The objective of this study was to determine the alleviating effect of cellulose on the biochemical properties of soil contaminated with nickel. Soil samples were contaminated with nickel chloride, and were fertilized with ammonium sulphate and cellulose. The experiment was carried out for 120 days, at a constant temperature and moisture content. The activity of soil enzymes (dehydrogenases, urease, acid phosphatase, alkaline phosphatase, arylsulphatase, β-gluosidase and catalase) was determined on the day the experiment was established, and on days 15, 30, 60, 90 and 120 of the experimental period. It was found that soil contamination with nickel had a negative impact on the activity of soil enzymes. The sensitivity of the analyzed enzymes to this heavy metal may be presented in the form of the following series: urease > dehydrogenases > alkaline phosphatase > acid phosphatase > catalase > arylsulphatase > β-glucosidase. The adverse effect of nickel on the activity of soil enzymes can be alleviated by soil enrichment with cellulose accompanied by fertilization with ammonium sulphate. The activity of the tested soil enzymes was subject to periodic fluctuations in samples incubated at a constant temperature and under constant moisture conditions.
W doświadczeniu laboratoryjnym testowano wpływ niklu na wzrost i rozwój w hodowlach stałych bakterii: Azotobacter spp., Arthobact.er spp., Bradyrhizobium sp. (lupini) i Rhizobium leguminosarum bv. viciae, promieniowców. Streptomyces intermedius, Streptomyces fumosus, Streptomyces longisporoflavus, Streptomyces odoriver i grzybów. Fusarium spp., Aspergillus spp., Penicillum spp., Rhizopus spp. Badania każdego gatunku wykonano na 10 izolatach, w trzech powtórzeniach. W doświadczeniu wykorzystano dwa rodzaje podłóż mikrobiologicznych: standardowe oraz wzbogacone w dodatkowe źródło węgla. Nikiel zastosowano w postaci dwóch związków. NiCl2·6H2O i NiSO4·7H2O w następujących dawkach. 2, 10, 50, 100, 250 mg Ni2+· krążek-1. W badaniach jednoznacznie wykazano, że bakterie były bardziej wrażliwe na wprowadzany do podłoża nikiel niż promieniowce i grzyby. Spośród badanych bakterii największą wrażliwością na nikiel charakteryzowały się Azotobacter spp. i Rhizobium leguminosarum bv. viciae, a następnie Arthobacter spp. i Bradyrhizobium sp. (lupini). Spośród promieniowców najbardziej negatywnie na nikiel dyfundujący z krążka do podłoża reagował Streptomyces odoriver. Pod względem negatywnej reakcji na nikiel grzyby można uszeregować następująco. Rhizopus spp. < Penicillium spp. < Fusarium spp. < Aspergillus spp.
The effect of soil contamination with nickel on the ammonification process was determined in a laboratory experiment. The experiment involved samples of soil collected from the humus arable horizon. Under natural conditions, it was proper brown soil of granulometric composition of heavy loamy sand and proper brown soil of granulometric composition of light silty loam. The experiment was carried out in three replications. Soil samples were contaminated with nickel in the form of two compounds: NiCl₂ · 6H₂O and NiSO₄ · 7H₂O in the following doses: 0, 100, 200, 300, 400 mg Ni²⁺ kg⁻¹ soil. Nitrogen was introduced in the amount of: 0, 250 mg N kg⁻¹ soil in the form of L-aspartic acid, L-arginine and DL-alanine. The soil prepared in such a way was incubated for 6, 12, 18, 24, 48 and 72 hours. Afterwards, following thorough mixing, the humidity of soil was brought up to 60% capillary water capacity. The results of the experiments demonstrated that the effect of nickel on the ammonification process depended on the type of ammonified organic compound, the type of soil, a dose of metal and the type of nickel compound. Contamination of soil with the amount of nickel between 100 and 400 mg Ni²⁺ kg⁻¹ had an inhibitory effect on the ammonification process. Nickel chloride was a stronger inhibitor of ammonification than nickel sulfate. The amount of ammonified nitrogen was larger in light silty loam than in heavy loamy sand. Nickel had lower inhibitory effect on this process in a heavier soil type than in a lighter one. Soil contamination with nickel compounds contributed to lowering soil pH.
