6

limit. Sulfur contents of sedimentary rock samples varied from

ArakidaArakidaTuffaceous sandstone
Tuffaceous gravelstone

-5

6.7

-6

n.d. ‡-6

3.7 × 10n.d. ‡

5.5 × 10
3.5 × 10

3.5 × 10-6 to 4.4 × 10-4 mg S g-1. The sulfur content in fresh

r7coarse-grained sandstone in the Oshimojo formation (r2-r4) was

Fertilizer

much higher than in highly weathered sandstone in the Oshimojo

BBC-284 (2)12.7

8.2 ± 0.2

NKC-201

0.1

6.1

formation (r1) and tuffaceous stones in the Arakida formation‡34(r5-r7). δ S values of r2 and r3 samples were much smaller than

ArakidaTuffaceous mudstoneThe‘n.d.’represent the data not determinedthose of other rock samples. The sulfur content in the fertilizer
BBC-284 was high relative to that in NKC-201. Fertilizer δ34S
values ranged from +6.1 ‰ to +8.3 ‰ .

using the data for 2008, although the precipitation in 2011 wasapproximately twice as great as in 2008. In order to meet the sulfur
mass balance of total sulfur influx to and outflux from the lake, theDiscussions

groundwater sulfur flux is estimated to be 280 kmol yr-1, calculated

The sulfur mass balance in 2011 showed similar contributions

by the sum of the difference between the surface influx and outflux

of surface sulfur influx to surface sulfur outflux, as estimated(245 kmol yr-1) and the total sedimentary sulfur flux of the whole17

Mayuko NAKAGAWA et al.
lake (34.2 kmol yr-1; Nakagawa et al., 2012). Thus, the sulfur mass

minerals has been reported to be small (<2 ‰) (Thode and Monster,balance in 2011 confirmed that most of the sulfate in the lake can

1965; Szaran et al., 1998). Thus the δ34S values of surface water

be attributed to the groundwater inflow (Table 2).

and groundwater input would be the mixing of the sedimentary

The contribution of sulfur in fertilizers can be estimated byrocks with high sulfur content in the Oshimojo and the sedimentary

the amount used and the isotopic values of the fertilizers. The

rocks with low sulfur content in the Arakida formations. If the2

area of a paddy field is approximately 2000 m . According to theisotopic composition of inflows to the lake originates from therice cultivation protocol of the Japan Agricultural Cooperatives

sulfate from the weathered rocks of the Arakida formation and thein Minami Shinshu, 0.5 kg m-2 of fertilizer BBC-284 is used in

Oshimojo formation, then the contribution of the sulfate originating-2

April, and 0.1 kg m of NKC-201 is used in the end of July. Thus,

from the Arakida formation would be estimated using the following

the sulfur input originating from fertilizers is 0.4 kmol yr-1 andequations:forms a very small contribution to the sulfur content in the lake.

fp + fhigh-S + flow-S = 1

Furthermore, the δ34S values of fertilizers BBC-284 and NKC-201

δ34Sinput = fp ×δ34Sp + fhigh-S ×δ34Shigh-S + flow-S ×δ34Slow-S

were typical values compared to those reported previously (>6.6 ‰ ;where fp, fhigh-S, and flow-S are the sulfur contributions of precipitation,

Mizota and Sasaki, 1996). Although the contribution of fertilizers

high-sulfur-content sedimentary rocks, and low-sulfur-content

34

as the origin of sulfur in the lake is small, the δ S of fertilizers

sedimentary rocks, respectively. δ34Sinput, δ34Sp, δ34Shigh-S, and δ

was observed in inflow channel c placed in the paddy field. The δ

34

34

S values of channel c are sometimes larger (approximately -13

high-sulfur-content sedimentary rocks (-23.8 ± 6.0 ‰), and low-‰) than the others (approximately -20 ‰) in the end of summer

sulfur-content sedimentary rocks (7.9 ± 1.7 ‰), respectively.

(August to October), when the sulfate concentration is higher.

The fp is the fraction of precipitation sulfur flux to the total sulfur

Slow-S are the δ34S values of the input to the lake, precipitation,

influx (0.02). If δ34Sinput is -15.0 ± 0.7 ‰, the fhigh-S and flow-S are

The average sulfate concentration of precipitation in Shimoina-1

gun is 10 ± 5 μmol L (the Limnology Committee of Shimoina

estimated to be 0.73 ± 0.16 and 0.27 ± 0.16, respectively. Further,

34

Kyoiku-kai, 2009) and the range of sulfate δ S value in Nagano

if δ34Sinput is -18.1 ± 1.5 ‰ , the fhigh-S and flow-S are estimated toPrefecture is 14.0 ± 1.7 ‰ (Akata et al., 2002). The sulfur flux

be 0.83 ± 0.18 and 0.17 ± 0.18, respectively. The geologicalsupplied by precipitation in the catchment area is 5.9 ± 3.0 kmolS

profile of the lake (Shikama, 1954) indicates that precipitation in

yr-1, and its contribution to the total sulfur influx (343 ± 30 kmol

the catchment area mainly goes through a longer pathway in the-1yr ) into the lake is less than 2 %.

Oshimojo formation than in Arakida formation.

The δ34S values of sedimentary rocks surrounding the lake

In summary, sulfur mass balance and δ34S analysis reveal the

showed great variation, from -28.3 ‰ to +9.1 ‰ (Table 2). The

origin of sulfur in the lake originates mainly from high-sulfur-

34

δ S values varied with the degree of weathering in rocks, which

content and low-sulfur-content sedimentary rocks; precipitation

correlates with sulfur contents. As the degree of weathering iscontributes to a small fraction of the sulfur content in the lake,34

higher and the sulfur content is lower, the δ S value (7.9 ± 1.7

while the contribution of fertilizers is negligibly small.

‰) is larger. On the other hand, low δ34S values (-23.8 ± 6.0 ‰)were observed in sedimentary rocks with higher sulfur content. The

Acknowledgments

variation of sulfur content and isotopic values of sedimentary rocks
seems to have a relation to the difference between inflow channels

We thank the Anan Town authorities in Shimoina-gun, Nagano

a-b and c-e about the sulfate concentration and isotopic values.

Prefecture, who provided facilities for this research. Sincere thanks

The inflow channels c-e showed higher sulfate concentration

are due to all the Yagi laboratory members for their cooperation and(approximately 1400 μmol L-1) with lower δ34S values (approximately

facilitation of this research. This study was supported by a Grant--18 ‰), and the sedimentary rocks that have high sulfate content

in-aid for Scientific Research (S) (23224013) from the Ministrywith low δ34S values (r1-r4) were sampled around there (Fig. 1).

of Education, Culture, Sports, Science and Technology (MEXT),The ease of sulfur dissolution from the rocks would beJapan, and the Global Environment Research Fund (A-0904) ofdependent on chemical composition and crystal structure of thethe Ministry of the Environment, Japan, and GCOE program‘Earthminerals although they are still uncertain. Thus, further chemical

to Earths’of MEXT, Japan.

and mineralogical study of the sedimentary rocks is needed forunderstanding the cause of the great variation in sulfur content

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18

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19