Directory UMM :Data Elmu:jurnal:A:Atmospheric Research:Vol54.Issue4.Aug2000:
Atmospheric Research 54 Ž2000. 279–283
www.elsevier.comrlocateratmos
Letter
Evaluation of ionic pollutants in cloud droplets at a
mountain ridge in northern Japan using constrained
oblique rotational factor analysis
Nobuaki Ogawa a,) , Ryoei Kikuchi a , Tomoko Okamura a ,
Junko Inotsume a , Tetsuya Adzuhata a , Toru Ozeki b,
Masahiro Kajikawa a
a
Faculty of Engineering and Resource Science, Akita UniÕersity, Tegata Gakuen-cho, Akita, 010-8502, Japan
b
Hyogo UniÕersity of Teacher Education, Yashiro-cho, Kato-gun, Hyogo 673-1494, Japan
Received 12 January 2000; received in revised form 6 April 2000; accepted 6 April 2000
The scavenging of aerosol particles by precipitation and fogrcloud plays an important role in the distribution and concentration of pollutants in the atmosphere. Our
research group has recently studied the acid precipitation in Hyogo and Akita Prefectures in Japan, combining chemical analysis of ions and analysis of meteorological
conditions, and has analyzed the ionic pollutants Žsalts. by factor analysis ŽOgawa et al.,
1998a,b, 1999a,b; Ozeki et al., 1995, 1997.. In general, it is known that fogrcloud water
is significantly more acidic and has higher concentrations of chemical components than
rain water Že.g., Waldman et al., 1982, Hosono et al., 1994, Ogawa et al., 1999a,b.. But
the mechanism of uptake of ion components into cloud droplets, especially for the
difference between ions, is not completely understood. In our previous works ŽOgawa et
al., 1999a,b., cloud water and rain water samples were collected at the Hachimantai
mountain range in Akita Prefecture in northern Japan to obtain information on the
mechanism of uptake of ion components into cloud droplets. We obtained the information about relationship among ion concentrations in the cloud water and droplet size
ŽOgawa et al., 1999a,b..
In this work, we tried to analyze the seasonal change of ionic pollutants in cloud
water due to a variation of mesoscale precipitation system and their dependence upon
the cloud droplet size using constrained oblique rotational factor analysis, which has
)
Corresponding author. Fax: q81-18-889-2601.
E-mail address: [email protected] ŽN. Ogawa..
0169-8095r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 1 6 9 - 8 0 9 5 Ž 0 0 . 0 0 0 5 0 - 8
280
N. Ogawa et al.r Atmospheric Research 54 (2000) 279–283
been developed to analyze quantitatively ionic pollutants in precipitation by our research
group ŽOgawa et al., 1998b; Ozeki et al., 1995, 1997..
Cloud water samples were collected along the mountainside Ž39856X N, 140851X E,
1465 m a.s.l.. of Mt. Mokkodake Ž1578 m, a.s.l.., a mountain ridge in the Hachimantai
range, while recording wind direction and temperature, using the passive fog sampler
ŽModel FWP-500, Usui Kogyo Kenkyusho. during the period from June to September
1998 ŽOgawa et al., 1999a,b.. Rain water samples were also collected at Akita City
ŽAkita University. Ž39843X N, 140808X E, 10 m a.s.l.., at Onuma Ž39859X N, 140848X E, 960
m a.s.l.. in the Hachimantai range and at the mountainside of Mt. Mokkodake with a
bulk sampler ŽOgawa et al., 1998a. during the same periods. The concentrations of
various ions in the cloud and rain water were analyzed by the method mentioned
elsewhere ŽOgawa et al., 1998a, 1999a,b.. The size of the cloud droplets was estimated
by the impaction of drops on oil-coated glass slides ŽOkita, 1961.. The cloud base of
stratocumulusrnimbostratus was 1100–1350 m a.s.l. during the period of cloud water
sampling.
