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Seasonal variation of atmospheric ammonia and particulate ammonium concentrations in the urban atmosphere of yokohama over a 5-year period
oooc6981/88 S3.oo+O.M
Atmospheric Environment Vol.22,No. 11.pp.2621-2623, 1988. Printed in Great Britain.
Pergamon b
plc
SEASONAL VARIATION OF ATMOSPHERIC AMMONIA AND PARTICULATE AMMONIUM CONCENTRATIONS IN THE URBAN ATMOSPHERE OF YOKOHAMA OVER A 5-YEAR PERIOD N. YAMAMOTO, N. KABEYA, M. ONODERA, S. TAKAHAHI, Y. KOMORI, E. NAKAZUKA
and
T. SHIRAI Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kouhoku-ku, Yokohama 223, Japan (First received 25 January 1988 and receivedfor publication 7 April 1988) Abstract-Measurements of ammonia and particulate ammonium were made in the daytime (1200-1500) at a urban site in Yokohama during the 5-year period, 1982-1986. Diurnal NH, concentrations showed a distinct seasonal trend with a maximum in summer. The diurnal monthly average concentrations were above 10 ppb during the late spring and summer months, while the concentrations during the winter months were between 1 and 5 ppb. The seasonal variation was found to be very similar to that of the average air temperature and showed a periodic pattern over 1 year. A good correlation was observed between diurnal NH, concentrations and average air temperatures during the 5-year period. The annual mean concentrations were in the range of 6.6-7.6 ppb with only a minor deviation. The diurnal monthly average concentrations of particulate NHf were between 1 and 4 pg m - 3 and no significant seasonal variations were seen. As a short-term study, simultaneous measurements of NH,, HNO, and particulate NO; were made. The diurnal mean concentrations of NH, and HNO, were 7.6and 0.8 ppb, respectively. The concentration of particulate NO; ranged from 0.3 to 6 pgm -3. Both HNO, and particulate NO; concentrations were relatively low and constant. Thus, NH, and HNO, levels did not agree with the concentrations predicted from the NH,NO, equilibrium constant. Key word index: Atmospheric measurement, ammonia, particulate ammonium, regression analysis, nitric acid, particulate nitrate, ammonium nitrate equilibrium.
INTRODUCHON
Ammonia is the only common alkaline gas in the atmosphere and it plays a major part in neutralizing H,SO, and HNO,. Important sources of atmospheric NH, in Europe are considered to be livestock wastes, fertilizers and some industrial activities (Buijsman et al., 1987). Particulate NH: is formed as a reaction product of NH,, acid gases and aerosols. NH, and particulate NH: are important atmospheric components of the acidic deposition processes. Long-term investigation of the concentrations of NH, and particulate NH: is necessary to understand the behavior of atmospheric NH,. In this study measurements were carried out over 5 years. Seasonal and annual variations were examined. Among particulate NH: salts, the dissociation of NH,NO, is very sensitive to temperature changes (Stelson et al., 1979; Appel et al.; 1980; Hildemann et al., 1984), and in this study, simultaneous measurements of NH,, HNO, and particulate NH: were made. Seasonal variations were examined and the results were compared to the NH,NO, equilibrium constant. EXPERIMENTAL
Measurement location and conditions Samplings were made at a site, 14 m above the ground level, at Keio University which is located at the northwest part of Yokohama, about 10 km from Tokyo Bay. Measurements of NH, and particulate NH: were made in the day time (12W1X83), 5 times a month between January 1982 and December 1986. As a short-term study, simultaneous meas-
seasonal variation,
