研究論文
1-11
Monitoring Study on Acid Rain in Kanagawa Prefecture, Central Japan
Hiromi Kobori 1, Maki Kumazawa 2, Yoshiki Kai
3
and Young-Sik Ham
4
Introduction
Acid deposition has a long historical background. In the 17th century, scientists noted the adverse effects that industry and acidic pollution had on vegetation and people. However, the term
acid rain was not coined until two centuries later when British scientist Robert Angus Smith published ‘Air and Rain : The Beginning of a Chemical Climatology’ in 1872. Acid deposition is defined as the atmospheric acids deposited on the earth as wet deposition (snow, rain, fog, mist, etc.)
and dry deposition (gas and dry particles). However, this paper deals exclusively with what is
commonly called “acid rain”. Acid rain forms in the air, and is caused by burning fossil fuels to
produce electricity and run automobiles. The burning of these fuels results in emissions of sulfur
dioxide and nitrous oxide into the air. In the 1960s, the problems associated with acid rain became an international concern when fishermen noticed declines in both fish numbers and diversity
in many lakes throughout North America and Europe. Indeed, acid rain has become one of the
most serious worldwide environmental problems to date.
The Environment Agency, Government of Japan−renamed the Ministry of the Environment,
Government of Japan in 2001−has been performing surveys of acid rain since 1983. In recent
years, acid rain in Japan has been observed at roughly the same levels as those in Europe and
North America (Ministry of the Environment, Government of Japan, 2004). In addition, starting in
1984, a more detailed investigation of acid rain began in Yokohama City−located in Central Japan−by the Yokohama Environmental Science Research Institute. They have been collecting and
analyzing rainfall and their initial 1 mm rainfalls, which were then used for determining the
differences within one-time collected rainfall. However, sampling sites for acid rain monitoring by
federal and local governments are limited, and it is necessary to accumulate more data in local areas in Japan.
The following study monitored acid rain at two sites in Kanagawa Prefecture where acid rain
previously had not been monitored. This study analyzed rainfall in 1 mm increments, in order to
(1) estimate the effect of acid rain on ecosystems and (2) explain the relationship between onetime collected rainfall and the initial 1 mm rainfall.
1
2
3
4
Professor, Faculty of Environmental and Information Studies, Musashi Institute of Technology
Furezenium Kawazui, Co.Ltd.
Chuhoku Seiyaku, Co.Ltd.
Visiting researcher, Faculty of Environmental and Information Studies, Musashi Institute of Technology
97
Materials and Methods
The rainfall was collected at a residential area in Kagawa, Chigasaki City, Kanagawa Prefecture (E139°
24′
, N35°
19′
) in May-December 2000 and in Eda-cho, Aoba area, Yokohama City,
Kanagawa Prefecture (N35°
33′
, E139°
33′
) in January-December 2002 (Figure 1). The rainfall
collector (Horiba, AR-8II) was set-up using one automatic open rain sensor cap and 8 cups used
for collecting the initial rainfall in 1 mm increments (Figure 2). Amounts over 8 mm of rainfall
were collected by one drainage cup up to 30 mm. After collection, the rainfall pH and electrical
conductivity (EC) of each cup were measured using a pH meter (Horiba, Twin pH B-212) and a
EC meter (Horiba, TwinCond B-173). Statistical analyses were conducted using XLSTAT software
(1995-2004 Addinsoft, XLSTAT 7.1) ; as described in the text, significant differences among the
rainfall data were analyzed by Student’s t test for paired samples (α<0.01) and Pearson’s correlation coefficient test (α<0.01).
Yokohama City point
Rain sensor cap
Drainage
Tokyo Bay
Chigasaki City point
10 km
Figure
pointsofofrainfall
rainfall
Figure1.1.The
The collecting
collecting points
in in
Kanagawa
Prefecture
Kanagawa Prefecture
Figure
Figure2.2.Rainfall
Rainfallcollector
collector
Results
Acid rain below pH 5.6 was observed in 83% of 103 rainfall samples collected in Chigasaki
City (2000) and Yokohama City (2002) (Figure 3). In the detailed result of the collected rainfall
sample, the volume-weighted mean pH (VWMpH) of rainfall showed an average pH of 4.7 in
Chigasaki City in 2000 (range from pH 3.6 to 7.7), and VWMpH of rainfall in Yokohama City
was estimated at an average pH of 5.3 in 2002 (range from 3.9 to 7.5).
