Anna Piotrowska-Długosz

The impact of the soil sealing degree on microbial biomass, enzymatic activity, and physicochemical properties in the Ekranic Technosols of Toruń (Poland)

PurposeArtificial soil sealing in urban areas has attracted increasing attention because of its potential hazard to urban ecosystem. Covering soils with impervious materials has a significant impact on their properties and is essentially an irreversible process. In contrast to natural, open soils, sealed soils undergo a significant alteration of their physicochemical properties, and in turn, negatively influence microbial biomass and enzymatic activity.Materials and methodsIn general, 33 soils from different parts of the city of Toruń (NW Poland) were sampled and divided into 3 groups according to the degree of soil sealing: (1) soils sealed with semi-pervious concrete paving slabs (A), (2) soils sealed with impervious surfaces, such as asphalt and concrete (B), and (3) non-sealed soils (the reference group—C). Soil samples were assayed for (1) microbial biomass carbon (MBC), and nitrogen (MBN) and soil respiration activity (RESP), (2) the activity of soil enzymes, and (3) physicochemical properties.Results and discussionSoil sealing significantly reduced the content of carbon and nitrogen (both total and microbial), soil respiration, the activity of urease, and fluorescein diacetate hydrolysis compared to non-sealed soils (C), while the degree of soil sealing did not significantly affect these properties. Soil moisture and nitrate reductase activity were the only properties significantly differentiated by the degree of soil sealing. Canonical correlation analysis indicated that soil biological activity was caused mainly by the variation in MBC and MBN content, as well as dehydrogenase, catalase, and cellulase activities. The highest correlation was obtained between the soil moisture and the first canonical variable for microbial biomass and enzymatic activity.ConclusionsThe results showed that the artificial sealing in urban areas can significantly alter the soils by reducing their carbon and nitrogen content as well as microbial biomass and its activity compared with open soils. The analysis of variance showed that the degree of soil sealing did not affect most of the studied soil properties, although the differences in raw data between impervious and semi-pervious sites were remarkable.

The Effects of Antibiotics on the Structure, Diversity, and Function of a Soil Microbial Community

Pharmaceutical antibiotics are widely applied to treat diseases of humans and animals or are added to animal feeds to improve the growth rate and feed efficiency. However, these antibiotics are often poorly metabolized and adsorbed by humans and animals. As a result, the majority of them are excreted unchanged, or as metabolites, in feces and urine and are then introduced to the soil with various materials such as manure or urban wastes. Since the application of manure or other organic amendments is a common practice throughout the world, the presence of antibiotics and their active metabolites in soils, especially in agricultural soils, is occurring quite often. Not only antibiotics but also considerable numbers of antibiotic-resistant bacteria and resistance genes (ARGs) are introduced into soil via organic fertilizer, thus raising serious environmental and human health concerns. This chapter, therefore, gives a brief overview of recent research in determining the impact of antibiotics, their bioactive metabolites, and ARGs that enter the soil on the structure, diversity, and function of soil microbial communities. The properties that are most often studied (e.g., bacterial and fungal populations, phospholipid fatty acids (PLFAs), community structure, community-level physiological profile (CLPP), enzymatic activity, nitrification/denitrification, iron reduction) and the appropriate techniques that are currently being used (e.g., PCR-DGGE of 16S rDNA, Biolog Ecoplates®, MicroResp™, gas chromatography (GC-MS), colorimetric quantification) are discussed. As was shown in the reviewed literature, antibiotics in soil differ significantly in their effectiveness on soil microorganisms, and both a positive and negative influence and a lack of any influence have been found. Possible changes were influenced by various natural and anthropogenic factors, such as soil texture, soil physicochemical properties, absorption into soil particles, degradation, and leaching. Furthermore, issues concerning dose-response and time-dependent effects of antibiotic impact on soil microbial communities were also analyzed. Additionally, methodological potential and limitations in determination and quantification of the effects of veterinary antibiotics applied with organic amendments on soil microbial communities and antibiotic resistance have been discussed. Finally, further research needs and directions concerning the effects of antibiotics on soil microbial communities have been outlined.

The Use of Enzymes in Bioremediation of Soil Xenobiotics

Environmental pollution with toxic compounds has become one of the biggest ecological problems of the world today. Therefore, there is a growing interest in developing new, cost-effective, and eco-friendly remediation technologies that are capable of the partial or total recovery of a polluted environment, with particular emphasis on soils. Bioremediation that uses the catabolic potential of microorganisms can be efficiently used to clean up certain pollutants, but for chemicals that exhibit a high xenobiotic character (polyaromatic hydrocarbons, chlorophenols, dioxins) microorganisms can be ineffective. Among biological agents, enzymes have a great potential to effectively transform and detoxify soil pollutants. The use of enzymes may represent a good alternative for overcoming most of the disadvantages related to the use of microorganisms. They can be used under extreme conditions that limit microbial activity and are effective at low pollutant concentrations. Enzymatic methods generally have low-energy requirements, are easy to control, and have a minimal environmental impact. This review has examined the possibility of using enzymes as an element of soil bioremediation technology and the main requirements that must be fulfilled when using this type of technology. Moreover, some classes of enzymes, mainly oxidoreductases and hydrolases, which are capable of transforming soil xenobiotics into innocuous products effectively, are characterized. Both plant-derived and microbial enzymes are discussed and special attention was paid to laccases, peroxidases, tyrosinases, lipases, proteases, and phosphotriesterases as well as to nitrile- and cyanide-degrading enzymes, which have a great potential to transform xenobiotic compounds. The main advantages as well as the disadvantages of the application of enzymes in the bioremediation of polluted soils are specified. Finally, the future perspective for the in situ application of enzymes in bioremediation of polluted environment is presented.

Influences of Catch Crop and Its Incorporation Time on Soil Carbon and Carbon-Related Enzymes

Abstract Catch crops that are cultivated for green manure play an important role in improving soil properties. A 3-year field experiment was conducted to investigate the effect of catch crop (pea, Pisum sativum L.) management, i.e., incorporation of catch crop in October/November (autumn) and March (spring), and without catch crop (control), on soil organic carbon (SOC), microbial biomass carbon (MBC) and the activities of carbon (C)-cycle enzymes, including cellulase (Cel), β -glucosidase (Glu) and invertase (Inv). Additionally, soil total nitrogen (TN) and pH KCl were investigated. The catch crop was cultivated from August to October each year during 2008–2010. Soil samples were collected from the field of spring barley ( Hordeum vulgare L.) that had been grown after the catch crop. Soil samples for microbial activity determination were taken in March, May, June and August in 2009, 2010 and 2011, while SOC and TN contents as well as pH KCl were determined in March and August. The chemical properties studied did not show significant changes as influenced by the experimental factors. The use of catch crop significantly increased the MBC content and the activities of C-cycle enzymes compared to the control. When the catch crop was incorporated in spring, a significantly higher MBC content was noted in March and May compared to autumn incorporation. Moreover, the spring incorporation of the catch crop significantly increased the Glu activity (except March), while the activities of Cel and Inv as well as the rate of soil basal respiration were usually unaffected by the time of catch crop incorporation. Greater microbial biomass and higher enzyme activities in the catch crop-treated soil, compared to the control, indicated that the application of the catch crop as a green manure could be recommended as a promising technique to increase the biological activity of the soil. Since there was no significant effect or no consistent results were obtained related to the time of catch crop incorporation, both spring and autumn applications can be recommended as a management tool to improve the status of soil properties during the growth of a subsequent crop.