地球環境研究，Vol.16（2014）

Distribution of Nitrate Contaminationfrom the Viewpoint of Recharge Year,
Land Use History and Groundwater Flow System
Seongwon LEE ＊, Maki TSUJIMURA ＊＊, Sujen Prashad AMATYA ＊＊ and Norio TASE ＊＊Seongwon LEE: leesw@ris.ac.jp
Maki TSUJIMURA: mktsuji@geoenv.tsukuba.ac.jp
Sujen Prashad AMATYA: sujenamatya@hotmail.com
Norio TASE: tase@geoenv.tsukuba.ac.jp

Abstract:
This study was carried out by using chlorofluorocarbons (CFCs) as tracers to examine the relationship between
the distribution of high concentrations of NO3- produced by an unlined disposal pit of animal waste and the site’sland use history. From the results of investigation, CFC-11 is decreased by degradation in the nitrate attenuation
zone of the study site. Recharge years using CFC-11 will make sites appear older than the actual values. Thus,
detailed hydrogeological surveys should be taken into account estimating recharge years using CFCs. In the study
site, recharge of high concentrations of NO3- caused by leakage from the unlined disposal pit occurred between thelate 1970s and about 1990. This result is consistent with the land use history of pig farming at this area, and it suggests that nitrate contamination from pig farming continues to have a large effect even now, more than 15 years
after farming ceased.
Keywords: CFCs; recharge year; groundwater; unlined disposal pit; land use history; NO3-

INTRODUCTION
The biggest cause of environmental problems accompanying livestock management is inappropriate disposal

with groundwater contamination problems, such as
assessing and restoring contaminated sites, it is essential to determine how long nitrogen remaining in abandoned or backfilled unlined disposal pits is retained.

and storage of animal waste, such as exposed piles

The 3H (Tritium) method of dating young groundwa-(Nodumi in Japanese) where animal waste in a solid

ter has come to be widely used in Japan for estimating

form is simply piled up and left, and unlined disposal

groundwater recharge years. However, recently, the 3H

pits (Subori in Japanese) in which liquid animal waste isconcentration of precipitation in Japan has fallen to its

stored in a hole dug in the ground. In recent years, gov-

natural level and the half-life of 3H is short, 3H hasernmental legislation has come into effect, such as the

become ineffective as a tracer (Yabusaki et al., 2003).

Law on Promoting Proper Management and Use of

Because of this, methods for estimating young ground-

Livestock Excreta (1999), and the number of farms thatwater using chlorofluorocarbons (CFCs) have been pro-do not meet the control standards is decreasing. How-

posed, and examples of their application are being

ever, there are concerns that much inappropriate dis-collected, particularly in North America and Europe

posal and storage of animal waste was done in unlined(IAEA, 2006). CFCs have properties that are very

disposal pits and exposed piles that have since been

advantageous in tracers; for example, they are only pro-abandoned or backfilled, and so are still potential con-duced artificially, are extremely stable, and the concen-

taminant sources (Lee et al., 2009). Therefore, in dealing
tration of CFCs in the atmosphere increased almost＊		 Department of Environmental Systems, Faculty of Geo-Environmental Science, Rissho University＊＊	Sustainable Environmental Studies, Graduate School of Life and Environmental Sciences, 
University of Tsukuba
1

Distrion of Nibutitrate Contamination from the Viewpoint of Recharge Year, Land use History and Groundwater Flow System（Seongwon LEE・Maki TSUJIMURA・Sujen Prashad AMATYA・Norio TASE）

Fig.1Studysitelocationandlanduse

monotonically until their legal regulation (Tsujimura etal., 2006).
Therefore, this study attempts to use CFCs to examine the relationship between the distribution of highconcentrations of NO3⊖ caused by unlined disposal pits
and local land use history.

Fig.2

(A):Watertable,(B)and(C):NO₃︲and
rechargeyearofgroundwateralong
crosssectionA-1₈

and piezometers were installed at a total of 19 points.

