Quantum Yields of Polychlorodibenzo-p-dioxins - ACS Symposium

Chapter 5

Quantum Yields of Polychlorodibenzo-p-dioxins In Water-Acetonitrile Mixtures and Their Environmental Phototransformation Rates Ghulam Ghaus Choudhry and G. R. Rarrie Webster

Downloaded by UNIV OF OKLAHOMA on March 8, 2013 | http://pubs.acs.org Publication Date: December 8, 1987 | doi: 10.1021/bk-1987-0327.ch005

Pesticide Research Laboratory, Department of Soil Science, The University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2

Photochemistry of four individual isomers of polychlorodibenzo-p-dioxins (PCDDs), namely 1,2,3,4,7pentachlorodibenzo-2-dioxin (1,2,3,4,7-PCDD) (1), 1,2,3,4,7,8-HCDD (2), 1,2,3,4,6,7,8-HCDD (3) and OCDD (4) in water-acetonitrile (2:3 v/v) was investigated using laboratory radiations of wavelength 313 nm. The quantum yields for the phototransformation of the dioxins 1-4 in these solvent systems were (9.8 ± 2.4) x 10 , (1.10 ± 0.02) x 10 , (1.53 ± 0.17)x10 and (2.26 ±0.33) x 10 , respectively. These quantum yields and the measured absorption spectra together with solar intensity data available in the literature were utilized to estimate the sunlight (environmental) phototransformation first-order rate constants of the PCDD congeners 1-4 in water under conditions of variable sunlight intensity during various seasons; the corresponding half-lives were also determined. In summer, typical half-lives for the phototransformation of the pollutants 1-4 near the surface of water bodies at 40° north latitude would be 15 ± 4, 6.3 ± 0.1, 47 ±5, and 18 ±3 days, respectively. 5

6

7

8

-5

-4

-5

-5

Concern has grown r e g a r d i n g e n v i r o n m e n t a l c o n t a m i n a t i o n b y p o l y c h l o r i n a t e d dibenzo-p_-dioxins (PCDDs). PCDDs i n c l u d e 75 congeners. Some o f t h e s e t r i c y c l i c a r o m a t i c s p o s s e s s r e m a r k a b l e t o x i c , t e r a t o g e n i c , mutagenic, and a c n e g e n i c c h a r a c t e r i s i t i c s ( 1 , 2 ) . For i n s t a n c e , t h e LD50 f o r 2 , 3,7 , 8 - t e t r a c h l o r o d i b e n z o - p . - d i o x i n (2,3,7,8-T4CDD) i n female r a t s i s 45 /ig/kg. A l t h o u g h t h e e x t e n t o f t o x i c i t y i s r e l a t e d t o t h e degree o f c h l o r i n a t i o n , t h e r o l e o f p o s i t i o n a l i s o m e r i s a t i o n i s a l s o c r i t i c a l and perhaps t h e dominant one; 2,3,7,8-T4CDD i s a t l e a s t 800 t i m e s more t o x i c t h a n 1,2,3,4T CDD ( 2 ) . R e c e n t l y , i n a d d i t i o n t o s e v e r a l o t h e r o r g a n i c compounds, PCDDs have been d e t e c t e d i n the f l u e gas and f l y a s h e m i t t e d b y some m u n i c i p a l and i n d u s t r i a l i n c i n e r a t o r s l o c a t e d i n Canada, J a p a n , S w i t z e r l a n d , and the N e t h e r l a n d s ( r e f e r e n c e s c i t e d i n Choudhry and 4

0097-6156/87/0327-0061506.00/0 © 1987 American Chemical Society

In Photochemistry of Environmental Aquatic Systems; Zika, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

