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Public Health Association: Washington, DC, 1976. (18) Dixon, W. T.; Brown, M. B. “Biomedical Computer Programs P-Series”;University of California Press: Berkley, CA, 1979. (19) Draper, N. R.; Smith, H. “Applied Regression Analysis”; Wiley: New York, 1981. (20) Hall, L. W., Jr.; Margrey, S. L.; Burton, D. T.; Graves, W. C. Arch. Environ. Contam. Toxicol., 1983, 12, 715. (21) Terpin, K. M.; Wyllie, M. L.; Holmstrom, E. R. Ichthyological Associates Inc., 1977, Bulletin No. 17. (22) Meldrim, J. W.; Gift, J. J.; Petrosky, B. R. Ichthyological Associates Inc., 1974, Bulletin No. 11. (23) Hall, L. W., Jr.; Margrey, S. L.; Graves, W. C.; Burton, D. T. In ”Water Chlorination: Environmental Impact and Health Effects”; Jolley, R. L.; Brungs, W. A.; Contruvo, J. A.; Cummings, R. B.; Mattice, J. S.; Jacobs, V. A., Eds.; Ann Arbor Science Publishers: Ann Arbor, MI, 1983; pp 983-991. (24) Helz, G. R.; HSU,R. Y. Limnol. Oceanogr. 1978,23, 858. (25) Gibson, C. I.; Tone, F. C.; Wilkinson, P.; Blaylock, J. W. Ozone: Sci. Eng. 1979, I, 47.
(26) Sprague, J. B.; Drury, D. E. In ”Advances in Water Pollution Research”;Jenkins, S. H., Ed.; Pergamon Press: Oxford, England, 1969; pp 169-179. (27) Giattina, J. D.; Cherry, D. S.; Cairns, J., Jr.; Larrick, S. R. Trans. Am. Fish. SOC.1981,110,526. (28) Cairns, J., Jr.; Cherry, D. S.; Giattina, J. D. In “Energy and Ecological Modelling”; Mitsch, W. J.; Bosserman, R. W.; Klopatek, J. M., Eds.; Elsevier: Amsterdam, Netherlands, 1982; pp 207-215. (29) Hose, J. E.; King, T. D.; Zerba, K. E.; Stoffel, R. S.; Stephens, J. S., Jr.; Dickson, J. A. In “Water Chlorination: Environmental Impact and Health Effects”; Jolley, R. L.; Brungs, W. A.; Contruvo, J. A.; Cumming, R. B.; Mattice, J. S.; Jacobs, V. A,, Eds.; Ann Arbor Science Publishers: Ann Arbor, MI, 1983; pp 967-982. (30) Cherry, D. S.; Cairns, J. Water Res. 1982, 16, 263.
Received for review July 1I, 1983. Revised manuscript received December 27,1983. Accepted February 1,1984. This work was supported by the Maryland Power Plant Siting Program (Contract 83-81 -04).
NOTES Decay Rates of Nitrogen Oxides in a Typical Japanese Living Room Shin’ichi Yamanaka Kyoto City Institute of Public Health, 1-2, Higashitakadacho, Mibu, Nakagyoku, Kyoto 604, Japan
Decay process of indoor-originated NOz and NO was surveyed in detail in a typical Japanese living room with a chemiluminescent autoanalyzer. It was demonstrated that the decay process of NOz, being considered to comprise homogeneous and heterogeneous processes as well as air exchange, follows approximately first-order kinetics. Each contribution was determined tentatively from the CO decay rate and the variation of the NOz decay rate accompanying change of relative humidity (RH) or interior surface property. Under low RH (43.5-50%), the sink rate of NOz was 0.99 f 0.19 h-l (air change) regardless of interior surface property. However, it increased in proportion to RH above 50% (-72.5%), depending on the interior surface property, too. The surface effect itself appeared to be dependent on RH. The parameters for the simple calculation of indoor NOz level were presented. Introduction
Recent works showed that individual exposure to NO2 is considerably attributed to indoor NOz since most people spend so much of their time indoors and NOz originates indoors as well as outdoors ( I , 2). Many investigations have been undertaken on indoor NOz,which involve the indoor-outdoor concentration ratio without any indoor NOz source and comparison of its level in homes with different types of heating or cooking appliances (3-8). Considering the adverse effect of low level NOz to a human being, it is essential to anticipate a probable NOz level in a room with some source by a simple calculation. It may be helpful also in the design of dwellings and selection or location of heating or cooking appliances. Although the 566
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emission data for several domestic appliances have been presented (9),such calculation has still been impossible since the decay process of NOz has remained to be elucidated. NOz is rather reactive and can be removed indoors through a process other than ventilation. The overall decay rate of NOz had been determined in several previous works (IO), and about the indoor decay of O3some comprehensive investigations have been carried out (11-13). The purpose of this study is to determine the dependency of the decay rate on relative humidity and interior surface property as well as air exchange separately in a typical Japanese living room and to approach a prediction method of indoor NOz level by a simple calculation. For in the environment without any other reactive pollutants like ordinary homes, relative humidity is considered to be a main factor in homogeneous gas-phase reaction of NOz; another process contributing to the decay of NOz may proceed on the interior surface. Materials and Methods Characterization of Test Room. A typical Japanese living room generally consists of floor mats, i.e., tatami in Japanese, paper slide doors, i.e., fusuma and/or shoji, clay
