The Chemistry of Acid Rain - American Chemical Society

Chapter 13

Measurement of Concentration and Oxidation Rate of S(IV) in Rainwater in Yokohama, Japan Shigeru Tanaka, Kazuo Yamanaka, and Yoshikazu Hashimoto Downloaded by UNIV LAVAL on July 11, 2016 | http://pubs.acs.org Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch013

Department of Applied Chemistry, Keio University, Hiyoshi, Yokohama 223, Japan

Sulfite and bisulfite in rain water are rapidly oxidized to sulfate by the catalytic effect of metallic ions such as Fe(III) and Mn(II). The rates of oxidation of S(IV) in test solutions were measured using ion chromatography. The rate constant, k, measured for a 12.5 μΜ S(IV) solution was found to be 0.6-10.4 hr at pH 3-6 in the presence of 1.8 μM Fe(III) and 0.18 μΜ Mn(II) catalysts, and 0.4-5.9 x 10-3 hr without the catalysts. Triethanolamine (TEA) was used to stabilize actual rain water samples prior to analysis. TEA masks the catalytic effect of metallic impurities found in the rain water. The concentrations and the rates of oxidation of S(IV) in rain waters from Yokohama, Japan measured by this method were 0.8-23.5 μΜ (16 samples) and 0.12-3.3 hr (8 samples), respectively. -1

-1

-1

In recent years, the effects of acid rain on lake water, heavy metals contaminated s o i l s and structural materials have been widely discussed (1). Sulfur and nitrogen contained in f o s s i l fuels are released into the atmosphere by combustion. Sulfur and nitrogen oxides dissolve in rain drops as b i s u l f i t e , s u l f i t e and n i t r i t e ions. These components are further oxidized into sulfate and n i t r a t e ions. Since these species lower pH, i t i s important to accurately determine them in rain water. However, these ions are d i f f i c u l t to analyze because they rapidly oxidize in the presence of catalysts such as f e r r i c and manganous ions. Light, temperature, and pH also affect the oxidation rate of S(IV). In t h i s study, the rate of S(IV) oxidation in test solutions was measured as a function of the concentration of metallic ions. The r e l a t i o n s between the rate of oxidation of S(IV) and the m e t a l l i c ions were also investigated using actual rain samples. The effect of pH on the oxidation of S(IV) to S(VI) was also examined.

0097-6156/87/0349-0158$06.00/0 © 1987 A m e r i c a n C h e m i c a l Society

Johnson et al.; The Chemistry of Acid Rain ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

13.

Concentration

TANAKA E T AL.

and Oxidation

Rate of S(IV) in Rainwater

159

Experimental

Downloaded by UNIV LAVAL on July 11, 2016 | http://pubs.acs.org Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch013

The oxidation of S(IV) i s a f i r s t order reaction with respect to S(IV) (2,3). This reaction i s accelerated by the presence of m e t a l l i c ions such as f e r r i c and manganous ions which act as catalysts (4-8). Therefore, the e f f e c t of the metallic ions on the oxidation of S(IV) was investigated by using test solutions. Table I shows experimental conditions f o r the oxidation of S(IV) in test solutions. The pH values of synthetic r a i n water samples were adjusted between 3 and 6. S(IV) concentration in the test solutions was adjusted to 12.5 yM; most of S(IV) existed as b i s u l f i t e at pH 36 (9). The rate of S(IV) oxidation was measured using ion chromato graphic analysis. The pH of each test solution was adjusted by using a buffer. In t h i s study, a Model IC 100 ion chromatograph made by Yokogawa Co. was used for determination of S(IV) in the s o l u t i o n . A 2 mM Na C03/4 mM NaHCOo eluent was used to separate c h l o r i d e , n i t r a t e , s u l f a t e , and s u l f i d e ions. 2

Table I. Experimental Conditions for the Oxidation of S(IV) in Test Solutions PH

3, 4, 5, 6

Catalyst

Fe , 3 +

1.8 yM

M n , 0.18 yM 2+

Fe , 3 +

Fe

3 +

S(IV)

12.5

Temp.

