air4

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Ion Chromatography (Dionex DX 100)

∫∑§—¥¬àÕ

Automated wet-only sampling

„π°√Õ∫§«“¡√à«¡¡◊Õ„π‚§√ß°“√‡§√◊Õ¢à“°“√»÷ ° …“°“√µ° – ¡¢Õß°√¥„π¿Ÿ ¡‘ ¿ “§‡Õ‡™’ µ–«—πÕÕ° (Acid Deposition Monitoring Network in East Asia, EANET) »Ÿπ¬å«‘®—¬·≈–Ωñ°Õ∫√¡¥â“π ‘Ë ß ·«¥≈â Õ ¡‰¥â ‡ ¢â “ √à « ¡‡ªì π §≥–∑”ß“π„π‚§√ß°“√ ¥— ß °≈à “ « ‚¥¬∑”°“√»÷ ° …“Õß§å ª √–°Õ∫∑“߇§¡’ „πµ— « Õ¬à “ ß πÈ” Ωπ„π‡¢µ™π∫∑¢Õߪ√–‡∑»‰∑°“√»÷°…“‰¥â∑”°“√‡°Á∫µ—«Õ¬à“ßπÈ”Ωπ (wet-only) √“¬«—π√–À«à“ß ƒ¥ŸΩπ¢Õߪï 2543 ≥ ∂“π’‡°Á∫ µ—«Õ¬à“ß»Ÿπ¬å«‘®—¬·≈–Ωñ°Õ∫√¡¥â“π ‘Ëß·«¥≈âÕ¡ ‡æ◊ËÕ ∑”°“√µ√«®«—¥§à“°“√π”‰øøÑ“ (conductivity) §à“ §«“¡‡ªìπ°√¥¥à“ß (pH) ·≈–Õ‘ÕÕπ∫«°·≈–Õ‘ÕÕπ≈∫ ‰¥â·°à ‚´‡¥’¬¡ (Na+) ‚ªµ— ‡´’¬¡ (K+) ·Õ¡‚¡‡π’¬¡ (NH4+) ·¡°‡π‡´’¬¡ (Mg2+) ·§≈‡´’¬¡ (Ca2+)

*»Ÿπ¬å«‘®—¬·≈–Ωñ°Õ∫√¡¥â“π ‘Ëß·«¥≈âÕ¡ °√¡ à߇ √‘¡§ÿ≥¿“æ ‘Ëß·«¥≈âÕ¡ ‡∑§‚π∏“π’ µ.§≈ÕßÀâ“ Õ.§≈ÕßÀ≈«ß ®.ª∑ÿ¡∏“π’ 12120 ‚∑√. 0-2577-1136 ‚∑√ “√. 0-2577-1138 Environmental Research and Training Center, Department of Environmental Quality Promotion. Technopolis. Klong 5 Klong Luang, Pathumthani 12120 e-mail: hathairat@myrealbox.com

§≈Õ‰√¥å (Cl-) ‰π‡µ√∑ (NO3-) ·≈–´—≈‡øµ (SO42-) ‚¥¬„™â ‡ ∑§π‘ § ‰ÕÕÕπ‚§√¡“‚µ°√“øï (Ion Chromatography) „π∑”πÕ߇¥’¬«°—π »Ÿπ¬å«‘®—¬·≈–Ωñ° Õ∫√¡¥â“π ‘Ëß·«¥≈âÕ¡‰¥â∑”°“√«‘‡§√“–ÀåÕߧåª√–°Õ∫ ∑“߇§¡’ „πµ—«Õ¬à“ßπÈ”Ωπ√«¡ (bulk) §«∫§Ÿà ‰ª°—∫°“√ ‡°Á∫µ—«Õ¬à“ßπÈ”Ωπ·∫∫ wet-only ‡æ◊ËÕ„Àâ∑√“∫∂÷ß Õ‘∑∏‘æ≈¢Õß°“√ªπ‡ªóôÕπ„π µ—«Õ¬à“ßπÈ”Ωπ Õ—π‡π◊ËÕß ¡“®“°ΩÿÉπ≈–ÕÕß„π∫√√¬“°“»∫√‘‡«≥∑’Ë∑”°“√‡°Á∫ µ—«Õ¬à“ß πÕ°®“°π’È °“√»÷°…“¬—߉¥âµ√«® Õ∫√–∫∫ §ÿ ≥ ¿“æ¢Õß°“√«‘ ‡ §√“–Àå Õ ß§å ª √–°Õ∫∑“߇§¡’ ¥—ß°≈à“«„πµ—«Õ¬à“ßπÈ”Ωπ ‡æ◊ËÕ„Àâ ‰¥â¢âÕ¡Ÿ≈∑’ˇ™◊ËÕ∂◊Õ‰¥â

