Local distribution of chlorinated hydrocarbons in the ambient air in Tokyo

LOCAL DISTRIBUTION OF CHLORINATED HYDROCARBONS IN THE AMBIENT AIR IN TOKYO TOMOHIRO OHTA, MASATOSHI MORITA and ISAMO MIZOGUCHI Department of Environmental Health. Public Health, 24-l Hyakunincho (First received 9 October

Tokyo Metropolitan 3chome, Shinjuku-ku,

in final

1975 and

form

Research Laboratory Tokyo 160, Japan

27 January

of

1976)

Abstract-The measurements of four chlorinated hydrocarbons were made in Tokyo air from May 1974 to April 1975. The annual average concentrations were 0.8 ppb(10m9), 1.4 ppb, 1.2 ppb, and 1.2 ppb, for l,l,l-trichloroethane, carbontetrachloride, trichloroethylene and perchloroethylene respectively. The correlations between the levels of these chemicals and the meteorological data were discussed and these results demonstrated that rain, the eastwind (seabreeze) for Tokyo and strong winds (the maximum velocity of the wind in a day is 10-15 m s- ‘) contributed to remove these chemicals from air, on the other hand, the cloudiness and the weaker wind contributed to keep these levels high and the southwind contributed to increase them. The distributions peaks of trichloroethylene and l,l,l-trichloroethane coincided with locations of machine or metal products plants which are the major user of both solvents, and furthermore the

distribution of carbontetrachloride showed a good relation with that of chemical factories. However perchloroethylene was distributed rather evenly. The concentration of carbontetrachloride was much larger than the expected production compared with that of l,l,l-trichloroethane, trichloroethylene and reason for this is not clearly understood at present

1. INTRODUCTION

In recent years there has been concern about the occurrence of chloroderivatives of methane, ethane and ethylene in the environment. Lovelock (1971) made direct measurements of ambient concentrations of atmospheric halogenated chemicals such as trichlorofluoromethane (CFC&) and sulfur hexafluoride (SF,) with electron-capture gas chromatography. Lovelock (1973) reported the measurement of the concentration of CFCl, , carbontetrachloride (Ccl,) in the air in rural and urban areas in the British Isles. Murray et ul. (1973) reported the occurrence of chloroform (CHCl& Ccl,, tetrachloroethylene (C&l,) and trichloroethylene (C2HCl,) in the air in both rural areas of Britain and over the North East Atlantic. Lovelock (1974) added the background concentration of CHCl,, l,l,l-trichloroethane (C,H,Cl,), C2HC13, C&l,, and dichlorodifluoromethane (CC12F,) over the North Atlantic Oceans and Western Ireland. These works have been, however, mainly focused on the contamination on a global scale and only limited information is available on the level and the distributions of these materials on a regional scale. Meanwhile, Simmonds et al. (1974) reported the average concentrations of C&l,, CFCl, , &H,Cl, and CCI, in the air over the Los Angeles Basin with the hope to demonstrate the correlation between the intrinsic labeling of a large urban air mass and known meteorological data such as night-time land breeze and day-time sea breeze. The main purpose of the present paper was to determine practically the distribution pattern of these

value from the annual perchloroethylene, the

chemicals in urban area where they are mainly used and discharged, and the correlation between the concentration level and some long term meteorological data. For this purpose, the ambient air in Tokyo metropolitan area was analysed at twenty-six sites monthly from May 1974 to April 1975. 2. SAMPLING

AND ANALYSIS

Air sampling was carried out on the roof of twentysix public buildings with three or four floors in daytime during three or four days of every month from May 1974 to April 1975. Sampling locations were grouped as follows: northern, southern, eastern and western part of Tokyo, for the convenience of sampling. Sampling at each site in a group was completed on the same day. Ten cm’ of fresh air was inspired and capped in 1Oml glass syringe and taken back to the laboratory for the analysis. The analysis was carried out within 20 h after sampling, using gas chromatography equipped with electron capture detector. Two cm’ of the sampled air was directly injected with the syringe. Quantification was made by the comparison of peak height calibrated with the known amount of four chlorinated hydrocarbons in ether solution. Gas chromatographic conditions employed were as follows; apparatus: Shimazu GC-SA; column: silicon DC 20% on chromosorb W, 1.5 m (glass); column temperature: 60°C; carrier gas flow rate: 6Ocm’ min-‘, N,; detector: Ni63. For the confirmation of chemical species, samples condensed on celite by cryogenic trapping from 501. 557

TOMOHIRO OHTA. MASAT~SHI MORITA and ISAMlj

MIZOGUWI

1

@@ax3 Fig.

