RAPID GEOCHEMICAL ASSESSMENT OF AGRICULTURAL INDUSTRIAL-POLLUTION FROM STREAM SEDIMENT DISPERSION FLOWS, SOUTH SIBERIA (IRKUTSK REGION)

Geochemical surveys were undertaken for dispersion flows in Irkutsk, and its surroundings, with the aim of selecting a rapid pollution assessment approach (1 sampling point/14 km). Bottom sediments (< 0.25, 0.25-1, 1-3 mm fractions), overflood sediments (< 0.25, 0.25-1 mm), surface water and plants were sampled. The samples were analyzed by rapid semi-quantitative (partly quantitative) atomic emission spectroscopy (AES) methods for Ag, Pb, Zn, Cu, As, Ni, Co, Mo, Cr, Li, Ga, Ge, Y, Bi, Sn, Mn, V, Ti, W, Be, P and B, as well as for Hg, F and U (by quantitative methods). Single-element maps, maps of geochemical classes (element associations) and ecological-geochemical regionalizations were compiled. The average concentration of the majority of trace elements in water and alluvial sediments are similar to those for other regions of the world. Overflood sediments (particularly the fine grained fraction) are enriched in the majority of trace elements. Anomalies in the fine fraction of overflood sediments are large and they coincide with hydrogeochemical and biogeochemical anomalies. Pollution anomalies correlate with industrial and economic activity: the industrial-settled zone of Irkutsk (Ag, Cu, Zn, Pb, Hg, Ni, Cr); the zone around Shelekhov with an aluminium plant (F, U, Cu, Mo, Pb, Cr, Ni); and the agricultural zone (Ni, Co, Ti, V, P, F, U, Mn, Hg). Small-scale geochemical surveys on the fine fractions (< 1 mm) of overflood sediments, based on cheap and rapid semi-quantitative multi-element AES analysis (up to 50 elements) may be successfully applied to the assessment of pollution by heavy metals and trace elements over large areas.