The fluxes of polyarenes in the Don, Kuban and Volga river deltas

The values of polyarene fluxes with suspended matter in the watercourses of the Don, Kuban and Volga river deltas have been calculated. Water flow rates and volumes of suspended matter differ many times in the studied deltas. However, the PAH fluxes are comparable: they vary from the first g/day to the first thousand g/day. The linear structures of delta flows are also different. The even distribution of flows is characteristic of the Don River delta; a pronounced maximum of flows at the entrance to the delta and their minimum in the lower part of the delta are characteristic of the Kuban River, while two contrasting maxima were recorded in the upper part and at the outlet from the Volga River delta. In addition, deltas differ in the input and output capacities of the polyarene fluxes, the gradients of decreasing flux intensity and the average values of PAH fluxes.
The formation of river flows of polyarenes is largely influenced by objects located within the delta or at a short distance upstream. The inlet capacities of the flows in the Kuban and Volga river deltas are 2165 and 1128 g/day, respectively. The Don River delta has the smallest flux of polyarenes (239 g/day), due to the absence of large industrial sources upstream. The intensity of polyarene fluxes decreases within deltas if there are no sources of pollutants. The greatest values of the gradients of flow intensity decrease are characteristic of the full-flowing sections of the channels in the upper reaches of the Don River delta (28.5 g/(day • km)), and the entrance to the Kuban delta (60 g/(day • km)).
Low-molecular-weight compounds prevail in the composition of polyarenes in the Don, Kuban, and Volga river deltas. Two- and three-ring polyarenes in the suspension accounts for 98%, on average. Homologues of naphthalene, phenanthrene and diphenyl predominate. Four-ring chrysene and pyrene are present in the composition of PAHs in bottom sediments, thus the low-molecular-weight polyarenes account for just 72-98%.
The diagnostic ratios of PAHs were calculated to determine the genesis of polyarenes. The ratios BaP/ (BaP + Cry), Ant/(Ant + Phe), and Tetr/(Tetr + Cry) were the most representative for the studied deltas, while the ratio of low-molecular-weight to high-molecular-weight polyarenes appeared less informative. According to the obtained values of PAH ratios, the regions of predominately pyrogenic polyarenes coincide with the regions where the largest industrial facilities are located.

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