ABSTRACT Within the framework of the Acid Deposition Monitoring Network in East Asia (EANET) project, Environmental Research and Training Center (ERTC) has been selected as a representative organization to provide data and information on the chemical compositions of precipitation in Thailand since 1997. In this report, wet as well as bulk depositions were collected for chemical analysis on a daily basis during January 1999 - September 1999 at ERTC sampling site. Regarding to the objectives of EANET, the specific objectives of this report are to identify the chemical species in wet deposition samples and to determine the ion and conductivity balances of those samples. While the chemical compositions of the corresponding bulk samples will be used to support the background assessment of the sampling site.

Besides, the reliability of the analysis was also given in terms of precision, detection limits and determination limits.

1. Introduction Acid deposition is widely recognized as one of the most serious global atmospheric pollution problems. The effects of acid deposition are becoming increasingly manifest, substantial and widespread, producing environmental damage of adverse impacts on aquatic and terrestrial ecosystems, §-26

building materials and human health. Over the years, there have been extensive studies on acid rain and its harmful impact on the environment in industrialized countries such as Europe and North America. Those studies have, in recent years, been extended to tropical sites and results have shown that acid rain, one thought to occur in industrialized countries, could affect remotes far from industrial source of acidifying compounds.

The Acid Deposition Monitoring Network in East Asia is dedicated to creating a common understanding of the status of the acid deposition among countries and organizations of the East Asia region, and to providing useful inputs to assessment of acid deposition for decision making at various levels aimed at preventing adverse impacts of acid deposition in the region. One of the goals of this network is to provide high-quality data and other information on the chemical composition of wet deposition from all parts of East Asia. Wet deposition is responsible for 30-50% of deposition fluxes to ecosystems.

Precipitation chemistry measurements provide information on the exchange of trace materials between the atmosphere and the earthûs surface.

2. Methods and Materials 2.1 Location of sampling site and its characteristics ERTC is located in Pathumthani province, which is located in the central region of Thailand. The province occupies an area of about 1,526 square kilometers and has a population of about 412,407. It has common boundary with Bangkok Metropolis in the south with the distance of 28 km. The average increasing rate of number of factories during 1970-1994 was about 20 percent per year, especially during 1989-1994, when the economic condition of the country was moving to the top of the peak, the increasing »Ÿπ¬å«‘®—¬·≈–Ωñ°Õ∫√¡¥â“π ‘Ëß·«¥≈âÕ¡ °√¡ à߇ √‘¡§ÿ≥¿“æ ‘Ëß·«¥≈âÕ¡

rate in this province was about 64 percent per year. Office of the Provincial Industry reported that in 1994 the total number of factories was 1,169 and they are mostly small to medium size factories, which concentrated in the middle part of the province.

Similar to Bangkok, the climate of the province is dominated by the monsoons.

A southwest monsoon predominant during February-October (summer) and with it comes the rainy season. A northeast monsoon predominant in November-January (winter) bringing drier air with relative rainfalls.

According to the prevailing wind direction, Pathumthani is either downwind or upwind of Bangkok.

There is a little change in temperature throughout the year in Pathumthani. The annual average temperature being 28-30 Ì C , the annual humidity at 70-80%, and the annual rainfall of over 200 mm (Meteorological Department), characteristic of a tropical climate.