urements of NH,, HNO, and particulate NO; were made between 1000 and 1500,5 timesa month between June 1984 and March 1985. Samplings and analytical methods NH, was collected in two bubblers, each containing 0.5% boric acid solution, with a Teflon pre-filter, at a flow rate of 2 Gmin- ’ for a 3 h period. The collection e&iency was over 90% with two bubblers for levels in the range of l-20 ppb. Measurements were made with a duplicate sampling system. Particulate NH: was simultaneously collected on a Teflon filter (Millipore FGLP, 40 mm, pore size 0.2 pm) at a flow rate of 17-19 dmin-’ and was extracted as NH: with 0.5% boric acid solution in an ultrasonic bath. Sampling solutions of NH, and particulate NHf were determined by the modified indophenol method using a 5 cm cell (Yamamoto et al., 1983).The detection limit for NH, was 0.5 ppb for a 3 h sampling period. The samplings of HNO, and particulate NH: were made using the dual filter method (Okita et al, 1976). For the first filter, a Teflon pre-filter (Millipore FGLP, 40 mm, pore size 0.2 pm) was used for the collection of particulate NH: and for the second filter, a NaCl-impregnated filter (Toyo, 51A, 5 cm) was used for the collection of HNO,. The pm.-filter and collection filter of HNO, were mounted in series. The collection efficiency of the NaCl-impregnated filter was 990% at a flow rate of 17.5 dmin-‘. HNO. collected on the filter and particulate NHf collected on the Teflon iilter were individually extracted with warm water in an ultrasonic bath for 20min. The aqueous extracts were individually determined as NHf by the NEDA method (Isobe et al., 1983).The
2621
2622
Short Communications
0
JMMJStdJMMJSNJMMJSNJMMJSNJMMJSN 1983 1982
1986
1985
I984
Month of the yeor Fig. 1. Seasonal variation in monthly average con~ntrations
of atmospheric ammonia in Yokohama from January 1982 to December 1986.
Table I. Annual average concentrations of atmospheric ammonia in Yokohama durina the 5-vear neriod (1982-1986) Numbers of Year
measurement
I982 1983 1984 1985 1986
60 61 58 S8 57
NH, concentration (ppb) Average Min. Max. 6.6 7.6 7.5 7.5 7.2
0.5 1.0 1.2 t.1 0.5
24.5 16.8 23.1 16.8 29.8
Average temp. (“C)
Linear corr. coeff. (I)*
19.2 18.5 18.6 18.5 18.5
0.76 0.80 0.80 0.76 0.59
* Linear regression: air temperature vs NH, concentrations.
detection limit of this measurement technique for HNO, was estimated to be 0.2 ppb for a 7 h sampling period. Although artificial errors for gaseous HNO, and NH, using the filter-based technique have been indicated (Ferns et ol., 1979; Mulawa et al., 1985), the HNO, concentrations (average 0.8 ppb) in this case were much lower than the NH, concentrations (average 7.6 ppb). Even if errors are present, they will barely influena: the results. RESULTS AND DiSCUSSION Measurement ofammonia and particulate ammonium concentrations
Thediumal monthly average NH, concentrations in Fig 1 show that the seasona variation was remarkably constant from year to year throughout the 5-year period. The seasonal variation curve was roughly parallel to that of the average air temperature and showed a periodic pattern over 1 year. The diurnal monthly average concentrations during the S-year period, shown in Fig. 2, appear to be closely related to average air temperatures measured during the same period. The NH, concentrations increased remarkably in the late spring, reaching over 10 ppb. The maximum concentrations appeared to occur during the high air temperatures in July, but were sIightIy reduced in August despite the ma~mum air temperature. Concentration deatascd staply with decreasing air temperature in the fall and stayed in the range of l-5 ppb during the winter months. The _ NH, ._ concentration . decreased rapidly in September, even t bough the air tfmpera-
Month Fig. 2. Monthly average concentrations of atmospheric ammonia and particulate ammonium in Yokohama during the 5-year period (1982-1986).
ture of September was almost the same as that of July. This may be due to the smaher NH, source in September. The annual mean ~n~ntrat~n and air temperature, given in Table 1, were in the range of 6.67.6 ppb and t8.5-19.2”C. respectively, with only minor deviations, even though higher k&s were observed duringthewintermontbs of VW-1986 and summer months of I!&+-1986. The good correiation between NH, concentrations and average air
2623
Short Communications -iE
-
. .
25
n
NH,
q HNO, 0
NOi
25
.
3 8
.
s i? g
.
