Role of the sediments in scavenging inorganic contaminants in the Syr Daria River and the Small Aral Sea (Kazakhstan)

Abstract

9-11 july 2008International audienceThis study is focused on the measurement and the behaviour of the inorganic pollutants in the Suspended Particulate Material (SPM) and the Bottom Sediments (BS) of the Syr Daria River in its Kazakh course, including its outlet in the Small Aral Sea. Two field campaigns were carried out during the low and the high water period. The results display that the current Syr Daria River sediments quality is influenced by several phenomena seasonally and locally controlled: carbonate precipitation, absorption by phytoplankton, scavenging by clay mineral, upstream ground leaching during the snow melting, various discharges (drainage canals, urban and industrial waste waters), connection with delta lakes during the flooding period and impact of the geochemical background. The study of the solid – liquid partition coefficients emphasizes the contrasted behaviour of trace elements with respect to different scavenging phases. As a result it appears that in spite of the mitigating action of the dam reservoirs, of the irrigated areas, of the overflow lakes and flood plains, the Aral Sea sediments are not completely preserved from the contamination