As shown in Figure 1, ERTC is located in the eastern part of Pathumthani where no significant man-made air pollution sources

surround, within the distance of about 8 km radius. There is also a highway with the density of about 65000 cars/day runs about 10 km far to the west. The rain sampler was placed at the West Side of ERTC building on a cement road that isolated from the daily activity of the Center. According to the sampling site classification of the network, ERTC is now classified as a rural site. We could say that the location of this site is still in the area with minimal influence from local emission and contamination sources and could actually satisfy the criteria only in some extents. However, due to the current industrial development in Pathumthani, the classification of this site should be reconsidered in the future.

2.2 Sample collection Rainwater samples were collected on an daily basis with an automated wet-dry sampler (Graseby, model T87-100) and a bulk collector. The wet-dry sampler will exposes the wet collector, a HDPE bucket, only when precipitation is falling. The device is equipped with a sensor that detects the precipitation episodes and activates a mechanism by which

Figure 1 Map of ERTC location in Pathumthani province for wet deposition sampling (EANET)

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§-27

the lid opens with the first drop of a shower and closes just after the rain event. The advantage of automated wet-dry sampler is that the contamination of rainwater by dust fall can be kept at the minimum before and after the event. The bulk collector have a polyethylene funnel with a short cylindrical upper part Ø = 200 mm and h = 20 mm.

Rainwater is collected in a 2 L polyethylene bottle. The bottle is covered with aluminum foil to shield against light. All samples were removed from the collector as soon as possible, certainly within 24 hours. To prevent atmospheric influences on the samples during transport from the collection site to the laboratory, the bucket and the polyethylene bottle were tightly covered with a cleaned aluminum foil.

After collection, the samples were weighed to determine the amount of water and then filtrated with a 0.45 µ m pore-size cellulose nitrate membrane filter paper. The samples were sealed and stored at 4 ÌC (in the dark) without any preservatives until further analysis usually carried out within 2 weeks.

2.3 Chemical Analysis Inorganic cations and anions (Na+, K+, NH4+, Mg2+, Ca2+, Cl-, NO3- and SO42-) in rainwater samples (wet and bulk) were analyzed separately by 2 sets of Ion Chromatography (Dionex DX100) with a conductivity detector. The anion analysis was proceeded using AS 12 A separator column with 4.25 mM Na2CO3 / 0.3 mM NaHCO3 mobile phase while cation analysis used CS 12 separator column with 20 mM MSA mobile phase. In both analyses, the samples were introduced by AS40 auto-sampler with 25 µl sample loop and 1 ml/min flow rate. The pH measurements were made by TOA model HM 30 V with ST5421C glass electrode. The conductivity (EC) was also measured by TOA model CM 40 with CG511B electrode. §-28

3. Results and discussion Reliability of the analysis are determined in terms of precision of the analytical methods, detection limits and determination limits as shown in Table 1 and 2, respectively. The precision of the measurements (based on 5 replications) is almost within the guideline (± 15%) except for Ca2+ (see Table 1). This may due to the fact that Calcium ion was obviously found contaminated in the de-ionized water.

Besides, the detection limit and the determination limit values are mostly within the guideline except for Mg2+, SO42-, and Ca2+ (see Table 2). Again this problem may be related to the poor quality of de-ionized water, which could affect the blank quality and hence poor analytical precision has been observed for low concentration analysis. The accuracy of the analysis could be assessed in this report using the analytical results of artificial rainwater samples sent by the Interim Network Center (INC) during May 1999 as summarized in Table 3. The results showed good accuracy for the analysis of high concentration rainwater (sample number 1), in contrast with the one of low concentration (sample number 2), only moderate accuracy could be obtained. Therefore, further improvement of low concentration rainwater analysis should be reconsidered. However, more than 90% of those ions in the samples show the measurement results higher than the detection limits without any dilutions.

