Journal of Environmental Quality 31:718-723 (2002)
© 2002 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
TECHNICAL REPORTS
Atmospheric Pollutants and Trace Gases
Air Pollution by Concrete Dust from the Great Hanshin Earthquake
Takao Gotoh*,a,
Takashi Nishimurab,
Minoru Nakatab,
Yuzuru Nakaguchib and
Keizo Hirakib
a Faculty of Engineering, Kobe Univ., Kobe, Japan
b Institution for Social Medicine, Yodogawa Workers' Welfare Association, Osaka, Japan
* Corresponding author (gotoh{at}kobe-u.ac.jp)
Received for publication May 22, 2000.
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ABSTRACT
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Air pollution in the areas affected by the Great Hanshin Earthquake (Hyogo, Japan) of 17 Jan. 1995 was quite serious. We performed three investigations of dust. In the first investigation, we measured the total suspended particulate (TSP) concentration in the greatly damaged areas, located around the Sannomiya Station where a few hundred thousand people walked by during the daytime of 3 February. The maximum concentration at five points reached 150 µg/m3. In the second investigation, eight samples, which were classified into three groups (concrete, mortar, and soil dusts) as sources, were analyzed elementally by X-ray fluorescence. The elements found in concrete dust (Ca and S) were similar to those found in mortar dust. These differed from those found in soil dust (Ti, Fe, and Zr). The elements found in soil dust were important from the viewpoint of heavy metal contamination. In the third investigation, the alkalinity of concrete dust was observed by dissolution. This solution was equivalent to pH 11 to 12 and electrical conductivity 20 to 30 µS/m. We suspect that the alkaline component in the dust from debris in all the devastated areas was approximately comparable with the alkaline solution by which the acid rain falling over the Hanshin district of Osaka Megalopolis in one year could be neutralized into water of pH 7.0.
Abbreviations: EC, electrical conductivity • JIS, Japanese Industrial Standard • JR, Japanese Railway • TSP, total suspended particulate • XRF, X-ray fluorescence
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INTRODUCTION
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THE HANSHIN URBAN AREA of Hyogo Prefecture, Japan was struck and destroyed by a tremendous earthquake at 0545 hours on 17 Jan. 1995. Seismometers recorded tremors of 6 to 7 on the Richter scale. More than 5500 people were killed, of whom more than 10% died from secondary damage (Gotoh, 1995). Environmental degradation contributed to this mortality. We investigated four causal phenomena. Our first investigation was of the conflagration following the earthquake (Gotoh, 1996a). Our second investigation was of the burning of debris in open fields from destroyed and demolished buildings (Gotoh, 1996b,c). Our third investigation was of the soil contamination due to liquefaction (Gotoh, 1997), and the fourth investigation was of dust from destroyed and demolished buildings and its alkalinity (Gotoh, 1999a). The results of these investigations are detailed in the above references.
After the Hanshin earthquake, many people in the devastated areas were exposed to air pollutants caused by burning chemical factories (and their products), liquefaction particles suspended in the air, damaged buildings being demolished, and gaseous industrial wastes and traffic congestion. Twenty-five percent of those who replied to the British Medical Research Council (BMRC)-type questionnaire complained about worsening health after the earthquake, and 67% of them complained about respiratory problems. The positive relationship between NO2 concentration and the number of people who complained about their worsening health after the earthquake was significant with a confidence of 95% (Gotoh, 1996a). These approximate investigations were continued each June for five years. The results indicated that the effects on children and older people were larger in the devastated area (Gotoh, 1999b). The relation between the earthquake disaster and health effect was reported in California (for the earthquake of 17 Oct. 1989) by Swislocki (1990). But the relation between the weakening of the environment after earthquake and the weakening of health was not clear until now.
This work emphasizes the fourth investigation of concrete dust due to the destruction and demolition of buildings detailed from the viewpoint of alkaline pollution in the devastated area.
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MATERIALS AND METHODS
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Measurement of Dust Concentration
Air pollution in the urban area where highways, high buildings, and houses were destroyed by the earthquake has not been investigated in detail until now, although the approximate extent of air pollution two weeks after the earthquake was investigated by the Japanese Environment Agency in 1995. From the air pollutant concentrations, which were measured at several air monitoring stations in the devastated areas, it was found that total suspended particulate (TSP) increased greatly in the heavily damaged areas. These values were more than 1.5 times the average TSP concentrations during the same period of the previous year at the same site (Japanese Environment Agency, 1995). And from the NO2 and SO2 concentrations in the same period, the above report presumed that the high TSP concentration was attributed to the destroyed or demolished buildings.
