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Dry deposition (downward, upward) concentration study of particulates and heavy metals during daytime, nighttime period at the traffic sampling site of Sha-Lu, Taiwan
Chemosphere 56 (2004) 509–518 www.elsevier.com/locate/chemosphere
Dry deposition (downward, upward) concentration study of particulates and heavy metals during daytime, nighttime period at the traffic sampling site of Sha-Lu, Taiwan Guor-Cheng Fang *, Yuh-Shen Wu, Shih-Han Huang, Jui-Yeh Rau Air Toxic and Environmental Analysis Laboratory, Department of Environmental Engineering, Hungkuang Institute of Technology, Hungkuang University, Sha-Lu, Taichung 433, Taiwan Received 25 November 2003; received in revised form 24 March 2004; accepted 20 April 2004
Abstract Downward, upward dry deposition fluxes and total suspended particulate of particulate heavy metals (Fe, Pb, Zn, Cu, Mg and Mn) were measured in daytime and nighttime period in Sha-Lu, a small city in the central Taiwan during summer period of 2003. The results showed that the total suspended particulate concentrations of particulate mass in the daytime period (averaged 996.2 g/m3 ) were higher than in nighttime period (averaged 560.7 g/m3 ). And the downward dry deposition fluxes (averaged 54.07 g/m2 s) were about two times as that of upward dry deposition fluxes (averaged 26.48 g/m2 s) in the daytime period. Furthermore, the average downward dry deposition fluxes (averaged 26.22 g/m2 s) were also about two times as that of upward dry deposition fluxes (averaged 12.11 g/m2 s) in the nighttime period. In addition, the average downward dry deposition fluxes are greater than the upward dry deposition fluxes for all the heavy metals in either daytime or nighttime period. The proposed reasons are that the wind speed and concentration difference for daytime and nighttime period lead to these results at the traffic sampling site of central Taiwan. In addition, the deposition velocity for mass, heavy metals (Fe, Pb, Zn, Cu, Mg and Mn) during daytime and nighttime period were also calculated. The average daytime dry deposition velocity for downward particulate mass, upward particulate mass, Fe, Pb, Zn, Cu, Mg and Mn were 5.56, 2.66, 1.71, 0.18, 1.06, 0.24, 0.47 and 0.11 (cm/s), respectively. And the average nighttime dry deposition velocity for downward particulate mass, upward particulate mass, Fe, Pb, Zn, Cu, Mg and Mn were 4.70, 2.11, 1.66, 0.18, 0.86, 0.23, 0.32 and 0.07 (cm/s), respectively at traffic sampling site of central Taiwan. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Dry deposition; Total suspended particulate; Metal; Traffic
1. Introduction Air pollution has become a more and more serious problem in Taiwan, especially in central Taiwan. It in-
*
Corresponding author. Tel.: +886-4-26318652x1110; fax: +886-4-23502102/26310744. E-mail address: [email protected] (G.-C. Fang).
cludes aerosol, effluvium, secondary pollutant and organic solvent vapor, etc. (Fang et al., 1996). Air pollution in the traffic centers is characterized by the emissions and concentrations of primary pollutants which have extremely strong spatial and temporal variations and the characterization of urban air pollution is fairly complicated. A balance between those factors, which lead to pollutant accumulation and those, which lead to pollutant dispersion controls the concentrations
0045-6535/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2004.04.032
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of pollutants in urban areas. There are usually strong gradients of gaseous and particulate pollutants both in the vertical and horizontal direction mainly due to activities of emission sources, and rapid mixing and dilution of street level emissions (Vakeva et al., 1999). However, dry deposition fluxes are difficult to measure directly and instead are often estimated as the product of the dry deposition velocity and the corresponding pollutant concentration. However, the dry deposition velocity itself strongly depends on various variables, such as particle size, meteorology-atmospheric stability, relative humidity, and wind speed, and characteristics of depositing surface (Caffrey et al., 1998). Atmospheric dry deposition involves the transport and removal of aerosols and gases from the atmosphere onto surfaces in the absence of precipitation. In spite of the fact that dry deposition is an important mechanism in controlling the fate of airborne material, many uncertainties exist in the methods used to measure and calculate dry deposition. Because the properties of ambient particles and dry deposition rates are strongly related to particle size, size distribution is one of the most important parameters in understanding chemical form and formation mechanisms and dry deposition (Noll and Fang, 1986, 1988). Considerable research has been conducted to investigate the dry deposition of air pollutants. Among these, heavy metals are of particular interest as most of them are toxic to humans and ecosystems. Dry deposition may be particularly important near urban/industrial areas adjacent to surface waters where particle concentrations and pollutants associated with them are relatively high (Shahin et al., 2000). Urban populations are exposed to metals in suspended particles and these are often well above natural background levels owing to anthropogenic processes. This results in elevated metal concentrations that can pose an important risk to human health (Antonio et al., 2001). Metal transfer through the atmosphere is a significant part of the biogeochemical cycle of these elements (Galloway et al., 1982). There are two processes which increase heavy metal concentrations in the atmosphere: natural and anthropogenic (D’Almeida et al., 1991). Understanding emissions from traffic includes identification of the sources, which is also crucial for designing control measures. Road traffic involves numerous potential sources of metals, e.g., combustion products from fuel and oil, wear products from tires, brake linings, bearings, coach and road construction materials, and resuspension of soil and road dust. (ElFadel and Hashisho, 2001, for a review). The objectives of this study are (1) to measure the dry deposition fluxes of particulate total mass and heavy metal elements in Sha-Lu, a small city located in the central Taiwan and (2) to characterize the mass, metallic elements dry deposition (downward and upward), con-
centrations during daytime and nighttime period at the traffic sampling site of central Taiwan, Sha-Lu. In additions, meteorological conditions such as wind speed, wind direction and temperature were also measured.
2. Experimental methods 2.1. Sampling program The sampling time was divided into daytime and nighttime period for this study. The daytime period was representing from 6:30 a.m. to 6:30 p.m. and the nighttime period was representing from 6:30 p.m. to 6:30 a.m. respectively. The sampling location was on the traffic island, which is located in front of Hungkuang University in Sha-Lu town of central Taiwan and can be seen in Fig. 1. The height of the sampling sites is approximately 1.5 m from ground level. Sampling was taken during the period of August–September in 2003 at the traffic sampling sites. The sampling work conducted during this period of time was that Taiwan schools were begin during this period. And the sampling site was just located in front of HKU (Hungkuang University). Thus, the influence of particulate and metallic elements dry deposition can be characterized. The sampling sites have three dry deposition plates and one PS-1 sampler in this study. Each of the sampling devices was apart 10 m. And the meteorological conditions such as time, temperature, wind speed and wind direction were also monitored. 2.2. Sample collection In this study, the ambient particle concentration was collected by PS-1 (Total Suspended Particle Sampler) and dry deposition plate. The PS-1 (GPS1 PUF Sampler, General Metal Work) is a completed air sampling system designed to simultaneously collect suspended airborne particles at flow rate up to 280 l/min and the flow rate was adjusted to 200 l/min. The quartz filter (diameter 10.2 cm) is used to filter the suspended particles in the study. The filters were first conditioned for 24 h in an electric chamber at humidity 50 ± 5% and temperature 25 ± 5 °C prior to both on and off weighing. Filters were placed in a sealed CD box during transport and storage. The dry deposition plate is made by PVC. It is 21.5 cm long, 7.6 cm wide and 0.65 cm thick with a sharp leading edge (<10° angle) that is pointed into the wind by a wind vane. Each plate was covered on top and bottom with a thick projection film filters coated with approximated 20 mg of silicone grease to collect impacted particles. After the grease was sprayed onto the strips, the strips were baked in an oven at 60 °C for 2 h to remove volatile substances. Then, placed in an electric chamber at humidity 50 ± 5% and temperature 25 ± 5 °C
G.-C. Fang et al. / Chemosphere 56 (2004) 509–518
511
Taiwan
Mainland China
N
HungKuang University
Tunghai University
Taichung thermal power plant
Taichung County Taichung City 0
50km
Taichung Wen Shan Incinerator
Taichung Industrial park
Fig. 1. Map of central Taiwan with locations of study sites.
at least 24 h before both on the off weight. The thick projection film is 8 cm long, 5.5 cm wide and 8 mm thick. The wind vane was made of aluminum and is 21.5 cm long, 17.5 cm wide. The plate was fitted with a galvanized iron stand. The stand can adjust its height between 130 and 200 cm. The distance between each stand can be regulated to prevent sample interactions.
1. Washing the cutted surrogate surface. 2. Coated the adsorbent (silicone grease or apenzon L grease). 3. Weighting after the moisture equilibrium (W0 ). 4. Exposing in the field and recording sampling time (t). 5. Reweighting after the moisture equilibrium (W1 ).
