Atmospheric Environment Vol. 24A, No. 8, pp. 2099 2103, 1990. 00046981/90 $3.00+0.00 Printed in Great Britain. Pergamon Press pie

SHORT COMMUNICATION

T R E N D S O F A I R Q U A L I T Y A N D A T M O S P H E R I C D E P O S I T I O N I N

T O K Y O

T. KOMEIJI, K. AOK! a n d I. KOYAMA

The Tokyo Metropolitan Research Institute for Environmental Protection, 1-7-5, Sinsuna, Koto-ku, Tokyo 136, Japan

a n d

T. OKITA

Obirin University, Tokiwa-cho 3758, Machida-shi, 190-02 Tokyo

(First received 15 February 1989 and receit, ed for publication 5 February 1990)

Abstract--The trends of air quality and atmospheric deposition in the past 20 or more years in Tokyo are summarized. In the late 1960s and early 1970s the levels of SO2, SO ] , airborne particulate matter and its elemental compositions were high but their levels have rapidly declined until the 1970s because of their emission control and fuel and material switching. Recently, however, the decline has slowed down. The number of days on which Mt. Fuji was visible from Tokyo have increased in coincidence with the decrease of particulate matter concentration. The decrease of deposition of SO 2- and other species also reflects the decline of air pollutant concentration. However, the atmospheric concentration and deposition of oxides of nitrogen did not decrease because of the increase of number of automobiles. It is also recognized that the alteration of structure of the city changes air quality.

Key word index: SO2, NO2, SO 2 , NO3, precipitation, deposition, trend, Tokyo.

INTRODUCTION particulate matter in Chiyoda and Okubo, respectively. The monitoring instruments are: electroconductivity analyzer for

Tokyo is probably one of the most rapidly changing cities in SOa, Salzman automatic colorimeter for NO2, neutral bufo the world. During urban and industrial developments in the fered automatic KI colorimeter for oxidants and continuous post-war period, the Tokyo area had severe air pollution nephelometer for particulates. Figures 5 and 6 show the similar to other major cities of the world and the pollution trends of annual mean concentration of S O l - and NO 3, peaked in 1960s and early 1970s. However, by virtue of and Fe, Zn, Pb and V measured at Okubo NASN station, control effort the pollution level has gradually declined; the respectively. SO 2 and particulate matter concentration trend has been observed by air and precipitation monitoring peaked in the late 1960s but then rapidly declined toward systems. In the following chapters the trends of air quality 25 ppb and 70/zg m - 3, respectively. After 1973 a slow decline and atmospheric deposition monitored in the last two to continued to the present time. It is interesting that the SOl - three decades in the Tokyo area are presented, concentration peak appeared several years later than the

Since in the Kanto area surrounding Tokyo about 30,000 peak of SO 2 and particulate matter concentrations, though people suffered from eye and skin irritations arising from the cause of this phenomenon cannot be explained because of contaminated drizzle droplets (Ohta et al., 1981), particularly a lack of reliable oxidants data before 1978. NO 2 concentra- in June and July of 1973-1975, a sequential wet-only sampler tion, on the other hand, has not declined so rapidly so that, has been developed to monitor contaminated rain. This wet- currently, NO 2 concentration is much higher than SO 2 only sampler has been used along with bulk samplers for the concentration. No large variation of oxidants concentration monitoring of wet deposition in the Tokyo area. has been observed since 1978. NO~ concentration has

increased to a current level of about the same as that of SO 2-. Figure 6 shows that within the last 20 years the

TREND OF AIR QUALITY concentrations of Fe, an, Pb and V has decreased by factors of 4~8.

Long-term air monitoring was started in 1965 in the Mt. Fuji (see photograph on the front cover of this issue), Tokyo area, when the Tokyo Metropolitan Government set the highest ",nountaln in Japan, is located in a WSW direction up a network of continuous air monitoring SO2, CO, NO2, about 90 km away from Tokyo (cf. Fig. 1). Since it is a oxidants and airborne particulate matter of sizes below beautiful mountain, many people in the Tokyo area like to 10/am. The National Air Surveillance Network (NASN) was observe it day after day. initiated in 1968 and at Okubo station (Fig. 1) of the NASN, Figure 7 shows one of the outcomes of the Mt. Fuji located in downtown Tokyo, high volume air sampling of watching, that is, the number of days when Mt. Fuji could be airborne particulate matter was made once a month to seen from Seikei University located in the central part of the determine its organic and inorganic components. Tokyo Metropolitan Area (Report of Seikei Weather Station,

Figures 2, 3 and 4 show the trends of annual mean 1986). The figure clearly indicates that in 1965 the number concentration of SO 2 and NO2, oxidants, and airborne was a minimum of 22 days, but then increased to about 75

2099

2100 Short Communicat ion

Pref.