Furthermore, it has been concluded that rainfall below pH 4.0 can damage certain varieties of
plants (Evans et al. 1980 ; Jacobson 1980). In our study, readings at or below pH 4.0 were observed 6 times in Chigasaki City and once in Yokohama City during the study periods of 2000
and 2002. Umeda and Katou (2002) reported that the rainfall pH in Yokohama City decreased as a
98
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2000
2001
2002
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㪛㪅㪈
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Collecting date
Figure
rainfall
pH inpH
Chigasaki
City (2000)
Yokohama
Figure3. The
3. The
rainfall
in Chigasaki
City and
(2000)
and
City (2002) in Kanagawa Prefecture (Dashed line : acid rain at pH
Yokohama City (2002) in Kanagawa Prefecture (The dashed
5.6 ; Solid line : acid rain at pH 4.0, crop-damageable level ; 2001 :
noline:
data)acid rain below pH 5.6, Solid line: crop-damageable level
below pH 4, 2001: no data)
result of volcanic gases emitted duing the eruption of Mt. Oyama (elevation : 813 m, location : N
34°
04′
43″
, E 139°
31′
46″
) in Miyakejima Island, which is located 160 km south of Chigasaki
City, during September 2000-August 2001. Also, particularly strong acid rain was detected in Chigasaki City from August to December 2000. This may be a result of differences in the intensity of
volcanic gases over time. As above-mentioned, it can be concluded that during the study periods
most of the rainfall pHs were observed in the 4.0 - 5.6 range.
Of particular note, acid rain below pH 5.6 was observed in 56% of 103 initial 1 mm rainfall
samples in Chigasaki City (2000) and Yokohama City (2002) (Figure 4). Contrasting with the result of Umeda and Katou (1998 and 2002), our data indicated a higer level of pH (less acidic) for
the initial 1 mm rainfall. Even though the reason for this result is not clearly understood, it is interesting to note that initial first 1 mm rainfall pHs were significantly different from one-time collected rainfall pHs in our study (Figure 5).
Umeda and Katou (1998) reported that the concentrations of each measured ion in initial first
1 mm rainfall were higher compared with its one-time collected rainfall. This result may reflect
that rainfall pH is dependent on the processes of proton (H+) formation and consumption of limited materials (e.g. : H2SO4, NH3, etc.) in the air. Consequently, there is a possibility that the
chemical property of the initial first 1 mm rainfall measurements was different from their rainfall
measurements. In our study, there was a significant difference between the initial first 1 mm rainfall electrical conductivity (EC)−which estimates the amount of total dissolved salts (TDS) or the
total amount of dissolved ions in the water−and the rainfall EC (Figure 5). In addition, as acid
rain pH decreased downward to pH 3.6 there was a corresponding increase in the acid rain EC,
with a significant correlation coefficient between pH and EC in each of the initial 1 mm acid rain
measurements and corresponding one-time full rainfall measurements below pH 5.6 (Figure 6).
99
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㪎
㪍
㪌
㪋
㪊
㪉
㪈
2001
2000
2002
㪤㪅㪈㪊㪄㪈㪋
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㪪㪅㪈㪎
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㪡㫃㪅㪉㪌
㪪㪅㪈㪊
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㪛㪅㪈
㪇
Collecting date
2
0
1
2
3
4
Figure 5.
initial
first 11 mm
mm
Figure
5. Means
Means ofof(1)
: (1)
Initial
rainfall
pHsand
and(2)(2)
colleted
rainfall pHs
theirone-time
rainfall pHs,
and
rainfall pHs ; (3) Initial 1 mm rainfall
(3) initial first 1 mm rainfall ECs and (4)
ECs and (4) one-time collected rainfall
their rainfall ECs. Vertical bars indicate
ECs.
