The influence of the Cucurbitaceae on mitigating the phytotoxicity and PCDD/PCDF content of soil amended with sewage sludge

The study evaluates the impact of sewage sludge on OECD - Organization for Economic Cooperation and Development and vegetable soil phytotoxicity, measured using three test species: Lepidium sativum, Sinapis alba and Sorghum saccharatum, and total and TEQ PCDD/PCDF (toxic equivalency polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans) soil concentration, measured using HRGC/HRMS - High Resolution Gas Chromatography/High Resolution Mass Spectrometry. It also evaluates the effect of zucchini and cucumber cultivation during 5-weeks period on mitigating these parameters. The application of 3, 9 and 18 t/ha of sewage sludge gradually increases the phytotoxicity of both OECD and vegetable soil. In the case of OECD soil, the highest roots growth inhibitions were observed for S. alba (73%, 86% and 87%, respectively) and the lowest for S. saccharatum (7%, 59% and 70%), while in vegetable soil inhibitions were averagely 25% lower. Sludge application also led to a 38% (3 t/ha), 169% (9 t/ha) and 506% (18 t/ha) increase in PCDD/PCDF concentration, and the TEQs were augmented by 15%, 159% and 251%. Both soil phytotoxicity and total and TEQ PCDD/PCDF concentrations were diminished as a result of zucchini and cucumber cultivation. The maximum reduction of soil phytotoxicity (83%) was observed as an effect of cucumber cultivation, while zucchini was 11% less effective. Zucchini, in turn, was more efficient in PCDD/PCDF removal (37% reduction), followed by cucumber (24%). Such differences were not observed in the case of TEQ reductions (68% and 66% for zucchini and cucumber cultivation, respectively).