Tokyo Metro. ~ _ Chibo Pref.

" "~ Oky '.-----, KonagQwa PreL ,,

} '~' Pacific Ocean o , ,--:,'~.. , Tokyo

o, Boy N

Fig. 1. Map of the Tokyo area and sampling sites. ©: Sampling sites for atmospheric deposition in 1962-1963. O: Okubo, Y: Yuraku, Ch: Chiyoda, F: Funato A, C, and D: see Table 1.

ioo

• S02 o NO2, Chiyoda 'E "Z A S02 '" NO2, Okubo ~ 400 f '

.~ .' e"~% ~E i t , / Chiyoda

.

~ 2oo , / , , z. ~ Okubo

o

I I I I I I 1963 1965 i97'0 197,5 1980 J985

Year I I I I I 1965 1970 1975 1980 1985

Fig. 2. Trends of annual mean SO2 and NO 2 concentrations Year at Chiyoda and Okubo.

Fig. 4. Trends of annual mean airborne particulate con- centrations at Chiyoda and Okubo.

~- o Chiyoda days in 1973 After 1973, on average, the number has ~ • Okul~ remained constant. Comparison of Fig. 4 with Fig. 7 indi-

cates the coincidence of the decline of particulate concentra- tion and increase in the number of the days when Mt. Fuji

_ • ~ e ~ e was visible. o~o- . . . . - -* . " " ~ o ~ ....0

I f I I J I I f I I COMPARISON OF BULK DEPOSITION OF ACIDIC AND 78 79 80 8J 82 83 84 85 86 87 ALKALINE SPECIESIN 1962-1963, 1980-1981 AND 1984-1987

Year IN THE TOKYO AREA

Fig. 3. Trends of annual mean oxidants concen- In the 1960s the Tokyo Metropoli tan Research Laborat- tration at Chiyoda and Okubo. ory of Public Health conducted a survey of dust deposition

Short Communication 2101

20 T- • •

- - ',"q

,968 1970 1975 ,980 ,985 ~ ~ 0 ~ :~ ~; ~ ~ ~ = ~; ~; ~ ~ ~ ~ :~ ~. Year .~ Z ~ 5 ~ ~ ¢ ; ~ 5 ~ ~

Fig. 5. Trends of annual mean concentrations of SO~- and N O 3 at Okubo.

I 0 - ~

E I r j ~ , , - ; , - - ; ~ ~ ~ : ~ c 5 ¢4~:~

' - A / % / % \ i_=

Pb [_~

• "x \ "

I . / . / oo, H I l I I

,9~6 ,970 ,975 ,980 ,985 Year = ~ -- ~ ~ ~ = --

Fig. 6. Trends of annual mean concentrations of Fe, Zn, Pb and V at Okubo. ~

".~,

IO0 - - ~

" T - - . . . .

oo ~ o " - ~ ~ , ~ r ~

1965 1970 1975 1980 1985 1988 Year

Fig. 7. Trend of number of days when Mt. Fuji was visible from Seikei University in Tokyo in a year.

2102 Short Communication

using glass jars of 20 cm mouth diameter at 24 sites in the of 30 cm in diameter is collected in a 70 ml glass bottle B and downtown area of Tokyo. Okita and Konno (1964) made the then every 1 mm of the following precipitation is sequentially determination of SO 42-, NO ~, Cl-, NH2, Na +, K +, Ca 2 +, collected in the second, third, fourth and fifth bottles. The rest Mg 2+ in rainwater collected in the jars (Fig. 1). of the precipitation is collected in a 10d polyethylene con-

With the advent of acid precipitation problems, the Tokyo taincr. Metropolitan Research Institute for Environmental Pro- Figure 9 shows trends in the annual average pH of the tection resumed the deposition survey using jars of mouth fractional and total precipitation between 1974 and 1987. It is diameter 15.4 cm at the three sites in the same area. found that the pH of all the fractions and of total pre-

Table 1 compares the depositions of acidic and alkaline cipitation steadily increased between 1977 and 1987. The pH species in the Tokyo area in 1962-1963, 1980-1981 and of the first is, on average, higher than that of the other 1984-1987. fractions by 0.5 due to higher Ca content in the first fraction.