STUDYSITE

Two to six piezometers were installed at each of point

The study site is located in the Tsukuba uplandat depths from 2 m to 13 m (Fig. 2). In addition, in order

about 15km west of the center of Tsukuba City, Ibaraki

to examine the geological conditions of the study site,

Prefecture, Japan, and is approximately 60km northeast

soil cores were collected by boring and soil texture wasof Tokyo (Fig. 1). Specifically, the study site, located indetermined. Ion chromatography (IC-7000, Yokogawa)the Konomata district and slightly extending in thewas used in the water quality analyses, while an ele-

west-east direction, measures about 450 m × 100 m

mental analyzer (EA 1108, Fison) and a stable isotope(about 4.5 ha). In the upstream western area of themass spectrometer (DELTA PLUS, Thermo Finnigan)

study site and surrounding region, land use consists ofwere used to measure δ15N.

forest, cropland, and paddy fields. The study site, in thecentral forested part of the upland, includes an aban-

Water Sampling and Analysis of CFCs

doned unlined animal waste storage pit (9.7 m × 10.2 m

In order to prevent contact with the atmosphere× 2.5 m) associated with a pig farm. Even today, highwhen collecting the groundwater samples, groundwater

concentrations of NO3― (approximately 150 mg/L) are

was pumped up using a tube pump, then placed in a

detected in the groundwater at approximately 50 m

125 mL glass bottle inside a stainless steel container via

downstream from this pit (Lee et al., 2009).

a copper tube. After the pumped groundwater wasallowed to overflow into the stainless steel container fora given period of time, the glass bottle was sealed

METHODS

under water and taken out (IAEA, 2006; Tsujimura etGeological Conditions, Groundwater Flow, Wateral, 2006; Asai et al., 2006). The groundwater samples

Quality, and δ N

were taken to a laboratory where the CFCs in the

1₅

In order to understand the water quality distribution

groundwater were isolated using a purge and trap

and groundwater flow system of the study site, wells

method and measured by introduction into a gas chro-2

地球環境研究，Vol.16（2014）

matograph-electron capture detector (GC-ECD) (Bullister and Wesis, 1988; Tsujimura et al., 2006). CFCs were

RESULTSANDDISCUSSION

analyzed at depths from 2 m to 13 m in samples from

Atmospheric Concentration of CFCs at the Study

points A, 4, 7, 11, 15, and 18 (a total of 25 piezometers),Sitefollowing the direction of groundwater flow (Fig. 2).

When estimating groundwater recharge years using

Samples were collected during the period from August

CFCs, long-term input information on atmosphericto October 2007.

CFCs at the study site is essential. Generally, atmospheric CFC concentration curves in the Northern

Estimation of Recharge Year Using Piston Flow

Hemisphere Average Values (NHAV) published by the

Model

United State Geological Survey (USGS) CFC Laboratory

Generally, the Piston Flow Model (PFM) assumes

are used for estimating recharge years using CFCs.

that the atmospheric concentration at the time of

However, although the distribution of the atmosphericrecharge does not change during the flow process. On

concentration of CFCs is relatively uniform, high con-the other hand, the Exponential Model (EM) assumes

centrations may occur locally in metropolitan areas andthat groundwater flowing into the aquifer mixes imme-

areas with a high density of industrial facilities. Japan isdiately with the groundwater in the aquifer. Althoughranked third in the world for output of CFCs (IAEA,

proportion of mixing rate in the groundwater flow dif-2006). Therefore, the atmospheric concentrations offers depending on the hydrogeological conditions, and

CFCs at Niihari, Tsuchiura City, Ibaraki Prefecture,

the PFM and EM combine in a complicated way. How-

located approximately 15km northeast of the study site

ever, the PFM is considered to be more suitable forin Tsukuba City, Ibaraki Prefecture (Ibaraki Prefecture,

determining the time that nitrogen remaining in a dis-

1993 to 2007), were compared with the Northern Hemi-

posal pit is retained because, in the case of groundwa-

sphere Average Values (IAEA, 2006) (Fig. 3). At Nii-

ter contamination such as nitrate contamination, thehari, the CFC-11 concentration was 7 % lower than thecontaminant flows in a plume shape.

Northern Hemisphere Average Value, while the CFC-

In steady state conditions and with a non-radioactive

12 concentration was 14 % higher. So, the CFC-11 andtracer, the relation between the input and output tracer

CFC-12 values were corrected in this study to reflect

concentrations in groundwater may be formulated as a

the difference from the Northern Hemisphere Average

convolution integral:

Values. Consequently, the reproducibility of corrected(1)

results were improved by shifted towards the PFM line
by mathematical model (Fig. 4).

where Cin and Cout are input and output tracers con-

Given this, it is possible that dating errors of 7 % tocentrations, τ is the residence time, and g(τ) is the

14 % will occur when estimating recharge years usingtransit time distribution function (the system response
or weighting function) of the mathematical model.
(Zuber, 1986; Leibundgut et al., 2009).
In the PFM model, the flow lines are assumed tohave the same transit time and hydrodynamic dispersion and diffusion are negligible. The transit time distribution function (g(τ)) for PFM model is as follows(Maloszewski and Zuber, 2002; Leibundgut et al., 2009):(2)
Fig.₃