25°C

1.8 yM; M n , 0.18 yM 2+

, 18 yM; M n , 1.8 yM 2+

or 125 yM

Results and Discussion The r e s u l t of measurements of the rate constant and half l i f e of S(IV) in the test solutions are shown in Table II. The rate of oxidation of S(IV) in the solution without a catalyst was 0.4-5.9 χ 10" hr . The rate increases by 2 to 4 orders of magnitude in the presence of m e t a l l i c ions, and a s i g n i f i c a n t c a t a l y t i c e f f e c t of f e r r i c and manganous ions was found in these experiments. In the t e s t solution containing both f e r r i c and manganous ions, the rate enhancement was additive. J

In the presence of these metallic ions, d i f f e r e n t oxidation rates were observed for each pH value. The maximum rate of oxidation occurred at pH 4 to 5. This i s due to the change of the chemical form of each metallic ion with changing pH.



25°C

12.5 yM

3

S(IV):

0.425 0.620 3.31 5.88

1

[hr" ]

k χ 10

Temp.:

3 4 5 6

PH

1630 1120 209 118

(hr]

*%

Pure Water

2600 3310 615 124

(hr" ] 1

k χ 10 3

0.27 0.21 1.13 5.58

\

[hr]

1.8 yM F e 3 +

311 336 479 83.5

[hr" ] 1

3

2.23 2.06 1.45 8.30

[hr]

2+

\

yM M n

k χ 10

0.18

μ

y

J +

0.18

5840 10400 6830 598

1

[hr" ]

3

2+

0.12 0.067 0.10 1.16

[hr]

t^

yM M n

1.8 M F e , k χ 10

Table II. Rate Constant and Half L i f e of S(IV) Oxidation in Test Solutions; 2 5 ° C , 12.5 Μ S(IV)


13.

Concentration

TANAKA ET AL.

and Oxidation


161


In urban areas l i k e Yokohama, Japan, the concentrations of f e r r i c and manganous ions in rain water are generally in the range of 0.2-2.0 μΜ and 0.02-0.2 μΜ respectively, and the pH value of r a i n water i s between 4 and 5. Therefore, a high S(IV) oxidation rate in rain water i s expected from the data in Table II. A half l i f e of several minutes to an hour i s predicted. Furthermore, S(IV) in r a i n water i s oxidized during sampling, making the measurement of S(IV) in r a i n water d i f f i c u l t . This f a s t oxidation rate must be one of the reasons why few reports are found on the measurement of S(IV) in rain water. In order to determine S(IV) in r a i n water, i t i s necessary to prevent the oxidation of S(IV) between sampling and analysis. The suppressive e f f e c t on the oxidation of S(IV) was investigated by the addition of EDTA (Ethylenediaminetetraacetate) or TEA (Triethanolamine) as masking reagents f o r F e and Mn . Table III shows the suppressive e f f e c t of EDTA or TEA at various pH values. The sup pressive e f f e c t was not observed between pH 3 and 5, because neither EDTA nor TEA chelate with F e and M n at these pH values. EDTA and TEA were found to be very e f f e c t i v e f o r the suppression of the oxidation of S(IV) in solutions having neutral and basic pH values. 3 +

J +

z +

Figure 1 shows ion chromatrogram of the test solution added with EDTA or TEA. It was d i f f i c u l t to determine S 0 " due to the overlapping peaks of EDTA and SO* . However, TEA was found to be suitable f o r determination of anions present in r a i n water by ion chromatography. 4

z

Table III. Suppressive E f f e c t of EDTA and TEA on the Oxidation of S(IV) at Various pH at 25°C (1)

EDTA 1.0 mM

(2)

\

TEA 0.25 mM

\

(3)

Fe % Mn 3

2+

\

pH of

k χ 10

sol 'n

[hr" ]

(hr]

[hr" ]

[hr]

[hr" ]

[hr]

39.6 16.6 9.04 4.26 0.96

17.5 41.7 76.7 163

5730 1420 5.24

0.12 0.49 132

5840 10400 6830 598

0.12 0.067 0.10 1.16

3 4 5 6 7 9.3

3

1

k χ 10

3

1

k χ 10

3

1

111 1.23

564

(1)

18 μΜ, F e ; 1.8 μΜ, Mr/ ; 125 M , S(IV)

(2)

1.8 μΜ, F e

(3)

18 μΜ, F e

J +

+

3 +

3 +

y

; 0.18 μΜ, M n ; 12.5 μ Μ , S(IV) 2 +

; 1.8 M , M n ; 12.5 μΜ, S(IV) V

2 +


162

THE CHEMISTRY OF ACID RAIN


(a) with EDTA

I

I

I

I

1

1

0

2

4

6

8

10

Time ( min )

Figure 1.

