Mining activities can lead to the generation of large quantities of heavy metal laden wastes which are released in an uncontrolled manner, causing widespread contamination of the ecosystem Though some heavy metals classified as essential are important for normal life physiological processes, higher concentrations above stipulated levels have deleterious effects on human health and biota Bacteria able to withstand high concentrations of these heavy metals are found in the environment as a result of various inherent biochemical, physiological, and/or genetic mechanisms These mechanisms can serve as potential tools for bioremediation of heavy metal polluted sites This review focuses on the effects of heavy metal wastes generated from gold mining activities on the environment and the various mechanisms used by bacteria to counteract the effect of these heavy metals in their immediate environment

Heavy Metal Pollution from Gold Mines: Environmental Effects and Bacterial Strategies for Resistance.

Biological approaches to tackle heavy metal pollution: A survey of literature

Environmental problems have always received immense attention from scientists. Toxicants pollution is a critical environmental concern that has posed serious threats to human health and agricultural production. Heavy metals and pesticides are top of the list of environmental toxicants endangering nature. This review focuses on the toxic effect of heavy metals (cadmium (Cd), lead (Pb), copper (Cu), and zinc (Zn)) and pesticides (insecticides, herbicides, and fungicides) adversely influencing the agricultural ecosystem (plant and soil) and human health. Furthermore, heavy metals accumulation and pesticide residues in soils and plants have been discussed in detail. In addition, the characteristics of contaminated soil and plant physiological parameters have been reviewed. Moreover, human diseases caused by exposure to heavy metals and pesticides were also reported. The bioaccumulation, mechanism of action, and transmission pathways of both heavy metals and pesticides are emphasized. In addition, the bioavailability in soil and plant uptake of these contaminants has also been considered. Meanwhile, the synergistic and antagonistic interactions between heavy metals and pesticides and their combined toxic effects have been discussed. Previous relevant studies are included to cover all aspects of this review. The information in this review provides deep insights into the understanding of environmental toxicants and their hazardous effects.

Heavy Metals and Pesticides Toxicity in Agricultural Soil and Plants: Ecological Risks and Human Health Implications.

The most common laboratory procedure used for DHA determination is the method developed by Casida et al. (1964). According this method, specific dyes such as the triphenyltetrazolium chloride (TTC), that can specify the flow of electrons are useful indicators of electron transport system (ETS) activity. By the reduction of colorless, water soluble substrate (TTC) by dehydrogenases present in the soil environment, an insoluble product with red color (triphenylformazan-TPF) is formed. TPF can be easily quantified calorimetrically at the range of visible light (485 nm). This test however, reflected positive answer only at neutral range of pH and in presence of calcium carbonate for buffering soil system. Briefly, if the red colors of soil samples prepared for spectrophotometer analyses are more intensive, the measured level of DHA is higher. Consequently, soil samples without red colors or those with light red colors are characterized by lower DHA values.

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Dehydrogenase Activity in the Soil Environment

Trace Elements in Soils

The aim of this research was to examine the correlation between the presence of microbes in soil and the degree of soil pollution with unleaded and 98 leaded petrol. Detoxication of soils contaminated by refinery products was performed using barley straw. The experiment was conducted in two series: on unsown soil and on soil sown with triticale. The results of the study have proved that contamination of soil by petroleum compounds stimulates the growth of Azotobacter sp., copiotrophic and oligotrophic bacteria, but inhibits the multiplication of fungi and actinomycetes. Fertilisation of soil with barley straw and cultivation of triticale improved microbiological properties of soil. The favourable effect of the treatments was attenuated by leaded and unleaded petrol.

Correlation between number of microbes and degree of soil contamination by petrol

An experiment has been performed to determine the activity of arylsulphatase in soil submitted to pressure of four polycyclic aromatic hydrocarbons: naphthalene, phenanthrene, anthracene, and pyrene, in the amount of: 0, 1,000, 2,000, and 4,000 mg kg−1 dm of soil. Soil samples were also applied some organic substances, such as: cellulose, sucrose, and compost, in the amount of 0 and 9 g kg−1 dm of soil. The experiment was run under laboratory conditions. It was established on soil which belonged to loamy sand. The soil resistance (RS) and resilience (RL) indices were computed. It has been discovered that the PAHs stimulated arylsulphatase activity, with anthracene raising the activity of the enzyme to the highest degree. The activity of arysulphatase depended significantly on the dose of a PAH, duration of pressure, and type of organic substances added to soil. The highest resistance (RS) was determined in soil exposed to phenanthrene, and the lowest one—in soil polluted with pyrene. Low values of the RL index prove that polycyclic aromatic hydrocarbons cause lasting disorders in the activity of arylsulphatase.