The arithmetic average of the pH of the cloud water samples was 4.43 Ž n s 64., and
that of the rain water samples collected in Akita City, Onuma and the mountainside of
Mt. Mokkodake was 4.97 Ž n s 46., 5.22 Ž n s 24. and 5.65 Ž n s 24., respectively. The
standard deviations Ž s . of the Hq concentrations of cloud Ž s s 59.3 meqrl. and rain
Ž s s 8.6, 8.0 and 2.7 meqrl. water were significant different at the 99% probability
level by F-test. The smallest pH value for cloud water was 3.61 and that for rain water
was 4.39 in Akita, 4.44 in Onuma and 5.01 in the mountainside of Mt. Mokkodake. The
x and wnss-SO42y x of the rain water samples, at Mt.
arithmetic average of wNOy
3
Mokkodake, was 6.2 and 11.2 meqrl, while that of the cloud water samples was 44.3
and 99.3 meqrl, respectively. That is to say, the cloud water was significantly more
acidic than the rain water in Akita City, Onuma and the mountainside of Mt. Mokkodake as well as for the sample in 1997 ŽOgawa et al., 1999a,b..
Instead of the ion concentration in each sample of cloud event, the absolute
equivalent of ion in cloud droplets Žthe product of the concentration and the droplet
volume calculated from the mean volume diameter, D . was used in our factor analysis,
because the absolute loading amount of pollutants in the droplet will contribute to the
scavenging mechanism. The ion concentration in the cloud water which was collected
using the passive fog sampler, can be regarded as a mean concentration of droplets. One
can also recognize the reason of using the absolute equivalent by the data which in our
previous work ŽOgawa et al. 1999a., the slope of the log–log-plots of the total ion
concentration versus the droplet size was near minus three. This result shows that the
cloud droplets will grow only by diffusion process without uptaking the ion component
after the nucleation scavenging. Since the droplet size of eight samples in all the samples
Ž n s 64. could not be measured during the cloud events, these samples were omitted
from the factor analysis. In the factor analysis, the data only in westerly wind direction
Žfrom the Sea of Japan. Ž n s 49. Žbecause the sample in easterly wind is only seven. and
the chemical data whose ion-balances Žthe ratio of the sum of equivalents of anions to
that of cations. are from 1.20 to 0.833 Ž1r1.2. are used Žfinally, n s 37, D s 8.8–35.5
mm, pH s 3.61–7.18.. The ‘‘non-negative constrained’’ needs the factor analysis because the ion concentration should not be negative. However, it is omitted only for Hq,
N. Ogawa et al.r Atmospheric Research 54 (2000) 279–283
281
and in the case of negative value, the value means OHy. The ‘‘oblique rotational’’
means that each factor is not orthogonal as a mathematical vector. We used the method
which referred to the ion balance Ž1.2 y Ž1r1.2.. in each factor in order to decide the
number of factors ŽOzeki et al., 1995, 1997; Ogawa et al., 1998b.. We analyzed with
good ion balances in the case that the number of factors was from one to four. However,
Fig. 1. Chemical compositions of three pollutants Ža. and their contributions Žvs. date Žb. and vs. the drop size
Žc.. obtained by the factor analysis.
282
N. Ogawa et al.r Atmospheric Research 54 (2000) 279–283
the fourth factor in the case of four factors consisted of NH 4 OH together with NaCl.
The combination of ionic substances is unreasonable and unrealistic in chemical and
meteorological senses. Therefore, we chose three as the number of factors.
Fig. 1 shows the chemical compositions of their pollutants and their contribution. As
a total, the three factors contribute 69.1% to the ionic pollutants contained in all the
cloud water samples. Fig. 1a shows the chemical compositions of three pollutants. The
factor A mainly consists of ŽNH 4 . 2 SO4 and H 2 SO4 . The factor B consists of sea-salts
with H 2 SO4 and HNO 3 . The factor C is of NH 4 NO 3 . These salts were well-known as
the composition of the cloud condensation nuclei ŽCCN. Že.g., Pruppacher and Klett,
1997.. There is no pollutant Žthe factor. which contains mainly Ca2q ion with OHy,
comparing the previous results of the factor analysis for the precipitation in Akita City,
Japan ŽOzeki et al, 1997; Ogawa et al, 1998b.. That is, the cloud water at the
mountainside did not contain so much Ca2q unlike in the precipitation in the city site.