-t -
. mwmtwe
Lo
20
f
20
P
0
I 5
IO
IS
20
Air temperature
25
30
ammonia
temperatures during the measurements was obtained by linear regression analysis. These results showed a constant level of source strength during the 5-year period. As shown in Fig. 3, the 294 data points measured during the 5-year period showed that the NH, concentration increased almost linearly with increasing air temperature. Although the seasonal pattern was similar to that of Cadle et al. (1982) which showed that NH, concentration increased in the late spring due to soil emission, parameters influencing NH, concentration in the atmosphere in addition to air temperature required further investigation. Simultaneously, particulate NH: concentrations were determined from June 1982 to December !986. The diurnal monthly average concentrations for the 5 years hardly changed over the 1 year period staying within the levels of OS-4 pgrn-‘, but some decreases were observed in the summer. This will be discussed in more detail. measurements
of HNO,,
Month of the year
PC)
Fig. 3. Relationship between atmospheric concentrations and air temperature.
Simultaneous NO;
ises
1984
35
NH,
and particulate
In order to investigate the effect of the dissociation of particulate NH,NO,, simultaneous measurements of gaseous NH,, HNO, and particulate NO; ivere performed! The diurnal monthly average concentrations of HNO,, NH, and particulate NO; during a lo-month period are shown in Fig. 4. The range of HNO, and particulate NO; levels were 0.2-2.6 ppb and 0.3-6.0 pgrnd3, respectively (concentrations averaged 0.8 ppb and 2 pg m-3, respectively). Both HNO, and NO; concentrations were relatively low and stable. In order to evaluate the effect of the equilibrium between NH,NO,, HNO, and NH,, the concentrations of gaseous HNO, and NH, were examined (Stelson et al., 1979). The levels of HNO, was generally below the values needed for saturation with respect to NH,NO, formation. Although some correlation between HNO, and NH, was observed during the lo-month period, the correlation was almost zero during the summer months (21 points). Thus, a negative correlation was observed between air temperature and particulate NH,NO, in this area. These facts may suggest the presence of another main source, independent of the particulate NH,NO,.
Fig. 4. Monthly average concentrations of atmospheric ammonia, nitric acid and particulate nitrate in Yokohama.
With our data, a very high correlation was obtained between In[NH,] and the reciprocal of air temperature (r =0.85). These facts also showed the presence of NH, source not originating from the dissociation of NH,NO,. REFERENCES
Appel B. R., Wail S. M., Tokiwa Y. and Haik M. (1980) Simultaneous nitric acid, particulate nitrate and acidity measurements in ambient air. Atmospheric Environment 14, 549-554.
Buijsman E., Maas H. F. M. and Asman W. A. H. (1987) Anthropogenic ammonia emissions in Europe.. Atmospheric Environment 21, 1009-1022. Cadle S. H., Countess R. J. and Kelly N. A. (1982) Nitroc acid and ammonia in urban and rural locations. Atmospheric Environment 16,2501-2506.
Ferm M. (1979) Method for determination of atmospheric ammonia. Atmospheric Enoironment. 13, 1385-1393. Hildemann M. L., Russell G. A. and Cass R. C. (1984) Ammonia and nitric acid cdncentrations in equilibrium with atmospheric aerosols. Experiment vs theory. Atmospheric Environment 18, 1737-1750. Isobe K., Akada H., Yanagisawa S., Inoue H. and Shirai T. (1983) Improved naphtylethylendiamine method for the determination of nitrogen oxides in flue gases. BUNSEKI KAGASKU. 32,425-429. Mulawa P. A. and Cadle S. H. (1985) A comparison of nitric acid and particulate nitrate measurements by the peneration and denuder difference method. Atmospheric Environment 19, 1317-1320. Okita T., Morimoto S., Izawa M. and Konno S. (1976) Measurement of gaseous and particulate nitrates in the atmosphere. Atmospheric Enuironment 10, 1085-1089. Stelson A. W., Friedlander S. K. and Seinfeld J. H. (1979) A note on the equilibrium relationship between ammonia and nitric acid and particulate ammonium nitrate. Atmospheric Environment 13, 369-371. Yamamoto N., Nakazuka E. and Shirai T. (1983) Determination of atmospheric ammonia by the indophenol method. Chem. Sot. Japan 1983, 12261230.