62

PHOTOCHEMISTRY OF ENVIRONMENTAL AQUATIC SYSTEMS

H u t z i n g e r (3,4) and Choudhry e t a l . ( 5 ) ) . F o r i n s t a n c e , i n c i n e r a t o r f l y a s h i s known t o c o n t a i n r e l a t i v e l y l a r g e amounts o f o c t a - , h e p t a - , and h e x a - c h l o r o isomers (OgCDD, HyCDDs, and H CDDs) o f d i o x i n b u t o n l y l o w l e v e l s o f 2,3,7,8-T4CDD ( 6 ) . Moreover, Jones ( 7 ) r e p o r t e d t h a t t h e PCDDs r e l e a s e d near t h e Dow Chemical Co., M i d l a n d , M i c h i g a n were > 99.5% HgCDDs, HyCDDs, and OgCDD, r e s p e c t i v e l y and t e t r a c h l o r o isomers o t h e r t h a n 2,3,7,8-T4CDD. I n a d d i t i o n , commercial 2 , 3 , 5 - t r i - , 2 , 4 , 6 - t r i - and p e n t a c h l o r o p h e n o l have been shown t o c o n t a i n 2 , 7 - d i c h l o r o d i b e n z o - p - d i o x i n (2,7-D2CDD) and 1,3,6,8-T4CDD t o g e t h e r w i t h HgCDDs, HyCDDs, and OgCDD i n ppm l e v e l s i n s p i t e o f improved m a n u f a c t u r i n g t e c h n i q u e s ( 7 ) . C h l o r i n a t e d p h e n o l s have w i d e s p r e a d use as f u n g i c i d e s , b a c t e r i c i d e s , s l i m i c i d e s , h e r b i c i d e s , e t c . , and t h e y a r e a l s o used i n t h e p r o d u c t i o n o f phenoxy a c i d s such as 2 , 4 - d i - and 2 , 4 , 5 - t r i c h l o r o p h e n o x y a c e t i c a c i d (2,4-D and 2,4,5-T, r e s p e c t i v e l y ( 8 ) . F o r a l m o s t f o u r decades, 2,4-D and 2,4,5-T and t h e i r d e r i v a t i v e s have r e c e i v e d wide use as h e r b i c i d e s , e s p e c i a l l y f o r t h e c o n t r o l o f b r u s h , j u n g l e v e g e t a t i o n , and a q u a t i c weeds. T e c h n i c a l 2,4-D h e r b i c i d e p r o d u c t s have been r e p o r t e d t o c o n t a i n 2.7-D2CDD and 1,3,6,8-T4CDD amounting t o 1.8-8.7 ppm ( 9 ) . L i k e w i s e , a mean o f more t h a n 1.9 and a maximum o f 47 ppm o f 2,3,7,8T4CDD has been i d e n t i f i e d i n t h e m i l i t a r y d e f o l i a n t Agent Orange ( b u t y l e s t e r s o f 2,4-D and 2,4,5-T i n e q u a l amounts ( 8 ) . Throughout the w o r l d on s e v e r a l o c c a s i o n s , p u b l i c a n x i e t y because o f t h e r e l e a s e o f PCDDs i n t o o u r environment has been seen. F o r example, i n t h e autumn o f 1957, m i l l i o n s o f c h i c k e n s i n t h e E a s t e r n and M i d w e s t e r n U n i t e d S t a t e s d i e d o f a d i s e a s e caused b y a whole s e r i e s o f PCDDs p r e s e n t i n t h e i r f e e d . On J u l y 10, 1976, a wide a r e a near Seveso, I t a l y was c o n t a m i n a t e d b y a n e x t r e m e l y t o x i c f a l l o u t c o n s i s i t i n g o f 2,3,7,8-T4CDD i n a c h e m i c a l m i x t u r e o f o t h e r o r g a n o c h l o r i n e compounds. S i m i l a r l y , a l a r g e q u a n t i t y o f Agent Orange h e a v i l y c o n t a m i n a t e d w i t h 2,3,7,8-T4CDD was a p p l i e d from t h e a i r over j u n g l e s i n South E a s t A s i a ( 8 ) . F i n a l l y , i n 1982, due t o an e l e c t r i c a l transformer ( f l u i d : 65% p o l y c h l o r o b i p h e n y l s ( A r o c l o r 1254) and 35% t r i - and t e t r a c h l o r o b e n z e n e s ) f i r e , an o f f i c e b u i l d i n g i n Binghamton, New Y o r k , U.S.A. was c o n t a m i n a t e d b y numerous d i o x i n congeners c o n t a i n i n g 4-8 c h l o r i n e c o n s t i t u e n t s ( 1 0 ) .


