A REVIEW OF PHYTOREMEDIATION STRATEGIES FOR SOILS POLLUTED WITH HEAVY METALS

Mining operations, industrial production and domestic and agricultural use of metal and metal containing compound have resulted in the release of toxic metals into the environment. Heavy metal pollution has serious implications for the human health and the environment. Since heavy metals are nonbiodegradable, they accumulate in the environment and subsequently contaminate the food chain. Few heavy metals are toxic and lethal in trace concentrations and can be teratogenic, mutagenic, endocrine disruptors while others can cause behavioral and neurological disorders among infants and children. Therefore, remediation of heavy metals contaminated soil could be the only effective option to reduce the negative effects on ecosystem health. Different physical and chemical methods used for this purpose suffer from serious limitations like high cost, intensive labor, alterationof soil properties and disturbance of soil native microorganisms. Phytoremediationis the use of plants and associated soil microbes to reduce the concentrations or toxic effects of contaminants in the environments. In this article are reviewed the stratagies in the phytoremediation for remediating heavy metals from polluted soils. Phytoextraction and phytostabilization are the most promising and alternative methods for soil reclamation

A REVIEW OF CYCLODEXTRINS POTENTIAL IN INCREASING PETROLEUM HYDROCARBONS BIODEGRADATION

Petroleum hydrocarbons are organic pollutants that are released into the environment mainly due to anthropogenic activities and are considered as priority pollutants. The petroleum hydrocarbons degrading microorganisms occur in most environments, where hydrocarbons may serve as organic carbon sources. Bioremediation is based on the use of microorganisms or microbial processes to degrade environmental contaminants, and offers several advantages over the conventional chemical and physical technologies. It can be a cost effective, environmental friendly technology. The intensity of biodegradation is influenced by several environmental factors, such as quality, quantity and activity of the indigenous microbial populations, levels of nutrients, aerobic conditions, pH, temperature, water content and other soil properties. Moreover, low biodegradability and bioavailability of the contaminants / pollutants may limit the biodegradation in a contaminated / polluted site. Cyclodextrins have successfully been used in soil cleaning technologies as solubilisercarrier molecules. These molecules can transfer the insoluble contaminants / pollutants from the soil surface to the aqueous phase by complex formation. In the aqueous phase the microorganisms can degrade the contaminants / pollutants much easier partly because these molecules become available for the microbial cells, partly because the entrapment of contaminants by cyclodextrins reduces their toxicity. The effects of cyclodextrins on the hydrocarbon contaminants in soils (solubilisation, enhancement of desorption from soil, toxicity and bioavailability modulation, catalytic and stabilising effects) have been recently reviewed. Addition of cyclodextrins in aqueous washing solutions has been shown to increase the removal efficiency several times, while being non-toxic agents

PHYTOTOXIC EFFECTS OF STEEL SLAG USED AS AMENDMENT FOR ACID SOILS

Application of the amendments restores the quality of the soil by balancing the pH, the organic matter intake, increasing the water retention capacity, reducing the soil compaction and restoring the microbial community. There are, however, some problems appear due to the use of soil amendments, and these problems may increase when the amendments are steel slag and furnace slag which are parts of ferrous slag. [NAC, 2003], [Ziemkiewicz and Skousen,1998]. The slag obtained from steel mill industry contains some metals in concentrations that are higher than normal concentrations in the soil. The toxicity of metal can occur when that metal (often a nutrient for plants) is present in high concentrations. The toxicity becomes more severe at a more acidic pH of the soil, or when it is combined with other nutrient deficiencies. The phytotoxicity of a heavy metal is a result of an imbalance between the absorption element and the inability of the process of metabolism of the plant to annihilate it at the cellular level. Following the experience installed on a support material of an acid soil, a luvosoil sampled from Albota region, with 6 doses of steel slag (0 g slag / kg soil; 1 g slag/ kg soil; 2 g slag / kg soil, 3 g slag / kg soil, 4 g slag / kg soil and 5 g slag / kg soil), and corn as test plant, there were presented observations and effects referring to the treatment on corn plants. From the point of view of heavy metals translocated in the corn plants, the paper presents variations of there contents depending on the treatment with steel slag. All the concentrations of heavy metals in the corn plants were placed generally within the normal content of the plant