Ion chroma to gram of S O 3 " and S 0 t + ~ i n the test s o l u t i o n added with EDTA(ethylenediaminetetraacetic a c i d ) , and with TEA(triethanolamine) S O 3 " c o n e ; 125yM, Temp.; 25°C (a) EDTA cone.; 1.OmM (b) TEA cone.; 2.5mM 2

2

2


13.

T A N A K A ET AL.

Concentration

and Oxidation


163

An anion chromatogram of the rain water sample i s shown in Figure 2. The upper ion chromatogram represents a sample where TEA was added to the r a i n c o l l e c t o r before sampling. In the sample to which TEA was added, S(IV) was determined to be 2.3 μΜ. On the other hand, only traces of S(IV) were detected in the sample without TEA because of the rapid S(IV) oxidation. Therefore, the addition of TEA to sample enables the determination of S(IV) in rain water. A 10 mL mixture that was 250 mM TEA and 250 mM Na C0 was added to s t a b i l i z e and buffer the solution. Less than 1 l i t e r r a i n water was collected so that the concentration of TEA would remain e f f e c t i v e .


2

3

Rain water samples were collected on the roof of the Faculty of Engineering Building at Keio University, Hiyoshi, Yokohama, from May to November, 1985. Hiyoshi, Yokohama i s located at 5 km to the south of Kawasaki, and i s affected by a i r p o l l u t i o n from the TokyoYokohama Industrial Zone. Analytical r e s u l t s of rain water collected at Hiyoshi, Yokohama, from May to November, 1985 are shown in Table IV. All samples were f i l t r a t e d with a membrane f i l t e r ( M i l l i p o r e Type HA), and then the concentration of each ion and the pH values were mea sured. Rain water was sampled 16 times in 13 d i s t i n c t rain events totaling 273 mm of p r e c i p i t a t i o n . The pH value ranged between 3.7 and 4.8 with an average of 4.4. Concentrations of S(IV) and S(VI) were determined to be 0.8-23.5 μΜ and 6.8-84.4 μΜ, respectively. The average concentrations were 5.7 μΜ for S(IV) and 30.7 μΜ for S(VI). The detection l i m i t of S(IV) by ion chromatography was estimated to be 0.3 μΜ at the i n j e c t i o n of 100 μ ΐ sample s o l u t i o n . Oxidation of S(IV) to S(VI) decreases the pH value of r a i n water. On the basis of the S(IV) concentration, the influence of the S(IV) oxidation on lowering pH values is shown in Table V. The c a l c u l a t i o n was made by subtracting the hydrogen ion concentration r e s u l t i n g from carbon dioxide equilibrium in the a i r from the measured hydrogen ion concentration in the r a i n samples, to obtain the hydrogen concentration caused by other acids. Then, the potential hydrogen concentration caused by the oxidation of S(IV) in r a i n water was calculated. The r a t i o between t h i s potential hydrogen concentration and that caused by other acids excluding carbon dioxide was calculated. The r e s u l t s given in Table V show that the contributions of S(IV) to the decrease of pH in r a i n water are in the range of 6-67%. Figure 3 shows the decay in the concentration of S(IV) f o r r a i n water collected at Hiyoshi, Yokohama. Five mL of 2.5 mM (S(IV) solution was added to 195 mL of r a i n water, and the i n i t i a l con centration of S(IV) was adjusted to 62.5 μΜ. The decay of S(IV) concentration was l i n e a r as seen in Figure 3. This i s consistent with a f i r s t order reaction with respect to S(IV). A difference of oxidation rate between f i l t r a t e d and n o n - f i l t r a t e d samples was observed. The high oxidation rates in the n o n - f i l t r a t e d r a i n water is assumed to be due to the presence of suspended p a r t i c u l a t e matter. Table VI shows the rates of S(IV) oxidation measured in r a i n water collected in Yokohama, 1985. The rate constants of the S(IV)



164


0.5uS/cm

Figure 2.

1

I

0

3

I

I

6 9 Time ( min )

I

1

12

15

Ion chromatogram of anion i n r a i n water a) without TEA(triethanolamine) b) added with TEA(triethanolamine) Rain water was c o l l e c t e d on May 20, 1985.


13.