A total of 55 wet-only daily basis precipitation samples were obtained during January-September 1999. Eight ionic species, pH, and conductivity were determined for each sample. Besides, the daily basis precipitation amounts were determined based on the diameter of the HDPE bucket. The daily wet-only precipitation results are given in the Table 4 in which the FORM (A) of the guideline is followed. Data quality for all »Ÿπ¬å«‘®—¬·≈–Ωñ°Õ∫√¡¥â“π ‘Ëß·«¥≈âÕ¡ °√¡ à߇ √‘¡§ÿ≥¿“æ ‘Ëß·«¥≈âÕ¡

Table 1 Analytical precision 1.1 Retention time (minutes) Ions Na+ NH4+ K+ Mg+ Ca2+ ClNO3SO42-

Injection 1 Injection 2 Injection 3 Injection 4 Injection 5 3.32 3.33 3.35 3.33 3.32 3.80 3.83 3.83 3.83 3.82 4.82 4.85 4.85 4.83 4.83 6.33 6.37 6.38 6.37 6.33 7.80 7.85 7.87 7.83 7.82 3.60 3.60 3.60 3.60 3.60 7.80 7.80 7.80 7.80 7.80 9.05 9.05 9.05 9.05 9.05

Average 3.33 3.82 4.84 6.36 7.83 3.60 7.80 9.05

SD 0.0122 0.0130 0.0134 0.0241 0.0270 0.0000 0.0000 0.0000

%RSD 0.37 0.34 0.28 0.38 0.34 0.00 0.00 0.00

Injection 1 1160313 1355962 680344 2011999 2909780 2787987 1330304 1686689

1.2 Peak area Ions Na+ NH4+ K+ Mg+ Ca2+ ClNO3SO42-

Injection 2 1104512 1201340 560395 1684673 1554434 2170555 1366326 1326251

Injection 3 1103418 1041559 495890 1758926 1750107 2742358 1178321 1574958

Injection 4 1203302 1109334 648919 1755372 1788789 2140347 1084768 1554371

Injection 5 1217419 1228057 628272 1455723 1730500 2196001 1275006 1478027

Average 1142886 1177049 596387 1802743 1697777 2351087 1209805 1485193

SD 5.E+04 1.E+05 7.E+04 2.E+05 5.E+05 3.E+05 1.E+05 1.E+05

%RSD 4.22 10.20 12.44 11.03 32.15 13.93 9.51 8.98

Injection 2 0.04700 0.05233 0.05115 0.05568 0.05427 0.11958 0.11006 0.15111

Injection 3 0.04600 0.04679 0.04818 0.05740 0.05910 0.11982 0.10422 0.18884

Injection 4 0.05100 0.04914 0.05523 0.05732 0.06006 0.11934 0.10423 0.18571

Injection 5 0.04269 0.05326 0.05428 0.05037 0.05862 0.10953 0.10603 0.17413

Average 0.04541 0.05184 0.05310 0.05681 0.06396 0.11805 0.10592 0.18111

SD 0.004 0.004 0.003 0.005 0.013 0.005 0.002 0.020

%RSD 9.66 8.03 6.44 8.12 21.08 4.13 2.29 11.17

1.3 Concentration (ppm) Ions Na+ NH4+ K+ Mg+ Ca2+ ClNO3SO42-

Injection 1 0.04036 0.05770 0.05668 0.06328 0.08775 0.12199 0.10508 0.20578

Table 2 Detection limits and determination limits including the precision of pH and EC measurements in this study Parameters Na+ NH4+ K+ Mg+ Ca2+ ClNO3SO42PH* EC**

Detection Limits (3 SD)

Detection Limits (10 SD)

0.5 (0.3) 0.7 (0.8) 0.3 (0.3) 0.6 (0.3) 1.0 (0.2) 0.4 (0.5) 0.2 (0.5) 0.6 (0.3)

1.9 (1.0) 2.3 (3.0) 0.9 (1.0) 1.9 (1.0) 3.4 (0.6) 1.4 (1.5) 0.4 (1.5) 2.1 (1.0)

Replicate measurement of RM was agree within ± 0.05 Replication measurement of de-ionized water (EC : < 1 µS cm-1) was within ± 0.2 µS cm-1

Number in the parentheses is the guideline value. * Results from the participation in the Inter-laboratory comparison, the analytical activities of EANET 1998 ** Results are based on 10 replications