People living in or walking around these areas were exposed to the high TSP concentrations of the emitted dust. The total mass of destroyed or demolished buildings was estimated to be 20 Tg in the devastated areas (Hyogo Prefecture, 1997). This mass is equivalent to the total mass of general wastes dumped for 10 years in the Hanshin district.
Figure 1
shows the temporal increase of total number of demolished structures and structures demolished per month following the earthquake (Hyogo Prefecture, 1997). Some materials were burned in the vacant reclaimed land facing Osaka Bay, which increased rapidly during the three months following the earthquake (Gotoh, 1996c). About 80% of the total structural demolition occurred in the first six months after the earthquake.
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Fig. 1. Total number of demolished structures and structures demolished per month after the Hanshin earthquake.
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Figure 2
shows the local distribution of demolished structures (Hyogo Prefecture, 1997). This number was the largest in Chuoku-Ku, the heart of Kobe City. Many people in and around those zones were apparently exposed to high concentrations of dusts. We therefore measured the dust concentration at 15 points in the devastated areas on 3 Feb. 1995 with a laser dust monitor (Shibata [Tokyo, Japan] LD-1). This monitor is designed with an inlet that removes particle sizes greater than 10 µm. Simultaneously, the relation between this particle concentration and capsule NO2 concentration was observed to be linear in the devastated area (Gotoh, 1996b). Further, the relation between capsule TSP and capsule NO2 concentrations was also observed to be linear. The latter method was already stated as the improved triethanolamine (TEA) capsule method. This TSP method measured the scattered light of particles (blackness) collected on TEA filter paper that was exposed in the capsule for 24 h. A relationship has been established between the blackness and daily mean value of TSP concentration at 12 monitoring stations in Kobe City (Gotoh, 1996b). The TSP measured was suspected to be coarse particles, and it is suspected that the health effect of coarse particles is smaller than that of fine particles (Wilson, 1997).
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Fig. 2. Local distribution of the demolished structures within six months after the earthquake. Broken line is the barrier between cities; dotted line is the barrier between Ku zones.
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Analysis of Debris from Demolished Buildings
The lower graph of Fig. 1 shows the number of demolished structures per month. This number reached a maximum (about 25000/month) in May 1995, and 1 Tg of debris was carried out by truck from the devastated areas to the disposal sites (Hyogo Prefecture, 1997). The demolished structure materials were generally classified into two groups of incombustibles (concrete and mortar) and two groups of combustibles (wood and plastics). Among these, the amount of concrete was the largest. Particles of concrete dust may have been able to enter the human lung, because the particles seemed to be very small by viewpoint of blue scattered sunlight, and the dust dispersed far away.
Nakata (1995) classified the exhaust dust due to demolition into three building material groups (concrete, mortar, and soil) by means of Japanese Industrial Standards (JIS) A5000 and K104. The particles of these dusts were generally larger than 1 µm, and they differed generally from diesel exhaust particles (Sakamoto et al., 1993). The first group was concrete dust emitted by demolition of concrete buildings. The second group was mortar and cement dust from demolition of mortar houses. The third group was soil dust associated with demolition of wooden houses. This classification was analogous to structure materials of JIS A5000-6000. Nakata collected eight block samples (larger than 10 x 10 x 2 cm) of the above three groups at demolition sites in Fig. 2. We analyzed elementally the above eight samples representing dust sources in the devastated areas. The samples were first pulverized in an agate mortar and pestle. The pulverized samples were then passed through a sieve (mesh size = 0.0053 mm) according to JIS Z8801. The fine dust that passed through the sieve was analyzed elementally by X-ray fluorescence (XRF).
