“Validazione dell’applicabilità del saggio di tossicità acuta con Eisenia fetida accoppiato ad un approccio multi-biomarker come strumento diagnostico nel monitoraggio della qualità ambientale di suoli industriali e agricoli soggetti a spandimento di fanghi di depurazione biologica e relativi hydrochars"

The soil is an extremely complex environmental matrix whose protection represent a priority for human survival, since it is the basis of production activities, as well as a source of nutrition. The compromising level reached by soils can limit the ability to maintain high ecosystem functions and to sustain biological productivity. Another great challenge is the sustainable management of sewage sludge (SS), inevitably linked to soil protection as soil amendment is the most widely used management method. It is also the cheapest and suitable disposal method to contrast soil erosion and climate change. Therefore, it is essential to standardize toxicity tests able to identify the mechanism of action of contaminants and their mixtures in order to characterize contaminated soils and define the environmental safety of new agricultural fertilizers such as SS and hydrochar resulting from their hydrothermal carbonization. To this purpose, after a first step invested to methods development in laboratory conditions, the ecological risk assessment of soils from the municipality of Taranto was carried out using the standardized acute toxicity test (OECD 207) with Eisenia fetida coupled to a battery of biomarkers (sub-lethal responses). The biomarkers of oxidative stress, cytotoxicity, genotoxicity and specific biomarkers of exposure to metals, were useful to identify the distribution of contaminants, and to outline areas of highest environmental criticalities and the contaminants most responsible for the observed biological effects. Then, the ecotoxicological assessment of SS from various wastewater plants in the Tuscany Region was carried out. The OECD 207 test with E. fetida, coupled to a battery of cellular and histological biomarkers, was applied to mixtures at different ratios of control soil LUFA 2.2 and SS. The observed effects identify the toxicological stress syndrome in exposed earthworms as the effect of contaminates present in SS. The presence of these contaminants are not recorded by the chemical analysis alone, which classify these SS suitable and safe for use in agricultural soils. The importance of studying the sub-lethal effects in E. fetida is further highlighted by mortality, that result contradictory and not able to identify the real ecological risk associated with the use of sludge to soil organisms. E. fetida mortality and morphology does not seem to be affected by hydrochars mixed with LUFA 2.2., even if it is more contaminated than the respective SS, suggesting a reduced bioavailability of the contaminants after hydrothermal carbonization. The multi-markers approach in E. fetida is a useful diagnostic tool in monitoring the environmental quality of industrial and agricultural soils fertilized by SS, capable to integrate the information obtained from chemical-analytical investigations, giving a significant contribution to the definition of mitigation actions and prevention of environmental and ecological risk.