6

The p h o t o c h e m i c a l d e g r a d a t i o n i s an i m p o r t a n t p r o c e s s w i t h a t m o s p h e r i c contaminants and some c h e m i c a l s t h a t r e s i d e on s u r f a c e s such as p e s t i c i d e s on l e a v e s and v e g e t a t i o n o r i n water b o d i e s . A l t h o u g h a good d e a l o f r e s e a r c h work on t h e p h o t o c h e m i c a l f a t e o f PCDDs, b o t h i n s o l u t i o n and i n t h e s o l i d phase has appeared ( 8 , 1 1 ) , t o t h e b e s t o f o u r knowledge no i n v e s t i g a t o r has r e p o r t e d t h e quantum y i e l d (φ) f o r t h e p h o t o l y s i s o f these e n v i r o n m e n t a l p o l l u t a n t s . We have d e t e r m i n e d t h e quantum y i e l d s (^ ) f o r t h e p h o t o c h e m i c a l t r a n s f o r m a t i o n r e a c t i o n s o f f o u r i n d i v i d u a l d i o x i n i s o m e r s , namely 1 , 2 , 3 , 4 , 7 - p e n t a c h l o r o d i b e n z o - p - d i o x i n (1,2,3,4,7-P CDD) ( 1 ) , 1,2,3,4,7,8-H CDD (2), 1,2,3,4,6,7,8-HyCDD (3) and 1,2,3,4,6,7,8,9OgCDD (4) i n w a t e r - a c e t o n i t r i l e (2:3 v / v ) s o l u t i o n u s i n g UV l i g h t o f m a i n l y 313 nm. The p r e s e n t c h a p t e r r e p o r t s t h e v a l u e s o f l a b o r a t o r y φ and t h e e s t i m a t e d s u n l i g h t p h o t o l y s i s h a l f - l i v e s ( ( t w 2 ) ) PCDDs 1-4. r

5

6

o

τ

f

S O

Experimental S u b s t r a t e s and S o l v e n t s .

Sources o f t h e s u b s t r a t e s , v i z . , PCDDs 1-4


Quantum Yields of Polychlorodibenzo-p-dioxins


CHOUDHRY AND WEBSTER


64

PHOTOCHEMISTRY OF ENVIRONMENTAL AQUATIC SYSTEMS

(Table I ) , o-nitrobenzaldehyde, o - n i t r o s o b e n z o i c a c i d , p.-nitrotoluene and 1 , 2 , 3 , 4 - t e t r a c h l o r o b e n z e n e and s o l v e n t s were the same as p r e v i o u s l y reported (12). P r e p a r a t i o n o f S o l u t i o n s o f PCDDs 1-4 i n W a t e r - A c e t o n i t r i l e (2:3 v/v). The p r o c e d u r e s f o r the p r e p r a t i o n o f the s o l u t i o n s o f 1,2,3,4,7-P CDD (1) and 1,2,3,4,7,8-H CDD (2) i n H 0-CH CN (2:3 v/v) have been d e s c r i b e d e l s e w h e r e ( 1 2 ) . Techniques f o r the p r e p a r a t i o n o f the s o l u t i o n o f HgCDD 2 i n w a t e r - a c e t o n i t r i l e (2:3 v/v) r e p o r t e d by Choudhry and Webster (12) were f o l l o w e d t o p r e p a r e s i m i l a r s o l u t i o n s o f d i o x i n s 3 and 4. For these i n v e s t i g a t i o n s , the c o n c e n t r a t i o n o f PCDDs 1-4 were 2.805, 3.328, 2.780 and 0.310 μΜ, r e s p e c t i v e l y (Table I I ) .