Table 1 shows the sampling sites (A–H) of demolition work and the types of structure materials. The locations of these sampling sites (A–H) are shown in Fig. 2. The XRF analyzer was a reflectance type (Rigaku [Tokyo, Japan] RIT6000). Aluminum could not be analyzed because the sample holder was made of aluminum. In this measurement, a sample of about 1 g was analyzed for 20 min by XRF. The elemental concentrations of the samples were expressed mainly by the k-
peak count of each element (Rigaku). Applying the concrete measured count value to the reference content of Portland cement allowed the exchange into elemental concentration from count number. The matrix effect was neglected because the samples analyzed would be homogenous for particle size.
pH and Conductivity Measurement of Concrete Dust
We previously observed the relation between the growth of a concrete icicle and the pH of acid rainwater (Gotoh, 1992). We found that the concrete icicle grew during the warm season when acid rain fell generally in the Hanshin district and that the water that dripped from the edge of the concrete icicle was an alkaline aqueous solution of pH 11 to 12. From this we surmised that the particles of concrete dust could be dissolved in water or that water vapor and alkaline water or alkaline mist would affect environmental or human health after the warm season. We therefore measured the pH and electrical conductivity (EC) of dispersed dust around the demolition work site. This survey was made by collecting the depositing concrete dust with a vinyl sheet for several minutes, dissolving about 10 mg of collected dust in about 10 mL of distilled water, and measuring a few drops of the solution with a pen-type pH meter and pen-type EC meter at points around the demolition work site.
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RESULTS
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Total Suspended Particulate Concentration around Sannomiya Station
Gotoh (1996b) pointed out quantitative and qualitative problems of the emitted dust after the Great Hanshin Earthquake. Because of that, we measured TSP concentration in the area around the Japanese Railway (JR) Sannomiya Station.
Figure 3
shows the five demolition work sites (A, B, C, D, and E) around JR Sannomiya Station and the measured results of TSP concentration. Each of these values is the average of three measurements. These five sites were located within a circular area with a radius of 250 m from JR Sannomiya Station. All of these demolition sites were higher than five stories. Because the demolition work was carried out above the ground, scattering dusts in various directions, the TSP concentration in the circular area increased rapidly after the demolition work, most of which was done all day. A few hundred thousand people had to walk by such demolition work sites every day for changing trains, and most of them were exposed to high concentrations of TSP due to the emitted dust. The TSP concentrations at the five points (a, b, c, d, and e) located in the above circular area were measured three times per minute with a laser dust monitor from 1400 to 1500 hours on 3 Feb. 1995. Point b, where the TSP concentration measured was highest (150 µg/m3), was located on the leeward side of demolished buildings A and B. In February, the main wind direction in the Hanshin district was from the west, and so the TSP concentration decreased rapidly in the easterly direction as shown in Fig. 3. But we suspected that the fine particles in the emitted dust drifted over to the eastern part of the Hanshin district. We measured simultaneously the TSP and NO2 concentrations in a larger area of the Hanshin district on 17 February by an improved triethanolamine (TEA) capsule method. Gotoh (1996b) examined these measurements.
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Fig. 3. Five demolition work sites (A, B, C, D, and E) around Japanese Railway Sannomiya Station, the sampling sites (a, b, c, d, and e), and the measured values of total suspended particulate (TSP) concentration.
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The relationship obtained between the capsule TSP and capsule NO2 concentrations differed for Nada-Ku, Higashinada-Ku, Ashiya City, Nishinomiya City, and Amagasaki City. The greater the damage of the devastated area, the higher the TSP concentration was for the same NO2 concentration. The ratio of TSP to NO2 reached a maximum in Nada-Ku and Higashinada-Ku. The next was Ashiya City, followed by Nishinomiya City and Amagasaki City. This result shows that the ranking of TSP concentrations is related to the number of the demolition work sites shown in Fig. 2.
Elemental Composition of Demolished Building Materials
It was made clear by Kasai (1994) that the dust composition emitted when the buildings were demolished differed slightly from site to site and by the method of demolition. However, in this study the methods were almost the same at the different sites and therefore the difference between the dust components due to demolition methods is negligible.
Each elemental XRF value was tabulated. The results showed the difference between the elemental concentrations in three concrete samples (A, B, and C).
