Jitka Bezchlebová

Novel approach to monitoring of the soil biological quality

In this study, a new approach to interpretation of results of the simple microbial biomass and respiration measurements in the soil microbiology is proposed. The principle is based on eight basal and derived microbial parameters, which are standardized and then plotted into sunray plots. The output is visual presentation of one plot for each soil, which makes possible the relative comparison and evaluation of soils in the monitored set. Problems of soil microbiology, such as the lack of benchmarking and reference values, can be avoided by using the proposed method. We found that eight parameters provide enough information for evaluation of the status of the soil microorganisms and, thus, for evaluation of the soil biological quality. The usage of rare parameters (potential respiration PR, ratio of potential and basal respiration PR/BR, biomass-specific potential respiration PR/C(bio), available organic carbon C(ext), and biomass-specific available organic carbon C(ext)/C(bio)) can be recommended, besides classical and well-known parameters (microbial biomass C(bio), basal respiration BR, metabolic coefficient qCO(2)). The combination of basal parameters and derived coefficients can also extend our knowledge about the condition of the soil microorganisms. In monitoring the case studies presented, we observed that soils evaluated to possess good biological quality displayed generally higher values of organic carbon, total nitrogen, clay, and cation exchange capacity. The soils of good biological quality can display higher levels of contaminants. This is probably related with the higher content of organic carbon and clay in these soils.

Monitoring microbial biomass and respiration in different soils from the Czech Republic—a summary of results

The microbial biomass (Cbio), respiration (basal respiration (BR) and potential respiration (PR)), and derived indices for 520 independent soil samples of 117 different soils from the Czech Republic were statistically analysed. The broad range of soil samples allowed the stepwise breakdown of the database into six reasonable categories of soil: arable soils, loamy grassland soils, sandy grassland soils with weak organic matter content, sandy grassland soils with moderate organic matter content, forest soils with moderate organic matter content, and forest organic soils with rich organic matter content. Because soil microbiology lacks benchmarking values, the ranges of the microbial characteristics for these categories were stated and are presented here. The separation into soil groups narrowed the ranges enough to be useful for comparative purposes. The groups displayed significant differences in basal microbial parameters. The lowest microbial biomass was found in arable soils and grassland sandy soils with weak organic matter content. The highest microbial biomass was shown by loamy grassland soils and organic forest soils. Respiration displayed similar results to the microbial biomass. The derived indices revealed less significant differences confirming their inner-standard nature. The relationships between the soil contamination and microbial parameters were not explored because of the confounding effect of soil organic matter. However, it was not shown by the category of grassland sandy soils with weak organic matter content suggesting they could be especially suitable for the biomonitoring of harmful effects of chemicals on soil microorganisms.

Toxicity of four nitrogen-heterocyclic polyaromatic hydrocarbons (NPAHs) to soil organisms

The aims of this study were: (i) to investigate the toxicity of N-heterocyclic polyaromatic hydrocarbons (NPAHs) quinoline, acridine, phenazine, and 1,10-phenanthroline to the soil invertebrates Eisenia fetida, Enchytraeus crypticus, Folsomia candida, and Caenorhabditis elegans, (ii) to compare the toxicity of four NPAHs and the species sensitivity, and (iii) to discuss possible risks of these compounds in soils. Different toxicities were found for the tested NPAHs which might be partially explained by their structure and properties. Effect concentrations expressed as soil pore-water concentrations were related to log K(ow), which indicated narcosis as the most probable mode of toxic action. The species sensitivity decreased in the rank: springtails >enchytraeids=earthworms> nematodes. Predicted no-effect concentration (PNEC) values were calculated for all tested species giving values from 0.5 to 6.8 mg/kg. It is unlikely that there is a risk for soil organisms in natural soils where lower NPAHs concentrations are expected.