The sensitivity of soil enzymes to soil contamination with zinc was analyzed. A laboratory experiment was performed on sandy loam at pH 7.0, sampled from arable land at a depth of 0 to 20 cm. Soil samples were passed through a sieve with 2 mm mesh size and contaminated with the following zinc doses: 0, 300, 600, 1200 and 2400 mg Zn 2+ kg-1 soil. Zinc was applied in the form of aqueous solution of ZnCl 2. Soil was mixed thoroughly with zinc, and its moisture content was brought to 50% capillary water capacity. The samples were incubated at 25°C. Beakers with soil samples were weighed once a week to replenish evaporated water. The activity of soil enzymes: dehydrogenases, urease, acid phosphatase, alkaline phosphatase, catalase, arylsulfatase and b-glucosidase, was determined after 15, 30, 60 and 120 days of the experiment. The results were used to calculate soil resistance (RS), ED 20 and ED 50 values. The results of the study indicate that soil enzymes are characterized by varied sensitivity to excessive zinc concentrations, and that the RS index is a reliable measure of enzymatic responses to zinc pollution. The analyzed enzymes were classified in the following decreasing order in terms of their resistance to zinc: b-glu-cosidase> acid phosphatase > urease >arylsulfatase = alkaline phosphatase> catalase > dehydrogenases. Zinc continued to exert a negative effect on soil enzymes throughout the experiment (120 days). ED 20 values for the analyzed enzymes in mg Zn 2+ kg-1 DM soil were determined at: 103 for dehydrogenases, 184 for alkaline phosphatase, 233 for urease, 247 for arylsulfatase, 416 for acid phosphatase, 419 for catalase and 1373 for b-glucosidase.

Nickel is a heavy metal which is a stable soil pollutant which is difficult to remediate. An attempt to reduce its impact on the environment can be made by changing its solubility. The right level of hydrogen ions and the content of mineral and organic colloids are crucial in this regard. Therefore, methods to neutralise heavy metals in soil are sought. There are no reports in the literature on the possibility of using minerals in the detoxication of a soil environment contaminated with metals. It is important to fill the gap in research on the effect of zeolites on the microbiological, biochemical and physicochemical properties of soils under pressure from heavy metals. Therefore, a pot experiment was conducted on two soils which examined the effect of various levels of contamination of soil with nickel on the activity of soil enzymes, physical and chemical properties and growth and development of plants. An alleviating effect of zeolite Bio.Zeo.S.01 on the negative impact of nickel on the soil and a plant (oats) was examined. The enzyme activity and the oat yield were found to be significantly and negatively affected by an excess of nickel in the soil, regardless of the soil type. The metal was accumulated more in the oat roots than in the above-ground parts. An addition of zeolite decreased the level of accumulation of nickel in oats grown only on sandy-silty loam. Zeolite Bio.Zeo.S.01 used in the study only slightly alleviated the negative effect of nickel on the biochemical properties of soil. Therefore, its usability in the remediation of soil contaminated with nickel is small.

This study evaluates the effectiveness of organic fertilizers in restoring the homeostasis of soils contaminated with zinc. The activity of selected enzymes participating in the transformation of carbon, nitrogen, phosphorus and sulfur and the sensitivity of white mustard plants to zinc were analyzed. A greenhouse pot experiment was carried out. Uncontaminated soil served as control. Six organic substances which potentially neutralize the adverse effects of zinc were used: tree bark, finely ground barley straw, pine sawdust, cattle manure, compost and cellulose. It was found that in less contaminated soil (300 mg Zn 2+ /kg), all of the analyzed organic substances minimized zinc adverse effects on the biochemical properties of soil, including the activity of dehydrogenases, catalase, urease, acid phosphatase, alkaline phosphatase, β-glucosidase and arylsulfatase. In more contaminated soil (600 mg Zn 2+ /kg), the negative consequences of zinc pollution were effectively mitigated only by cellulose, barley straw and manure. Cellulose had the highest soil restoration potential, as demonstrated by resistance indicator values for different enzymes. Cellulose, compost, manure and straw increased the resistance of white mustard plants to zinc, but only in treatments contaminated with 300 mg Zn 2+ /kg. Bark and sawdust potentiated zinc toxic effects on mustard plants.

This study was undertaken to evaluate zinc's influence on the resistance of organotrophic bacteria, actinomyces, fungi, dehydrogenases, catalase and urease. The experiment was conducted in a greenhouse of the University of Warmia and Mazury (UWM) in Olsztyn, Poland. Plastic pots were filled with 3 kg of sandy loam with pHKCl - 7.0 each. The experimental variables were: zinc applied to soil at six doses: 100, 300, 600, 1,200, 2,400 and 4,800 mg of Zn(2+) kg(-1) in the form of ZnCl2 (zinc chloride), and species of plant: oat (Avena sativa L.) cv. Chwat and white mustard (Sinapis alba) cv. Rota. Soil without the addition of zinc served as the control. During the growing season, soil samples were subjected to microbiological analyses on experimental days 25 and 50 to determine the abundance of organotrophic bacteria, actinomyces and fungi, and the activity of dehydrogenases, catalase and urease, which provided a basis for determining the soil resistance index (RS). The physicochemical properties of soil were determined after harvest. The results of this study indicate that excessive concentrations of zinc have an adverse impact on microbial growth and the activity of soil enzymes. The resistance of organotrophic bacteria, actinomyces, fungi, dehydrogenases, catalase and urease decreased with an increase in the degree of soil contamination with zinc. Dehydrogenases were most sensitive and urease was least sensitive to soil contamination with zinc. Zinc also exerted an adverse influence on the physicochemical properties of soil and plant development. The growth of oat and white mustard plants was almost completely inhibited in response to the highest zinc doses of 2,400 and 4,800 mg Zn(2+) kg(-1).

Zinc is an essential element for all living organisms, but overexposure to this element can have strongly toxic effects. A pot experiment was carried out to evaluate the influence of different zinc concentrations (0, 100, 300, 600, 1200, 2400, 4800 mg Zn 2+ kg-1 of soil) on the soil biological activity by analyzing changes in soil stability over time and by determining the resistance (RS) of microorganisms and soil enzyme activity. The influence of Zn 2+ on the growth and development of oat and white mustard was evaluated. Overexposure to zinc inhibited the growth of soil microorganisms, the activity of soil enzymes, and the growth and development of plants. Excessive zinc doses cause lower microbial biodiversity and enzyme activity. Bacteria of the genus Azotobacter were most sensitive and spore-forming oligotrophic bacteria were least sensitive to excessive zinc doses. β-glucosidase was most resistant and arylsulfatase was least resistant to the analyzed element. The resistance of the tested microorganisms and enzymes decreased with an increase in zinc accumulation in the soil environment. White mustard was more sensitive to zinc contamination than oat and zinc doses of 2400 and 4800 mg Zn 2+ kg-1 led to the death of white mustard plants. The results of this study indicate that soil contamination with zinc poses a threat for living organisms. In areas with a higher risk of zinc deposition, the content of this element in soils should be monitored more frequently than prescribed by environmental protection regulations.