Environmental evaluation of remediation alternatives of the historically polluted Karosta Canal disposal site, Liepaja Port, Latvia

Abstract

Polluted sediments from the Karosta Canal (Latvia) were recently disposed into an adjacent 7 ha semi-closed basin, connected to the canal through two pipes presenting a risk of spreading contaminants. Sediments and water samples for determination of contaminants were taken from the disposal site and analyzed in an accredited laboratory in Latvia. Samples for greenhouse gases (GHG) concentration and emissions were also collected. Concentrations of metals, polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyl compounds (PCBs) and oil (hydrocarbons) were classified according to relevant classification systems, and all showed levels of concern. Water classification was incomplete because some limits of quantification were above class limits. The impact of different management alternatives, including capping sediment, filling up the disposal site and/or installing floating solar panels (FPV), on GHG emissions and contaminant releases to the canal were estimated through modelling. The disposal site emits 150-220 tons CO2 equivalent annually, mostly from CH4. Without capping, PCBs, PAHs, hydrocarbons, and metals releases to the canal accumulate to 193 g, 57 kg, 5 tons and 623 kg, respectively, over 100 years. Capping reduces GHG emissions by 70% and contaminant releases by several orders of magnitude. FPV lower emissions by 10% but increase contaminant release by 6%. Capping and filling minimize GHG emissions and contaminant exports. Further studies are needed for more accurate modelling results.