Chromium (Cr) is a very important element examined for last decades on many expert fields. Its toxicity, mobility and bio-availability are strongly dependent on its oxidation state, Cr(III) and Cr(VI). Hexavalent form Cr(VI) is a known carcinogen with many harmful effects on living organisms, on the other hand trivalent Cr(III) form is an important micronutrient necessary for lipid metabolism. Contamination of the environment by Cr may come from anthropogenic industrial pollution or from naturally enriched sites, especially ultramafic rocks and their derived soils. Environmental conditions of soils and water represent a very complex system, which makes reliable assessment of its fate and potential toxicity and transport a really difficult task. A number of studies have been performed to describe Cr behaviour in these systems, as well as to optimize its determination, especially speciation methods. The main objective of this contribution is to summarize and present the today’s knowledge about the occurrence, speciation, and behaviour of Cr in soil environment, with a specific emphasis to description of differences between naturally enriched and anthropogenically contaminated soils.
ABSTRACTŠlapáková B., Jeřábková J., Voříšek K., Tejnecký V., Drábek O. (2018): The biochar effect on soil respiration and nitrification. Plant Soil Environ., 64: 114-119.Soil microorganisms play a main role in the nutrient cycle and they also play an important role in soil health. This article studies the influence of three rates of biochar (0.5, 1 and 3%) in comparison with control (0 biochar) in two different soils (Valečov and Čistá) on soil microbiota activities. The biochar was prepared from 80% of digestate from Zea mays L. and 20% of cellulose fibres by pyrolysis (470°C, 17 min). The biochar ability to influence microbial processes in soil was determined by respiration and nitrification tests. There were no significant differences between basal respiration of control samples and biochar-amended samples. Basal respiration in the Valečov soil reached average amounts from 1.32 to 1.52 mg CO 2 /h/100 g. In the Čistá soil, basal respiration reached average amounts from 1.40 to 1.49 mg CO 2 /h/100 g. No significant differences were proved also in nitrification tests of both soils. Nitrifying potential was the highest in 3% rate of biochar amendment. There were no negative changes in the measured soil parameters. CO 2 efflux was not higher in biochar-amended soil.
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