DISTRIBUTION AND COMPOSITION OF POLYCYCLIC AROMATIC HYDROCARBONS IN THERMAL WATERS OF THE CENTRAL PART OF THE BAIKAL RIFT ZONE
N.A. Mukhortina, E. V. Zippa
1Tomsk Branch of Trofimuk Institute of Petroleum Geology and Geophysics of Siberian Branch Russian Academy of Sciences, Tomsk, Russia
Keywords: polycyclic aromatic hydrocarbons, thermal waters, genesis of PAHs, technogenic load, water-rock system
Abstract
New data on the composition and distribution of polycyclic aromatic hydrocarbons (PAHС) in thermal waters and host rocks in Baikal Rift Zone were obtained. It was shown that the total content of all identified individual compounds is 0.17-1.15 μg/L in the thermal springs and is 0.021-1.19 μg/kg in the rock. Naphthalene, phenanthrene, and dibenzo[a,h]anthracene dominate in the water. Phenanthrene, fluoranthene, and dibenzo[a,h]anthracene are predominant in the rock. The total PAHC content increased with TDS of water and with N2 and He growth in escaped gases. The calculated coefficients of technogenic load showed a low level of pollution for all studied sources. According to indicator ratios, the PAHC origin was determined. On the one hand, PAHC in thermal waters had petrogenic origin and were formed due to geochemical transformations of organic matter under high temperatures and pressures and microbial activity, entered with aqueous and gas along faults and fractures. On the other hand, some compounds have a natural pyrogenic origin, where pyrolysis products enter springs either at near-surface conditions or when mixing. The results let to characterize the composition of thermal waters in more detail and to describe a conceptual model the thermal waters composition formation in the studied region.
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