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§-29

Table 3 Accuracy assessment using the artificial rainwater samples of INC SO42NO3CLNa+ K+ Ca2+ Mg2+ NH4+ R1 R2 m mol/L m mol/L m mol/L m mol/L m mol/L m mol/L m mol/L m mol/L

pH

EC (mS/m)

sample number 1 True value Data count Average Minimum Maximum Standard deviation

4.02 4.05 14 4.07 3.97 4.12 0.04

7.47 7.93 14 7.50 7.01 7.86 0.20

79.90 83.00 14 82.52 69.80 99.00 8.24

89.10 93.00 14 93.06 79.90 109.00 7.02

131.00 129.00 14 127.95 111.30 149.00 9.65

91.70 96.00 14 89.42 15.90 107.00 22.90

8.42 11.00 14 10.28 1.22 13.20 3.08

34.80 41.00 14 38.81 6.21 60.30 11.23

7.59 13.00 14 13.09 0.82 28.97 6.19

83.30 -2.2 2.7 85.00 - 14 - 82.67 - 18.60 -46.2 -13.2 122.00 9.0 7.3 21.54 - -

sample number 2 True value Data count Average Minimum Maximum Standard deviation

4.44 4.51 14 4.55 4.44 4.69 0.06

2.73 2.82 14 2.69 2.41 2.85 0.11

31.30 29.00 14 27.44 13.90 36.00 5.09

43.60 36.00 14 36.16 27.90 43.60 3.73

57.40 45.00 14 43.57 25.30 57.40 6.80

27.50 33.00 14 31.00 3.82 39.60 8.73

3.30 7.40 14 6.38 0.54 8.79 2.20

9.89 14.00 14 13.66 1.87 20.70 4.47

0.00 4.80 14 4.49 0.00 13.50 3.13

23.20 -19.6 4.2 30.00 - 14 - 28.87 - 3.21 -37.0 -28.1 43.20 12.0 5.0 8.65 - -

Rainwater

Figure 2 Comparison of Ca2+, SO42- and NO3- concentrations obtained from the wet only and bulk collectors.

Figure 3 Comparison of the correlation between Na+ and SO42- and Ca2+ and SO42-

§-30

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§-31

Date

24/3/99 26/3/99 4/7/99 4/12/99 19/4/99 21/4/99 22/4/99 23/4/99 28/4/99 29/4/99 30/4/99 5/3/99 5/6/99 5/10/99 5/11/99 5/12/99 18/5/99 19/5/99 20/5/99 21/5/99 24/5/99 6/1/99 6/2/99 6/3/99 6/4/99 6/7/99 6/11/99 14/6/99 21/6/99 7/5/99 15/7/99 19/7/99

Sample

ERTC-w4 ERTC-w5 ERTC-w7 ERTC-w8 ERTC-w10 ERTC-w11 ERTC-w12 ERTC-w13 ERTC-w15 ERTC-w16 ERTC-w17 ERTC-w18 ERTC-w19 ERTC-w20 ERTC-w21 ERTC-w22 ERTC-w23 ERTC-w24 ERTC-w25 ERTC-w26 ERTC-w27 ERTC-w28 ERTC-w29 ERTC-w30 ERTC-w31 ERTC-w32 ERTC-w34 ERTC-w35 ERTC-w36 ERTC-w37 ERTC-w39 ERTC-w40

3.48 -4.22 17.18 -8.47 23.70 1.31 -6.02 7.54 0.93 62.15 10.34 -1.41 9.06 8.89 -2.19 -1.86 -0.20 4.92 4.26 3.03 -3.11 0.27 13.73 8.95 11.86 7.37 1.71 6.28 6.95 6.41 10.16 10.26

0.57 -4.28 17.33 -11.70 12.88 -0.04 5.93 -4.12 -17.33 -36.96 -9.63 -1.96 -4.45 -7.87 -20.31 -12.00 -1.11 -7.38 -6.61 -11.23 -0.79 1.42 -9.71 3.08 -7.07 2.06 0.29 -6.28 -4.21 -3.20 4.70 -0.85 66.83 55.42 5.78 53.52 19.08 65.82 29.72 16.77 13.82 2.63 10.41 31.47 10.19 21.83 15.21 16.36 29.83 15.61 20.33 14.49 33.57 29.19 11.21 49.08 15.25 58.01 33.57 17.00 13.63 34.25 101.97 10.87

