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- Title
ВЛИЯНИЕ НА PbИ CdВЪРХУ МИКРОБИОЛОГИЧНА И ЕНЗИМНА ПОЧВЕНА АКТИВНОСТ - ЛАБОРАТОРЕН ЕКСПЕРИМЕНТ
- Authors
Малчева, Бойка
- Abstract
A laboratoryexperimentwasconducted to investigatetheeffect of differentconcentrations of Pband Cd (individuallyandincombinations) onthemicrobiologicalandenzymaticactivity of agrogenicsoil, unpolluted, not fertilized, without vegetation, from the field of town ElinPelin. The combined effect of Pb and Cd limits the microbiological activity of the soil to a greater extent than the action of these heavy metals individually. This trend is proportional to the increasing concentrations of the elements. For the variants with the separate addition of lead and cadmium, it is also found that soil biogenicity decreases with increasing concentration of the heavy metals studied, this trend being more pronounced under the influence of cadmium. Non-spore-forming bacteria, followed by the bacilli, play a major role in the composition of the total microflora. With increasing concentrations of Pb and Cd, spores-forming bacteria (bacilli) survive better and their amount increases. Actinomycetes and micromycetes are the least represented in the composition of the total microflora and most strongly suppressed by the influence of the analyzed heavy metals. The amount of bacteria digesting mineral nitrogen decreases with increasing concentrations of lead and cadmium. The rate of degradation of organic matter in soil is represented by calculating a mineralization coefficient as a ratio between the group of bacteria digesting mineral nitrogen and the amount ofammonifying bacteria (non-spore and bacilli). The values of the mineralization coefficient show that, compared to the control, the degradation of organic substances is difficult with the addition of lead and cadmium, in proportion to the increase of their concentrations. A higher rate of soil organic matter mineralization is found in the variants with lead than in these with cadmium. The degradation of carbohydrates in soil is represented by the study of enzymes: cellulase, amylase and invertase. The combined effect of Pb and Cd inhibits the enzyme activity of the soil to a greater extent than the action of these heavy metals individually. This tendency is proportional to the increase of their concentrations and correlates with the tendencies in the development of the microorganisms. In the variants with the separate addition of lead and cadmium, it was found that, compared to the control, the cellulase activity decreased under the influence of Cd, to the highest extent with the addition of the highest element concentration. While leadadded variants show increased cellulase activity. Amylase activity increased almost twice when the lowest Pb concentration was added compared to the control sample, but high concentrations began to suppress enzyme activity. A reverse tendency was observed for this enzyme when cadmium was added - suppressed at the lowest added Cd concentration and poor activation with increasing concentrations, the values of the enzyme being close to the controls. Invertase activity is suppressed under the influence of both heavy metals separately, to a greater extent with the addition of cadmium. Possibly better development of microorganisms in the samples with Pb than in samples with Cd leads to an increase in their enzymatic activity, and consequently an increased mineralization of the organic substances (confirmed by the mineralization coefficient values) and the initiation of self-purification processes of the soil from Pb.
- Publication
Knowledge: International Journal, 2019, Vol 35, Issue 3, p835
- ISSN
2545-4439
- Publication type
Article