Abstract
The industrial environmental “hot spots” create significant ecological hazards for terrestrial and aquatic ecosystems. Guidelines and legislation often refer to the total amount of contamination without estimating the complex relationship between the environmental factors and the toxicant. In cases of suspicion for adverse effect on the environment bio-assessment can be used as a tool to detect the presence of hazardous chemicals. Bioassays with vascular plants are considered to be universal tools of identifying the combined effects of pollutants in ecotoxicology. The purpose of this article was to evaluate the toxicological effect
of plant-soil complex treated with waste water from Radomir Metal Industries, Bulgaria. The conclusion is that the sewage from the metallurgical plant Radomir Metal is used properly for irrigation of arable land. The question can be which kind of plants are suitable to be cultivated there. The effluent seems toxic for the aquatic systems and has a slight negative impact on the soil breathing and germination of treated plants. Nevertheless, in the bioassay for all examined plants a stimulating effect on the weight of roots and stems was registered under the treatment with soil extract.Keywords: ecotoxicology, soil pollution, soil respiration, energy of germination, germination, early development, culture plant
Introduction
Human activities all over the world have increased environmental pollution by heavy metals in agricultural soil. contamination with heavy metals is a major problem for crop quality, human health, and environmental quality. Most of the heavy metals are persistent in soil because of their immobile nature (4, 11). Chemical analyses are often insufficient to provide insight into the potential ecological risk, since they do not allow an evaluation of possible combined effects of the different contaminants mixed together, as well as to their bioavailabilty. Guidelines and legislation often refer to the total metal content in the soil without taking into consideration what proportion of that total amount may be biologically available to the organisms. Actually, the toxic effects are related to the bioavailability of metals in soils. therefore, bioassays which can mitigate these constraints are recommended for the assessment of ecological risks in soils or other matrices (5). contaminated areas create serious environmental hazards for terrestrial and aquatic ecosystems. they are sources of pollution and may bring about ecotoxicological effects. At severely contaminated spots acute effects occur, but the core problem lies in possible long-term chronic effects (7). effects of toxicants at high concentrations that induce a high rate of acute mortality are observed easily, even in complex communities. the effects of toxicants at low concentrations that do not immediately result in acute mortality are much more difficultly detectable. In such cases, communities are shaped not only by the effects of the toxicants but also to a great extent by other environmental factors. As a result, the complex relationship between a multitude of environmental factors and the composition of the community obscures the effects of the toxicants (13). ecotoxicological effects occur at all levels of the biological organization, from the molecular to the ecosystem level. not only may certain organisms be affected, but the ecosystems as a whole in their functions and structure (6, 7). in ecotoxicology on the basis of conducted bioassays with sensitive test objects or test objects from treated ecosystems the toxic effects on the whole ecosystem are evaluated. the purpose of this study was to make an ecotoxical assessment of the culture plant-soil complex in agroecosystems treated with waste water from Radomir Metal industries, Bulgaria, by using a set of bioassays with cultivated plants in the region.
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ECOTOXICOLOGICAL ASSESSMENT MODEL OF CULTURAL PLANT-SOIL COMPLEX TREATED WITH WASTE WATER