2.3. Chemical analysis
The particle concentration and dry deposition flux are calculated by follows:
After final weighing, all the projection film filters and quartz filters by dry deposition plate and PS-1 sampler were cut into one-half and one-eighth, respectively. Then they were put into 200 ml bottles for each sampling group. Projection film filters need to reaction by hexane to remove the grease. Thirty milliliter hexane was added to each bottle and mixed for 40 min. And these solutions were heated to dry. There were only dry particulates left in this empty bottle at this moment. Than 10 ml ultrapure HNO3 was added to digest these particulates at 200–250 °C for 2 h, After above procedure this solution was added with distilled-deionized water to 30 ml. A Hitachi Z-5000 series polarized Zeeman flame atomic absorption spectrophotometer was used to measure the trace metal concentration after digestion process.
concentration ¼ Flux ¼
W1 W0 ðgÞ t ðsÞ Q ðl=sÞ
W1 W0 ðgÞ area ðcm2 Þ t ðdayÞ
2.4.1. Dry deposition velocities of total suspended particulate mass and metals The dry deposition velocity of total suspended particulate mass was calculated as follows: Vd;TM ¼ K ðFTM Þ=ðCTSP Þ ¼ ð1000 mg=mgÞ ðday=86 400 sÞ ð100 cm=sÞ ¼ 1:1574 ðmg=mgÞ ðday=sÞ ðcm=mÞ
2.4. Formula and calculate Vd;TM Mass measurement was to weight and record the surface weight after exposing in the atmosphere and allowed them to equilibrate. The procedures can be divided into followed steps:
K FTM
the dry deposition velocity of total suspended particulate mass (cm/s) units conversion factor dry deposition flux of total suspended particulate mass (mg/m2 /day)
512
CTSP
G.-C. Fang et al. / Chemosphere 56 (2004) 509–518
ambient air concentration of total suspended particulate (mg/m3 )
The dry deposition velocity of metals was calculated as follows: Vd;M ¼ K ðFM Þ=ðCM Þ ¼ ð1000 mg=mgÞ ðday=86 400 sÞ ð100 cm=mÞ
cally different from a blank. The detection limits of the elements in this study were 0.026, 0.039, 0.011, 0.015, 0.012 and 0.014 mg/l for Fe, Pb, Zn, Cu, Mg and Mn, respectively. Method detection limit was determined from selected the concentration slightly higher than the low concentration of the standard line, repeated this concentration for twelve times to estimate the standard deviation (S). The MDL was equally to be (3 S).
¼ 1:1574 ðmg=mgÞ ðday=sÞ ðcm=mÞ Vd;M K FM CM
the dry deposition velocity of metals (cm/s) units conversion factor dry deposition flux of metals (mg/m2 /day) ambient air concentration of metals (mg/m3 )
2.5. Quality control 2.5.1. Blank test Background contamination was monitored by using operational blanks (unexposed projection film and quartz filter) were processed simultaneously with field samples. The field blanks were exposed in the field when the field sampling box was opened to remove and replace field samples. Background contamination of heavy metals was accounted for by subtracting field blank values from the concentrations. Field blank values were very low, usually, below or around the method detection limits. In this study, the background contamination is insignificant and can be ignored. The results of the blank test are 0.5, 0.35, 0.42, 0.10, 0.30 and 0.32 g for Fe, Pb, Zn, Cu, Mg and Mn, respectively. 2.5.2. Recovery efficiency test At least 10% of the samples are analyzed in spiking with a known amount of metal to calculate recovery efficiencies. The analysis procedure for the recovery test is the same as that described for the field samples. The recovery tests of metallic elements were 100%, 100%, 100%, 100%, 110% and 90% for Fe, Pb, Zn, Cu, Mg and Mn, respectively. The range of recovery efficiency test varies between 90% and 110% and the relative standard deviation is smaller than 10%. 2.5.3. Reproducibility test Repeat the analysis of the same standard solution for many times. The reproducibility test can be displayed the stability of instruments. The relative standard deviation varied between 95% and 105%, the mean relative deviation is smaller than 5%. 2.5.4. Detection limit Detection limit was used to determine the lowest concentration level that can be detected to be statisti-
3. Results and discussion 3.1. The sampling information Table 1 shows the sampling information which include the sampling date, dry deposition flux (downward, upward), TSP concentration, dry deposition velocity (downward, upward) and meteorological data at the traffic sampling site of central Taiwan during summer period of 2003. The average sampling temperature was 32.0 and 27.9 °C for the daytime and nighttime period, respectively. And this is the highest temperature variation range in central Taiwan. Table 1 indicated that the average downward dry deposition fluxes during the daytime period are all greater than nighttime period. The average downward dry deposition fluxes for the daytime and nighttime period are 57.3 and 26.2 g/m2 s, respectively. And the ranges for the daytime and nighttime for the downward dry deposition fluxes are between 42.0 and 76.7 g/m2 s and 18.2 and 37.6 g/m2 s, respectively. Moreover, this study also measured the upward dry deposition fluxes for the daytime and nighttime period. The results also revealed that the average upward dry deposition fluxes for the daytime and nighttime period are 27.0 and 12.1 g/m2 s, respectively. And the ranges for the daytime and nighttime for the upward dry deposition fluxes are between 11.1 and 52.0 g/m2 s and 7.26 and 20.0 g/m2 s, respectively. In addition, the total suspended particulate concentration in the traffic area was also monitored. The average total suspended particulate for the daytime and nighttime period were 981 and 551 g/m3 , respectively. The average daytime TSP concentrations are about two times as that of nighttime period. Besides, the ambient air particulate dry deposition velocity for the daytime and nighttime period was also calculated. The average calculated downward dry deposition velocities are 5.56 and 4.70 cm/s for the daytime and nighttime period, respectively. And the average calculated upward dry deposition velocities are 2.66 and 2.11 cm/s for the daytime and nighttime period, respectively. The average wind direction is SWW. And the average wind speeds are 4.51 and 1.65 cm/s for the daytime and nighttime, respectively. In general, the average daytime wind speed was about 2.5 times as that of nighttime period. Previous studies (Fang et al., 1999) have already used coarse
Table 1 The sampling information for dry deposition flux, TSP concentration, dry deposition velocity, temperature, wind speed and prevailing wind direction during the sampling period
8/9–8/10/2003 8/11,8/13/2003 8/13–8/14/2003 8/14–8/15/2003 8/16–8/17/2003 8/18–8/19/2003 8/21–8/22/2003 8/25–8/26/2003 8/27–8/28/2003 8/29–8/30/2003 9/1–9/2/2003 9/3–9/4/2003 9/6–9/7/2003 9/10–9/11/2003 Average
SamDry deposition flux (lg/m2 s) pling no. Downward Upward
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Total suspended particulate concentration (lg/m3 )
Dry deposition velocity (cm/s) Downward
Upward
Temperature (°C)
Wind speed (m/s)
Prevailing wind
Day
Night
Day
Night
Day
Night
Day
Night
Day
Night
Day
Night
Day
Night
Day
Night
71.0 76.7 75.4 54.2 42.0 48.0 60.2 44.3 48.9 61.4 51.6 58.0 63.6 47.0
37.6 20.0 18.2 26.6 29.6 23.4 27.5 25.4 30.2 32.7 26.7 23.5 23.0 22.6
41.1 24.4 52.0 28.1 25.0 12.6 41.9 27.6 18.6 31.6 11.1 25.6 14.6 24.7
20.6 7.30 9.30 8.10 12.0 10.0 14.8 8.00 12.9 16.5 18.4 9.6 12.0 10.1
– – 982 979 979 980 982 980 981 980 979 984 983 979
– 551 – 562 552 542 548 558 557 557 547 557 539 542
– – 7.67 5.53 4.29 4.90 6.13 4.51 4.99 6.26 5.27 5.90 6.47 4.80
– 3.63 – 4.73 5.37 4.32 5.02 4.55 5.42 5.87 4.88 4.21 4.27 4.17
– – 5.29 2.87 2.55 1.29 4.27 2.82 1.90 3.22 1.13 2.60 1.48 2.53
– 1.32 – 1.44 2.18 1.84 2.70 1.43 2.32 2.96 3.37 1.73 2.22 1.86
33.9 31.3 31.6 31.8 32.2 32.3 31.6 31.5 30.8 32.4 33.2 32.7 31.9 31.4
29.6 27.6 28.2 27.6 28.4 27.8 27.3 27.3 27.1 28.1 28.2 27.4 27.5 28.3
4.88 4.71 5.00 4.32 4.22 3.99 4.60 4.20 4.70 4.60 4.10 4.80 4.70 4.30
2.31 1.38 1.42 1.81 1.82 1.16 1.50 1.70 1.90 2.10 1.90 1.40 1.20 1.50
SWW W SW SWW SWW SWW SWW SWW SW SW W SWW SWW SWW
SW W W W SWW SWW W W SWW SWW SWW W W SWW
57.3
26.2
27.1
12.1
981
551
5.56
4.70
2.66
2.11
32.0
27.9
4.51
1.65
–
–
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G.-C. Fang et al. / Chemosphere 56 (2004) 509–518
particle sample device Noll Rotary Impactor (NRI) and micro-orifice uniform deposit impactor (MOUDI) to sample ambient air coarse and fine particles, respectively. Dry deposition velocities were also calculated on the base of above study. And the previous study has also reflected that the dry deposition velocity calculated by Flux and TSP were about 10% lower than the value calculated by Flux combined with NRI and MOUDI. Thus, this values obtained in this study will be thus underestimated the dry deposition velocities. 3.2. Effects of meteorological parameters
Total suspended particulate concentration (µg/m3)
Table 1 illustrated the relationship between upward, downward and dry deposition flux and wind speed at the traffic sampling sites of central Taiwan. Fig. 2(A) and (B) was the contrasts by downward, upward dry deposition flux and wind speed in the daytime and nighttime period, respectively. The correlation coefficients between dry deposition flux and wind speed are 0.65 and 0.38 for
Daytime (A)
80
Dry deposition flux (µg/m2-sec)
2
Downward R =0.63 2 Upward R =0.38
70
the downward and upward dry deposition flux in the daytime period, respectively. The correlation coefficients between dry deposition flux and wind speed are 0.74 and 0.44 for the downward and upward dry deposition flux in the nighttime period, respectively. The above results indicated that the downward dry depositions are all highly correlated to the wind speed than the upward dry deposition in either daytime or nighttime period. And the correlation coefficients (R2 ) for downward dry deposition, upward dry deposition vs. wind speed, the results indicated that correlation coefficient is all higher in the nighttime period than the daytime period for either downward or upward dry deposition. The possible reason is that the less traffic vehicles and activities during the nighttime period were thus increasing the correlation coefficient. As for the relationship between total suspended particulate concentrations vs. wind speed, the results are displayed in Fig. 3(A) and (B). The correlation
60
50
40
30
20
10 3.8
4.0
4.2
4.4
4.6
4.8
5.0
984
Daytime (A) 2
R =0.64 983
982
981
980
979
978
5.2
3.8
4.0
Wind speed (m/sec)
Dry deposition flux (µg/m2-sec)
2
Downward R =0.74 2 Upward R =0.44
35
30
25
20
15
10
5 1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
Wind speed (m/sec)
Fig. 2. The correlation coefficients (R2 ) for downward, upward dry deposition fluxes vs. wind speed between daytime and nighttime period.
