TABLE 2 



Kinetic characteristics of photochemical transformation of 

 BaP in seawater under solar irradiation in the following areas: 



(a) the Bering Sea 



(b) the tropical part of the Pacific 



(c) the Caroline Atoll 



(47th cruise of the R/V Akademik Korolev, July-November 19881. 



C/Co 



c 

 o 



c 



— 



c 



<u 

 o 



c 

 o 

 o 



a. 



CO 



o 







? 



t .hour 



Fig. 2. Kinetics of BaP degradation under sunlight irradiation at the surface 

 of the Bering Sea (coordinates: 67°42'N 1 15°43'W): a) in sterilized 

 seawater: b) in non-sterilized seawater; and cl by autoxidation (w/o 

 light). 



Thus, in the areas of exposure the rate constant values of 

 BaP autoxidation in seawater differed within one order of 

 magnitude. The shape of the kinetic curves (Figs. 2-4) also 

 gives evidence of a negligible decrease in BaP concentration 

 over time without sunhght. 



While in laboratory experiments by photo-initiated 

 UV-irradiation within a relatively wide wavelength range — 

 around 200 nm — and a high oxygen atmosphere in a liquid 

 medium, the degradation of BaP did not change until the 



C/Co 

 1.0 



c 

 o 



•5 0.5 



c 

 o 

 o 



(X 



a 



CO 



Fig. 3. 



o 







9 



t .hour 



Kinetics of BaP degradation under sunlight irradiation at the surface 

 ofthe Bering Sea (coordinates: 53°58'N 175°28'W): a) in sterilized 

 seawater: b) in non-sterilized seawater; and c) by autoxidation 

 (w/o light). 



disappearance of the initial substance (zero-order reaction) 

 (Gubergritse/fl/., 1975: Paalme etal, 1983). Under natural 

 conditions in water (i.e., by sunlight photolysis), a decrease in 

 the reaction rate is observed after the first hour of exposure 

 (Figs. 2-5 ). This is especially noticeable in the Bering Sea area 

 ( Figs. 2-3 ). From the graphs ( Figs. 2-5 ), it follows that the BaP 

 half-decay times (t" : ) in the Bering Sea waters were not less 

 than 1 h. but in the tropical part ofthe Pacific, they were 0.6 h. 

 The initial rate constant value of sunlight photolysis of BaP in 

 the tropical zone water averaged 8.9 x 1 O 12 mole s ', exceeding 



199 



