Abstract
Soil contamination with cresol is a problem of the 21st century and poses a threat to soil microorganisms, humans, animals, and plants. The lack of precise data on the potential toxicity of o-cresol in soil microbiome and biochemical activity, as well as the search for effective remediation methods, inspired the aim of this study. Soil is subjected to four levels of contamination with o-cresol: 0, 0.1, 1, 10, and 50 mg o-cresol kg−1 dry matter (DM) of soil and the following are determined: the count of eight groups of microorganisms, colony development index (CD) and ecophysiological diversity index (EP) for organotrophic bacteria, actinobacteria and fungi, and the bacterial genetic diversity. Moreover, the responses of seven soil enzymes are investigated. Perna canaliculus is a recognized biosorbent of organic pollutants. Therefore, microbial biostimulation with Perna canaliculus shells is used to eliminate the negative effect of the phenolic compound on the soil microbiome. Fungi appears to be the microorganisms most sensitive to o-cresol, while Pseudomonas sp. is the least sensitive. In o-cresol-contaminated soils, the microbiome is represented mainly by the bacteria of the Proteobacteria and Firmicutes phyla. Acid phosphatase, alkaline phosphatase and urease can be regarded as sensitive indicators of soil disturbance. Perna canaliculus shells prove to be an effective biostimulator of soil under pressure with o-cresol.
Highlights
The European Commission (EC) and the United States Environmental ProtectionAgency (USEPA) have listed cresols as priority contaminants based on toxicity and environmental concerns [1]
On day 15 of the experiment, o-cresol applied into the soil at a level of 50 mg kg−1 dry matter (DM) of soil moderated the development of microorganisms, while contributing to an almost two-fold increase in the count of organotrophic bacteria, ammonifying bacteria and actinobacteria, and an almost three-fold increase in the count of nitrogen-immobilising bacteria
The presence of o-cresol increased the count of Pseudomonas sp. by 14.07% in relation to the control pots, whereas the lowest contamination level of 0.1 mg o-cresol kg−1 DM of soil triggered a similar response in this group of microorganisms
Summary
The European Commission (EC) and the United States Environmental ProtectionAgency (USEPA) have listed cresols as priority contaminants based on toxicity and environmental concerns [1]. The production capacity for cresol currently amounts to more than 3 × 109 kg [3]. For this reason, o-cresol, a phenolic derivative belonging to volatile organic compounds, is widespread in many types of industrial wastewater, 14% of which penetrates into the soil [2,4]. Surface and ground waters and soils become contaminated with phenolic compounds as a result of anthropogenic operations, such as waste incineration and wood-burning [12]. Significant cresol sources of great concern include flotation processes in mining and metallurgical industries, copper flotation, oil refining and coal conversion [3,6].
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