Total suspended particulate concentration (µg/m3)
Nighttime (B)
40
4.2
4.4
4.6
4.8
Wind speed (m/sec) Nighttime (B) 565 2
R =0.38 560
555
550
545
540
535 1.0
1.2
1.4
1.6
1.8
2.0
2.2
Wind speed (m/sec)
Fig. 3. The correlation coefficients (R2 ) for total suspended particulate concentration vs. wind speed between daytime and nighttime period.
Table 2 The metal elements information during day and night period Downward dry deposition flux (lg/m2 day)
TSP concentration (lg/m3 )
Sampling no.
Fe
Pb
Zn
Cu
Mg
Mn
Fe
Pb
Zn
Cu
Mg
Mn
Fe
Pb
Zn
Cu
Mg
Mn
Panel A Daytime 1 2 3 4 5 6 7 8 9 10 11 12 13 14
27 121 15 470 11 368 10 561 13 106 9136 27 141 15 278 10 734 13 249 9942 10 721 16 284 11 082
379 227 291 227 379 227 303 267 284 319 231 275 314 358
14 545 9242 4920 5879 8333 12 318 7045 6272 11 728 7138 8216 7098 11 842 9067
303 303 296 326 297 303 303 314 298 284 336 307 295 308
909 606 502 276 152 606 818 294 846 524 615 498 625 594
326 267 314 227 303 268 582 492 332 266 384 396 396 328
2.42 1.14 1.26 2.19 1.33 1.89 1.67 1.62 1.78 1.54 1.36 1.77 1.82 2.12
0.14 0.14 0.23 0.14 0.25 0.25 0.17 0.16 0.15 0.15 0.22 0.19 0.26 0.13
1.06 0.92 0.95 0.89 0.89 1.14 1.58 0.92 1.14 0.98 1.02 1.36 0.95 1.10
0.22 0.19 0.25 0.22 0.28 0.22 0.33 0.19 0.31 0.26 0.24 0.32 0.19 0.16
0.61 0.52 0.49 0.67 0.28 0.39 0.36 0.31 0.56 0.52 0.38 0.64 0.33 0.47
0.08 0.08 0.12 0.11 0.09 0.08 0.14 0.09 0.13 0.16 0.07 0.12 0.15 0.09
12.99 15.72 10.44 5.57 11.38 5.60 18.85 10.92 6.98 9.96 8.46 7.01 10.36 6.05
3.16 1.89 1.46 1.89 1.75 1.05 2.10 1.93 2.19 2.46 1.22 1.68 1.40 3.19
15.95 11.67 5.99 7.65 10.85 12.52 5.15 7.89 11.91 8.43 9.32 6.04 14.43 9.54
1.58 1.80 1.37 1.70 1.24 1.58 1.05 1.91 1.11 1.26 1.62 1.11 1.80 2.23
1.72 1.34 1.19 0.48 0.63 1.80 2.60 1.10 1.75 1.17 1.87 0.90 2.19 1.46
4.72 3.71 3.03 2.37 3.90 3.72 4.85 6.33 2.96 1.92 6.35 3.82 3.06 4.22
Average
14 371
292
8832
305
562
349
1.71
0.18
1.06
0.24
0.47
0.11
10.02
1.96
9.81
1.53
1.44
3.92
Nighttime 1 2 3 4 5 6 7 8 9 10 11 12 13 14
9364 11 412 9091 7294 10 348 9030 7015 9146 10 287 8422 9612 7546 10 976 8420
227 210 227 128 303 152 227 184 195 216 207 186 205 178
7045 6246 5288 4357 7485 3788 2121 4136 5698 4673 6018 5422 4769 4361
227 242 303 245 227 237 227 242 258 266 251 283 224 248
0 129 0 242 379 152 227 102 246 138 0 312 297 125
227 208 283 219 251 254 227 248 216 207 220 269 281 208
1.16 1.02 2.03 1.39 2.94 1.33 1.19 2.02 2.16 1.28 1.22 1.76 1.64 2.13
0.17 0.21 0.14 0.25 0.16 0.14 0.17 0.23 0.18 0.22 0.16 0.14 0.20 0.21
0.72 0.83 0.96 0.78 0.73 1.08 0.92 0.76 0.98 0.77 0.90 0.96 0.88 0.82
0.11 0.23 0.25 0.16 0.28 0.17 0.36 0.16 0.33 0.24 0.33 0.18 0.25 0.11
0.13 0.12 0.31 0.54 0.50 0.25 0.28 0.52 0.16 0.22 0.21 0.38 0.45 0.39
0.08 0.07 0.08 0.06 0.07 0.08 0.08 0.08 0.06 0.06 0.07 0.07 0.09 0.06
9.34 12.95 5.19 6.07 4.07 7.84 6.80 5.24 5.51 7.62 9.12 4.96 7.75 4.58
1.58 1.16 1.89 0.59 2.19 1.26 1.58 0.93 1.25 1.14 1.50 1.54 1.19 0.98
11.29 8.71 6.38 6.47 11.87 4.05 2.68 6.30 6.73 7.02 7.74 6.54 6.27 6.16
2.37 1.22 1.40 1.77 0.95 1.65 0.73 1.75 0.90 1.28 0.88 1.82 1.04 2.61
0.00 1.24 0.00 0.52 0.88 0.70 0.95 0.23 1.78 0.73 0.00 0.95 0.76 0.37
3.29 3.44 3.93 4.22 4.15 3.53 3.16 3.59 4.17 3.99 3.64 4.45 3.61 4.01
Average
9140
203
5101
249
168
237
1.66
0.18
0.86
0.23
0.32
0.07
6.93
1.34
7.01
1.45
0.65
3.80
Panel B Daytime 1 2
6455 7303
152 157
1985 3106
220 248
0 0
152 227
2.42 1.14
0.14 0.14
1.06 0.92
0.22 0.19
0.61 0.52
0.08 0.08
3.09 7.42
1.26 1.30
2.18 3.92
1.15 1.48
0.00 0.00
2.19 3.16
Dry deposition velocity (cm/s)
G.-C. Fang et al. / Chemosphere 56 (2004) 509–518 515
516
Table 2 (continued) Sampling no.