The contribution of the factors A, B and C is 30.8%, 23.6% and 14.7% Žtotal: 69.1%.,
respectively. This result shows that the CCN in the season of June to September would
be mainly ŽNH 4 . 2 SO4 and H 2 SO4 . Figure 1b shows plots of the contribution of each
pollutant to each cloud event versus date. The pollutants A and C have high contribution
in July. Plentiful rain Žespecially, much rain and cloudrfog at the mountainside. is
produced by a stationary front ŽBaiu front. in the Japanese rainy season from June to
July Žespecially, in Akita in July.. In July, therefore, the CCN would be mainly
ŽNH 4 . 2 SO4 , H 2 SO4 andror NH 4 NO 3 . However, pollutant B contributes strongly in
September. We also have plentiful rain produced by a stationary front ŽAkisame front. in
another Japanese rainy season in September. The CCN would be mainly sea-salt because
sea-salt was transported to Akita and the mountainside with the westerly wind from the
Sea of Japan, which began to become strong from September in Akita Prefecture
ŽOgawa et al., 1998a,b.. Fig. 1c shows plots of the contribution of each pollutant to each
cloud event versus the droplet size. The factor A of ŽNH 4 . 2 SO4 and H 2 SO4 has high
contribution in the range of small droplet size, while the factor B of sea-salt is high in
the larger size range Ž D s 20–25 mm.. The factor C of NH 4 NO 3 is high in the middle
size range between the factor A and B. These results are in agreement with the
well-known description of the large CCN, such as the aerosol of NaCl, which results in
the large droplet, and the small CCN, such as ŽNH 4 . 2 SO4 , which results in the small
droplet Že.g., Pruppacher and Klett, 1997.. We found in this work that our factor
analysis gave the quantitative explanation in the seasonal change and in the droplet size
change for cloudrfog water chemistry.
References
Hosono, T., Okochi, H., Igawa, M., 1994. Fogwater chemistry at a mountainside in Japan. Bull. Chem. Soc.
Jpn. 67, 368–374.
Ogawa, N., Adzuhata, T., Kajikawa, M., 1998a. Chemical characterization of acid snowfall in the coast and
inland areas of Akita Prefecture in Japan. Seppyo 60 Ž2., 143–156.
Ogawa, N., Kikuchi, R., Goto, H., Kajikawa, M., Ozeki, T., 1998b. Evaluation of sea-salt origin pollutants in
precipitation at Akita using constrained oblique rotational factor analysis. Bunseki Kagaku 47 Ž8.,
503–511, Žin Japanese..
N. Ogawa et al.r Atmospheric Research 54 (2000) 279–283
283
Ogawa, N., Kikuchi, R., Okamura, T., Adzuhata, T., Kajikawa, M., Ozeki, T., 1999a. Cloud droplet size
dependence of the concentrations of various ions in cloud water at a mountain ridge in northern Japan.
Atmos. Res. 51, 77–80.
Ogawa, N., Kikuchi, R., Okamura, T., Kajikawa, M., Adzuhata, T., Iwata, Y., Ozeki, T., 1999b. Chemical
characterization of acid fog and rain of Akita in northern Japan. Int. J. Soc. Mat. Eng. Resour. 7 Ž2.,
282–295.
Okita, T., 1961. Size distribution of large droplets in precipitating clouds. Tellus 13, 509–521.
Ozeki, T., Koide, K., Kimoto, T., 1995. Evaluation of sources of acidity in rainwater using a constrained
oblique rotational factor analysis. Environ. Sci. Technol. 29, 1638–1645.
Ozeki, T., Koide, K., Ogawa, N., Adzuhata, T., Kajikawa, M., Kimoto, T., 1997. Numerical evaluation of
contributions of pollutant sources extracted by constrained oblique rotational factor analysis for precipitation data. Extraction of features of precipitations at Hyogo and Akita areas. Anal. Sci. 13, 169–176.
Pruppacher, H.R., Klett, J.D., 1997. In: Microphysics of clouds and precipitation. Kluwer Academic
Publishers, pp. 700–791, Chap. 17.