Ion Conductivity SO42Balance Balance m mol/L

NO3m mol/L 53.72 46.90 21.18 60.60 26.48 89.48 46.34 30.39 35.67 4.36 17.12 45.34 11.89 12.06 17.99 14.23 20.03 10.55 16.84 11.05 17.76 12.33 9.56 38.10 8.82 23.57 50.47 16.34 12.01 28.37 76.09 4.72

Table 4 Wet-only precipitation chemistry results (1999) Station: Environmental Research and Training Center (ERTC) CLm mol/L 50.05 33.36 4.26 11.70 11.90 12.83 15.43 9.56 5.74 0.87 5.71 10.65 7.15 7.31 2.18 1.94 10.07 3.77 5.17 1.66 25.18 13.75 7.28 12.04 3.86 17.43 14.82 7.14 7.92 9.75 46.65 8.50 NH4+ m mol/L 95.99 45.88 30.76 48.99 75.13 85.27 62.39 38.42 29.04 5.89 14.39 43.78 7.69 11.73 20.51 13.46 36.21 20.82 17.50 9.66 29.95 28.71 27.05 96.10 27.85 99.21 55.49 37.16 21.35 55.66 134.31 17.99

Na+ m mol/L 40.98 25.66 3.67 14.84 8.65 9.38 5.61 6.38 11.95 0.96 9.25 9.16 21.96 18.80 3.18 1.75 10.11 3.05 5.59 4.68 28.10 11.95 5.74 8.78 1.85 10.94 37.08 7.72 7.36 4.41 34.01 7.56

K+ m mol/L 4.14 2.06 1.78 2.07 1.45 2.53 2.50 1.15 1.25 0.37 0.68 1.93 1.72 6.50 0.57 0.27 1.77 0.94 0.62 0.24 1.77 1.83 0.47 2.14 0.89 2.98 1.97 3.73 1.01 2.04 7.84 0.59 Ca2+ m mol/L 43.21 20.68 3.91 26.13 9.33 21.71 14.60 10.85 6.88 0.83 4.26 17.91 4.11 14.42 4.35 2.28 13.37 2.96 2.85 2.04 9.66 15.65 6.62 30.80 9.98 29.23 15.33 6.38 10.36 18.77 100.65 4.08

Mg2+ Total cond. m mol/L mS/m 7.36 37.60 4.10 44.50 0.58 6.14 2.50 39.90 0.80 15.27 2.05 61.10 0.42 16.44 1.69 16.67 0.11 19.59 0.23 30.70 0.69 14.92 1.01 24.10 0.70 8.30 4.20 11.41 0.50 16.95 0.38 18.32 0.69 16.93 0.67 14.01 0.42 23.00 0.26 16.61 2.17 21.00 1.11 14.15 1.42 8.66 3.33 23.10 0.32 9.30 4.21 24.00 2.61 20.50 0.39 10.99 1.74 8.73 1.90 22.80 13.86 46.80 1.26 7.70 4.91 4.28 5.09 4.55 4.72 4.02 5.16 4.84 4.85 4.44 4.71 4.64 5.20 5.97 4.84 4.58 4.88 4.74 4.42 4.60 4.70 5.05 5.62 5.41 5.44 5.70 5.18 5.52 5.57 4.75 5.93 5.15

pH 605.9 764.4 1716.1 234.9 1609 1412.6 412 1018.8 448.9 3527.4 477.7 445.7 2034 665.6 3739 3697.9 1431.3 1589.1 1307 2402.2 681.8 1339.9 962.1 639.3 2572.4 296.7 251.3 270.9 2420.7 1055.5 215.3 3652.5

Sample (g) 8.57 10.81 24.27 3.32 22.75 19.98 5.83 14.41 6.35 49.88 6.76 6.30 28.76 9.41 52.87 52.29 20.24 22.47 18.48 33.97 9.64 18.95 13.61 9.04 36.38 4.20 3.55 3.83 34.23 14.93 3.04 51.65

ppt. (mm)

