Effect of the selected organic solvents on the activity of soil microorganisms

W badaniach ekotoksykologicznych mających na celu ocenę oddziaływania stałych hydrofobowych substancji organicznych niezbędne jest stosowanie rozpuszczalników organicznych, które ze swej strony mogą wpływać na aktywność biologiczną gleb. Oceniono oddziaływanie dwóch powszechnie stosowanych rozpuszczalników (aceton i dichlorometan) na ogólną i specyficzną aktywność mikroorganizmów glebowych w zróżnicowanych warunkach eksperymentalnych.The aim of the study was to evaluate the effect of organic solvents, commonly used in ecotoxicity studies on the activity of soil microorganisms. Two solvents, often applied in the studies of the effects of hydrophobic organic contaminants in the environment, acetone and dichloromethane, were employed in the experiments. The evaluation of the effects of the solvents was based on the measurements of two parameters describing the overall activity of soil microorganisms (activity of dehydrogenases) and the activity of the specific group of nitrification bacteria (potential of nitrification). The experiments included different laboratory conditions (soil material properties, time of contact, methods of solvent amendment). The results show that the solvents introduced to soils in the amount commonly used in the ecotoxicity studies (10-20 cm3 kg-1) may inhibit the activity of soils microorganisms: the effect was particularly visible in the case of potential of nitrification determinations. Employment of the method of gradual application of the solvents to soils led to significant decrease of those negative effects

Soil quality index for agricultural areas under different levels of anthropopressure

Different individual soil parameters or simple indices are widely used in soil quality evaluation, but this approach has many limitations. The aim of the study was to determine an integrated soil quality index in agricultural soils as affected by different levels of anthropopressure. The soil quality index was calculated through: the selection of the appropriate indicators for a minimum data set, score assignation for selected indicators and the integration of indicators in an index. The study was carried out in two areas under agricultural use with similar soil cover but with a different history and intensity of exposure to pollution input. Soil samples collected from the surface layer (0-30 cm) were analysed for physicochemical (i.e. texture, fractional composition of soil organic matter, pH), and biological (respiration, dehydrogenase activity, microbial biomass and nitrification) properties and the levels of contaminants (16PAHs and heavy metals). The level of anthropopressure was assessed on the basis of pollutants emission indices. A statistical evaluation based on principal component analysis enabled the selection of indicators of significant importance to soil quality. The level of anthropopressure was found to be an important factor influencing soil quality; higher soil quality index values (0.50) were determined for the area of low anthropopressure

Assessment of soil quality after biochar application based on enzymatic activity and microbial composition

Soil microorganisms play a key role in many biochemical processes essential for the environment and for the ecological and production functions of soils, hence they are very important quality indicators. The study aimed at evaluating the effect of 1 and 2% additions of wheat and miscanthus straw biochars on soil enzymatic activity (dehydrogenases, urease, phosphatases) and the number of microorganisms (bacteria, fungi, actinobacteria). Pot experiments were carried out on soil with a loamy sand texture. The geometric mean of enzyme activities, biological index of fertility, and the integrated total enzyme activity index were used to explore the relationships between soil enzyme activities and the microbiological and chemical properties of soil. The addition of 1% miscanthus straw biochar had the most beneficial effect on the number of bacteria and fungi (increase by 380 and 26%, respectively), and 1% wheat straw biochar on the number of actinomycetes (increase by 273%). The correlation analysis between the number of actinomycetes and the chemical parameters of the soil showed the significant effect of the content of Ntotal (r = 0.76) and Ctotal (r = 0.85). The values of biological index of fertility, total enzyme activity index and geometric mean of enzyme activities indexes showed that the best quality of soil was produced by a 2% addition of wheat straw biochar

Microbial, Plant, and Invertebrate Test Methods in Regulatory Soil Ecotoxicology

International audienceStandard tests have been used in soil ecotoxicology for about 40 years, but there is still room for improvement, such as (1) increased use of such tests because of regulatory requirements, in particular for the risk assessment of chemicals (mainly pesticides) and, to a lesser extent, of contaminated soils; (2) increased efforts regarding the standardization of ecotoxicological methods, handled either by OECD (Organization for Economic Cooperation and Development) prospectively for individual chemicals or by ISO (International Organization for Standardization) retrospectively for contaminated soils; (3) increased inclusion of ecological aspects, i.e., by performing higher-tier tests under semi-field and field conditions. However, until quite recently, nominal concentrations of the stressors are used, meaning that their bioavailability was not taken into account. We are providing an overview on currently required and/or proposed ecotoxicological effect tests, covering OECD and ISO methods for main soil organism groups (microbes, invertebrates, and plants). Based on this overview, we discuss how the current set of test methods could be improved, trying to capture ecological reality by addressing issues such as different soils, species, endpoints, and exposure (i.e., bioavailable instead of nominal/total concentrations). The TRIAD approach is highlighted as an example how bioavailability could be implemented in soil quality regulations