1

d

I. Correlation

between the level for each contaminant and the weather on sampling days.

of ambient air were subjected to gas chromatography -mass spectrometry. Identified chlorinated hydrocarbons were CHCI,, Ccl,, C,H,CI,, C2HCl,, C,CI,, dichloromethane and dichloroethane.

3. RESULTS AND

DISCIJSSION

The method for air sampling employed here was very convenient but it had a possibility to give a systematic error to the analysis owing to the air exchange in the storage hours through glass syringe. The effect of air exchange between sampled air and ambient air was so large that the sampling was not suitable for the determination of CHCl, because CHCI, was occurred often ten or hundred times higher in the laboratory air than in the outdoor air. It was, however, practically negligible for the analysis of C,H,Cl,, Ccl,, C,HCl, and &Cl,. Replicated analysis revealed that the analytical error was below IO”I/

N

north

wend

S

south

wind

E east

wmd

-

(a)

o-5

m 5~’

(b)

5-10

m s-’

(c)

IO-15 In s-1

Im 1 c!bc

~

i

Ll t

b c

Fig. 3. Correlation between the level for each contaminant and the maximum

velocity

of the wind on sampling

day.

The annual average concentrations of these four 1.2 ppb and species were 0.8 ppb( 10. “), 1.4ppb. 1.2ppb respectively for C2H,C1,, Ccl,. C,HCl, and C,Cl,. These levels are almost the same as those found over the Los Angeles Basin in 1972. .(Simmonds c’t trl.. 1974 fotmd 0.37 pph. for C’,H,Cl,. 0.22 ppb fol Ccl, and I.25 ppb for C>CI,. and demonstrated the correlation between their distribution on a few sampling days and known meteorological data such as night-time land breeze and day-time sea breeze.) An attempt was made to correlate the level of these materials to the weather conditions. All sampling days were grouped into four such as rainy, overcast, fair (2 -8 tenths) and clear days and the concentration for each chemical on every sampling day was further averaged within each group. The results are illustrated in Fig. I. The levels of these materials were somewhat lower on rainy days and clear days. This implies that the rain helps to remove these substances from air in spite of their low solubility in water. and the cloud keeps an inversion layer to sustain these contaminants in higher lc\el. In sunshine. these chlorinated hydrocarbons might be decomposed by reacting with such reactive species as nitrogen dioxide, ozone or other secondary products from the reaction in air photochemistry. (However. the reactivities or

D

B

JL NSE

i NSE

Fig. 2. Correlation between the level for each contaminant and

the direction

of the maximum velocity on sampling day.

of the wind

Fig. 4. Distribution of annual average C2H,CI,. l sites with above average

concentration concentration.

of

Local

distribution

Fig. 5. Distribution of annual average concentration Ccl,. 0 sites with above average concentration.

of chlorinated

of

the rate constants in these reactions have not been demonstrated and further studies are required.) The direction of wind at the Tokyo Meteorological Station when the speed was greatest was used to divide the data in three groups, north, south, east (west was not observed). The average concentration of each chemical in every group is illustrated in Fig. 2, which shows the east wind in the Tokyo area decreases the concentration for each chemical, but the south wind increases this. Tokyo Bay and the Pacific Ocean are to the east but there is a big industrial zone to the south. The data were also divided into three groups of the maximum velocity of the wind in a day; G5, 510 and lGl5m s-l, and the average concentration of each chemical in every group is illustrated in Fig. 3. On the days of strong wind, all chemical species examined were in the lowest concentration in accordance with our daily experience that the air on windy days is clear. Apparently the wind with more than 10 m s- 1 of maximum velocity effectively blows away the chemicals but lighter winds were less effective. The distributions of these chlorinated hydrocarbons in the ambient air in Tokyo area is illustrated in Figs. 4 to 7, and the distribution of factories or shops which are suspected to discharge the materials is in Figs. 8 and 9. It is noteworthy that the distributions of C,HCl, and C,H,Cl, are correlated to that of machine or metalwork industry. These facts indicate that C,HCl, and C,H,Cl, are primarily dis-