We presumed that the medium concentration of three samples was nearly equal to the concentration of Portland cement. The elements that were applied to this method were Si, S, Ca, and Fe. The efficiencies of these elements (%/counts of XRF) were 0.0018 to 0.056, and the relation between the efficiency and atomic number could be expressed as a secondary equation formula. From this relation, the elemental content (%) could be estimated. Table 2 shows the estimated content (%) of elements analyzed in eight samples. First, titanium, iron, and zirconium were found in high concentrations in the soil samples in comparison with those in the concrete and mortar dusts. In contrast, calcium and sulfur were found in high concentrations in the concrete and mortar dusts. Only the concrete dust contained chlorine. Heavy metal concentrations were suspected to be due to the soil dust.
pH and Conductivity of Collected Dust
We measured the pH and electric conductivity (EC) values of the dust at five points around five demolition work sites, two of which were located around JR Sannomiya Station, two around JR Rokkomichi Station (Nada-Ku), and one located 1 km southwest of Sannomiya station on 16 Feb. 1995. The following results were obtained.
All the measured pH values of the dust collected at the five points exceeded 11.5 and all the measured EC values exceeded 20 µS/m. From these results, it was suspected that these areas were polluted by alkaline concrete dust resulting from the demolition of deserted buildings. In order to find the relation between the concrete dust and alkalinity, we measured the pH and EC values of aqueous solutions, prepared by dissolving about 10 mg of each the three concrete dust samples (A, B, and C) shown in Table 2 into 10 mL of distilled water.
Figure 4
shows the relationship between the pH and EC values of the three measured samples (A, B, and C) and of standard block samples (JIS R5000). The values are each the average of three measured values. It appears that the amplitude of EC values was related to the concentration of various elements, particularly alkaline metal and halogen elements, such as potassium and chlorine, as shown in Table 2. These results agreed well with the theory of dissolution of concrete materials (Czernin, 1964). In order to find the pH and EC values of standard concrete materials, we measured the pH and EC values of new concrete block, which was produced in June 1999 in a laboratory at Kobe University, and an old concrete block, which was produced in June 1985 in the same laboratory for a compression test and was kept in the same room for 14 yr. After pulverizing pieces of these blocks, the powder was passed through a sieve (0.053 mm), and about 10 mg was dissolved in 10 mL of distilled water for measurement with pen-type pH and EC meters. Three samples were taken from different parts of each block. As shown in Fig. 4, although the EC values of the three samples were similar to one another, the pH values were scattered but with a similar trend. It was suspected that a part of Ca(OH)2 in this block reacted with CO2 gas when the sample was warmed by pulverization. The pH values of the A, B, and C samples shown in Fig. 4 were analogous to those of the two blocks (pH = 11.6–12.6), but the EC values were all higher (EC = 20 µS/m). Therefore, in the greatly damaged areas, many people were exposed to high concentrations of suspended dust, which changed into alkaline solutions with high EC values by dissolution in water.
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Fig. 4. Relationship between the pH and electrical conductivity (EC) values of three samples measured (A, B, and C), and those of the standard block samples.
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DISCUSSION
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Estimation of Emitted Concrete Dust Mass
The total amount of the demolished building materials carried out from the devastated areas to disposal sites for 1.5 years after the earthquake was 20 Tg. About 70% of this mass was incombustibles such as concrete and mortar. A part of these materials was emitted into the air as suspended particulate materials. When the buildings collapsed because of the earthquake or were demolished later, a part of the building materials scattered over the devastated areas as dust, and when the materials were carried out from the devastated areas to disposal sites by truck, a part of these materials scattered again from the trucks, and a further part was emitted from the smokestacks of incineration plants. The amount of the demolished building materials that were emitted as dust in the devastated areas was suspected to be more than 0.1% of the total amount, or 20 Gg. If half of the above amount was assumed to be concrete dust, the emitted amount of concrete dust would be about 10 Gg.
Estimation of Alkaline Loading of the Environment
From the above results, 10 mg of concrete dust is equivalent to 10 mL of alkaline aqueous solution with a pH value of 11 to 12 and an EC value of several tens of µS/m. We estimated the amount of concrete dust that was emitted into the environment in the devastated areas to be about 10 Gg in the previous section. Therefore, the total amount of the alkaline load in the form of aqueous solution would be about 1 Tg. This alkaline load can be neutralized to water of pH 7.0 by the acid rain falling over the Hanshin district of Osaka Megalopolis in one year.