Atmospheric Environment Vol.22,No. 11.pp.2621-2623, 1988. Printed in Great Britain.
Pergamon b
plc
SEASONAL VARIATION OF ATMOSPHERIC AMMONIA AND PARTICULATE AMMONIUM CONCENTRATIONS IN THE URBAN ATMOSPHERE OF YOKOHAMA OVER A 5-YEAR PERIOD N. YAMAMOTO, N. KABEYA, M. ONODERA, S. TAKAHAHI, Y. KOMORI, E. NAKAZUKA
and
T. SHIRAI Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kouhoku-ku, Yokohama 223, Japan (First received 25 January 1988 and receivedfor publication 7 April 1988) Abstract-Measurements of ammonia and particulate ammonium were made in the daytime (1200-1500) at a urban site in Yokohama during the 5-year period, 1982-1986. Diurnal NH, concentrations showed a distinct seasonal trend with a maximum in summer. The diurnal monthly average concentrations were above 10 ppb during the late spring and summer months, while the concentrations during the winter months were between 1 and 5 ppb. The seasonal variation was found to be very similar to that of the average air temperature and showed a periodic pattern over 1 year. A good correlation was observed between diurnal NH, concentrations and average air temperatures during the 5-year period. The annual mean concentrations were in the range of 6.6-7.6 ppb with only a minor deviation. The diurnal monthly average concentrations of particulate NHf were between 1 and 4 pg m - 3 and no significant seasonal variations were seen. As a short-term study, simultaneous measurements of NH,, HNO, and particulate NO; were made. The diurnal mean concentrations of NH, and HNO, were 7.6and 0.8 ppb, respectively. The concentration of particulate NO; ranged from 0.3 to 6 pgm -3. Both HNO, and particulate NO; concentrations were relatively low and constant. Thus, NH, and HNO, levels did not agree with the concentrations predicted from the NH,NO, equilibrium constant. Key word index: Atmospheric measurement, ammonia, particulate ammonium, regression analysis, nitric acid, particulate nitrate, ammonium nitrate equilibrium.
INTRODUCHON
Ammonia is the only common alkaline gas in the atmosphere and it plays a major part in neutralizing H,SO, and HNO,. Important sources of atmospheric NH, in Europe are considered to be livestock wastes, fertilizers and some industrial activities (Buijsman et al., 1987). Particulate NH: is formed as a reaction product of NH,, acid gases and aerosols. NH, and particulate NH: are important atmospheric components of the acidic deposition processes. Long-term investigation of the concentrations of NH, and particulate NH: is necessary to understand the behavior of atmospheric NH,. In this study measurements were carried out over 5 years. Seasonal and annual variations were examined. Among particulate NH: salts, the dissociation of NH,NO, is very sensitive to temperature changes (Stelson et al., 1979; Appel et al.; 1980; Hildemann et al., 1984), and in this study, simultaneous measurements of NH,, HNO, and particulate NH: were made. Seasonal variations were examined and the results were compared to the NH,NO, equilibrium constant. EXPERIMENTAL
Measurement location and conditions Samplings were made at a site, 14 m above the ground level, at Keio University which is located at the northwest part of Yokohama, about 10 km from Tokyo Bay. Measurements of NH, and particulate NH: were made in the day time (12W1X83), 5 times a month between January 1982 and December 1986. As a short-term study, simultaneous meas-
seasonal variation,