Remark

§-32

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ERTC-w41 ERTC-w42 ERTC-w43 ERTC-w44 ERTC-w45 ERTC-w46 ERTC-w47 ERTC-w48 ERTC-w49 ERTC-w50 ERTC-w51 ERTC-w52 ERTC-w53 ERTC-w54 ERTC-w55 ERTC-w56 ERTC-w57 ERTC-w58 ERTC-w59 ERTC-w60 ERTC-w61 ERTC-w62 ERTC-w63 ERTC-w64 ERTC-w65 ERTC-w66 ERTC-w67 ERTC-w68 ERTC-w69 ERTC-w70 ERTC-w71

Sample

20/7/99 21/7/99 23/7/99 26/7/99 29/7/99 8/2/99 8/3/99 8/9/99 8/10/99 17/8/99 20/8/99 24/8/99 25/8/99 26/8/99 27/8/99 30/8/99 9/1/99 9/3/99 9/7/99 9/10/99 13/9/99 20/9/99 21/9/99 27/9/99 28/9/99 29/9/99 10/4/99 10/8/99 10/11/99 14/10/99 18/10/99

Date

1.53 0.45 29.33 7.94 7.39 2.65 1.90 6.50 13.58 37.62 46.46 -50.70 -7.53 -51.69 22.45 2.21 -1.05 -2.91 9.79 8.01 12.26 18.97 9.08 1.22 2.85 14.46 4.83 8.09 1.36 23.97 -9.92

-8.70 -8.27 -1.87 -5.99 -2.05 -2.70 -18.54 -0.28 -2.93 29.18 26.61 -19.57 -15.69 -53.69 15.68 -9.75 5.07 -9.16 3.81 -1.38 4.80 6.82 1.88 3.08 3.92 4.01 8.76 -11.60 -0.14 11.46 2.20 11.28 20.93 37.16 24.81 25.33 25.49 33.21 41.13 20.15 29.20 13.73 61.17 8.28 30.50 42.89 21.40 29.60 27.07 40.05 13.47 22.30 35.37 18.47 50.51 19.49 9.14 14.75 29.83 55.50 16.10 10.61

Ion Conductivity SO42Balance Balance m mol/L 5.28 8.27 31.90 10.86 11.68 5.34 22.15 13.45 10.06 34.22 15.51 76.58 5.32 40.26 41.58 21.67 16.33 14.73 21.10 9.35 12.83 22.64 34.83 70.53 14.61 16.17 15.72 52.45 50.44 21.89 5.14

NO3m mol/L

Table 4 Wet-only precipitation chemistry results (1999) Station: Environmental Research and Training Center (ERTC)

10.78 11.21 19.34 13.85 25.83 9.99 29.79 36.81 15.69 11.35 4.92 29.92 7.90 8.16 20.84 3.36 9.35 5.97 7.00 13.08 8.74 12.60 18.49 10.43 3.06 3.90 3.15 13.37 6.34 10.15 2.44

CLm mol/L 12.18 32.93 86.46 50.14 27.36 40.53 0.00 65.33 32.83 70.88 69.80 34.93 1.63 0.44 89.74 33.53 60.66 53.20 69.44 29.46 49.06 64.84 53.42 67.00 22.10 25.11 28.37 80.20 66.45 38.99 9.05

NH4+ m mol/L 11.13 9.35 12.55 10.74 20.35 6.86 11.76 31.99 27.62 16.50 9.42 5.14 6.35 11.49 21.47 5.22 3.29 7.54 7.07 5.56 8.12 10.25 17.52 6.74 1.62 2.86 1.46 5.88 5.08 10.27 2.40

Na+ m mol/L 0.54 1.43 2.43 0.64 2.14 0.84 33.68 1.78 1.14 31.14 3.90 2.80 9.79 2.76 8.94 2.70 0.72 0.42 2.92 0.45 2.69 3.47 2.94 2.08 0.13 0.13 0.13 2.25 0.13 1.71 0.13