Since separate analysis of Ca 2 + and Mg 2 + by titration in 1962-1963 data had the possibility of being uncertain, only the concentrations of Ca 2 + + Mg 2 + are compared. Com- DISCUSSION AND CONCLUSION paring the depositions of the acidic and alkaline species in 1962-1963 and 1980-1981 it is found that the deposition of In the preceding sections the variations of air quality and Ca 2+ +Mg 2+, Na +, K +, and NH~ had been reduced by~a atmospheric deposition in the past 20 or more years in the factor of 3.9, 1.33, 1.82, and 1.28, respectively (Okita and Tokyo area are reviewed. In 1960s the air in Tokyo was Komeiji, 1983). The deposition of SO 2- and CI- also had heavily polluted due to coal combustion and insufficient been reduced by a factor of 2.5 and lag, respectively. Only emission control. Pollution peaked in the 1960s and early NO ~- concentration has incrgased during this period. After 1970s. But switching of major fuel consumption from coal to 1982 it seems that the deposition of all species has further oil and the installation of dust collectors reduced particulate decreased, emission (Fig. 10). Increase of road surfacing and housing

5 CONTINUOUS MEASUREMENT OF PRECIPITATION

USING AN AUTOMATIC WET-ONLY SAMPLER AT x / x CHIYODA ~ / C Heovy oil

O / A sequential wet-only sampler shown in Fig. 8 was in- ~0 4 x / stalled at Chiyoda, a business and commercial center of x

Tokyo. The initial 1 mm of precipitation received by a funnel o x

I - x - - - x " " B Heavy o i l

Sompting bo'~t Le (every I mm precipitotion)

o ] ] I [ 1960 1962 1964 1966

Year .u.

Fig. 10. Trends of coal and oil consumption in Fig. 8. Sequential wet-only sampler, the Tokyo area in 1960-1965.

• 0-I mm o 5<mm

6.C o 1 - 2 m m ® To taL • 2 - 3 m m

5,~ A 5 - 4 r a m • 4 - 5 m m • • ®

• . -I- 5.C •

Q" • • • o 0 ~ _ • _ . . . . - ~ . - - ~ " u I ~ A -~A rgo_ 4 5 ~ a , A

A I Y = 0 . 0 7 X + b 4 0

I f f I I [ I I ) I I I I I 1974 1975 1976 1977 1978 1979 #980 1981 )982 1983 1984 1985 1986 1987

Year

Fig. 9. Trends in the annual mean pH of fractional and total precipitation collected into the sequential wet-only sampler at Chiyoda.

Short Communication 2103

2 0 - -

o

× I 0

,o \

J I I I J J I I 1 19681970 1975 1980 1985

Yeor

Fig. 11. Trends of SO 2 emission in the Tokyo area in 1968-1985.

5 1.0

4-- ~-08

o ~ ~ '~ 3 - • - 0 6 ,:.

::L

8. o . . _ _ _ . . r . - - . - F . . o ~. .__.z-- 8 o

C~ 2-- , NOz/S02 - 0 . 4 0 ~ o~ o N O V SO~- " -

- - Y = O . 6 4 X + b 0

z I - - - - Y = O I 4 , S X . e b - 0 , 2 z

I I I I I I I I I I 197e 1979 1980 1981 1982 1983 1984 1985 1986 1987

Yeor

Fig. 12. Comparison of trends ofNO2/SO 2 in the air with NO~/SO~- in precipitation at Chiyoda.

also reduced the generation of soil dust (Table 1). Although REFERENCES the usage of heavy oil of high sulfur content temporarily increases SO2 concentration, the introduction of desulfuriz- Ohta S., Okita T. and Kato C. (1981) A numerical model of ation processes for heavy oil reduced the SO 2 concentration acidification of cloud water. J. Met. Soc. Japan 59, drastically (Fig. 11). Concurrently, SO 2- concentrations in 892-901. rainwater also rapidly declined. On the other hand, despite Okita T. and Komeiji T. (1983) Comparison of depositions of significant emission control of NOx, from stationary and acidic and alkaline species in Tokyo between t962-1963 mobile sources, NOx and consequent NO~ levels in air and and 1980-1981. Abstracts of 24th Japan Soc. Air Pollut., p. precipitation have not reduced. This is due to the increased 550 (in Japanese). number of automobiles, particularly of diesel powered Okita T. and Konno S. (1964) Chemical analysis of inorganic trucks. The increased ratios of NO2/SO2 in air and of water soluble components in deposited dust in Tokyo. NO~/SO~- in precipitation, measured using wet-only sam- Bull. Natl. Inst. Public Hlth 13, 121-125 (in Japanese). piers, are in agreement, as shown in Fig. 12. Report of Seikei Weather Station, Seikei University (1989).

In Table 1 the reduction of C1- and Na + is also remark- Tokyo Metropolitan Government (1963-1986) Report of Air able. This result reflects the control of emission of HCI from Monitoring at Regular Stations. Environmental Protec- incinerators and reclamation of the Tokyo Bay. Therefore it tion Bureau. is concluded that the change in the structure of the city as well Tokyo Metropolitan Government (1968-1985) Annual Re- as emission control leads to the changes in air quality and view of Activity. Environmental Protection Bureau. atmospheric deposition.