urements of NH,, HNO, and particulate NO; were made between 1000 and 1500,5 timesa month between June 1984 and March 1985. Samplings and analytical methods NH, was collected in two bubblers, each containing 0.5% boric acid solution, with a Teflon pre-filter, at a flow rate of 2 Gmin- ’ for a 3 h period. The collection e&iency was over 90% with two bubblers for levels in the range of l-20 ppb. Measurements were made with a duplicate sampling system. Particulate NH: was simultaneously collected on a Teflon filter (Millipore FGLP, 40 mm, pore size 0.2 pm) at a flow rate of 17-19 dmin-’ and was extracted as NH: with 0.5% boric acid solution in an ultrasonic bath. Sampling solutions of NH, and particulate NHf were determined by the modified indophenol method using a 5 cm cell (Yamamoto et al., 1983).The detection limit for NH, was 0.5 ppb for a 3 h sampling period. The samplings of HNO, and particulate NH: were made using the dual filter method (Okita et al, 1976). For the first filter, a Teflon pre-filter (Millipore FGLP, 40 mm, pore size 0.2 pm) was used for the collection of particulate NH: and for the second filter, a NaCl-impregnated filter (Toyo, 51A, 5 cm) was used for the collection of HNO,. The pm.-filter and collection filter of HNO, were mounted in series. The collection efficiency of the NaCl-impregnated filter was 990% at a flow rate of 17.5 dmin-‘. HNO. collected on the filter and particulate NHf collected on the Teflon iilter were individually extracted with warm water in an ultrasonic bath for 20min. The aqueous extracts were individually determined as NHf by the NEDA method (Isobe et al., 1983).The
2621
2622
Short Communications
0
JMMJStdJMMJSNJMMJSNJMMJSNJMMJSN 1983 1982
1986
1985
I984
Month of the yeor Fig. 1. Seasonal variation in monthly average con~ntrations
of atmospheric ammonia in Yokohama from January 1982 to December 1986.
Table I. Annual average concentrations of atmospheric ammonia in Yokohama durina the 5-vear neriod (1982-1986) Numbers of Year
measurement
I982 1983 1984 1985 1986
60 61 58 S8 57
NH, concentration (ppb) Average Min. Max. 6.6 7.6 7.5 7.5 7.2
0.5 1.0 1.2 t.1 0.5
24.5 16.8 23.1 16.8 29.8
Average temp. (“C)
Linear corr. coeff. (I)*
19.2 18.5 18.6 18.5 18.5
0.76 0.80 0.80 0.76 0.59
* Linear regression: air temperature vs NH, concentrations.
detection limit of this measurement technique for HNO, was estimated to be 0.2 ppb for a 7 h sampling period. Although artificial errors for gaseous HNO, and NH, using the filter-based technique have been indicated (Ferns et ol., 1979; Mulawa et al., 1985), the HNO, concentrations (average 0.8 ppb) in this case were much lower than the NH, concentrations (average 7.6 ppb). Even if errors are present, they will barely influena: the results. RESULTS AND DiSCUSSION Measurement ofammonia and particulate ammonium concentrations
Thediumal monthly average NH, concentrations in Fig 1 show that the seasona variation was remarkably constant from year to year throughout the 5-year period. The seasonal variation curve was roughly parallel to that of the average air temperature and showed a periodic pattern over 1 year. The diurnal monthly average concentrations during the S-year period, shown in Fig. 2, appear to be closely related to average air temperatures measured during the same period. The NH, concentrations increased remarkably in the late spring, reaching over 10 ppb. The maximum concentrations appeared to occur during the high air temperatures in July, but were sIightIy reduced in August despite the ma~mum air temperature. Concentration deatascd staply with decreasing air temperature in the fall and stayed in the range of l-5 ppb during the winter months. The _ NH, ._ concentration . decreased rapidly in September, even t bough the air tfmpera-
Month Fig. 2. Monthly average concentrations of atmospheric ammonia and particulate ammonium in Yokohama during the 5-year period (1982-1986).
ture of September was almost the same as that of July. This may be due to the smaher NH, source in September. The annual mean ~n~ntrat~n and air temperature, given in Table 1, were in the range of 6.67.6 ppb and t8.5-19.2”C. respectively, with only minor deviations, even though higher k&s were observed duringthewintermontbs of VW-1986 and summer months of I!&+-1986. The good correiation between NH, concentrations and average air
2623
Short Communications -iE
-
. .
25
n
NH,
q HNO, 0
NOi
25
.
3 8
.
s i? g
.