Downward dry deposition flux (lg/m2 day) Fe
Pb
Zn
TSP concentration (lg/m3 )
Dry deposition velocity (cm/s)
Cu
Mg
Mn
Fe
Pb
Zn
Cu
Mg
Mn
Fe
Pb
Zn
Cu
Mg
Mn
4510 3182 4606 3776 3947 5512 4691 3980 4410 6606 5323 4012
206 164 189 227 231 168 220 212 186 195 215 175
2492 3333 4470 8030 5545 2260 7844 2360 4475 4846 3233 3957
254 227 249 224 244 235 222 237 242 248 212 238
12 0 0 0 27 10 0 0 8 0 15 14
231 252 379 227 379 166 283 210 364 182 241 397
1.26 2.19 1.33 1.89 1.67 1.62 1.78 1.54 1.36 1.77 1.82 2.12
0.23 0.14 0.25 0.25 0.17 0.16 0.15 0.15 0.22 0.19 0.26 0.13
0.95 0.89 0.89 1.14 1.58 0.92 1.14 0.98 1.02 1.36 0.95 1.10
0.25 0.22 0.28 0.22 0.33 0.19 0.31 0.26 0.24 0.32 0.19 0.16
0.49 0.67 0.28 0.39 0.36 0.31 0.56 0.52 0.38 0.64 0.33 0.47
0.12 0.11 0.09 0.08 0.14 0.09 0.13 0.16 0.07 0.12 0.15 0.09
4.14 1.68 4.00 2.31 2.74 3.94 3.05 2.99 3.75 4.32 3.39 2.19
1.04 1.37 0.88 1.05 1.61 1.22 1.70 1.64 0.98 1.19 0.96 1.56
3.04 4.34 5.82 8.16 4.05 2.84 7.96 2.79 5.08 4.12 3.94 4.16
1.18 1.18 1.04 1.17 0.85 1.43 0.83 1.06 1.17 0.90 1.29 1.72
0.03 0.00 0.00 0.00 0.09 0.04 0.00 0.00 0.02 0.00 0.05 0.03
2.23 2.63 4.87 3.16 3.16 2.13 2.52 1.52 6.02 1.76 1.86 5.11
Average
4879
193
4138
236
6
264
1.71
0.18
1.06
0.24
0.47
0.11
3.50
1.27
4.46
1.17
0.02
3.02
Nighttime 1 2 3 4 5 6 7 8 9 10 11 12 13 14
5273 1856 2197 2033 3091 3347 2048 2864 1598 2966 2138 3390 3714 2208
141 166 152 142 174 128 144 148 169 171 128 124 163 185
1939 1440 1652 1582 3015 2004 2965 2438 2066 1804 1276 2724 2039 2912
162 160 152 180 214 203 194 177 194 220 142 206 173 152
0 0 0 0 0 0 0 0 0 0 0 0 0 0
143 140 152 158 198 164 183 172 140 201 176 158 174 155
1.16 1.02 2.03 1.39 2.94 1.33 1.19 2.02 2.16 1.28 1.22 1.76 1.64 2.13
0.17 0.21 0.14 0.25 0.16 0.14 0.17 0.14 0.18 0.22 0.16 0.14 0.20 0.21
0.72 0.83 0.96 0.78 0.73 1.08 0.92 0.76 0.98 0.77 0.90 0.96 0.88 0.82
0.11 0.23 0.25 0.16 0.28 0.17 0.36 0.16 0.33 0.24 0.33 0.18 0.25 0.11
0.13 0.12 0.31 0.54 0.50 0.25 0.28 0.52 0.16 0.22 0.21 0.38 0.45 0.39
0.08 0.07 0.08 0.06 0.07 0.08 0.08 0.08 0.06 0.06 0.07 0.07 0.09 0.06
5.26 2.11 1.25 1.69 1.21 2.91 1.98 1.64 0.86 2.68 2.03 2.23 2.62 1.20
0.98 0.91 1.26 0.66 1.26 1.07 1.00 1.22 1.09 0.90 0.93 1.03 0.94 1.02
3.11 2.01 1.99 2.35 4.78 2.14 3.74 3.71 2.44 2.71 1.64 3.28 2.68 4.11
1.69 0.81 0.70 1.30 0.89 1.41 0.62 1.28 0.68 1.06 0.50 1.32 0.80 1.60
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
2.07 2.31 2.10 3.05 3.27 2.28 2.54 2.49 2.70 3.88 2.91 2.61 2.24 2.99
Average
2766
152
2133
181
0
165
1.66
0.18
0.86
0.23
0.32
0.07
2.12
1.02
2.91
1.05
0.00
2.67
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coefficients between total suspended particulate concentrations vs. wind speed are 0.64 and 0.38 in the daytime and nighttime, respectively. The results obtained in this study revealed that the total suspended particulate concentrations are highly correlated to the wind speed in the daytime period than nighttime period. It is just opposite to the results obtained for the dry deposition (downward, upward) vs. wind speed in the daytime and nighttime period. The possible reason provides here is beyond traffic vehicles, wind speed variation between daytime and nighttime period is the large parameter to influence this result. The traffic is more on the road near the sampling site, and the passing by vehicles on the road resuspended the road dust to the atmosphere. Thus, the relationship in the daytime period was higher than the nighttime period.
3.3. Ambient airborne particle of heavy metals The data of metal elements with downward and upward dry deposition flux, total suspended particulate concentration and dry deposition velocity was shown in Table 2(panels A and B). Table 2 comprise panels A and B which represent downward and upward dry deposition flux with respect to total suspended particulates concentration and dry deposition velocity, respectively. Table 2(panel A) indicated that the downward dry deposition fluxes with metal elements (Fe, Pb, Zn, Cu, Mg and Mn) for the daytime period are 14 371, 292, 8832, 305, 562 and 349 g/m2 day, respectively. The average downward dry deposition fluxes with metal elements (Fe, Pb, Zn, Cu, Mg and Mn) for the nighttime period are 9140, 203, 5101, 249, 168 and 237 g/m2 day, respectively. Table 2(panel B) indicated that the upward dry deposition fluxes with metal elements (Fe, Pb, Zn, Cu, Mg and Mn) for the daytime period are 4879, 193, 4138, 236, 6 and 264 g/ m2 day, respectively. The average upward dry deposition fluxes with metal elements (Fe, Pb, Zn, Cu, Mg and Mn) for the nighttime period are 2766, 152, 2133, 181, 0 and 165 g/m2 day, respectively. The average total suspended particulate concentration with metal elements (Fe, Pb, Zn, Cu, Mg and Mn) in the daytime period and nighttime period are 1.71, 0.18, 1.06, 0.24, 0.47, 0.11 and 1.66, 0.18, 0.86, 0.23, 0.32, 0.07 g/m3 , respectively. The results revealed that the average downward and upward dry deposition fluxes with metal elements in the daytime period were higher than in nighttime period. And the total suspended particulate concentrations with metal elements were also had this phenomenal. The results also showed the range of metal elements with Fe, Zn and Mg were larger than Pb, Cu and Mn whether dry deposition fluxes or total suspended particulate concentrations.
517
4. Conclusions The dry deposition fluxes and total suspended particulate of particulate total mass and heavy metals in Sha-Lu, Taiwan were measured. The average downward dry deposition mass fluxes in the daytime and nighttime period were found to be 54.1 and 26.2 g/m2 s, respectively. And the average upward dry deposition mass fluxes in the daytime and nighttime period were found to be 26.5 and 12.1 g/m2 s, respectively. In addition, the total suspended particulate concentrations in the daytime and nighttime period were 981 and 551 g/m3 , respectively. Heavy metals such as Fe, Zn and Mg show a higher average value than those of Mn, Cu and Pb in dry depositions and total suspended particulate for either daytime or nighttime period. The correlation coefficients (R2 ) for downward, upward dry deposition fluxes vs. wind speed, the results also indicated that correlation coefficients in the nighttime period are all higher than that of daytime period for either downward or upward dry deposition. The possible reason is that the less traffic vehicles and activities during the nighttime period were thus increased the correlation coefficients. The correlation coefficients (R2 ) between total suspended particulate concentrations vs. wind speed, the results obtained displayed that the total suspended particulate concentrations are highly correlated to the wind speed in the daytime period than nighttime period. These results just opposite to the results obtained for the dry deposition (downward, upward) vs. wind speed in the daytime and nighttime period. The possible reason provides here is beyond traffic vehicles, wind speed variation between daytime and nighttime period is the large parameter to influence this result.
Acknowledgements The authors gratefully acknowledge the National Science Council of the ROC (Taiwan) for financial support under project no. NSC 92-2211-E-241-002.
References Antonio, J., Espinsa, F., Rodriguez, M.T., Francisco, J., de la Rosa, B., Juan, C., Sanchez, J., 2001. Size distribution of metals in urban aerosols in Seville (Spain). Atmospheric Environment 35, 2595–2601. Caffrey, P.F., Ondov, J.M., Zufall, M.J., Davidson, C.I., 1998. Determination of size dependent dry particle deposition velocities with multiple intrinsic elemental tracers. Environmental Science and Technology 32, 1615–1622. D’Almeida, G.A., Koepke, P., Shettle, E.P., 1991. Atmospheric Aerosols: Global Climatology and Radiative Characteristics. A. Deepak publishing. 561 pp.
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El-Fadel, M., Hashisho, Z., 2001. Vehicular emissions in roadway tunnels: a critical review. Critical Reviews in Environmental Science and Technology 31, 125–174. Fang, G.C., Chang, C.N., Wu, Y.S., Fu, P.P.C., Chang, K.F., Yang, D.G., 1999. The characteristic study of TSP, PM2.5_10 and PM2.5 in the rural site of central Taiwan. Science of the Total Environment 232, 177–5184. Galloway, J.N., Thorton, J.D., Norton, S.A., Volchok, H.L., McLean, R.A.N., 1982. Trace metals in atmospheric deposition: a review and assessment. Atmospheric Environment 16 (7), 1677–1700. Noll, K.E., Fang, K.Y., 1986. Air Pollution Control Association, 79th Annual Meeting, Minneapolis, Minnesota, June 22–27.
Noll, K.E., Fang, K.Y., 1988. Development of a dry deposition model for atmospheric coarse particles. Atmospheric Environment 23 (3), 585–594. Shahin, U.M., Lu, J., Yi, S.M., Paode, R.D., Holsen, T.M., 2000. Long-term elemental dry deposition fluxes measured around Lake Michigan with an automated dry deposition sampler. Environmental Science and Technology 34, 1887– 1892. Vakeva, M., Hameri, K., Kulmala, M., Lahdes, R., Ruuskanen, J., Laitinen, T., 1999. Street level versus rooftop concentrations of submicron aerosol particles and gaseous pollutants in an urban street canyon. Atmospheric Environment 33, 1385–1397.