5

6

2

3

UV A b s o r p t i o n S p e c t r o s c o p y . UV a b s o r p t i o n s p e c t r a l d a t a f o r d i o x i n s 1-4 documented i n T a b l e I were o b t a i n e d u s i n g a s i n g l e beam Bausch and Lomb S p e c t r o n i c 710 S p e c t r o p h o t o m e t e r . I r r a d i a t i o n Equipment and E x p e r i m e n t s . The p r e v i o u s l y d e s c r i b e d (11,14) Rayonet P h o t o c h e m i c a l R e a c t o r ( h a v i n g an energy o u t p u t o f 90% between 290 and 310 nm) e q u i p p e d w i t h a merry-go-round a p p a r a t u s was used. The P y r e x p h o t o r e a c t i o n c e l l s ( p a t h l e n g t h ( i ) , 1 cm) and c h e m i c a l f i l t e r s o l u t i o n ( c o n s i s t i n g o f l ^ C r O ^ (0.270 g/L) and Na2C0 (1.000 g/L) i n w a t e r ) u s e d f o r the i s o l a t i o n o f 313 nm l i n e from the R a y o n e t t RPR 3000 A lamps have been d e s c r i b e d ( 1 2 ) . O p t i c a l l y t h i c k s o l u t i o n s of o-nitrobenzaldehyde (10 mM) i n a c e t o n i t r i l e were u t i l i z e d as a c h e m i c a l a c t i n o m e t e r f o r the d e t e r m i n a t i o n o f the i n t e n s i t y (Ι ) o f t h e f i l t e r e d i n c i d e n t l i g h t ( 1 2 J L 5 ) . For t h i s p u r p o s e , the c o n c e n t r a t i o n o f the p h o t o p r o d u c t o - n i t r o s o b e n z o i c a c i d a r i s i n g from the a c t i n o m e t e r was m o n i t o r e d ( 1 2 ) . 3

λ

Analyses. A l l a n a l y s e s were c a r r i e d out by HPLC on a Waters S c i e n t i f i c l i q u i d chromatograph (Model 6000A pump, U6K i n j e c t o r , and an M440 UV absorbance d e t e c t o r ) . S e p a r a t i o n s were made w i t h a 30 cm χ 3.9 mm /iBondapak C^g column ( r e v e r s e phase, RP) ( 1 2 ) . The a n a l y s e s o f the sample s o l u t i o n o f the HyCDD 3 and OgCDD 4 were p e r f o r m e d by t h i s RP-HPLC u s i n g CH OH-H 0 (19:1 v/v) and CH3OH as e l u a n t s , r e s p e c t i v e l y a t a f l o w r a t e o f 1.0 mL/min. I n the c a s e o f 3 and 4, 20 μL o f p - n i t r o t o l u e n e (2.055 mM) and 90 /iL o f 1,2,3,4t e t r a c h l o r o b e n z e n e (0.757 mM) b o t h i n CH3CN, were added r e s p e c t i v e l y t o e a c h 2.0 mL sample s o l u t i o n as i n t e r n a l s t a n d a r d p r i o r t o analyses. A n a l y t i c a l p r o c e d u r e s f o r 1,2,3,4,7-P5CDD ( 1 ) , 1,2,3,4,7,8-H5CDD (2) and a c t i n o m e t r y have been d e s c r i b e d e l s e w h e r e 3

2

(12).