The yearly mean pH of rain that fell on Osaka Megalopolis in a recent year was about 5.0, and the yearly mean amount was 1500 mm. The alkalinity due to the emission of concrete dust into the atmosphere was equivalent to the alkaline amount that is neutralized yearly by acid rain that fell on the Hanshin district (70 km2) of Osaka Megalopolis. Furthermore, it is suspected from Fig. 1 that about 80% of the emitted concrete dust amount was emitted during five months prior to June 1995.
This trend accorded with the results of asbestos concentration in the general atmosphere (Terazono, 1999). The monthly mean of asbestos concentration reached a maximum (2.5 times normal) in June 1995 at the site around JR Sannomiya Station shown in Fig. 2 in the months between February 1995 and July 1996.
These results mean that the air pollution for a half-year after the earthquake was important to human health and environmental risk.
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CONCLUSION
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Dust pollution in the devastated areas after the Great Hanshin Earthquake was quite serious because about 3500 deserted structures were demolished and a part of the debris (12 Tg) was scattered over the devastated areas shown in Fig. 2 as dust particles. When the debris was carried out from the devastated areas for incineration, additional dust was emitted.
We measured the TSP concentration in the devastated areas with a laser dust monitor and analyzed the component elements of such dust. The following results were obtained. First, in the area around Sannomiya Station shown in Fig. 3, where the demolition of the deserted buildings was conducted simultaneously and in a relatively small area, the maximum value of TSP concentration reached 150 µg/m3. The average value at five points exceeded 100 µg/m3. The few hundreds of thousands of people who walked through the area were exposed to high concentrations of dust during the demolition work. Second, the incombustibles among the deserted building materials were classified into three groups: concrete, mortar, and soil. Eight samples were analyzed elementally by an X-ray fluorescence analyzer. The elemental concentrations of Ti, Fe, and Zr were higher in the soil, and the concentrations of Ca and S were higher in concrete and mortar. Further, the element Cl was seen only in the concrete dust. In general, the soil dust contained heavy metals such as Fe and Zr in high concentrations. Third, we observed that 10 mg of the concrete dust would become 10 mL of alkaline aqueous solution of pH 11 to 12 by dissolving in 10 mL of distilled water, and the EC values were greater than 20 µS/m. From these results, it was suspected that the devastated area was polluted by an alkaline solution of concrete dust particles. In our estimation, the alkaline load, which scattered over the devastated area, would represent a few teragrams of alkaline water with a pH value of 11 to 12 and an EC value of more than 20 µS/m.
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REFERENCES
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- Czernin, W. 1964. Zementchemie fur Bauingeneure. Bauvelag Bmbh, Wiesbaden-Berlin, Germany.
- Gotoh, T. 1992. The survey of concrete icicle on the scholar houses of Kobe University and examination from a viewpoint of pollution (In Japanese). J. Jpn. Soc. Safety Eng. 31:22–27.
- Gotoh, T. 1995. Report of urban construction damage and civic life damage destroyed by right under type earthquake of the 6–7 degree on the seismic scale (In Japanese). J. Jpn. Soc. Safety Eng. 34:183–185.
- Gotoh, T. 1996a. Surveyed examination of environmental impacts due to earthquake conflagration since Hanshin Awaji earthquake disaster. J. Jpn. Soc. Nat. Disaster Sci. 15:195–204.
- Gotoh, T. 1996b. Surveyed examination of air environmental problems in Hanshin disaster since Hanshin Awaji earthquake (In Japanese). J. Jpn. Soc. Safety Eng. 35:81–92.
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- Gotoh, T. 1997. Investigation of soil concentration due to liquefaction since Hanshin Awaji earthquake disaster (In Japanese). J. Jpn. Soc. Safety Eng. 36:348–349.
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- Gotoh, T. 1999b. The progress of the surveyed suffers' health according to BMRC type questionnaire after the Hanshin earthquake disaster (In Japanese). J. Jpn. Soc. Nat. Disaster Sci. 18:289–300.
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- Sakamoto, K., et al. 1993. Behavior and source apportionments of ambient aerosols in early winter at South-Kanto area. Jpn. Chem. Express 8:345–348.
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- Wilson, W.E. 1997. Fine and coarse particles: Concentration relationship relevant to epidemiological studies. J. Air Waste Manage. Assoc. 47:1238–1249.[Medline]
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ABSTRACT
INTRODUCTION