-t -
. mwmtwe
Lo
20
f
20
P
0
I 5
IO
IS
20
Air temperature
25
30
ammonia
temperatures during the measurements was obtained by linear regression analysis. These results showed a constant level of source strength during the 5-year period. As shown in Fig. 3, the 294 data points measured during the 5-year period showed that the NH, concentration increased almost linearly with increasing air temperature. Although the seasonal pattern was similar to that of Cadle et al. (1982) which showed that NH, concentration increased in the late spring due to soil emission, parameters influencing NH, concentration in the atmosphere in addition to air temperature required further investigation. Simultaneously, particulate NH: concentrations were determined from June 1982 to December !986. The diurnal monthly average concentrations for the 5 years hardly changed over the 1 year period staying within the levels of OS-4 pgrn-‘, but some decreases were observed in the summer. This will be discussed in more detail. measurements
of HNO,,
Month of the year
PC)
Fig. 3. Relationship between atmospheric concentrations and air temperature.
Simultaneous NO;
ises
1984
35
NH,
and particulate
In order to investigate the effect of the dissociation of particulate NH,NO,, simultaneous measurements of gaseous NH,, HNO, and particulate NO; ivere performed! The diurnal monthly average concentrations of HNO,, NH, and particulate NO; during a lo-month period are shown in Fig. 4. The range of HNO, and particulate NO; levels were 0.2-2.6 ppb and 0.3-6.0 pgrnd3, respectively (concentrations averaged 0.8 ppb and 2 pg m-3, respectively). Both HNO, and NO; concentrations were relatively low and stable. In order to evaluate the effect of the equilibrium between NH,NO,, HNO, and NH,, the concentrations of gaseous HNO, and NH, were examined (Stelson et al., 1979). The levels of HNO, was generally below the values needed for saturation with respect to NH,NO, formation. Although some correlation between HNO, and NH, was observed during the lo-month period, the correlation was almost zero during the summer months (21 points). Thus, a negative correlation was observed between air temperature and particulate NH,NO, in this area. These facts may suggest the presence of another main source, independent of the particulate NH,NO,.
Fig. 4. Monthly average concentrations of atmospheric ammonia, nitric acid and particulate nitrate in Yokohama.
With our data, a very high correlation was obtained between In[NH,] and the reciprocal of air temperature (r =0.85). These facts also showed the presence of NH, source not originating from the dissociation of NH,NO,. REFERENCES
Appel B. R., Wail S. M., Tokiwa Y. and Haik M. (1980) Simultaneous nitric acid, particulate nitrate and acidity measurements in ambient air. Atmospheric Environment 14, 549-554.
Buijsman E., Maas H. F. M. and Asman W. A. H. (1987) Anthropogenic ammonia emissions in Europe.. Atmospheric Environment 21, 1009-1022. Cadle S. H., Countess R. J. and Kelly N. A. (1982) Nitroc acid and ammonia in urban and rural locations. Atmospheric Environment 16,2501-2506.
Ferm M. (1979) Method for determination of atmospheric ammonia. Atmospheric Enoironment. 13, 1385-1393. Hildemann M. L., Russell G. A. and Cass R. C. (1984) Ammonia and nitric acid cdncentrations in equilibrium with atmospheric aerosols. Experiment vs theory. Atmospheric Environment 18, 1737-1750. Isobe K., Akada H., Yanagisawa S., Inoue H. and Shirai T. (1983) Improved naphtylethylendiamine method for the determination of nitrogen oxides in flue gases. BUNSEKI KAGASKU. 32,425-429. Mulawa P. A. and Cadle S. H. (1985) A comparison of nitric acid and particulate nitrate measurements by the peneration and denuder difference method. Atmospheric Environment 19, 1317-1320. Okita T., Morimoto S., Izawa M. and Konno S. (1976) Measurement of gaseous and particulate nitrates in the atmosphere. Atmospheric Enuironment 10, 1085-1089. Stelson A. W., Friedlander S. K. and Seinfeld J. H. (1979) A note on the equilibrium relationship between ammonia and nitric acid and particulate ammonium nitrate. Atmospheric Environment 13, 369-371. Yamamoto N., Nakazuka E. and Shirai T. (1983) Determination of atmospheric ammonia by the indophenol method. Chem. Sot. Japan 1983, 12261230.