AtmosphericconcentrationsofCFCs
(NorthernHemisphereAverageValues
(NHAV)andNiihari(Japan))3

Distrion of Nibutitrate Contamination from the Viewpoint of Recharge Year, Land use History and Groundwater Flow System（Seongwon LEE・Maki TSUJIMURA・Sujen Prashad AMATYA・Norio TASE）

Fig.₄

ComparisonofCFC-11andCFC-12concentrationsandPFMmodelestimatesFig.₅

ComparisonofNO₃︲concentrationsand
rechargeyearsingroundwaterwithlandusehistory

Northern Hemisphere Average Values, and long-term

years at Point A, 8 m below the surface. Thus we seemonitoring of atmospheric concentrations of CFCs atthat not only NO3- but also CFC-11 is degraded in theeach site is needed to reduce the error.

attenuation zone at the study site, which suggests thatthe recharge years calculated using CFC-11 will appear

Degradation of CFCs in a Reductive Environment

to be older than actual ones. Therefore, CFC-12, which

A dramatic decrease in the concentration of CFC-11

is insusceptible to microbial degradation, was used to

was observed near a depth of 6 m (inside the bluish-

estimate recharge years at the study site, and thegray clay) at Point A in the forest area (Fig. 4). Micro-

results were compared with the local land use history

bial degradation (denitrification) due to reductiveof livestock farming.

environmental conditions has been reported in thevicinity of the bluish-gray clay at the study site, indi-

Consistency between Recharge Year Using

cated by drastic decreases in NO 3 and ORP, and

CFCs and Livestock Farming Land Use History-

increases in NO3 , etc. (Lee et al., 2009). It is known that

According to the Census of Agriculture and Forestry

CFCs can be degraded by microbes under reductive

2000 (Ministry of Agriculture, 2000), farms at the study

environmental conditions, and CFC-11 is the most easilysite in Konomata, Tsukuba City, Ibaraki Prefecture had

degraded, followed by CFC-13 and CFC-12 (Khalil andabout 554 to 725 pigs (Table 1). The farmers went on

Rasmussen, 1989；Semprini et al., 1992). In other words,

pig farming for more than 25 years (from before 1970

a groundwater recharge year estimated for a site with

until 1994), and more than 15 years have passed since ita reductive environment may be older than the actual

ceased (Table. 1). Fig. 5 presents the relationship-recharge year due to degradation of CFC-11, etc. At
this study site, CFC-11 concentrations drop significantly

Table1.

at depths of 6 m, 8 m, and 10 m at Point A, where themost denitrification occurs (Fig. 4). This means that
CFC-11, which is more easily degradable in a reductive
environment, is degrading faster than CFC-12. This canalso be confirmed in Fig. 5. Points marked with ▲ indicate drops in CFC-11 due to microbial degradation
under a reductive environment. Due to these drops,
recharge years calculated using CFC-11 concentrations
shift downward (Fig. 5). The maximum discrepancy inrecharge year due to microbial degradation was 21
4

Changesinlivestockindustry（pig
farming）inKonomata（Ministry of Agriculture, ₂₀₀₀）

Year

Number of pig farms（100 pigs or more）

Number of pigs

1970

3

554

1975

3

606

1980

4

725

1985

2

629

1990

0

0

1995

0

0

2000

0

0

There has been no breeding of cows or chickens.

地球環境研究，Vol.16（2014）

between recharge years and high concentrations of

the study site in Ibaraki Prefecture with the Northern

NO3 by animal waste. Here, the stable nitrogen isotope

Hemisphere Average Values showed errors ranging

ratio (δ N) was used to select points affected by thefrom 7 % to 14 %. Long-term monitoring of atmo-

animal wastes in the unlined disposal pit. δ N values

spheric CFC concentrations at each study site is neces-of nitrate contamination sources range from -5 ‰ to +3

sary in order to reduce this error. We compared the‰ for chemical fertilizer and from +10 ‰ to +20 ‰ for

atmospheric concentrations of CFCs published in the

animal waste. Because of this difference in δ N values,

Northern Hemisphere Average Values to those at theidentification of contaminant sources is possible (Tase,study site in Ibaraki Prefecture. Unfortunately, data2003). From Fig. 5, we estimate that groundwater con-

was only available for the study site from 1993 to 2007.

taining the high concentration of NO3 ( ◆ marks indi-

Therefore, we compared 1993 to 2007 and extrapolatedcate δ N≧+10 ‰ ) due to the animal waste in thethe difference to previous years. It will be necessary in

unlined disposal pit was recharged between late 1970s

the future to develop a highly accurate correction

and around 1990, and we estimate that the NO3 willmodel that takes into account CFC output before 1993

flow out into the rivers with a residence time of about

in the area around the study site.

