The effect of PCB-contaminated sewage sludge and sediment on metabolism of cucumber plants (Cucumis sativus L.)

Abstract

Increasing amounts of sewage sludge are produced nowadays, which need to be disposed of in a safe and responsible manner. Likewise, bottom sediments from small urban water bodies undergo periodical dredging and need to be utilized. These deposits often contain Persistant Organic Pollutants (POPs) and other toxic substances. Plants can be used to reduce these pollutants during or before disposal to land (phytoremediation). Cucurbitaceae are known to accumulate high levels of POPs, including polychlorinated biphenyls (PCB), compared with other plant species but such accumulation may lead to secondary oxidative stress that may limit their value. This study examined the impact of sewage sludge and urban lake sediment on soil toxicity, measured as PCB concentration, and changes in the antioxidative system of cucumber plants grown in the soils.There was an average reduction of PCB by 38.63% and 27.38% in soil amended with sewage sludge and sediment, respectively after 5 weeks of cucumber plant cultivation. In the case of plants grown with sewage sludge, guaiacol peroxidase (POx) activity significantly decreased to 49% of the control at the highest dose given, while that of glutathione S-transferase (GST) increased to 172% of the control value in the same treatment. α-Tocopherol concentration was higher in the plants grown in the sewage sludge amended soil.