Biodegradation and toxicological evaluation of lubricant oils
The aim of this work was to compare different toxicity levels of lubricant oils. The tests were performed using the earthworm (Eisenia andrei), arugula seeds (Eruca sativa) and lettuce seeds (Lactuca sativa), with three types of contaminants (mineral lubricant oil, synthetic lubricant oil and used lubricant oil) for various biodegradation periods in the soil. The toxicity tests indirectly measured the biodegradation of the contaminants. The samples were analyzed at t0, t60, t120 and t180 days of biodegradation. The used lubricant oil was proved very toxic in all the tests and even after biodegradation its toxicity was high. The mineral and synthetic oils were biodegraded efficiently in the soil although their toxicity did not disappear completely after 180 days.
Review of the ecotoxicological effects of emerging contaminants to soil biota
ABSTRACT In recent years, emerging contaminants (e.g. pesticides and their metabolites, pharmaceuticals, personal and house care products, life-style compounds, food additives, industrial products and wastes, as well as nanomaterials) have become a problem to the environment. In fact, the cumulative use of a panoply of chemical substances in agriculture, industrial activities, in our homes and in health care services has led to their recent appearance in detectable levels in soils, surface, and groundwater resources, with unpredictable consequences for these ecosystems. Few data exist regarding the toxicity and potential for bioaccumulation in biota. When available, data were obtained only for some representatives of the main groups of chemical substances, and for a limited number of species, following non-standard protocols. This makes difficult the calculation of predicted no effect concentrations (PNEC) and the existence of sufficient data to set limits for their release into the environment. This is particularly concerning for the soil compartment, since only recently the scientific community, regulators, and the public have realised the importance of protecting this natural resource and its services to guarantee the sustainability of terrestrial ecosystems and human well-being. In this context, this review paper aims to identify the major groups of soil emerging contaminants, their sources, pathways and receptors, and in parallel to analyse existing ecotoxicological data for soil biota.
Kinetic modeling of the biodegradation of the aqueous p-xylene in the immobilized soil bioreactor
Abstract Biodegradation kinetics of p -xylene in aqueous solution was studied in a new type of biofilm reactor—immobilized soil bioreactor. Biofilm modeling was performed in order to determine the concentration gradients within the biofilm based on a coupled diffusion-reaction model for cylindrical geometry. The total amount of biomass in the 0.83 L bioreactor changed from 460 to 780 mg during continuous operation. The concentration gradient was typical for a shallow biofilm and also predicts low mass transfer resistance within the biofilm. Rate constants for the continuous regime were determined based on the biomass growth and the amount of substrate utilization, resulting in the values of: maximum specific growth rate ( μ max ) of 0.0047 h −1 , half saturation constant ( K s ) of 3.9 mg L −1 and yield ( Y x/s ) of 0.05 mg biomass mg −1 substrate. For batch operation, a similar yield coefficient was assumed and the experimental data was fitted to the Monod equation. μ max of 0.0047 h −1 (similar to continuous) and K s of 10 mg L −1 were obtained.