Environmental photochemistry of PCDDs. 2. Quantum yields of the direct phototransformation of 1,2,3,7-tetra-, 1,3,6,8-tetra-, 1,2,3,4,6,7,8-hepta, and 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin in aqueous acetonitrile and their sunlight half-lives

Journal Article · · Journal of Agricultural and Food Chemistry; (USA)

DOI:https://doi.org/10.1021/jf00085a059· OSTI ID:7003008

Choudhry, G G; Webster, G R.B. ^[1]

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1. Univ. of Manitoba, Winnipeg (Canada)

Photochemistry of four polychlorodibenzo-p-dioxins (PCDDs), namely 1,2,3,7-tetrachlorodibenzo-p-dioxin (1,2,3,7-T{sub 4}CDD), 1,3,6,8-T{sub 4}CDD, 1,2,3,4,6,7,8-H{sub 7}CDD, and 1,2,3,4,6,7,8,9-O{sub 8}CDD, in water-acetonitrile (2:3, v/v) was investigated at 313 nm; the quantum yields for the direct phototransformation of the candidate PCDD isomers in these solvent systems were (5.42 {plus minus} 0.42) {times} 10{sup {minus}4}, (2.17 {plus minus} 0.14) {times} 10{sup {minus}3}, (1.53 {plus minus} 0.17) {times} 10{sup {minus}5}, and (2.26 {plus minus} 0.33) {times} 10{sup {minus}5}, respectively. These quantum yields and the measured absorption spectra together with solar intensity data available in the literature were utilized to estimate the direct sunlight (environmental) phototransformation first-order rate constants of these PCDD congeners in water under conditions of variable sunlight intensity during various seasons; the corresponding half-lives were also determined. In summer, typical midday, midseason half-lives for the direct phototransformation of 1,2,3,7-T{sub 4}CDD, 1,3,6,8-T{sub 4}CDD, 1,2,3,4,6,7,8-H{sub 7}CDD, and O{sub 8}CDD near the surface of water bodies at 40{degree} north latitude would be 1.8 {plus minus} 0.1, 0.31 {plus minus} 0.02, 47 {plus minus} 5, and 18 {plus minus} 3 days, respectively, time being expressed in terms of 24-h day. Furthermore, the experimentally determined sunlight photolysis half-life of {sup 14}C-labeled 1,3,6,8-T{sub 4}CDD in pond water was 3.5 days.

• OSTI ID: 7003008
• Journal Information: Journal of Agricultural and Food Chemistry; (USA), Vol. 37:1; ISSN 0021-8561
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
54 ENVIRONMENTAL SCIENCES
CHLORINATED AROMATIC HYDROCARBONS
PHOTOCHEMISTRY
ACETONITRILE
CARBON 14 COMPOUNDS
DIOXIN
PHOTOLYSIS
SURFACE WATERS
VISIBLE RADIATION
AROMATICS
CHEMICAL REACTIONS
CHEMISTRY
DECOMPOSITION
ELECTROMAGNETIC RADIATION
HALOGENATED AROMATIC HYDROCARBONS
HETEROCYCLIC COMPOUNDS
LABELLED COMPOUNDS
NITRILES
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
RADIATIONS
400500* - Photochemistry
540311 - Environment
Aquatic- Basic Studies- Radiometric Techniques- (1990-)