The general trend observed was an increase in metal toxicity measured by the biotest with increasing available metal contents in soils. All the soil samples were classified into toxicity class III, which means that they are toxic and present severe danger. Biotest are a good complement to chemical analyses in the assessment of quality of soils as well as in properly managing them.
Mining and processing of zinc—lead ores are activities that can enrich surrounding area with heavy metals Muhammad et al. In many regions of the world where zinc and lead ores are mined and processed, zinc, cadmium, lead, arsenic, thallium, and iron are transported to the environment Lee and Kao ; Degeyse et al. The adverse effects of heavy metals in these areas are connected with their transfer in the trophic chain, from soil through plants to animal and human Torres and Johnson ; Wolterbeek and Verburg Most human exposure to metals is associated with contaminated groundwater and soils Aelion and Davis Currently, the pollution of soil by heavy metals is evaluated with an assessment, which involves a chemical analysis of the concentration of heavy metals.
Soil monitoring in Poland is based mainly on the maximum permissible contents which are given in the Regulation of the Minister of Environment However, chemical monitoring alone does not always reveal the real threat connected with the presence of heavy metals in the soil Alvarenga et al. Single and sequential extraction protocols have been designed to predict both the retention and release of metals in soils Zhang et al.
However, these methods are empirical and can only estimate the potential availability of metals for organisms Sahuquillo et al.
For this reason, chemical analyses are seldom suited for the evaluation of potential ecological risks, since they do not take into account the possible combined effects of different contaminants as well as their bioavailability Boularbah et al. Due to the fact that organisms differ in sensitivity to various substances, it is essential to select appropriate organisms for test, searching for different taxonomic groups and candidates to represent different links of the trophic chain Mankiewicz-Boczek et al. Plants are important components of ecosystems; they are the primary food producers and therefore it is important to identify the magnitude of the toxic effects on these organisms Garcia-Lorenzo et al.
Bacteria play a role as decomposers in environment, and hence there is justification for their inclusion in a battery of tests for assessing soil toxicity Kahru et al. The obtained information may provide a better understand the limitations and benefits of chemical and ecotoxicological methods for conducting the environmental risk assessment of heavy metal polluted soils. This plant is located in the Olkusz zinc and lead ore mining and metallurgical area.
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It is an area where high concentrations of heavy metals in soil, plants, and animal organisms have been recorded. The chemical composition of soils in the Olkusz region largely results from the composition of parent rocks which form them. The substratum of the Triassic carbonates of the Olkusz district consists of Cambrian, Ordovician, and Sylurian rocks, which are covered by sequences of Devonian carbonates as well as Lower and Upper Carboniferous carbonates, sandstones, and clays.
Ninety-two percent of the zinc-lead mineralization is hosted by ore-bearing dolomites. Compared with other soils in Poland, soils located in that region are distinguished by increased contents of cadmium, lead, zinc, and iron and other trace elements.
The trace elements are more concentrated in the soil surface layer, which may be a result of the present and past ways of acquiring and processing Zn—Pb ores Cabala and Teper The areas of former mining and processing of zinc-lead ores in the region are characterized by increased concentrations of harmful elements, caused mainly by primitive methods of mining and processing. Unfortunately, most traces of past mining-metallurgical activities have been expunged and now only the high metals content in the soils remains as evidence, presenting a severe danger to organisms living within these places.
Sampling sites. An internal standard and a certified reference material, CRMTrace Metals-Sandy Loam 7 RT Corporation , were added to each series of determinations in order to verify their precision. Each sample of the soil material was analysed in two replications. A Microsoft Excel spreadsheet and Statistica 10 package were used for analysis and presentation of the obtained results. The degree of soil pollution with cadmium, zinc and lead was evaluated using the pollution index PI Wei and Yang The PI value was calculated as a ratio of the metal content in the sample being evaluated to its geochemical background according to the following formula:.
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The research involved screening tests with consisted non-diluted samples. A characteristic property of Vibrio bacteria is the large amount of metabolic energy used for luminescence. Luminescent bacteria emit visible light as an effect of their normal metabolic processes. Any change in metabolism caused by a toxic substance leads to a change in the intensity of the emitted light. Data analysis was performed using the Microtox Omni software and the standard test procedure Three replicate samples were tested. For the second Phytotoxkit biotest was used to determine chronic toxicity of the soil samples on higher plants.
The measurement parameters were the inhibition of seed germination IG and root length inhibition IR in the tested soil in comparison with the control soil. The test was conducted in accordance with the procedure recommended by the manufacturer Phytotoxkit Percent germination inhibition IG and percent root growth inhibition IR were calculated according to the following formula:.
Among various phytotoxicity indices based on germination and early growth of higher plants, the germination index GI appears to be a good method for assessing the toxicity of bottom sediments, composts, and soils Beltrami et al. GI was calculated according to the formula for the combined evaluation of the two parameters Beltrami et al. The toxicity classification system developed by Persoone et al. After determining the percentage effect for each biotest, a soil sample was classified into one of five classes based on the highest toxicity value indicated by at least one test:.
A high diversity in pH 4. Values of hydrolytic acidity in the studied soils varied from 5. The S value is the index of sorptive capacity of soil in relation to alkali cations, and it depends on the grain size, content of organic matter and soil acidity. The higher the acidity, the lower the participation of alkali cations in the soil sorptive complex. Values of alkali cations S in the studied soil samples were from The highest cation-sorptive capacity was found in a soil sample collected from sampling site 2 Total cadmium concentration varied between 0.