K+ m mol/L 3.05 5.01 63.07 12.35 25.24 10.02 25.93 20.62 12.38 19.87 15.42 11.55 0.86 6.98 39.25 9.39 1.90 0.86 9.73 6.49 9.33 36.40 15.37 12.22 1.74 7.14 4.62 21.60 10.95 22.86 2.41

Ca2+ m mol/L 1.48 0.12 4.28 2.56 3.84 0.13 12.03 4.54 2.10 6.21 0.89 1.28 2.12 2.12 3.71 1.87 1.55 1.44 1.64 1.59 1.63 1.43 0.28 1.52 0.14 0.50 0.14 1.58 1.50 2.16 0.14 8.86 13.20 26.30 13.81 14.39 10.88 25.00 20.50 11.90 21.90 9.96 36.30 6.90 37.10 25.30 14.47 14.38 14.99 23.90 10.09 11.10 17.06 14.78 47.07 16.30 7.93 9.45 29.24 46.25 10.08 5.50

Mg2+ Total cond. m mol/L mS/m 5.16 5.10 5.88 5.92 6.02 5.86 5.80 5.81 5.85 4.23 4.79 5.18 5.48 5.58 4.55 5.16 4.92 5.24 4.53 5.14 5.35 5.44 5.34 4.08 4.49 5.10 4.86 4.89 4.12 5.43 5.16

pH 4074.4 1020.7 1136.5 627.3 478.4 488.9 65.5 710.5 390.4 1190.6 552.5 119.6 545.2 1140.6 76.9 1990.5 278.4 259.7 1145.1 855.7 1972.3 675.6 114 874 4152.6 927.5 844.8 1422.3 414.2 432.8 1447

Sample (g) 57.62 14.43 16.07 8.87 6.77 6.91 0.93 10.05 5.52 16.84 7.81 1.69 7.71 16.13 1.09 28.15 3.94 3.67 16.19 12.10 27.89 9.55 1.61 12.36 58.72 13.12 11.95 20.11 5.86 6.12 20.46

ppt. (mm)

Remark

samples was found to be fairly good in terms of ion balance (R1) whereas very good agreement was found between measured and predicted conductivity (R2). The pH values ranged from 4.02 to 6.02 with an arithmetic mean of 5.12 and about 42% of the samples had pH values less than 5.0.

Parallel with wet-only samples, bulk precipitation samples were also collected. The results were used to assess the background level of dry deposition during the same day of rain event. The comparison of Ca2+, SO42-, and NO3- concentrations between wet-only and bulk collectors is demonstrated in the Figure 2.

It can be noted from the results that there is an enhancement of Calcium ions in the bulk samples while no significant difference between the wet-only and bulk collectors were obtained for SO42- and NO3-. Yoshizumi et al. (1996) has demonstrated that Ca of Calcium carbonate origin is one of the strongest factors determining the characteristics of the atmospheric environment around Bangkok. Additionally, Ca2+ is presumably soil-derived and road dust component which has distribution on coarse mode particles with

an appreciable fall velocity and thus could explain the extra deposition. Regarding SO42-, the Figure 3 showed higher correlation between SO42- and Ca2+ (r2 = 0.59) than the one between SO42- and Na+ (r2 = 0.17).

The results may suggest that the SO4 2present in the rainwater at ERTC site may derive from the reaction of H 2 SO 4 with CaCO3, which is of anthropogenic origin, rather than derive from sea salt origin.

4. References 1. Environmental Agency, Government of Japan, (1997), Guidelines and Technical Manuals for Acid Deposition Monitoring Network in East Asia.

2. Meteorological Department, Ministry of Transport and Communications, Thailand, (1994), Climatological Data of Thailand for 30-Year Period (1961-1990).

3. Yoshizumi, K., Ishibashi, Y., Garivait, H., Paranamara, M., Suksomsunk, K., and Tabucanon, M. S., (1996), Size Distributions and Chemical Composition of Atmospheric Aerosols in a Suburb of Bangkok Thailand.

Environ. Technol. 17, pp. 777-782.

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