Vertical bars indicate maximum and
maximum values
and minimum
values (n=103).
minimum
(n=103). Symbol
of ***
shows
Symbol aofsignificant
*** shows adifference
significant(Student’s
difference
t(Student's
test for paired
samples,
α
=
0.001)
t test for paired samples, α =
0.001)
100
-1
Initial first 1 mm
4
rain fall EC (µS cm )
6
300
R = 㵥0.701***
200
100
0
3
-1
***
Rain fall EC (µS cm )
pH
8
1400
1200
1000
800
600
400
200
0
***
-1
10
E C ( µS c m )
Figure
4. 4.The
Figure
Theinitial
initialfirst
first1 1mm
mmrainfall
rainfallpHs
pH in
in Chigasaki
Chigasaki City
City
(2000)
Yokohama
City City
(2002)(2002)
(Dashed
: acid rain
at pH
(2000)andand
Yokohama
in line
Kanagawa
Prefecture
5.6 ; Solid line : acid rain at pH 4.0, crop-damageable level. 2001 :
(Dashed line: acid rain below pH 5.6, Solid line: crop-damageable
no data)
level below pH 4, 2001: no data)
150
4
5
Initial first 1 mm rainfall pH
6
R = 㵥0.578***
100
50
0
3
4
5
Rainfall pH
6
Figure
between
initial
first
Figure 6.6.Relationships
Relationships
between
initial
mm rainfall
rainfallpH
pHand
andECEC(n=58,
(n=58,
up11 mm
upper),
per), and one-time collected rainfall
pH and EC (n=85, bottom). Symbol of
bottom). Symbols of *** show significant
*** shows significant correlation coefcorrelation
coefficients
ficients (Pearson’s
correlation(Pearson's
coefficient test, α
= 0.001)test, α = 0.001)
correlation
coefficient
and their rainfall pH and EC (n=85,
Conclusion
This study showed acid rain in Kanagawa Prefecture was still observed with a high frequency
of 83% in 103 rainfall samples in Chigasaki City (2000) and Yokohama City (2002). Also, there
was a significant difference between the initial 1 mm rainfall pH and the one-time collected rainfall pH in Kanagawa Prefecture through the study periods of 2000 and 2002. Significantly, acid
rain was more acidified with increasing acid rain EC in this study. Furthermore, the initial first 1
mm rainfall ECs were higher compared with their one-time collected rainfall ECs. This result suggests that a high concentration of dissolved ions was absorbed by the initial first 1 mm rainfall.
Consequently, this study suggests that further study on effect of the frequency of rainfall on an
ecosystem is required to illuminate the complex ecological effects of acid rain. Especially in
unique conditions such as active volcanoes, acid rain can be further acidified within a regional
wide area in Japan. Consequently, a successive monitoring study of acid rain in Japan is needed to
explain acid rain and elucidate possible countermeasures.
Acknowledgments
We thank Ms. Brenda Bushell, Musashi Institute of Technology and Mr. Adam Lobel for their
help during the preparation of this article.
References
Evans, L. S., C. A. Conway and Lewin (1980) Yield responses of field-grown soybeans exposed
to simulated acid rain. In Proceedings of an International Conference of Ecological Impact of
Acid Precipitation, Sandefjord, Norway, March 11-14, 1980, Eds. D Drablös and A Tollan, p.
162-163, Oslo-Aas, Norway : SNSF project
Jacobson, J. S. (1980) The influence of rainfall composition on the yield and quality of agricultural crops. In Proceedings of an International Conference of Ecological Impact of Acid Precipitation, Sandefjord, Norway, March 11-14, 1980, Eds. D Drablos and A Tollan, p. 41-46,
Oslo-Aas, Norway : SNSF project
Kanagawa Prefecture Agriculture, Forestry and Fisheries Information Center (2004) Meteorological Information Database. http : //web05.agri.pref.kanagawa.jp/kisyo/
Ministry of the Environment of Japan (2004) State of the Global Environment at a Glance : Acid
Deposition. http : //www.env.go.jp/en/topic/acid/acid_situ.html
Umeda, T and Y. Katou (1998) Successive progress of pH and chemical property in rainfall in
Yokohama City (Japanese title was translated into English by author). In Annual Report of
Yokohama Evironmental Science Research Institute. p. 11-20, Yokohama Environmental Science Research Institute, Yokohama (in Japanese)
Umeda, T and Y. Katou (2002) Acid rain by volcanic gases from Miyakejima (Part. 2). In Annual
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Umeda, T and Y. Katou (2002) Survey of Acid Rain in Yokohama City. -Rain acidity data from
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