-

15

15

15

-

15

-

30 years. However, while the number of pigs being

In addition, in the nitrate attenuation zone of the

farmed decreased starting in 1985, the high concentra-

study site, CFC-11 is degraded, which suggests thattion of NO ( ◆ ) caused by the unlined disposal pit does

recharge years estimated using CFC-11 can be in error,

not start to decrease until around 1990, a gap of

appearing to be older than they are. Therefore, it isapproximately 5 years (Fig. 5). The reasons are as fol-necessary to carry out detailed hydrogeological surveys

lows: 1) a temporal gap until the high concentration of

to taken into account estimating recharge years using

NO3 from the unlined disposal pit leaches into the aqui-

CFCs.

3

-

fer, 2) mixing from the ground surface with precipita-

On the other hand, we estimated that the high con-tion having a higher concentration of CFCs than thecentration of NO3- caused by the unlined animal waste

groundwater aside from the piston flow, and/or 3) an

disposal pit was recharged between late 1970s andanthropogenic impact caused by animal waste itself,

around 1990. This is consistent with the land use his-etc.

tory of livestock farming at the study site. This sug-

The high concentration of NO3 from the unlined dis-gests that the high concentration of NO3- in the study

posal pit flows from a depth of 4m at Point A, downsite still has a large effect on shallow groundwater andthrough 6m at Points 4 and 7 and into deeper layers at

is a potential contaminant source even after approxi-

Points 11 and 15, and upwards near 10m at Point 18.

mately 15 years has passed since pig farming stopped,

This shows a trend that is similar to groundwater flow

and urgent countermeasures are believed to bemapped by recharge year (Fig. 2). As mentioned above,

required.

-

our results showed good agreement between therecharge year of the high concentration of NO3- fromthe unlined disposal pit and the land use history of live-

ACKNOWLEDGEMENTS

stock farming. From above, we can also see that theDuring this study, we received a great deal of advice

distribution of high concentrations of NO3 in the study

from Em. Prof. Dr. Tadashi Tanaka, Prof. Dr. Michiakisite are consistent with the recharge year and land use

Sugita, Prof. Dr. Jun Asanuma, and Assoc. Prof. Dr.

history, estimation of recharge year using CFCs in shal-

Tsutomu Yamanaka of the Graduate School of Life andlow groundwater is considered to be valid.

Environmental Sciences, Univ. Tsukuba, for which we-would like to express our sincere thanks.

CONCLUSIONS
Comparing of atmospheric concentrations of CFCs at

SUPPLEMENTS
S 1. Recharge year estimates based on CFC-11 and CFC-12

5

Distrion of Nibutitrate Contamination from the Viewpoint of Recharge Year, Land use History and Groundwater Flow System（Seongwon LEE・Maki TSUJIMURA・Sujen Prashad AMATYA・Norio TASE）

S 1. Recharge year estimates based on CFC-11 and CFC-12
After Correction
CFC-11（pptv） CFC-12（pptv）
1784
9006

Recharge Year
CFC-11（Year） CFC-12（Year）
Contam.
Contam.

Sample

CFC-11（pptv）

CFC-12（pptv）

WA 4m

1670

10449

WA 6m

162

840

173

724

1981

Contam.

WA 8m

112

623

120

537

1975

1996

WA 10m

120

480

129

413

1976

1986

WA 13m

135

433

144

374

1977

1984

W4 4m

240

536

257

462

1989

1988

W4 6m

243

661

259

570

1989

ModernW4 10m

151

292

161

252

1979

1976

W7 2m

232

592

248

510

1988

1992

W7 4m

245

585

261

504

1989

1991

W7 6m

258

552

275

476

1995

1989

W7 10m

74

300

79

259

1972

1977

W11 2m

241

577

258

497

1989

1991

W11 4m

257

612

275

528

1995

1994

W11 6m

222

606

237

523

1987

1993

W11 10m

240

557

256

480

1989

1989

W15 2m

148

340

158

293

1979

1978

W15 4m

219

520

234

449

1987

1987

W15 6m

231

550

247

474

1988

1989

W15 8m

261

548

279

472

1995

1989

W15 10m

252

537

270

463

1991

1988

W15 12m

233

567

249

489

1988

1990

W18 4m

223

578

238

498

1987

1991

W18 6m

250

587

267

506

1991

1991

W18 10m
111
287
119
247
Modern：within the possible range of the modern atmosphere
Contam.：greater than maximum concentrations in the atmosphere