Dry deposition (downward, upward) concentration study of particulates and heavy metals during daytime, nighttime period at the traffic sampling site of Sha-Lu, Taiwan Guor-Cheng Fang *, Yuh-Shen Wu, Shih-Han Huang, Jui-Yeh Rau Air Toxic and Environmental Analysis Laboratory, Department of Environmental Engineering, Hungkuang Institute of Technology, Hungkuang University, Sha-Lu, Taichung 433, Taiwan Received 25 November 2003; received in revised form 24 March 2004; accepted 20 April 2004
Abstract Downward, upward dry deposition fluxes and total suspended particulate of particulate heavy metals (Fe, Pb, Zn, Cu, Mg and Mn) were measured in daytime and nighttime period in Sha-Lu, a small city in the central Taiwan during summer period of 2003. The results showed that the total suspended particulate concentrations of particulate mass in the daytime period (averaged 996.2 g/m3 ) were higher than in nighttime period (averaged 560.7 g/m3 ). And the downward dry deposition fluxes (averaged 54.07 g/m2 s) were about two times as that of upward dry deposition fluxes (averaged 26.48 g/m2 s) in the daytime period. Furthermore, the average downward dry deposition fluxes (averaged 26.22 g/m2 s) were also about two times as that of upward dry deposition fluxes (averaged 12.11 g/m2 s) in the nighttime period. In addition, the average downward dry deposition fluxes are greater than the upward dry deposition fluxes for all the heavy metals in either daytime or nighttime period. The proposed reasons are that the wind speed and concentration difference for daytime and nighttime period lead to these results at the traffic sampling site of central Taiwan. In addition, the deposition velocity for mass, heavy metals (Fe, Pb, Zn, Cu, Mg and Mn) during daytime and nighttime period were also calculated. The average daytime dry deposition velocity for downward particulate mass, upward particulate mass, Fe, Pb, Zn, Cu, Mg and Mn were 5.56, 2.66, 1.71, 0.18, 1.06, 0.24, 0.47 and 0.11 (cm/s), respectively. And the average nighttime dry deposition velocity for downward particulate mass, upward particulate mass, Fe, Pb, Zn, Cu, Mg and Mn were 4.70, 2.11, 1.66, 0.18, 0.86, 0.23, 0.32 and 0.07 (cm/s), respectively at traffic sampling site of central Taiwan. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Dry deposition; Total suspended particulate; Metal; Traffic
1. Introduction Air pollution has become a more and more serious problem in Taiwan, especially in central Taiwan. It in-
*
Corresponding author. Tel.: +886-4-26318652x1110; fax: +886-4-23502102/26310744. E-mail address: [email protected] (G.-C. Fang).
cludes aerosol, effluvium, secondary pollutant and organic solvent vapor, etc. (Fang et al., 1996). Air pollution in the traffic centers is characterized by the emissions and concentrations of primary pollutants which have extremely strong spatial and temporal variations and the characterization of urban air pollution is fairly complicated. A balance between those factors, which lead to pollutant accumulation and those, which lead to pollutant dispersion controls the concentrations
0045-6535/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2004.04.032
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of pollutants in urban areas. There are usually strong gradients of gaseous and particulate pollutants both in the vertical and horizontal direction mainly due to activities of emission sources, and rapid mixing and dilution of street level emissions (Vakeva et al., 1999). However, dry deposition fluxes are difficult to measure directly and instead are often estimated as the product of the dry deposition velocity and the corresponding pollutant concentration. However, the dry deposition velocity itself strongly depends on various variables, such as particle size, meteorology-atmospheric stability, relative humidity, and wind speed, and characteristics of depositing surface (Caffrey et al., 1998). Atmospheric dry deposition involves the transport and removal of aerosols and gases from the atmosphere onto surfaces in the absence of precipitation. In spite of the fact that dry deposition is an important mechanism in controlling the fate of airborne material, many uncertainties exist in the methods used to measure and calculate dry deposition. Because the properties of ambient particles and dry deposition rates are strongly related to particle size, size distribution is one of the most important parameters in understanding chemical form and formation mechanisms and dry deposition (Noll and Fang, 1986, 1988). Considerable research has been conducted to investigate the dry deposition of air pollutants. Among these, heavy metals are of particular interest as most of them are toxic to humans and ecosystems. Dry deposition may be particularly important near urban/industrial areas adjacent to surface waters where particle concentrations and pollutants associated with them are relatively high (Shahin et al., 2000). Urban populations are exposed to metals in suspended particles and these are often well above natural background levels owing to anthropogenic processes. This results in elevated metal concentrations that can pose an important risk to human health (Antonio et al., 2001). Metal transfer through the atmosphere is a significant part of the biogeochemical cycle of these elements (Galloway et al., 1982). There are two processes which increase heavy metal concentrations in the atmosphere: natural and anthropogenic (D’Almeida et al., 1991). Understanding emissions from traffic includes identification of the sources, which is also crucial for designing control measures. Road traffic involves numerous potential sources of metals, e.g., combustion products from fuel and oil, wear products from tires, brake linings, bearings, coach and road construction materials, and resuspension of soil and road dust. (ElFadel and Hashisho, 2001, for a review). The objectives of this study are (1) to measure the dry deposition fluxes of particulate total mass and heavy metal elements in Sha-Lu, a small city located in the central Taiwan and (2) to characterize the mass, metallic elements dry deposition (downward and upward), con-
centrations during daytime and nighttime period at the traffic sampling site of central Taiwan, Sha-Lu. In additions, meteorological conditions such as wind speed, wind direction and temperature were also measured.
2. Experimental methods 2.1. Sampling program The sampling time was divided into daytime and nighttime period for this study. The daytime period was representing from 6:30 a.m. to 6:30 p.m. and the nighttime period was representing from 6:30 p.m. to 6:30 a.m. respectively. The sampling location was on the traffic island, which is located in front of Hungkuang University in Sha-Lu town of central Taiwan and can be seen in Fig. 1. The height of the sampling sites is approximately 1.5 m from ground level. Sampling was taken during the period of August–September in 2003 at the traffic sampling sites. The sampling work conducted during this period of time was that Taiwan schools were begin during this period. And the sampling site was just located in front of HKU (Hungkuang University). Thus, the influence of particulate and metallic elements dry deposition can be characterized. The sampling sites have three dry deposition plates and one PS-1 sampler in this study. Each of the sampling devices was apart 10 m. And the meteorological conditions such as time, temperature, wind speed and wind direction were also monitored. 2.2. Sample collection In this study, the ambient particle concentration was collected by PS-1 (Total Suspended Particle Sampler) and dry deposition plate. The PS-1 (GPS1 PUF Sampler, General Metal Work) is a completed air sampling system designed to simultaneously collect suspended airborne particles at flow rate up to 280 l/min and the flow rate was adjusted to 200 l/min. The quartz filter (diameter 10.2 cm) is used to filter the suspended particles in the study. The filters were first conditioned for 24 h in an electric chamber at humidity 50 ± 5% and temperature 25 ± 5 °C prior to both on and off weighing. Filters were placed in a sealed CD box during transport and storage. The dry deposition plate is made by PVC. It is 21.5 cm long, 7.6 cm wide and 0.65 cm thick with a sharp leading edge (<10° angle) that is pointed into the wind by a wind vane. Each plate was covered on top and bottom with a thick projection film filters coated with approximated 20 mg of silicone grease to collect impacted particles. After the grease was sprayed onto the strips, the strips were baked in an oven at 60 °C for 2 h to remove volatile substances. Then, placed in an electric chamber at humidity 50 ± 5% and temperature 25 ± 5 °C
G.-C. Fang et al. / Chemosphere 56 (2004) 509–518
511
Taiwan
Mainland China
N
HungKuang University
Tunghai University
Taichung thermal power plant
Taichung County Taichung City 0
50km
Taichung Wen Shan Incinerator
Taichung Industrial park
Fig. 1. Map of central Taiwan with locations of study sites.
at least 24 h before both on the off weight. The thick projection film is 8 cm long, 5.5 cm wide and 8 mm thick. The wind vane was made of aluminum and is 21.5 cm long, 17.5 cm wide. The plate was fitted with a galvanized iron stand. The stand can adjust its height between 130 and 200 cm. The distance between each stand can be regulated to prevent sample interactions.
1. Washing the cutted surrogate surface. 2. Coated the adsorbent (silicone grease or apenzon L grease). 3. Weighting after the moisture equilibrium (W0 ). 4. Exposing in the field and recording sampling time (t). 5. Reweighting after the moisture equilibrium (W1 ).