The calculated values of the pollution index assumed the following values: from 16 to for cadmium, from 9 to for zinc, and from 6 to for lead. They are indicative of heavy metal pollution of the studied soils. However, on assessing the concentration of metals in the soils, based on the maximum permissible values for soils given in the Regulation of the Minister of Environment , it was established that they met the standards for soils of group C industrial areas, surface mining land in use, transportation areas.
Apart from information on the total metals concentrations in the soil, knowledge of their easily soluble forms is also useful due to the possibility of mobilizing them from the solid phase and permeation to the environment. However, using ammonium nitrate enables the isolation of a mobile, readily available fraction of heavy metals from soils.
Under natural conditions, this fraction may be released into soil solution, presenting a real danger to living organisms. In general, hydrochloric acid washes away metals associated with the exchangeable fraction, carbonate fraction, fraction of Fe—Mn oxides, and organic matter fraction.
It is commonly acknowledged that lead is the least mobile metal in the environment, whereas zinc and cadmium are among the most mobile metals Kabata-Pendias and Pendias Numerous researches studies have proved that cadmium is very mobile in soil environments and shows potentially high toxicity for living organisms, even at low concentrations An A linear dependency between individual heavy metals in soil may be a result of their geochemical connections, and it can also inform about their mobility and sources of origin Guo et al.
A strongly positive correlation between total contents of zinc, cadmium, and lead was found in the studied soils. Strong linear correlations between individual pairs of heavy metals confirm that they are of similar origin, usually connected with human activities and particularly with mining as well as the processing of zinc and lead ores. Correlations between heavy metal concentrations and soil properties and their toxicity to the test organisms.
Among the test plants, the highest germination inhibition was found in S. Among the studied soil samples, the strongest inhibition of S. Similarly to germination, the highest root growth inhibition was found in S. The root growth inhibition of S. Depending on the studied soil sample, V. The highest luminescence inhibition of V.
Percentage toxic effects of the soils, for the test organisms and toxicity classification of the soils. Germination index values for S. This means that all the studied soil samples caused growth inhibition of this plant. The germination index for L. Only soil samples collected from sampling sites 2 and 7 were not toxic for L. The lowest GI values were found for S. Similarly to S. According to the toxicity classification system proposed by Persoone et al. The essential positive values of the correlation coefficients in this research indicate a connection between metal content in soil and toxicity for organisms, whereas negative values due to the lack of significance mean that the studied metal did not influence the increase in sample toxicity.
A significant positive correlation was found between the total concentration of the metals and luminescence inhibition in V.
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In general, negative correlations with the concentration of metals were found in the case of S. The research also did not find a significant correlation between root growth inhibition of L. In turn, research by Garcia-Lorenzo et al. These metals are concentrated mainly in the soil surface layer, which, because of its environmental functions, has a significant influence on the entire biosphere.
Research of Trafas et al. The high variation in the metals concentration in the studied soils is connected with the occurrence of metalliferous minerals whose accumulations depend on natural and anthropogenic factors.
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The most important of these factors include: geological structure and erosion of shallow ore-bearing Triassic formations; historical mining as well as processing of zinc and lead ores, which are responsible for the surface deposition of waste rich in zinc, lead and cadmium; the emission of metal-rich dust from the zinc works; the high emission of industrial dust from the Upper Silesian Industrial Region as well as the eolian redeposition of zinc-lead-iron minerals from above ground landfills designed for postflotation and post metallurgical waste.
In the studied soils, zinc, lead and cadmium most often occurred in the ratio of sampling sites 1, 3, 4, 5, 7 , which corresponds to ratios determined in zinc-lead ores Cabala and Teper ; Cabala et al. Based on that it can be concluded that the metals content in the studied soils is connected with the same mineral complexes as the ones that occur in primary or oxidized ores as well as in postflotation waste created as a consequence of their processing. In the studied region, the level of heavy metals concentration in the soils depended also on the distance from the sources of pollution.
Changes in the metals concentration in the research area indicate that the content decreases along with the distance from the landfills designed for postflotation waste and waste from zinc smelter. Zinc, cadmium and lead concentrations in soils were highest close to the landfill and the works sampling sites 2 and 4.
Accounting for local conditions
Krzaklewski et al. Many research studies suggest that soil reaction, content of organic matter, and content of the finest fraction may influence the mobility of metals in the environment Venditti et al. It was proved that solubility and consequently bioavailability of heavy metals increases at low soil pH acid and very acid soils Venditti et al. As already mentioned, the studied area is exposed to the direct influence of industrial activities connected with mining and the processing of zinc—lead ores. However, it is important to remember that despite a significant influence of the reaction of the substratum on the assimilability of heavy metals by soil organisms, the total concentration of an element has the greatest influence on its bioavailability and toxicity Favas et al.
The total metal concentration in soil samples correlated in a significantly positive way with the response of the test organisms S. The quality of soils is generally assessed based on physico-chemical indices, without taking microbiological and ecotoxicological parameters into consideration.
The total concentration metals of metals in soils gives little information on their mobility and toxicity.
Furthermore, chemical fractionation methods using several extractants do not give adequate information about metal bioavailability for all the metals present in a multi-contaminated soil Boularbah et al. Many authors have shown that biotests give a general indication of metal bioavailability in soils and are recommended for the assessment of ecological risks in soil Boularbah et al.
The analysis of results obtained from the conducted research indicates that it seems necessary, however, to apply a battery of bioassays that uses organisms from different trophic levels and with different sensitivity to substances present in soil. It is important that each species and test procedure have their own sensitive pattern to toxicants, because one single species is not sensitive to all chemicals Matejczyk et al.
In the research, the test organisms were exposed to substances dissolved in water Microtox as well to substances absorbed on the surface of solid particles Phytotoxkit. It is important because heavy metals undergo sorption on non-organic and organic particles and are available only during direct contact.