Abstract
High concentration of labile metals in soil directly affects soil quality, water health and human safety. Decreasing mobility of metals, especially in contaminated soils, by cost-effective amendments may alleviate environmental problems. Natural diatomite was investigated to immobilize toxic elements of zinc, lead, copper and cadmium in a contaminated calcareous soil. The diatomite was characterized using X-ray fluorescence spectrometry and scanning electron microscopy. Contaminated soil was incubated with 0, 2 and 5 weight -% of diatomite at 25 °C for 8 weeks. Tessier sequential extraction method was also used as a suitable method for identification of chemical forms of heavy metals; metal stability index and mobility factor were calculated. Results showed that application of diatomite in soil significantly decreased the metals in the exchangeable fraction and increased them in the residual fraction. The exchangeable metal fractions decreased by 66–88%, and residual fractions increased by 18–94% in the 5 weight -% of diatomite treatment after 8-week incubation. With an increase in the amount of diatomite applied and the incubation time, metal mobility factor values significantly decreased and soil pH values increased. Application of diatomite caused the heavy metals redistribution toward more stable forms and leads to an increase in stability index values. In conclusion, in situ immobilization of heavy metals by application of diatomite, as a low-cost amendment, had a significant potential to stabilize metals in the contaminated calcareous soil.
Highlights
Human activities are the main reasons for contamination of water, air and soil with heavy metals (Park et al 2011)
The X-ray fluorescence spectrometry (XRF) results show that SiO2 (73.2%), A l2O3 (11.60%), Fe2O3 (1.5%), MgO (1.5%), Na2O (1%), K2O (0.50%) and CaO (1.3%) are the chemical composition of diatomite
0 Dia2% Dia5% 7 14 21 28 35 42 49 56 63 Incubation(day) significant difference was found in use between high (5% w/w) and low (2% w/w) dose of diatomite, application of 2% of diatomite is recommend in a hypothetical remediation
Summary
Human activities are the main reasons for contamination of water, air and soil with heavy metals (Park et al 2011). Especially cadmium (Cd), lead (Pb), copper (Cu) and zinc (Zn), in soil can result in contamination of ground water due to movement of metals. University, Urmia, Iran via aqueous phase of soils and may affect food safety and environmental and human health (Hu et al 2017). Mobility of metals are controlled by soil factors, especially pH, clay content, calcium carbonate content and Fe and Mn oxides. The chemical properties of soil and the soil processes (such as adsorption, desorption, precipitation and ion exchange) control relative proportions of heavy metal fractions from soluble and insoluble chemical forms (Jin et al 2005; Powell et al 2005)
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