2.3. Chemical analysis
The particle concentration and dry deposition flux are calculated by follows:
After final weighing, all the projection film filters and quartz filters by dry deposition plate and PS-1 sampler were cut into one-half and one-eighth, respectively. Then they were put into 200 ml bottles for each sampling group. Projection film filters need to reaction by hexane to remove the grease. Thirty milliliter hexane was added to each bottle and mixed for 40 min. And these solutions were heated to dry. There were only dry particulates left in this empty bottle at this moment. Than 10 ml ultrapure HNO3 was added to digest these particulates at 200–250 °C for 2 h, After above procedure this solution was added with distilled-deionized water to 30 ml. A Hitachi Z-5000 series polarized Zeeman flame atomic absorption spectrophotometer was used to measure the trace metal concentration after digestion process.
concentration ¼ Flux ¼
W1 W0 ðgÞ t ðsÞ Q ðl=sÞ
W1 W0 ðgÞ area ðcm2 Þ t ðdayÞ
2.4.1. Dry deposition velocities of total suspended particulate mass and metals The dry deposition velocity of total suspended particulate mass was calculated as follows: Vd;TM ¼ K ðFTM Þ=ðCTSP Þ ¼ ð1000 mg=mgÞ ðday=86 400 sÞ ð100 cm=sÞ ¼ 1:1574 ðmg=mgÞ ðday=sÞ ðcm=mÞ
2.4. Formula and calculate Vd;TM Mass measurement was to weight and record the surface weight after exposing in the atmosphere and allowed them to equilibrate. The procedures can be divided into followed steps:
K FTM
the dry deposition velocity of total suspended particulate mass (cm/s) units conversion factor dry deposition flux of total suspended particulate mass (mg/m2 /day)
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CTSP
G.-C. Fang et al. / Chemosphere 56 (2004) 509–518
ambient air concentration of total suspended particulate (mg/m3 )
The dry deposition velocity of metals was calculated as follows: Vd;M ¼ K ðFM Þ=ðCM Þ ¼ ð1000 mg=mgÞ ðday=86 400 sÞ ð100 cm=mÞ
cally different from a blank. The detection limits of the elements in this study were 0.026, 0.039, 0.011, 0.015, 0.012 and 0.014 mg/l for Fe, Pb, Zn, Cu, Mg and Mn, respectively. Method detection limit was determined from selected the concentration slightly higher than the low concentration of the standard line, repeated this concentration for twelve times to estimate the standard deviation (S). The MDL was equally to be (3 S).
¼ 1:1574 ðmg=mgÞ ðday=sÞ ðcm=mÞ Vd;M K FM CM
the dry deposition velocity of metals (cm/s) units conversion factor dry deposition flux of metals (mg/m2 /day) ambient air concentration of metals (mg/m3 )
2.5. Quality control 2.5.1. Blank test Background contamination was monitored by using operational blanks (unexposed projection film and quartz filter) were processed simultaneously with field samples. The field blanks were exposed in the field when the field sampling box was opened to remove and replace field samples. Background contamination of heavy metals was accounted for by subtracting field blank values from the concentrations. Field blank values were very low, usually, below or around the method detection limits. In this study, the background contamination is insignificant and can be ignored. The results of the blank test are 0.5, 0.35, 0.42, 0.10, 0.30 and 0.32 g for Fe, Pb, Zn, Cu, Mg and Mn, respectively. 2.5.2. Recovery efficiency test At least 10% of the samples are analyzed in spiking with a known amount of metal to calculate recovery efficiencies. The analysis procedure for the recovery test is the same as that described for the field samples. The recovery tests of metallic elements were 100%, 100%, 100%, 100%, 110% and 90% for Fe, Pb, Zn, Cu, Mg and Mn, respectively. The range of recovery efficiency test varies between 90% and 110% and the relative standard deviation is smaller than 10%. 2.5.3. Reproducibility test Repeat the analysis of the same standard solution for many times. The reproducibility test can be displayed the stability of instruments. The relative standard deviation varied between 95% and 105%, the mean relative deviation is smaller than 5%. 2.5.4. Detection limit Detection limit was used to determine the lowest concentration level that can be detected to be statisti-
3. Results and discussion 3.1. The sampling information Table 1 shows the sampling information which include the sampling date, dry deposition flux (downward, upward), TSP concentration, dry deposition velocity (downward, upward) and meteorological data at the traffic sampling site of central Taiwan during summer period of 2003. The average sampling temperature was 32.0 and 27.9 °C for the daytime and nighttime period, respectively. And this is the highest temperature variation range in central Taiwan. Table 1 indicated that the average downward dry deposition fluxes during the daytime period are all greater than nighttime period. The average downward dry deposition fluxes for the daytime and nighttime period are 57.3 and 26.2 g/m2 s, respectively. And the ranges for the daytime and nighttime for the downward dry deposition fluxes are between 42.0 and 76.7 g/m2 s and 18.2 and 37.6 g/m2 s, respectively. Moreover, this study also measured the upward dry deposition fluxes for the daytime and nighttime period. The results also revealed that the average upward dry deposition fluxes for the daytime and nighttime period are 27.0 and 12.1 g/m2 s, respectively. And the ranges for the daytime and nighttime for the upward dry deposition fluxes are between 11.1 and 52.0 g/m2 s and 7.26 and 20.0 g/m2 s, respectively. In addition, the total suspended particulate concentration in the traffic area was also monitored. The average total suspended particulate for the daytime and nighttime period were 981 and 551 g/m3 , respectively. The average daytime TSP concentrations are about two times as that of nighttime period. Besides, the ambient air particulate dry deposition velocity for the daytime and nighttime period was also calculated. The average calculated downward dry deposition velocities are 5.56 and 4.70 cm/s for the daytime and nighttime period, respectively. And the average calculated upward dry deposition velocities are 2.66 and 2.11 cm/s for the daytime and nighttime period, respectively. The average wind direction is SWW. And the average wind speeds are 4.51 and 1.65 cm/s for the daytime and nighttime, respectively. In general, the average daytime wind speed was about 2.5 times as that of nighttime period. Previous studies (Fang et al., 1999) have already used coarse
Table 1 The sampling information for dry deposition flux, TSP concentration, dry deposition velocity, temperature, wind speed and prevailing wind direction during the sampling period
8/9–8/10/2003 8/11,8/13/2003 8/13–8/14/2003 8/14–8/15/2003 8/16–8/17/2003 8/18–8/19/2003 8/21–8/22/2003 8/25–8/26/2003 8/27–8/28/2003 8/29–8/30/2003 9/1–9/2/2003 9/3–9/4/2003 9/6–9/7/2003 9/10–9/11/2003 Average
SamDry deposition flux (lg/m2 s) pling no. Downward Upward
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Total suspended particulate concentration (lg/m3 )
Dry deposition velocity (cm/s) Downward
Upward
Temperature (°C)
Wind speed (m/s)
Prevailing wind
Day
Night
Day
Night
Day
Night
Day
Night
Day
Night
Day
Night
Day
Night
Day
Night
71.0 76.7 75.4 54.2 42.0 48.0 60.2 44.3 48.9 61.4 51.6 58.0 63.6 47.0
37.6 20.0 18.2 26.6 29.6 23.4 27.5 25.4 30.2 32.7 26.7 23.5 23.0 22.6
41.1 24.4 52.0 28.1 25.0 12.6 41.9 27.6 18.6 31.6 11.1 25.6 14.6 24.7
20.6 7.30 9.30 8.10 12.0 10.0 14.8 8.00 12.9 16.5 18.4 9.6 12.0 10.1
– – 982 979 979 980 982 980 981 980 979 984 983 979
– 551 – 562 552 542 548 558 557 557 547 557 539 542
– – 7.67 5.53 4.29 4.90 6.13 4.51 4.99 6.26 5.27 5.90 6.47 4.80
– 3.63 – 4.73 5.37 4.32 5.02 4.55 5.42 5.87 4.88 4.21 4.27 4.17
– – 5.29 2.87 2.55 1.29 4.27 2.82 1.90 3.22 1.13 2.60 1.48 2.53
– 1.32 – 1.44 2.18 1.84 2.70 1.43 2.32 2.96 3.37 1.73 2.22 1.86
33.9 31.3 31.6 31.8 32.2 32.3 31.6 31.5 30.8 32.4 33.2 32.7 31.9 31.4
29.6 27.6 28.2 27.6 28.4 27.8 27.3 27.3 27.1 28.1 28.2 27.4 27.5 28.3
4.88 4.71 5.00 4.32 4.22 3.99 4.60 4.20 4.70 4.60 4.10 4.80 4.70 4.30
2.31 1.38 1.42 1.81 1.82 1.16 1.50 1.70 1.90 2.10 1.90 1.40 1.20 1.50
SWW W SW SWW SWW SWW SWW SWW SW SW W SWW SWW SWW
SW W W W SWW SWW W W SWW SWW SWW W W SWW
57.3
26.2
27.1
12.1
981
551
5.56
4.70
2.66
2.11
32.0
27.9
4.51
1.65
–
–
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particle sample device Noll Rotary Impactor (NRI) and micro-orifice uniform deposit impactor (MOUDI) to sample ambient air coarse and fine particles, respectively. Dry deposition velocities were also calculated on the base of above study. And the previous study has also reflected that the dry deposition velocity calculated by Flux and TSP were about 10% lower than the value calculated by Flux combined with NRI and MOUDI. Thus, this values obtained in this study will be thus underestimated the dry deposition velocities. 3.2. Effects of meteorological parameters
Total suspended particulate concentration (µg/m3)
Table 1 illustrated the relationship between upward, downward and dry deposition flux and wind speed at the traffic sampling sites of central Taiwan. Fig. 2(A) and (B) was the contrasts by downward, upward dry deposition flux and wind speed in the daytime and nighttime period, respectively. The correlation coefficients between dry deposition flux and wind speed are 0.65 and 0.38 for
Daytime (A)
80
Dry deposition flux (µg/m2-sec)
2
Downward R =0.63 2 Upward R =0.38
70
the downward and upward dry deposition flux in the daytime period, respectively. The correlation coefficients between dry deposition flux and wind speed are 0.74 and 0.44 for the downward and upward dry deposition flux in the nighttime period, respectively. The above results indicated that the downward dry depositions are all highly correlated to the wind speed than the upward dry deposition in either daytime or nighttime period. And the correlation coefficients (R2 ) for downward dry deposition, upward dry deposition vs. wind speed, the results indicated that correlation coefficient is all higher in the nighttime period than the daytime period for either downward or upward dry deposition. The possible reason is that the less traffic vehicles and activities during the nighttime period were thus increasing the correlation coefficient. As for the relationship between total suspended particulate concentrations vs. wind speed, the results are displayed in Fig. 3(A) and (B). The correlation
60
50
40
30
20
10 3.8
4.0
4.2
4.4
4.6
4.8
5.0
984
Daytime (A) 2
R =0.64 983
982
981
980
979
978
5.2
3.8
4.0
Wind speed (m/sec)
Dry deposition flux (µg/m2-sec)
2
Downward R =0.74 2 Upward R =0.44
35
30
25
20
15
10
5 1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
Wind speed (m/sec)
Fig. 2. The correlation coefficients (R2 ) for downward, upward dry deposition fluxes vs. wind speed between daytime and nighttime period.