Waldman, J.M., Munger, J.W., Jacob, D.J., Flagan, R.C., Morgan, J.J., Hoffmann, M.R., 1982. Chemical
composition of acid fog. Science 218, 677–680.
www.elsevier.comrlocateratmos
Letter
Evaluation of ionic pollutants in cloud droplets at a
mountain ridge in northern Japan using constrained
oblique rotational factor analysis
Nobuaki Ogawa a,) , Ryoei Kikuchi a , Tomoko Okamura a ,
Junko Inotsume a , Tetsuya Adzuhata a , Toru Ozeki b,
Masahiro Kajikawa a
a
Faculty of Engineering and Resource Science, Akita UniÕersity, Tegata Gakuen-cho, Akita, 010-8502, Japan
b
Hyogo UniÕersity of Teacher Education, Yashiro-cho, Kato-gun, Hyogo 673-1494, Japan
Received 12 January 2000; received in revised form 6 April 2000; accepted 6 April 2000
The scavenging of aerosol particles by precipitation and fogrcloud plays an important role in the distribution and concentration of pollutants in the atmosphere. Our
research group has recently studied the acid precipitation in Hyogo and Akita Prefectures in Japan, combining chemical analysis of ions and analysis of meteorological
conditions, and has analyzed the ionic pollutants Žsalts. by factor analysis ŽOgawa et al.,
1998a,b, 1999a,b; Ozeki et al., 1995, 1997.. In general, it is known that fogrcloud water
is significantly more acidic and has higher concentrations of chemical components than
rain water Že.g., Waldman et al., 1982, Hosono et al., 1994, Ogawa et al., 1999a,b.. But
the mechanism of uptake of ion components into cloud droplets, especially for the
difference between ions, is not completely understood. In our previous works ŽOgawa et
al., 1999a,b., cloud water and rain water samples were collected at the Hachimantai
mountain range in Akita Prefecture in northern Japan to obtain information on the
mechanism of uptake of ion components into cloud droplets. We obtained the information about relationship among ion concentrations in the cloud water and droplet size
ŽOgawa et al., 1999a,b..
In this work, we tried to analyze the seasonal change of ionic pollutants in cloud
water due to a variation of mesoscale precipitation system and their dependence upon
the cloud droplet size using constrained oblique rotational factor analysis, which has
)
Corresponding author. Fax: q81-18-889-2601.
E-mail address: [email protected] ŽN. Ogawa..
0169-8095r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 1 6 9 - 8 0 9 5 Ž 0 0 . 0 0 0 5 0 - 8
280
N. Ogawa et al.r Atmospheric Research 54 (2000) 279–283
been developed to analyze quantitatively ionic pollutants in precipitation by our research
group ŽOgawa et al., 1998b; Ozeki et al., 1995, 1997..
Cloud water samples were collected along the mountainside Ž39856X N, 140851X E,
1465 m a.s.l.. of Mt. Mokkodake Ž1578 m, a.s.l.., a mountain ridge in the Hachimantai
range, while recording wind direction and temperature, using the passive fog sampler
ŽModel FWP-500, Usui Kogyo Kenkyusho. during the period from June to September
1998 ŽOgawa et al., 1999a,b.. Rain water samples were also collected at Akita City
ŽAkita University. Ž39843X N, 140808X E, 10 m a.s.l.., at Onuma Ž39859X N, 140848X E, 960
m a.s.l.. in the Hachimantai range and at the mountainside of Mt. Mokkodake with a
bulk sampler ŽOgawa et al., 1998a. during the same periods. The concentrations of
various ions in the cloud and rain water were analyzed by the method mentioned
elsewhere ŽOgawa et al., 1998a, 1999a,b.. The size of the cloud droplets was estimated
by the impaction of drops on oil-coated glass slides ŽOkita, 1961.. The cloud base of
stratocumulusrnimbostratus was 1100–1350 m a.s.l. during the period of cloud water
sampling.
