8.2.2 Distribution of PAH's 



NATALYA I. IRHA, EHA R. URBAS, and UVE E. KIRSO 

 Institute of Chemistry, Estonian Academy of Sciences, Tallinn, USSR 



Introduction 



Among the more than 50,000 known pollutants in the 

 hydrosphere, the carcinogenic polycyclic aromatic 

 hydrocarbons (PAH" s) are detected in almost all compartments 

 of marine ecosystems. The pathways for the movement of 

 PAH's into seawater is still a subject of much discussion by the 

 scientific community. Human activities (Kirso et al.. 1988) 

 and natural processes (Lisitsyn, 1989) are considered two 

 likeliest routes. A large amount of data has been obtained on 

 the regularities of the distribution of a typical carcinogenic 

 PAH — benzo(a)pyrene (BaP) — in the marine environment. In 

 order to describe the modem distribution of PAH's, one must 

 consider historical changes in man's culture (Izrael &Tsyban, 

 1985a). Due to their high hydrophobicity and low solubility, 

 the investigation of PAH's in contact zones of the ocean 

 (Vinogradov, 1990) (i.e., at the sediment-water and air-water 

 interfaces, where so-called zones of 'condensed life' have been 

 observed) are of interest (Fig. 1 ). 



Fig. 1 . Scheme of natural agents contributing to the transformation of PAH in 

 marine ecosystems. 



To obtain further information on the characteristics of the 

 spatial and temporal variations in PAH pollution, a complex 

 study of PAH concentration in the ecosystem of the Bering and 

 Chukchi Seas (specifically the suspended matter, bottom 

 sediments, and biota) during the cruise of the R/V 

 Akademik Korolev was undertaken (47th cruise, July-November 

 1988). 



Sampling, Processing, and Analysis of Samples 



Sampling 



Preparation and analysis of samples of water, bottom 

 sediments, plankton, benthos, and hydrobionts were carried 

 out using standard methods (Tsyban et al., 1988). All the 

 solvents used were preliminarily purified by passing them 

 through activated carbon. 



To take samples from the surface microlayer (SML), a 

 metal screen (cells 2x2 mm) was pulled horizontally across 

 the sea surface. Samples from the other horizons were taken 

 using a standard water sampler. The bottom sediments were 

 taken with a dredge. These samples were dried at 50-60°C and 

 stored in polyethylene bags. 



Suspended matter samples were taken from different 

 horizons by means of a 'Midia' pump equipped with filters 

 0.5 |a m in pore diameter. The filters were previously purified 

 with hexane. The filters with suspended matter were dried at 

 room temperature and stored in polyethylene bags. Plankton 

 and neuston samples were collected with plankton nets, and 

 benthos were collected with a bottom trawl. Plankton and 

 neuston samples were collected on filter paper and dried on foil 

 in a drying oven. 



Extraction 



Water ( 2.5-5.0 1 ) was twice extracted with hexane ( 1 00 ml 

 each) with a magnetic stirrer for 2 h. The combined extracts 

 were dewatered with sodium sulphate, evaporated to 0. 1 ml 

 and dried at room temperature. Bottom sediment samples 

 (10.0 g) were extracted with 50 ml benzene under static 

 conditions at room temperature in the dark for 48 h. The solids 

 were removed and the extract was evaporated to 1-2 ml. Air- 

 dried samples of plankton, neuston, and benthos tissues were 

 saponified with a 92% ethanol-KOH mixture (25 ml of ethanol 

 and 1 g of KOH per g of sample) at 45°C in a water bath for 

 48 h. The hydrolysate was extracted with hexane ( 10 ml each); 

 the extract was concentrated and dried. 



Chromatographic fractionation of the extracts was carried 

 out using thin layer chromatography plates, which were coated 

 with aluminum oxide . The solvents for developing the plates 

 were chosen as follows: 



(a) for separation of total PAH fractions, used a 

 benzene:acetone mixture (9:1). 



(b) for separation of BaP, used a mixture of petroleum 

 ether (fraction 40-70°) and chloroform (9: 1 ). 



The zones containing the PAH's on the plate was marked 

 using fluorescence UV-irradiation (A^^^ ~ 360 nm). 



For identifying BaP, a BaP standard was used (a BaP 

 solution in benzene, concentration 5 x 10"^ g/ml). The zone 

 containing PAH's was collected and washed off with a 1:1 

 mixture of benzene:acetone. The extract was evaporated and 



301 