Results T a b l e I r e c o r d s the molar e x t i n c t i o n c o e f f i c i e n t (ε ) a t v a r i o u s w a v e l e n g t h s (λ), o f s o l u t i o n s o f PCDDs 1-4. W a t e r - a c e t o n i t r i l e (2:3 v/v) was u s e d as a s o l v e n t f o r compounds 1-3; whereas, i n the case o f Og-CDD 4, the s o l v e n t was n e a t a c e t o n i t r i l e . These s p e c t r a l d a t a were u s e d i n the p r e d i c t i o n o f the d i r e c t s u n l i g h t p h o t o l y s i s r a t e s , i . e . , k p and c o r r e s p o n d i n g h a l f - l i f e ( t ] y 2 ) s p ) p o l l u t a n t s 1-4 i n a q u a t i c e n v i r o n m e n t s (see b e l o w ) . T y p i c a l f i r s t - o r d e r p l o t s ( E q u a t i o n 1) o f the p h o t o l y s i s d a t e f o r λ

o f

t l i e

S


In Photochemistry of Environmental Aquatic Systems; Zika, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987. 3

D a t a f o r PCDDs 1-3 were r e c o r d e d u s i n g t h e s o l u t i o n s o f t h e p o l l u t a n t s i n H 0-CH CN (2:3 v / v ) ; w h i l e i n . t h e case o f 4_, t h e s o l v e n t was neat CH-CN. The c o n c e n t r a t i o n s o f PCDDs 1-4 were 47881, 3.328, 2.780 and 6.218 μΜ, r e s p e c t i v e l y . 2

44068 5307 4986 4825 4664 4342 4182 4182 4182 4021 4021 3860 3217 965 483 322 322 161 161 0 23020 3597 3597 3957 3957 3957 4316 4316 4316 4316 4316 3237 2158 360 0

25244 9015 8114 6912 6311 5409 5109 4808 4808 4808 3907 3306 2104 301 0

10434 2660 2660 2660 2660 2455 2455 2455 2250 2250 2250 2046 1227 0

254.0 297.5 300.0 302.5 305.0 307.5 310.0 312.5 313.0 315.0 317.5 320.0 323.1 330.0 340.0 350.0 360.0 370.0 380.0 390.0

a

1,2,3,4,6,7,8,9OgCDD (4)

?

1,2,3,4,6,7,8H CDD (3)

6

) for

1,2,3,4,7,8H CDD (2)

.cm

1,2,3,4,7P CDD (1)

(L.Mol

o f PCDDs

Wavelength, λ (nm)

5

3

Molar e x t i n c t i o n c o e f f i c i e n t s ,

Table I . L i g h t A b s o r p t i o n S p e c t r a



b

Y

(1.1±0.02) χ 1 0 " (1.53±0.17)x 1 0 " (2.26±0.33)x 1 0 "

24.5±0.1 191±20 184±24

7.86±0.03 1.02±0.11 1.0610.14

87.2 39.1 52.9

72

72

112

2.780

0.310

5

(9.8±2.4) χ 1 0 "

3

4

1η2 t, = ^ — ρ

3.328

2

C a l c u l a t e d using the f o l l o w i n g r e l a t i o n s h i p : E q u a t i o n 2 was u t i l i z e d .

72

2.805

1

\

45.9±7.4

1

4.31±0.70

(%)

(h)

t

71.2

6

a

Absolute half-life ,

(h)

6

t

Maximum irradiation time, max

I n i t i a l concen t r a t i o n of the starting dioxin, Ρ ο (10" M)

Subst rate No.

b Quantum y i e l d f o r the photo degradation, Φ r

(2:3 v/v) a t 313 nm

Photolysis f i r s t order rate constant k Ρ (10~ sec" )

Average p e r centage d i s appearance o f the s t a r t i n g dioxin after max

Table I I . P h o t o l y s i s o f PCDDs i n W a t e r - A c e t o n i t r i l e


5

5

4

m

Ά

C 25 η c/s ·
Ο

53

ζ

m

ο ζ

< 53

X Ο Η Ο η se m § En H < Ο •η m Ζ

Os ON

CHOUDHRY A N D WEBSTER

5.

Quantum Yields of Polychbrodibenzo-p-dioxins

I n ( P / P ) - kp t Q

67

(1)

t

d i l u t e s o l u t i o n s (absorbance b e i n g

Quantum Yields of Polychlorodibenzo-p-dioxins - ACS Symposium

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