The arithmetic average of the pH of the cloud water samples was 4.43 Ž n s 64., and
that of the rain water samples collected in Akita City, Onuma and the mountainside of
Mt. Mokkodake was 4.97 Ž n s 46., 5.22 Ž n s 24. and 5.65 Ž n s 24., respectively. The
standard deviations Ž s . of the Hq concentrations of cloud Ž s s 59.3 meqrl. and rain
Ž s s 8.6, 8.0 and 2.7 meqrl. water were significant different at the 99% probability
level by F-test. The smallest pH value for cloud water was 3.61 and that for rain water
was 4.39 in Akita, 4.44 in Onuma and 5.01 in the mountainside of Mt. Mokkodake. The
x and wnss-SO42y x of the rain water samples, at Mt.
arithmetic average of wNOy
3
Mokkodake, was 6.2 and 11.2 meqrl, while that of the cloud water samples was 44.3
and 99.3 meqrl, respectively. That is to say, the cloud water was significantly more
acidic than the rain water in Akita City, Onuma and the mountainside of Mt. Mokkodake as well as for the sample in 1997 ŽOgawa et al., 1999a,b..
Instead of the ion concentration in each sample of cloud event, the absolute
equivalent of ion in cloud droplets Žthe product of the concentration and the droplet
volume calculated from the mean volume diameter, D . was used in our factor analysis,
because the absolute loading amount of pollutants in the droplet will contribute to the
scavenging mechanism. The ion concentration in the cloud water which was collected
using the passive fog sampler, can be regarded as a mean concentration of droplets. One
can also recognize the reason of using the absolute equivalent by the data which in our
previous work ŽOgawa et al. 1999a., the slope of the log–log-plots of the total ion
concentration versus the droplet size was near minus three. This result shows that the
cloud droplets will grow only by diffusion process without uptaking the ion component
after the nucleation scavenging. Since the droplet size of eight samples in all the samples
Ž n s 64. could not be measured during the cloud events, these samples were omitted
from the factor analysis. In the factor analysis, the data only in westerly wind direction
Žfrom the Sea of Japan. Ž n s 49. Žbecause the sample in easterly wind is only seven. and
the chemical data whose ion-balances Žthe ratio of the sum of equivalents of anions to
that of cations. are from 1.20 to 0.833 Ž1r1.2. are used Žfinally, n s 37, D s 8.8–35.5
mm, pH s 3.61–7.18.. The ‘‘non-negative constrained’’ needs the factor analysis because the ion concentration should not be negative. However, it is omitted only for Hq,
N. Ogawa et al.r Atmospheric Research 54 (2000) 279–283
281
and in the case of negative value, the value means OHy. The ‘‘oblique rotational’’
means that each factor is not orthogonal as a mathematical vector. We used the method
which referred to the ion balance Ž1.2 y Ž1r1.2.. in each factor in order to decide the
number of factors ŽOzeki et al., 1995, 1997; Ogawa et al., 1998b.. We analyzed with
good ion balances in the case that the number of factors was from one to four. However,
Fig. 1. Chemical compositions of three pollutants Ža. and their contributions Žvs. date Žb. and vs. the drop size
Žc.. obtained by the factor analysis.
282
N. Ogawa et al.r Atmospheric Research 54 (2000) 279–283
the fourth factor in the case of four factors consisted of NH 4 OH together with NaCl.
The combination of ionic substances is unreasonable and unrealistic in chemical and
meteorological senses. Therefore, we chose three as the number of factors.
Fig. 1 shows the chemical compositions of their pollutants and their contribution. As
a total, the three factors contribute 69.1% to the ionic pollutants contained in all the
cloud water samples. Fig. 1a shows the chemical compositions of three pollutants. The
factor A mainly consists of ŽNH 4 . 2 SO4 and H 2 SO4 . The factor B consists of sea-salts
with H 2 SO4 and HNO 3 . The factor C is of NH 4 NO 3 . These salts were well-known as
the composition of the cloud condensation nuclei ŽCCN. Že.g., Pruppacher and Klett,
1997.. There is no pollutant Žthe factor. which contains mainly Ca2q ion with OHy,
comparing the previous results of the factor analysis for the precipitation in Akita City,
Japan ŽOzeki et al, 1997; Ogawa et al, 1998b.. That is, the cloud water at the
mountainside did not contain so much Ca2q unlike in the precipitation in the city site.