The effect of soil contamination with diesel oil and petrol on the nitrification process was investigated in a laboratory experiment. Samples of typical brown soil developed from loamy sand, of pH of 6.6 in 1M KCl, Hh -11.38 mmol+ kg-1 soil, S — 77.67 mmol+ kg-1 soil and Corg - 8.50 g kg-1 were analyzed. The experiment was performed in three replications, and for each test 100 g air-dry soil sample was placed in 150 cm3 beakers. Soil samples were contaminated with diesel oil and petrol with the addition of rapeseed oil and ethanol. The source of nitrogen was ammonium sulfate in the amount of 0 and 250 mg N per kg-1 soil. The content of N-NO3- and N-NH4+ was determined on experimental days 14, 28 and 42. Soil moisture was kept constant at 50% capillary water capacity throughout the experiment. Fertilizer nitrogen was subject to strong immobilization in soil contaminated with diesel oil and petrol. Both pollutants strongly inhibited the nitrification process. Diesel oil had a much stronger inhibitory effect on nitrification than petrol. Rapeseed oil also proved to be a powerful inhibiting factor. On experimental day 42, diesel oil reduced ammonium cation oxidation by 99%, and petrol - by 88%.
The effect of contamination of loamy sand with single heavy metals (Cd2+, Cu2+, Zn2+, Pb2+) and with their mixtures on the number of copiotrophic, ammonifying, nitrogen immobilising, cellulolytic bacteria and bacteria of the Arthrobacter and Pseudomonas genera was examined in a pot experiment. The research was performed in two series: with soil sown with oat and unsown soil. It was found that the sensitivity of bacteria to Cd2+, Cu2+, Zn2+ and Pb2+ is a specific characteristic related to the content of these metals in soil and to the method of soil use. The development of the bacteria of Arthrobacter and Pseudomonas was most strongly inhibited in the soil sown with oat, while ammonifying, nitrogen immobilising, and cellulolytic bacteria were most inhibited in the unsown soil. Copiotrophic, cellulolytic, nitrogen immobilising and ammonifying bacteria proved to be more resistant to this contamination than bacteria of Arthrobacter and Pseudomonas genera. Increasing the number of heavy metals simultaneously contaminating the soil to two (Cd2+ and Cu2+; Cd2+ and Zn2+; Cd2+ and Pb2+) and to three (Cd2+, Cu2+ and Zn2+; Cd2+, Cu2+, and Pb2+; Cd2+, Pb2+ and Zn2+) generally did not increase the intensity of their effect on the examined bacteria. Changes brought about by these mixtures were usually similar to changes caused by individual heavy metals.
A pot experiment was performed to determine the effect of soil contamination with nickel, applied at a dose of 100, 200, 300 and 400 mg kg-1, on the activity of dehydrogenases, urease, acid phosphatase and alkaline phosphatase. The impact of nickel on the enzymatic activity of soil was studied on samples of heavy loamy sand and light silty loam. The experiment was conducted in two series: in the first one soil was cropped to yellow lupine, and in the second one it was left uncropped. Soil samples were analyzed on day 14, 28, 42 and 56. It was found that soil contamination with nickel reduced the activity of all the enzymes. This negative influence was most noticeable in the case of dehydrogenase. The activity of urease and alkaline phosphatase was higher in light silty loam, while the activity of dehydrogenases and acid phosphatase was higher in heavy loamy sand. The activity of dehydrogenases and urease was higher in soil cropped to yellow lupine, whereas the activity of acid phosphatase and alkaline phosphatase was higher in uncropped soil. Yellow lupine was sensitive to excessive amounts of nickel in the soil, and partly alleviated the adverse impact of this heavy metal on urease activity, but did not reduce its inhibitory effect on the other enzymes.