Fig. 6. Distribution of annual C2HC13. 0 sites with above

average average

concentration concentration.

hydrocarbons

Fig. 7. Distribution of annual average concentration C,CI,. l sites with above average concentration.

of

charged from machine or metalwork industry where these solvents are used mainly as degreasing. Furthermore the distribution of Ccl, was found to correlate to that of chemical plants suggesting that Ccl, was mainly used in the plants. In the contrast, C&l, was found to occur rather evenly over Tokyo area and no correlation was demonstrable between the distribution of C&l, and that of any kind of manufacturing industries. Tetrachloroethylene is mainly employed for drycleaning in more than ten thousand locations in Tokyo with a fairly homogeneous distribution. Industrial output of these materials in 1973 in Japan was 50000, 62000, 110000 and 57000 tons respectively for C2H3CI,, CCl,, C2HCl, and &Cl,. The quotients of the annual average concentration

Fig. 8. Distribution

of machine or metalwork

industrv.

of Fig. 9. Distribution

of chemical

plants.

(m)

560

T~MUHIRO OHTA. MASATOSHI MORITA and ISAMU MIZOGI'CHI

Table

I. The quotient

of the annual

average

concentration

in Tokyo

Average

(lo-” v/v) Chemical

C:ses

(A)

C,H,CI,

0.8

CCI,

1.4

C,HCI,

1.2

czcl,

1.3

Annual output in Japan (ton)

Degreasing (go”,,) Solvents (20” II) Intermediate to freon (99”,,) Degreasing (go”,,) Solvents (20” ) Dry cleaner (%Y’,,) Degreasing (25”,,) Solvents (25”“)

Acknowlrci+~~mts

The

authors

wish

to thank

Messrs

estimated

amount

Estimated amount of discharge (ton) (B)

of discharge

in Japan

(A)/(B) ppbiton

50000

so 000

1.6 x 10 ’

61000

620

2.3 x IO L

110000

I 10000

I.1 x IO i

57 000

7.1 x 10 5

5 7 000

tn Tokyo divided by the estimated amount of discharge in Japan are listed in Table 1. The values are almost the same among three compounds; C,H,Cl,, C,HCl, and C,CI,. That of Ccl,, however, shows thousand times higher than that of the rest. Supposed that the output of Ccl, is underestimated, the ratio seems so large to be quite differerit from these of other three species. Although further experiments are necessary to elucidate this, differences of life-time in air or formation by unexpected reaction in chemical plants might be responsible for the ratio. These results lead us to confirm that the local distribution of each chemical species primarily depends on that of the places where these chemicals are used, while the level of air contaminant is affected by meteorological conditions.

and

Sate. Ohsawa. Makmo. Kane. Tada and sampling for a long term, and also thank his constructive discussion.

Fukuda for the Dr. G. Ohi for

REFERENCES Lovelock J. E. (1971) Atmospheric fluorine compounds as indicators of air movement. Nature 230, 379. Lovelock J. E. (1974) Atmospheric halocarbons and stratospheric ozone. Nature 252, 292-294. Lovelock J. E.. Maggs R. J. and Wade R. J. (1973) Halogenated hydrocarbons in and over the Atlantic. Nature 241, 194- 196. Murray A. J. and Riley J. P. (1973) Occurrence of some chlorinated aliphatic hydrocarbons in the environment. Nature 242, 37.-38. Simmonds P. G., Kerrin S. L.. Lovelock J. E. and Shair F. H. (1974) Distribution of atmospheric halocarbons in the air over the Los Angeles Basin. Atmospheric En~Gmmrnt 8, 209-216.