Concentration

TANAKA ET AL.

and Oxidation

Rate of S(IV) in

165

Rainwater

Table IV. A n a l y t i c a l R e s u l t s of Rain Water by Ion Chromatography, Yokohama, 1985


Sample*

C o n c e n t r a t i o n (μΜ) S(VI) cr

NO3-

S(IV)

53

4.8

2.3

21.5

11.6

7.1

1200-1645 1700-1800

10.2 15.4

4.5 4.6

2.1 2.2

22.8 18.7

8.4 33.5

9.8 14.0

1850-1150 1200-1700

4.1 6.1

4.5 4.5

9.1 2.8

49.0 17.7

16.6 15.8

26.0 18.6

830-1300

7.4

4.2

2.0

11.1

30.1

52.3

3.4

3.8

5.4

84.4

Time

May 20-21

1745-1100

May 24 24-25 May 28-29 June 8

Rain F a l l (mm)

pH_

Date

June 11-12

191

151

June 12-13

2300-1615

20.4

4.4

2.5

19.3

26.8

28.6

June 18 18-19

1100-1840 1900-1230

5.7 27.5

4.2 4.8

4.1 0.8

51.2 6.8

94.9 12.1

45.3 10.2

S e p t . 24-25

830-1015

2.3

3.7

11.9

62.7

S e p t . 28-30

1500-900

34

4.5

2.0

15.9

42.5

15.2

65

4.7

1.1

14.5

25.6

9.7

278

55.8

Oct.

5-6

Oct.

29-30

1300-

4.8

4.1

23.5

39.5

Nov.

1

1040-1800

4.4

4.1

14.6

39.0

42.5

33.2

Nov.

6

1030-1500

8.9

4.5

4.4

16.7

73.0

16.3

min.

_

3.7

0.8

6.8

8.4

7.1

max.

-

4.8

23.5

84.4

Av.

_

4.4

5.7

30.7

* Samples were f i l t r a t e d

by M i l l i p o r e membrane f i l t e r

110

26.8

278

151 32.5

63.3

(pore s i z e :

0.45


ym).

166


Table V.

C o n t r i b u t i o n of S ( I V ) O x i d a t i o n on Lowering pH of R a i n Water C o n c e n t r a t i o n (yM) Time


Date

pH_

H

+

JUL

S(IV)

H **/H' +

May 20-21

1745-1100

4.8

14.8

12.3

2.3

4.6

0.37

May 24-25 24-25

1200-1645 1700-1800

4.5 4.6

30.9 24.5

28.4 22.0

2.1 2.2

4.3 4.5

0.15 0.20

May 28-29 29

1850-1150 1200-1700

4.5 4.5

35.5 35.5

33.0 33.0

9.1 2.8

18.2 5.5

0.56 0.17

830-1300

4.2

70.8

68.3

2.0

4.0

0.06

5.4

10.7

0.06

June 8

3.8

June 11-12

174

171

June 12-13

2300-1615

4.4

37.2

34.6

2.5

5.1

0.15

June 18 18-19

1100-1840 1900-1230

4.2 4.8

67.6 17.0

65.1 14.5

4.1 0.8

8.2 1.6

0.13 0.11

S e p t . 24-25

830-1015

3.7

11.9

23.8

0.12

S e p t . 28-30

1500-900

4.5

34.5

32.9

2.0

4.0

0.12

4.7

21.3

18.«

1.1

2.2

0.11

1300-

4.1

72.4

69.9

23.5

47.0

0.67

Nov. 1

1040-1800

4.1

83.1

80.6

14.6

29.2

0.36

Nov. 6

1030-1500

4.5

34.7

32.2

4.4

8.7

0.27

min.

3.7

14.8

12.3

0.8

1.6

0.06

max.

4.8

23.5

47.0

0.67

Av.

4.4

5.7

11.4

0.23

Oct.

5-6

Oct.

29-30

194

194 59.2

191

191 56.7

H *:

The hydrogen i o n c o n c e n t r a t i o n c o r r e c t e d f o r 2 . 5 yM carbon d i o x i d e concentration.

H **:

Nominal hydrogen i o n c o n c e n t r a t i o n generated by o x i d a t i o n of S ( I V ) .

+

+


Johnson et al.; The Chemistry of Acid Rain ACS Symposium Series; American Chemical Society: Washington, DC, 1987. 0.12 3.31

0.166

0.084 2.04

0.020

0.016 0.498 0.094

4.4

1.1 23.5 6.9

4.5

3.8 4.8 4.4

1030-1500

min.

max.

Av.

* Samples were f i l t r a t e d by Mi H i pore membrane f i l t e r

25°C

6

Nov.

Temp.;

1

Nov.