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Activity of Arylsulphatase in Soil Contaminated with Polycyclic Aromatic Hydrocarbons.

The presence of fungicides in the natural environment, either resulting from deliberate actions or not, has become a serious threat to many ecosystems, including soil. This can be prevented by taking appropriate measures to clear the environment of organic contamination, including fungicides. Therefore, a study was conducted aimed at determining the effect of bioaugmentation of soil exposed to azoxystrobin on its degradation and activity of selected enzymes (dehydrogenases, catalase, urease, acidic phosphatase, alkaline phosphatase). A model experiment was conducted for 90 days on two types of soil: loamy sand (pHKCl—5.6) and sandy loam (pHKCl—7.0), which were contaminated by azoxystrobin at 22.50 mg kg−1 DM of soil and inoculated with a specific consortium of microorganisms. Four strains of bacteria were used in the experiment (Bacillus sp. LM655314.1, B. cereus KC848897.1, B. weihenstephanensis KF831381.1, B. megaterium KJ843149.1) and two strains of mould fungi (Aphanoascus terreus AB861677.1, A. fulvescens JN943451.1). Inoculation of soil with the consortium of microorganisms accelerated the degradation of azoxystrobin. The isolated microorganisms were more active in loamy sand because within 90 days azoxystrobin was degraded by 24% (Bacillus sp., B. cereus, B. weihenstephanensis, B. megaterium) to 78% (Aphanoascus terreus, A. fulvescens). In sandy loam, azoxystrobin was degraded by 9% (Aphanoascus terreus, A. fulvescens) to 29% (Bacillus sp., B. cereus, B. weihenstephanensis, B. megaterium and Aphanoascus terreus, A. fulvescens). The activity of soil enzymes was also changed as a result of inoculation of soil with microorganisms. The activity of all of the enzymes under study was found to have increased when soil augmentation was performed.

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Bioaugmentation of Soil Contaminated with Azoxystrobin

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%.

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The effect of soil contamination with diesel oil and petrol on the nitrification process

The effect of soil contamination with nickel applied in the doses of 100, 200, 300 and 400 mg Ni/kg of soil on the ac tivity of dehydrogenases, urease and acid and alkaline phosphatase was studied in a pot experiment. Heavy loamy sand and silty light loam were used in the experiment that comprised of two series: with spring barley cultivation and without plant cultivation. The enzyme activity was determined on day 14, 28, 42 and 56 of the experiment. Based on the study, it was found that soil contamination with nickel applied as NiCl 2 .6 H 2 O decreased the activity of dehydrogenases, urease and acid and alkaline phosphatase. This decrease was determined by the applied dose of this metal. Nickel exhibited a stronger effect on the soil with spring barley cultivation than on the unsown soil. In the heavy loa my sand sown with spring barley, more than 50% inhibition of the activity of dehydrogenases was caused by 300 and 400 mg Ni contamination, and in the case of urease by 200, 300 and 400 mg Ni/kg of soil. In the silty light loam sown with spring barley, more than 50% decrease in the activity of dehydrogenases and alkaline phosphatase was observed under 400 mg Ni contamination. The inhibition of the other enzyme activities did not exceed 50%. Urease and alkaline phosphatase exhibited a higher activity in the heavier soil, whereas dehydrogenases and acid phosphatase exhibited a higher activity in the lighter soil. In the nickel-free soil, spring barley cultivation had a positive effect on the enzyme activity and a positive correlation between the spring barley yield and the activity of dehydrogenases, urease and acid and alkaline phosphatase was observed.

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Jan Kucharski

Papers

Correlation between number of microbes and degree of soil contamination by petrol

Activity of Arylsulphatase in Soil Contaminated with Polycyclic Aromatic Hydrocarbons.

Bioaugmentation of Soil Contaminated with Azoxystrobin

The effect of soil contamination with diesel oil and petrol on the nitrification process

Effect of nickel contamination on soil enzymatic activities