1975

1976

disposal pits on groundwater quality. Journal of ground-

REFERENCES
Asai, K., K. Hasegawa, K. Ohta, M. Tsujimura, 2006. Application to groundwater age dating and method of CFCs ingroundwater. Proceedings of 2006 Fall Meeting of theJapanese Association of Groundwater Hydrology 274-279(in Japanese).
Bullister, J. L., R. F. Wesis, 1988. Determination of CCl3F
and CCL2F2 in seawater. Deep-Sea Research 42: 11512283.
IAEA, 2006. IAEA Guidebook on the use of chlorofluorocarbons in hydrology 2004 edition. Technical Report Series
438. 236pp.
Ibaraki Prefecture, 1993-2007. Environmental white paper
1993-2007 (in Japanese).
Khalil, M. A. K., R.A. Rasmussen, 1989. The potential of soils
as a sink chlorofluorocarbons and other man-madechlorocarbons. Geophysical Research Letters 16: 679-682.
Lee, S. W. A. Hosaka, N. Tase, 2009. Influnce of animal waste

6

water hydrology 51: 3-14 (in Japanese with English
abstract).
Leibundgut, C., P. Malozewski, C. Külls, 2009. -5. Mathematical Modeling of Experimental Data-. Tracers in Hydrology. Leibundgut, C., P. Malozewski, C. Külls (eds). John
Wiley & Sons: West Sussex; 123-174.
Ministry of Agriculture, Forestry and Fisheries of Japan,
2000. Census of Agriculture and Forestry 2000 (in Japanese).
Maloszewski, P., A. Zuber, 2002. Manual on lumped-parameter models used for the 19 interpretation of environmental
tracer data in groundwaters. In use of Isotopes 20 for
Analyses of Flow and Transport Dynamic in Groundwater Systems, 21 Yurtsever Y (ed.). IAEA-UIAGS/CD no.
02-00131. IAEA: Vienna; 1-50.
Tase, N., 2003. Present situation and research on nitrate contamination in groundwater. Journal of japan society on
water environment 26(9): 546-550 (in Japanese).

地球環境研究，Vol.16（2014）
Tsujimura, M., K. Ohta, K. Asai, K. Hasegawa, J. Shimada,Yabusaki, S., M. Tsujimura, N. Tase, 2003. Recent trend of

2006. Fundamental study based on groundwater dating

tritium concentration in precipitation in Kanto Plane,

method by CFC. Proceedings of 2006 Spring Meeting ofJapan. Bulletin of the Terrestrial Environment Research

the Japanese Association of Groundwater Hydrology

Center, the University of Tsukuba 4: 119-124 (in Japanese122-127 (in Japanese).

with English abstract).

Semprini, L., G.D. Hopkins, P.L. McCarty, P.V. Roberts, 1992.

Zuber A., 1986. Mathematical models for the interpretation

In-situtransformation of carbontetrachloride and otherof environmental radioisotope in groundwater systems.

compounds resulting from biostimulation under anoxic

Handbook of Environmental Isotope Geochemistry, Fritz

conditions. Environmental Science & Technology 26:

p. Fontes J. C. (eds). Elsevier: Amsterdam; 1-59.

2454–2461.

涵養年代、汚染履歴、地下水流動系からみた硝酸性窒素汚染の分布
李盛 源＊

辻 村 真 貴＊＊Sujen Prashad AMATYA ＊＊田 瀬 則 雄＊＊キーワード：CFCs、涵養年代、地下水、素掘り、汚染履歴、NO3－

要旨本研究において、CFCs（Chlorofluorocarbons）を用いて調査を行い、素掘り廃棄ピットによる高濃度の NO3- の分
布と汚染履歴（land use history）との関係について考察を行った。その結果、本研究対象地域の窒素還元場では、
CFC－11も分解されており、CFC－11による涵養年代推定法では実際より古く見積もられることが示唆された。そのため、涵養年代を推定する際には、詳細な水文地質学的環境を調査する必要があることが明らかになった。また、素掘り廃棄ピットによる高濃度の NO3- は、1970年代後半から1990年前後にかけて涵養されたものと推定された。この結果は、本研究対象地域における畜産業による汚染履歴と整合性があり、養豚を止めてから約15年以上が経過している
現在にも大きな影響を及ぼしていることが示唆される。
＊		 立正大学地球環境科学部＊＊
筑波大学大学院生命環境科学研究科

7