Evidence of sensitized photolysis of polychlorinated dibenzo-p-dioxins in natural waters under sunlight conditions

Journal Article · Thu Nov 01 00:00:00 EST 1990 · Environmental Science and Technology; (USA)

DOI:https://doi.org/10.1021/es00081a018· OSTI ID:6039870

Friesen, K J; Webster, G R.B. ^[1]; Muir, D C.G. ^[2]

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1. Univ. of Manitoba, Winnipeg (Canada)
2. Freshwater Institute, Winnipeg, Manitoba (Canada)

The sunlight photolysis of carbon-14 labeled 1,2,3,4,7-pentachlorodibenzo-p-dioxin (P{sub 5}CDD) and 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (H{sub 7}CDD) was studied at 50{degree} N latitude in filter-sterilized natural water and in distilled water-acetonitrile (2:3, v/v) solutions to determine the extent of direct versus indirect photolysis under environmental conditions. Under midsummer sunlight conditions, pseudo-first-order sunlight photolysis rate constants (k{sub p}) of 0.74 and 0.28 day{sup {minus}1} were measured for P{sub 5}CDD and H{sub 7}CDD, respectively, in natural water. However, considerably slower direct aqueous photolysis rates were observed for the two PCDD congeners in distilled water-acetonitrile, with rate constants of 0.058 and 0.019 day{sup {minus}1} for P{sub 5}CDD and H{sub 7}CDD, respectively, in relatively good agreement with predicted rates of direct aqueous photolysis. The results indicate that an indirect or sensitized photolytic mechanism may dominate the photodegradation of PCDDs in natural waters. The major degradation product(s) appeared as nonextractable {sup 14}C activity, with increases in this fraction paralleling the disappearance of the parent PCDD.

• OSTI ID: 6039870
• Journal Information: Environmental Science and Technology; (USA), Vol. 24:11; ISSN 0013-936X
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
DIOXIN
PHOTOLYSIS
CARBON 14 EMISSION DECAY
DECOMPOSITION
ORGANIC CHLORINE COMPOUNDS
RADIOCHEMICAL ANALYSIS
SURFACE WATERS
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
DECAY
HEAVY ION EMISSION DECAY
HETEROCYCLIC COMPOUNDS
NUCLEAR DECAY
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
QUANTITATIVE CHEMICAL ANALYSIS
540310* - Environment
Aquatic- Basic Studies- (1990-)