Regional Contamination History Revealed in Coal-Mining-Impacted Oxbow Lake Sediments
2020
Sedláček, Jan | Tolaszová, Jitka | Kříženecká, Sylvie | Bábek, Ondřej | Zimová, Kristýna
The aim of this study is to investigate complex pollution history and spatial trends of pollution (heavy metals and organic pollutants) in the selected oxbow lake (at the border between the Czech Republic and Poland) along the Odra River, located in the heavily polluted Ostrava urban agglomeration. Contaminant distribution is affected by position in the lake; the highest heavy metal concentrations were found in the central parts. Depth trends in ¹³⁷Cs mass activity, hexachlorobenzene, and DDT metabolites were used as additional date levels. Depth profiles of heavy metals and their enrichment factors and multi-proxy stratigraphic analysis allowed two stages of oxbow lake evolution to be recognized. The initial stage was characterized by higher sediment accumulation rates in the whole oxbow lake, while during the second stage, sediment was deposited in a plug bar and in proximal parts of the lake, providing a more complete pollution record. Coal-rich layers were found in the deeper parts of the sedimentary record, related to coal mining activities. Samples rich in coal revealed a negative correlation with CIEL* (brightness) and conversely a positive correlation with specific biomarkers (homo hopanes and 16 α(H)-phyllocladane) and PAHs (secondary sorption to coal-rich strata). The sedimentary record since the oxbow lake cut-off event in 1966 showed a distinct vertical distribution of all pollutants. Maximum concentrations were attained during 1970s and 1980s, while a decreasing trend occurred after 1989 due to political and socio-economical changes in the former Czechoslovakia (now the Czech Republic).
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