0.86

(pore s i z e ; 0 . 4 5 ym)

0.526

0.22

0.623

0.057

14.6

4.1

1040-1800

29-30

Oct. 0.82

1.22

0.625

0.063

23.5

4.1

1300-

0.26

0.120

0.022

1500-900 1.1

4.7

5-6

28-30

Oct.

Sept.

June 11-12 0.28

4.5

0.66

0.215

2.0

3.8

0.337

0.12

0.016

0.498

5.4

4.6

1200-1800

May 24-25

0.084

3.31

0.051

2.2

4.8

1745-1100

May 20-21

1

k (hr" )

Rate C o n s t ,

2.04

0.025

2.3

PH

Time

Date

2.1

5.8

0.21

3.2

0.85

0.57

2.7

2.5

0.21

1.1

5.8

Half L i f e \ (hr)

i n Rain Water, Yokohama, 1985

Metal Cone. Mn Fe (yM)

O x i d a t i o n Rate and H a l f L i f e of S(IV)

S(IV) cone. (yM)

Sample*

Table V I .



168


0

2

4

6

8

Time ( h r ) Figure 3.

Variation of S(IV) concentration in rain water with time by an addition of S(IV) I n i t i a l S(IV) concentration; 62.5μΜ Rain water was collected on May 20-21, 1985. #; Filtrated by Millipore membrane f i l t e r (pore size 0.45ym) O ; Not filtrated Rain water was collected on May 24-25, 1985 • ; Filtrated by Millipore membrane f i l t e r (pore size 0.45ym) Λ ; Not filtrated

* Metal ion concentration (yM) Figure 4.

Rate constant of oxidation of S(IV) end metallic Ion concentration in rain water · ; Filtrated by Millipore membrane f i l t e r (pore size 0.45ym) Ο ; Not filtrated * Total Concentration of Fe and Mn


13.

TANAKAETAL.

Concentration

and Oxidation


169

1

oxidation, k, are 0.12-3.3 h r " , which are s i m i l a r to the oxidation rates in the test solutions in Table I I . A large v a r i a t i o n of the measured oxidation rates was observed in the r a i n water samples. It i s assumed that the oxidation rate depends on the F e and Mn^ con centration. J +

+

Figure 4 shows the relationship between the oxidation rate of S(IV) and the metallic concentration of F e and Mn^ in r a i n water. The concentrations of iron and manganese in the r a i n water were analyzed by atomic absorption spectrometry. The increase of the oxidation rate with the increase of the metal ion concentration i s shown in Figure 4. Therefore, a strong c a t a l y t i c effect of F e and Mn^ on the oxidation of S(IV) in r a i n water was observed. J +

+

J +


+

Summary The oxidation reaction of S(IV) in both test solutions and r a i n water was found to be a f i r s t order reaction. M e t a l l i c ions such as f e r r i c and manganous ions strongly catalyze the oxidation of S(IV) in r a i n water. A c o r r e l a t i o n was found between the concentration of metallic ions and the rate of S(IV) oxidation. The rate constant for the oxidation of S(IV) was found to be 0.12-3.3 h r " (half l i f e : 0.21-5.8 hr) in r a i n water samples collected at Yokohama, Japan, 1985. Hydrogen ions produced by the oxidation of S(IV) in r a i n water contribute substantially to a c i d i t y . 1

Literature Cited 1.

Likens, G.E, Wright, R.F., Galloway, J.N., and Butler, T.J., Scientific American, 1978, 241, 29-47.

2. Beilke, S. and Gravenhorst, G., Atoms. Environ., 1978, 12, 231-239. 3. Hegg, D.A. and Hobbs, P.V., Atmos. Environ., 1978, 12, 241-253. 4. Junge, C.E. and Ryan, T.G., Q.J.R. met. Soc., 1958, 84, 46. 5. Moller, D., Atmos. Environ., 1980, 14, 1067-1076. 6. Huss, Α., Jr., Lim, P.K., and Eckert, C.A., J. Phys. Chem., 1982, 86, 4224-4228, 4229-4233, 4233-4237. 7.

Ibusuki, T., Atmos. Environ., 1984, 18, 145-151.

8. Altwicker, E.R. and Nass, K.K., Atmos. Environ., 1983, 17, 187-190. 9. Butler, J.N. "Ionic Equilibrium", Addison-Wesley, Massachusetts, 1964. RECEIVED June 12, 1987


The Chemistry of Acid Rain - American Chemical Society

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