Soil profile as a natural membrane for heavy metals from wastewater

Abstract

A b s t r a c t. The effect of intensive irrigation with wastewater on the zinc (Zn) and cadmium (Cd) concentration in soil solution was investigated. The experiment was parallel conducted on two soil profiles. The soil microcosms were watered with purified wastewater and purified wastewater with an the addition of zinc and cadmium. The results indicate clearly that neither intensive overhead irrigation of the soil nor its flooding with these wastewater and exceeded sorptive capacity. The application of treated wastewater and wastewater with heavy metals addition did not appear to pose a threat to the natural environment. In all the cases under analysis, zinc and cadmium concentrations in the soil solution were several-fold lower than the permissible levels.K e y w o r d s: soil profile, wastewater, zinc, cadmium INTRODUCTIONHeavy metals commonly occur in soils, due to their release from the parent rocks in the course of soil formation. Their natural concentration, generally do not pose a threat to the ecosystems (Basta et al., 2005). Undesirable concentration of metals can occur in soil as a result of agricultural and anthropogenic activities (Hayian and Stuanos, 2003). The protective role of the soil lasts as long as its biogeochemical balance is not disturbed. Thanks to its sorptive properties, the soil acts as a natural filter and absorbs, among other things, toxic compounds (Malkoc et al., 2010). Soil profile represents a major sink for heavy metals in the terrestrial environment (Foster and Charlesworth, 1996). It is evident that heavy metals introduced with compost or wastewater cause the accumulation of soil organic matter (Hanc et al., 2008) and decrease the turnover rate of organic matter, presumably because of inhibitory effects of heavy metals on microbial biomass. The sorption of heavy metals by organic matter retards metal movement within the soil environment and reduces the potential for toxicity. Usman et al. (2005) found that the addition of clay minerals, especially of Na-bentonite and Ca-bentonite, decreases the extractability of zinc (Zn), cadmium (Cd), copper (Cu) and nickel (Ni) during incubation. Soil reaction (pH) largely determines the mobility and bioavailability of heavy metals with increasing acidification (Kashem and Singh, 2001). Change in soil reaction in alkaline direction reduces the uptake of heavy metals by plants and inhibits their migration to the groundwater (Gondek et al., 2010;Lepp and Madejón, 2007;Li et al., 2010;Singh and Agrawal, 2007). It was found that a woodland dominated by willow (Salix) represented a potentially sustainable remediation option for sequestration of zinc and cadmium through the soil and willow downloads (uptake) (Guo and Marschner, 1995).In some cases industrial wastewater constitutes a serious threat for the water environment, but on the other hand draining liquid wastes to the ground is the oldest form of their disposal (Mehler, 2010). It is the most natural method, as the substances return to the point of their introduction, and also the proces...

The Effect of Petroleum-Derived Substances on the Growth and Chemical Composition of Vicia faba L.

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Methane fermentation process for utilization of organic waste

“…The quantity and quality of sludge depend on physicochemical characteristics of wastewater and technological system of the waste treatment plant (Singh and Agrawal, 2008;W³odarczyk et al, 2012). The mass of sludge depends on a technology of waste treatment.…”

Effect of pH and zinc stress on micropore system of rye roots

“…Zinc is absorbed by the plants as the microelement and is used in the activation of many enzymes. Zinc phytotoxicity is observed when the concentration of this metal in the soil solution is high (Hejazi et al, 2011;W³odarczyk et al, 2012) . The increase of the mobility of the Zn ions is influenced among others by pH and the proportion of the ions Ca +2 /Zn +2 in the soil solution.…”