The contribution of the factors A, B and C is 30.8%, 23.6% and 14.7% Žtotal: 69.1%.,
respectively. This result shows that the CCN in the season of June to September would
be mainly ŽNH 4 . 2 SO4 and H 2 SO4 . Figure 1b shows plots of the contribution of each
pollutant to each cloud event versus date. The pollutants A and C have high contribution
in July. Plentiful rain Žespecially, much rain and cloudrfog at the mountainside. is
produced by a stationary front ŽBaiu front. in the Japanese rainy season from June to
July Žespecially, in Akita in July.. In July, therefore, the CCN would be mainly
ŽNH 4 . 2 SO4 , H 2 SO4 andror NH 4 NO 3 . However, pollutant B contributes strongly in
September. We also have plentiful rain produced by a stationary front ŽAkisame front. in
another Japanese rainy season in September. The CCN would be mainly sea-salt because
sea-salt was transported to Akita and the mountainside with the westerly wind from the
Sea of Japan, which began to become strong from September in Akita Prefecture
ŽOgawa et al., 1998a,b.. Fig. 1c shows plots of the contribution of each pollutant to each
cloud event versus the droplet size. The factor A of ŽNH 4 . 2 SO4 and H 2 SO4 has high
contribution in the range of small droplet size, while the factor B of sea-salt is high in
the larger size range Ž D s 20–25 mm.. The factor C of NH 4 NO 3 is high in the middle
size range between the factor A and B. These results are in agreement with the
well-known description of the large CCN, such as the aerosol of NaCl, which results in
the large droplet, and the small CCN, such as ŽNH 4 . 2 SO4 , which results in the small
droplet Že.g., Pruppacher and Klett, 1997.. We found in this work that our factor
analysis gave the quantitative explanation in the seasonal change and in the droplet size
change for cloudrfog water chemistry.
References
Hosono, T., Okochi, H., Igawa, M., 1994. Fogwater chemistry at a mountainside in Japan. Bull. Chem. Soc.
Jpn. 67, 368–374.
Ogawa, N., Adzuhata, T., Kajikawa, M., 1998a. Chemical characterization of acid snowfall in the coast and
inland areas of Akita Prefecture in Japan. Seppyo 60 Ž2., 143–156.
Ogawa, N., Kikuchi, R., Goto, H., Kajikawa, M., Ozeki, T., 1998b. Evaluation of sea-salt origin pollutants in
precipitation at Akita using constrained oblique rotational factor analysis. Bunseki Kagaku 47 Ž8.,
503–511, Žin Japanese..
N. Ogawa et al.r Atmospheric Research 54 (2000) 279–283
283
Ogawa, N., Kikuchi, R., Okamura, T., Adzuhata, T., Kajikawa, M., Ozeki, T., 1999a. Cloud droplet size
dependence of the concentrations of various ions in cloud water at a mountain ridge in northern Japan.
Atmos. Res. 51, 77–80.
Ogawa, N., Kikuchi, R., Okamura, T., Kajikawa, M., Adzuhata, T., Iwata, Y., Ozeki, T., 1999b. Chemical
characterization of acid fog and rain of Akita in northern Japan. Int. J. Soc. Mat. Eng. Resour. 7 Ž2.,
282–295.
Okita, T., 1961. Size distribution of large droplets in precipitating clouds. Tellus 13, 509–521.
Ozeki, T., Koide, K., Kimoto, T., 1995. Evaluation of sources of acidity in rainwater using a constrained
oblique rotational factor analysis. Environ. Sci. Technol. 29, 1638–1645.
Ozeki, T., Koide, K., Ogawa, N., Adzuhata, T., Kajikawa, M., Kimoto, T., 1997. Numerical evaluation of
contributions of pollutant sources extracted by constrained oblique rotational factor analysis for precipitation data. Extraction of features of precipitations at Hyogo and Akita areas. Anal. Sci. 13, 169–176.
Pruppacher, H.R., Klett, J.D., 1997. In: Microphysics of clouds and precipitation. Kluwer Academic
Publishers, pp. 700–791, Chap. 17.
Waldman, J.M., Munger, J.W., Jacob, D.J., Flagan, R.C., Morgan, J.J., Hoffmann, M.R., 1982. Chemical
composition of acid fog. Science 218, 677–680.