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HEALTH AND ENVIRONMENTAL EFFECTS OF HEAVY METALS RESULTED FROM FLY ASH AND CEMENT OBTAINING AND TRIALS TO REDUCE THEIR POLLUTANT CONCENTRATION BY A PROCESS OF COMBINING-EXCLUSION

Catalina Mihaela Gradinaru

Abstract

Environmental pollution with heavy metals is important by its effects on all the segments of the ecosystem: soil, water, air, plants, animals, and humans. Humans and animals contamination is achieved either by direct contact with polluting particles, or indirectly by consuming the contaminated vegetables. It is also known the human contamination by eating products obtained from animals bred in polluted areas. The effects of heavy metal pollution are well-known at the level of soil and superior organisms. Soils contaminated with heavy metals are considered with a low fertility, with subsequent effects in vegetable productions decreasing due to leaves necrosis and roots growth affecting. Moreover, natural pathways for heavy metal content decreasing in soil are limited in their efficacy, and superior organisms presents the effect of bioaccumulation. In humans and animals, heavy metals accumulate in liver, kidney, thyroid, and/or bone marrow. Some of heavy metals causes various genetic effects. Worldwide, the building sector is in a continuous development involving, most often, an increased production of cement and concrete. The process of cement obtaining has a negative impact on the environment through the consumed energy and emitted combustion gases. Furthermore, many of the raw materials used in this process generates small particles with different contents in heavy metals such as Pb, Ni, Zn, Mn, Cd, Cr, Cu, Hg, Co. These particles are carried by the wind and pollute the neighboring regions of cement factories, which usually are located near to raw materials, in the hill and mountain areas. Big cities are affected by other source of heavy metal particles, the power plants based on coal burning. The resulted waste, the fly ash, is usually deposited near to such targets and can be engaged by the wind, polluting the neighboring regions. Various studies demonstrated the improvement of concrete quality by replacing a part of cement with fly ash. Thereby, the rate of fly ash consumption will increase and the cement demand is expected to drop. In this way, it is achieved a double benefit: a reduction of heavy metal pollution due to fly ash residues consuming, and the conservation of natural resources, such as limestone, marl lime, clay stone or sand used as raw materials for cement production and also generators of polluted particulates with heavy metals. The aim of this paper is to review the literature about the effects of environmental pollution with heavy metals on soil and higher organisms, to describe two of the most important sources in this regard (fly ash and particles of raw materials used in the cement manufacture), and to argue the combining of the two types of matrices in order to reduce a part of the cement from the concrete composition.

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