Total suspended particulate concentration (µg/m3)
Nighttime (B)
40
4.2
4.4
4.6
4.8
Wind speed (m/sec) Nighttime (B) 565 2
R =0.38 560
555
550
545
540
535 1.0
1.2
1.4
1.6
1.8
2.0
2.2
Wind speed (m/sec)
Fig. 3. The correlation coefficients (R2 ) for total suspended particulate concentration vs. wind speed between daytime and nighttime period.
Table 2 The metal elements information during day and night period Downward dry deposition flux (lg/m2 day)
TSP concentration (lg/m3 )
Sampling no.
Fe
Pb
Zn
Cu
Mg
Mn
Fe
Pb
Zn
Cu
Mg
Mn
Fe
Pb
Zn
Cu
Mg
Mn
Panel A Daytime 1 2 3 4 5 6 7 8 9 10 11 12 13 14
27 121 15 470 11 368 10 561 13 106 9136 27 141 15 278 10 734 13 249 9942 10 721 16 284 11 082
379 227 291 227 379 227 303 267 284 319 231 275 314 358
14 545 9242 4920 5879 8333 12 318 7045 6272 11 728 7138 8216 7098 11 842 9067
303 303 296 326 297 303 303 314 298 284 336 307 295 308
909 606 502 276 152 606 818 294 846 524 615 498 625 594
326 267 314 227 303 268 582 492 332 266 384 396 396 328
2.42 1.14 1.26 2.19 1.33 1.89 1.67 1.62 1.78 1.54 1.36 1.77 1.82 2.12
0.14 0.14 0.23 0.14 0.25 0.25 0.17 0.16 0.15 0.15 0.22 0.19 0.26 0.13
1.06 0.92 0.95 0.89 0.89 1.14 1.58 0.92 1.14 0.98 1.02 1.36 0.95 1.10
0.22 0.19 0.25 0.22 0.28 0.22 0.33 0.19 0.31 0.26 0.24 0.32 0.19 0.16
0.61 0.52 0.49 0.67 0.28 0.39 0.36 0.31 0.56 0.52 0.38 0.64 0.33 0.47
0.08 0.08 0.12 0.11 0.09 0.08 0.14 0.09 0.13 0.16 0.07 0.12 0.15 0.09
12.99 15.72 10.44 5.57 11.38 5.60 18.85 10.92 6.98 9.96 8.46 7.01 10.36 6.05
3.16 1.89 1.46 1.89 1.75 1.05 2.10 1.93 2.19 2.46 1.22 1.68 1.40 3.19
15.95 11.67 5.99 7.65 10.85 12.52 5.15 7.89 11.91 8.43 9.32 6.04 14.43 9.54
1.58 1.80 1.37 1.70 1.24 1.58 1.05 1.91 1.11 1.26 1.62 1.11 1.80 2.23
1.72 1.34 1.19 0.48 0.63 1.80 2.60 1.10 1.75 1.17 1.87 0.90 2.19 1.46
4.72 3.71 3.03 2.37 3.90 3.72 4.85 6.33 2.96 1.92 6.35 3.82 3.06 4.22
Average
14 371
292
8832
305
562
349
1.71
0.18
1.06
0.24
0.47
0.11
10.02
1.96
9.81
1.53
1.44
3.92
Nighttime 1 2 3 4 5 6 7 8 9 10 11 12 13 14
9364 11 412 9091 7294 10 348 9030 7015 9146 10 287 8422 9612 7546 10 976 8420
227 210 227 128 303 152 227 184 195 216 207 186 205 178
7045 6246 5288 4357 7485 3788 2121 4136 5698 4673 6018 5422 4769 4361
227 242 303 245 227 237 227 242 258 266 251 283 224 248
0 129 0 242 379 152 227 102 246 138 0 312 297 125
227 208 283 219 251 254 227 248 216 207 220 269 281 208
1.16 1.02 2.03 1.39 2.94 1.33 1.19 2.02 2.16 1.28 1.22 1.76 1.64 2.13
0.17 0.21 0.14 0.25 0.16 0.14 0.17 0.23 0.18 0.22 0.16 0.14 0.20 0.21
0.72 0.83 0.96 0.78 0.73 1.08 0.92 0.76 0.98 0.77 0.90 0.96 0.88 0.82
0.11 0.23 0.25 0.16 0.28 0.17 0.36 0.16 0.33 0.24 0.33 0.18 0.25 0.11
0.13 0.12 0.31 0.54 0.50 0.25 0.28 0.52 0.16 0.22 0.21 0.38 0.45 0.39
0.08 0.07 0.08 0.06 0.07 0.08 0.08 0.08 0.06 0.06 0.07 0.07 0.09 0.06
9.34 12.95 5.19 6.07 4.07 7.84 6.80 5.24 5.51 7.62 9.12 4.96 7.75 4.58
1.58 1.16 1.89 0.59 2.19 1.26 1.58 0.93 1.25 1.14 1.50 1.54 1.19 0.98
11.29 8.71 6.38 6.47 11.87 4.05 2.68 6.30 6.73 7.02 7.74 6.54 6.27 6.16
2.37 1.22 1.40 1.77 0.95 1.65 0.73 1.75 0.90 1.28 0.88 1.82 1.04 2.61
0.00 1.24 0.00 0.52 0.88 0.70 0.95 0.23 1.78 0.73 0.00 0.95 0.76 0.37
3.29 3.44 3.93 4.22 4.15 3.53 3.16 3.59 4.17 3.99 3.64 4.45 3.61 4.01
Average
9140
203
5101
249
168
237
1.66
0.18
0.86
0.23
0.32
0.07
6.93
1.34
7.01
1.45
0.65
3.80
Panel B Daytime 1 2
6455 7303
152 157
1985 3106
220 248
0 0
152 227
2.42 1.14
0.14 0.14
1.06 0.92
0.22 0.19
0.61 0.52
0.08 0.08
3.09 7.42
1.26 1.30
2.18 3.92
1.15 1.48
0.00 0.00
2.19 3.16
Dry deposition velocity (cm/s)
G.-C. Fang et al. / Chemosphere 56 (2004) 509–518 515
516
Table 2 (continued) Sampling no.