walls and a wood board ceiling. With respect to the interior surface property, little variation is found among the Japanese living rooms compared with that among the western styles which have a wide variety of surfaces such as carpet, curtains, clothed walls, painted boards, etc. The room studied here had 9.8 mz of floor mats (six pieces), 13.6 mz of clay wall, 12.9 mz of paper slide doors, and 10.1 mz of wood board ceiling, in all 46.4 mz of apparent surface area and also 23.4 m3 of air volume. Since there was almost
0013-936X/84/0918-0566$01.50/0
0 1984 American Chemical Society
no other pollution source, the indoor level of other reactive pollutants such as O3 and SO2may be extremely low. Indoor NO2Source and Running. A gas-fired radiant or a kerosene-fired convective type unvented heater was used as a source of NO2, and they also emitted NO and CO together. The former has 6.9 MJ/h fuel consumption rate, and the latter has 7.4 MJ/h. One run took 3 h: for the first 70 min the heater was operating, and for the remainder of the time the heater was turned off with all the doors and windows shut. During that time, NO2,NO, and CO concentrations, room temperature, and relative humidity (RH) were automatically recorded while a fan was operated at one corner of the room to mix the air. High RH (-60%) was achieved by a certain amount of hot water in a plate on an electric heater at the center of the room. In an other case, RH naturally varied according to meteorological condition, Le., lower in clear days and higher in cloudy or rainy days. Air samples were introduced to the instruments through Teflon tubings from a point at 1.3-m height. Modification of Interior Surface. It is presumable that the smoother and chemically stabler is the surface, to the less extent NO2 removal on it may occur. In this study, the interior surface was covered with polyethylene film (0.3-mm thickness) in part or completely to alter the property with respect to NO2 removal, in the preliminary experiment, polyethylene (PE) was found to be useful for this purpose. Infiltration rate was always monitored with the decay rate of inert gas, CO. In some runs, a carpet made of acrylic fiber was used to cover the floor mats. Analytical Instruments. A chemiluminescent NO, analyzer equipped with a recorder, ACL-14D (Yanagimoto Mfg. Co. Ltd.), which could record NO2, NO, and NO, (NO2+ NO), was used; the efficiency of NO2cunverter had been confiied to be more than 95% in the inspection just before use. An electrochemical CO analyzer equipped with the filter to eliminate interference, “Ecolyzer Model 2600” (Energetics Science Co. Ltd.), and a recorder, R-102 (Rikadenki Kogyo Co. Ltd.), were also used. They were calibrated once a day with 92 ppm of NO and 39.2 ppm of CO standard gas (Seitetsu Kagaku Kogyo Co. Ltd.), respectively. The room temperature and RH recorded with a thermohygrograph (Isuzu Seisakusho Co. Ltd.).
Results and Discussion NO2Decay Rate in Polyethylene Bag. A totalof 0.04 ppm of NO2 in dried N2 was packed into a P E bag (150 L volume, 1.58 m2 of inner surface area), and the decay of NO2 was followed regularly. Prior to use, this bag was washed out with dried Np In order to minimize penetration or diffusion of NO2 out of the bag and the homogeneous gas-phase reaction, the concentration in dried N2 comparable to the outer level was preferred, being stored in a dark room. NO2in this bag decayed only slightly (5%) after 2 h. Consequently, it was found that for about 1 or 2 h the heterogeneous reaction of NO2 on P E film can be neglected. Hence, if the interior surface is covered with PE film completely, the decay attributable to it may be considered to be minimum in the room concerned. Variation Pattern of NO2, NO,and CO Concentrations. The typical variation patterns of NO2,NO, and CO concentrations in one run with a gas-fired radiant type unvented heater are shown in Figure 1. NO2concentration continued to increase, reaching the peak level which is a steady state, while NO concentration initially rather decreased slightly and then exhibited little variation. NO did not appear to be oxidized in air as described later but appeared to be oxidized slightly through the flame of the
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