4.3.1 Transformation of Benzo(a)pyrene 



YURIY L. VOLODKOVICH and OLGA L. BELYAEVA 



Institute of Global Climate and Ecology. State Committee for Hydrometeorology and Academy of Sciences, Moscow. USSR 



Introduction 



Microorganisms, distributed in the World Ocean, play a 

 leading role in the functioning of these ecological systems and 

 in biogeochemical cycles. Microflora is the most active 

 component in these ecological systems (Izrael & Tsyban, 

 1982). Its biomass in the upper 1 00 m layer of the World Ocean 

 reaches 25 x 10''GC/m-, which is similarto plankton biomass. 

 While possessing functional enzyme systems and high 

 biochemical activity, the microbial communities influence 

 oceanic biogeochemical cycles of carbon. Many polycyclic 

 aromatic hydrocarbons (PAH's) that are distributed in sea and 

 ocean ecological systems possess toxic, mutagenic, and 

 carcinogenic properties, which can manifest a clear threat to 

 biotic components and possibly to human health. 



Microbial transformation of aromatic hydrocarbons and 

 heterocyclic compounds has been well studied (Rodoff, 1961 ; 

 Treccan, 1963; Bumpus, 1989). However, the rates of 

 benzo(a)pyrene (BaP) transformation in seawateras well as the 

 significance of this process in local and regional systems have 

 not yet been studied. This paper reports on BaP transformation 

 as a process that eliminates this dangerous compound from the 

 sea. The investigations were conducted in the Bering and 

 Chukchi Seas as part of an all-round investigation of PAH's 

 that started in 1981 (Tsyban et ai. 1987d). 



Methods and Materials 



Studies on the transformation of PAH's were conducted at 

 nine stations in the Bering Sea and in the southern part of the 

 Chukchi Sea in August 1988. This cruise was the Third Joint 

 US-USSR Bering & Chukchi Seas Expedition on board the 

 research vessel Academik Korolev. 



Seawater was collected in sterile samplers. Surface 

 microlayers was sampled with metal screens (0.02 mm). Water 

 column was sampled with Niskin (depths: 0.5, 2 and, 10 m). 

 Water samples with natural microbial communities were 

 transferred in sterile glass bottles for microbiological studies 

 on board ship. 



The rates of BaP transformation by natural bacterioplankton 

 was conducted under //; situ conditions. Water samples of 

 250- ml volume was transferred into 500 ml dark glass bottles 

 along with BaP dissolved in acetone. Four BaP concentrations 

 were used: 100 and 20 |ig/l (10 days) and, 1.0 and 10 ng/1 

 (21 days). Abiotic factors were followed in sterile water from 

 each depth with respective BaP concentrations. These 

 experiments and controls were repeated 2-3 times. 



To simulate in situ conditions, samples were incubated on 

 the ship's deck in running water for 10-21 days. To temiinate 

 the microflora activity, a few milliliters of concentrated HCl 

 were used. Residual concentrations of BaP were extracted in 

 250 ml of benzol and stored until analyzed. 



The BaP benzol extracts were olated and evaporated. The 

 evaporated part of the benzol extract was eluted by 2 ml of 

 solution of 1,12 benzapareline in octane (concentration 

 0. 1 mg/ml) and also used as an inner standard. 



The concentration of BaP in non-octane solution was 

 determined by spectral and fluorescent analysis with the use of 

 Shpolsky at 196°C on spectrographer C-12 (Shpolsky et al.. 

 1952; Fedoseevaera/., 1986). Sensitivity of the method was 

 determined at 1 x lO'" g/ml + 10%. The rate was determined 

 as the difference between the initial (artificially introduced) 

 and final mass of BaP. Rates are expressed in percent of BaP 

 transformed. 



Results and Discussion 



One consequence of PAH's circulation in the sea is its 

 distribution relative to specific microflora that are adapted to 

 new hydrochemical conditions and capable of transforming 

 these dangerous compounds. Our results show that BaP 

 transformation occurs in Bering Sea waters (Tsyban et al., 

 1987c ). During the 1988 cruise in the subarctic region of the 

 Chukchi Sea, BaP transformation was again confirmed. The 

 distribution of BaP transformers was patchy with numbers in 

 the 0.5 m surface layer ranging from 10 to 1,000 cells/ml. The 

 maximum density occurred in the Chirikov basin at Station 89 

 where more than 10' cells/ml were found. 



The potential activity of the microflora to transform BaP 

 was studied in 10 //; situ simulation experiments. The results 

 show that bacterioplankton from the Bering and Chukchi Seas 

 possess the ability to transform BaP (Fig. 1). Microbial 

 transformation of BaP varied from 8 to 5 1 % (Table 1 ) with little 

 variation between replicates. The lowest transformation 

 (2-3%), which is within experimental error, was found in the 

 central part of the Chirikov basin. 



Comparison of 1984 and 1988 data (Fig. 1; Tsyban et al.. 

 1986; Izrael et al., 1987) shows that BaP transformation is 

 relatively stable in the Bering Sea. At North Polygon, BaP 

 transformations ( 1 0-day incubation ) were about 45-55% during 

 these years. Considering the differences in experimental 

 conditions, the results show that maximum biodegradation 

 occurred in the 0.5 m level of the Gulf of Anadyr waters. The 

 rate was 39 mg of BaP/1 over a period of 10 days. In the 



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