Downward dry deposition flux (lg/m2 day) Fe
Pb
Zn
TSP concentration (lg/m3 )
Dry deposition velocity (cm/s)
Cu
Mg
Mn
Fe
Pb
Zn
Cu
Mg
Mn
Fe
Pb
Zn
Cu
Mg
Mn
4510 3182 4606 3776 3947 5512 4691 3980 4410 6606 5323 4012
206 164 189 227 231 168 220 212 186 195 215 175
2492 3333 4470 8030 5545 2260 7844 2360 4475 4846 3233 3957
254 227 249 224 244 235 222 237 242 248 212 238
12 0 0 0 27 10 0 0 8 0 15 14
231 252 379 227 379 166 283 210 364 182 241 397
1.26 2.19 1.33 1.89 1.67 1.62 1.78 1.54 1.36 1.77 1.82 2.12
0.23 0.14 0.25 0.25 0.17 0.16 0.15 0.15 0.22 0.19 0.26 0.13
0.95 0.89 0.89 1.14 1.58 0.92 1.14 0.98 1.02 1.36 0.95 1.10
0.25 0.22 0.28 0.22 0.33 0.19 0.31 0.26 0.24 0.32 0.19 0.16
0.49 0.67 0.28 0.39 0.36 0.31 0.56 0.52 0.38 0.64 0.33 0.47
0.12 0.11 0.09 0.08 0.14 0.09 0.13 0.16 0.07 0.12 0.15 0.09
4.14 1.68 4.00 2.31 2.74 3.94 3.05 2.99 3.75 4.32 3.39 2.19
1.04 1.37 0.88 1.05 1.61 1.22 1.70 1.64 0.98 1.19 0.96 1.56
3.04 4.34 5.82 8.16 4.05 2.84 7.96 2.79 5.08 4.12 3.94 4.16
1.18 1.18 1.04 1.17 0.85 1.43 0.83 1.06 1.17 0.90 1.29 1.72
0.03 0.00 0.00 0.00 0.09 0.04 0.00 0.00 0.02 0.00 0.05 0.03
2.23 2.63 4.87 3.16 3.16 2.13 2.52 1.52 6.02 1.76 1.86 5.11
Average
4879
193
4138
236
6
264
1.71
0.18
1.06
0.24
0.47
0.11
3.50
1.27
4.46
1.17
0.02
3.02
Nighttime 1 2 3 4 5 6 7 8 9 10 11 12 13 14
5273 1856 2197 2033 3091 3347 2048 2864 1598 2966 2138 3390 3714 2208
141 166 152 142 174 128 144 148 169 171 128 124 163 185
1939 1440 1652 1582 3015 2004 2965 2438 2066 1804 1276 2724 2039 2912
162 160 152 180 214 203 194 177 194 220 142 206 173 152
0 0 0 0 0 0 0 0 0 0 0 0 0 0
143 140 152 158 198 164 183 172 140 201 176 158 174 155
1.16 1.02 2.03 1.39 2.94 1.33 1.19 2.02 2.16 1.28 1.22 1.76 1.64 2.13
0.17 0.21 0.14 0.25 0.16 0.14 0.17 0.14 0.18 0.22 0.16 0.14 0.20 0.21
0.72 0.83 0.96 0.78 0.73 1.08 0.92 0.76 0.98 0.77 0.90 0.96 0.88 0.82
0.11 0.23 0.25 0.16 0.28 0.17 0.36 0.16 0.33 0.24 0.33 0.18 0.25 0.11
0.13 0.12 0.31 0.54 0.50 0.25 0.28 0.52 0.16 0.22 0.21 0.38 0.45 0.39
0.08 0.07 0.08 0.06 0.07 0.08 0.08 0.08 0.06 0.06 0.07 0.07 0.09 0.06
5.26 2.11 1.25 1.69 1.21 2.91 1.98 1.64 0.86 2.68 2.03 2.23 2.62 1.20
0.98 0.91 1.26 0.66 1.26 1.07 1.00 1.22 1.09 0.90 0.93 1.03 0.94 1.02
3.11 2.01 1.99 2.35 4.78 2.14 3.74 3.71 2.44 2.71 1.64 3.28 2.68 4.11
1.69 0.81 0.70 1.30 0.89 1.41 0.62 1.28 0.68 1.06 0.50 1.32 0.80 1.60
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
2.07 2.31 2.10 3.05 3.27 2.28 2.54 2.49 2.70 3.88 2.91 2.61 2.24 2.99
Average
2766
152
2133
181
0
165
1.66
0.18
0.86
0.23
0.32
0.07
2.12
1.02
2.91
1.05
0.00
2.67
G.-C. Fang et al. / Chemosphere 56 (2004) 509–518
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coefficients between total suspended particulate concentrations vs. wind speed are 0.64 and 0.38 in the daytime and nighttime, respectively. The results obtained in this study revealed that the total suspended particulate concentrations are highly correlated to the wind speed in the daytime period than nighttime period. It is just opposite to the results obtained for the dry deposition (downward, upward) vs. wind speed in the daytime and nighttime period. The possible reason provides here is beyond traffic vehicles, wind speed variation between daytime and nighttime period is the large parameter to influence this result. The traffic is more on the road near the sampling site, and the passing by vehicles on the road resuspended the road dust to the atmosphere. Thus, the relationship in the daytime period was higher than the nighttime period.
3.3. Ambient airborne particle of heavy metals The data of metal elements with downward and upward dry deposition flux, total suspended particulate concentration and dry deposition velocity was shown in Table 2(panels A and B). Table 2 comprise panels A and B which represent downward and upward dry deposition flux with respect to total suspended particulates concentration and dry deposition velocity, respectively. Table 2(panel A) indicated that the downward dry deposition fluxes with metal elements (Fe, Pb, Zn, Cu, Mg and Mn) for the daytime period are 14 371, 292, 8832, 305, 562 and 349 g/m2 day, respectively. The average downward dry deposition fluxes with metal elements (Fe, Pb, Zn, Cu, Mg and Mn) for the nighttime period are 9140, 203, 5101, 249, 168 and 237 g/m2 day, respectively. Table 2(panel B) indicated that the upward dry deposition fluxes with metal elements (Fe, Pb, Zn, Cu, Mg and Mn) for the daytime period are 4879, 193, 4138, 236, 6 and 264 g/ m2 day, respectively. The average upward dry deposition fluxes with metal elements (Fe, Pb, Zn, Cu, Mg and Mn) for the nighttime period are 2766, 152, 2133, 181, 0 and 165 g/m2 day, respectively. The average total suspended particulate concentration with metal elements (Fe, Pb, Zn, Cu, Mg and Mn) in the daytime period and nighttime period are 1.71, 0.18, 1.06, 0.24, 0.47, 0.11 and 1.66, 0.18, 0.86, 0.23, 0.32, 0.07 g/m3 , respectively. The results revealed that the average downward and upward dry deposition fluxes with metal elements in the daytime period were higher than in nighttime period. And the total suspended particulate concentrations with metal elements were also had this phenomenal. The results also showed the range of metal elements with Fe, Zn and Mg were larger than Pb, Cu and Mn whether dry deposition fluxes or total suspended particulate concentrations.
517
4. Conclusions The dry deposition fluxes and total suspended particulate of particulate total mass and heavy metals in Sha-Lu, Taiwan were measured. The average downward dry deposition mass fluxes in the daytime and nighttime period were found to be 54.1 and 26.2 g/m2 s, respectively. And the average upward dry deposition mass fluxes in the daytime and nighttime period were found to be 26.5 and 12.1 g/m2 s, respectively. In addition, the total suspended particulate concentrations in the daytime and nighttime period were 981 and 551 g/m3 , respectively. Heavy metals such as Fe, Zn and Mg show a higher average value than those of Mn, Cu and Pb in dry depositions and total suspended particulate for either daytime or nighttime period. The correlation coefficients (R2 ) for downward, upward dry deposition fluxes vs. wind speed, the results also indicated that correlation coefficients in the nighttime period are all higher than that of daytime period for either downward or upward dry deposition. The possible reason is that the less traffic vehicles and activities during the nighttime period were thus increased the correlation coefficients. The correlation coefficients (R2 ) between total suspended particulate concentrations vs. wind speed, the results obtained displayed that the total suspended particulate concentrations are highly correlated to the wind speed in the daytime period than nighttime period. These results just opposite to the results obtained for the dry deposition (downward, upward) vs. wind speed in the daytime and nighttime period. The possible reason provides here is beyond traffic vehicles, wind speed variation between daytime and nighttime period is the large parameter to influence this result.
Acknowledgements The authors gratefully acknowledge the National Science Council of the ROC (Taiwan) for financial support under project no. NSC 92-2211-E-241-002.
References Antonio, J., Espinsa, F., Rodriguez, M.T., Francisco, J., de la Rosa, B., Juan, C., Sanchez, J., 2001. Size distribution of metals in urban aerosols in Seville (Spain). Atmospheric Environment 35, 2595–2601. Caffrey, P.F., Ondov, J.M., Zufall, M.J., Davidson, C.I., 1998. Determination of size dependent dry particle deposition velocities with multiple intrinsic elemental tracers. Environmental Science and Technology 32, 1615–1622. D’Almeida, G.A., Koepke, P., Shettle, E.P., 1991. Atmospheric Aerosols: Global Climatology and Radiative Characteristics. A. Deepak publishing. 561 pp.
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G.-C. Fang et al. / Chemosphere 56 (2004) 509–518
El-Fadel, M., Hashisho, Z., 2001. Vehicular emissions in roadway tunnels: a critical review. Critical Reviews in Environmental Science and Technology 31, 125–174. Fang, G.C., Chang, C.N., Wu, Y.S., Fu, P.P.C., Chang, K.F., Yang, D.G., 1999. The characteristic study of TSP, PM2.5_10 and PM2.5 in the rural site of central Taiwan. Science of the Total Environment 232, 177–5184. Galloway, J.N., Thorton, J.D., Norton, S.A., Volchok, H.L., McLean, R.A.N., 1982. Trace metals in atmospheric deposition: a review and assessment. Atmospheric Environment 16 (7), 1677–1700. Noll, K.E., Fang, K.Y., 1986. Air Pollution Control Association, 79th Annual Meeting, Minneapolis, Minnesota, June 22–27.
Noll, K.E., Fang, K.Y., 1988. Development of a dry deposition model for atmospheric coarse particles. Atmospheric Environment 23 (3), 585–594. Shahin, U.M., Lu, J., Yi, S.M., Paode, R.D., Holsen, T.M., 2000. Long-term elemental dry deposition fluxes measured around Lake Michigan with an automated dry deposition sampler. Environmental Science and Technology 34, 1887– 1892. Vakeva, M., Hameri, K., Kulmala, M., Lahdes, R., Ruuskanen, J., Laitinen, T., 1999. Street level versus rooftop concentrations of submicron aerosol particles and gaseous pollutants in an urban street canyon. Atmospheric Environment 33, 1385–1397.