Modeling phytoextraction of heavy metals at multiply contaminated soils with hyperaccumulator plants

Abstract

Soils and waters contaminated with heavy metals pose a major environmental and human health problem that needs an effective and affordable technological solution. Phytoextraction offers a reasonable technology which uses plants to extract the heavy metals from soils. However, the effectiveness of this new method needs to be demonstrated by means of mathematical modeling. The phytoextraction models also are needed to manage the contaminated soils. A thorough literature review indicates that very few models have yet been developed for phytoextraction due to complexities involved within the soil-water-chemicals-plant system, even for a single metal contamination in the laboratory scale. Furthermore, the complexity increases in the field scale problems where the soils are multi-contaminated and also are with high heterogeneity involved in soil physico-chemical properties. On the other hand, in the case of hyperaccumulator plants there are a great deal of data spread worldwide because of the attentions that have been made to test the phytoextration technology in the last years. Consequently, analysis of the existing database of measured phytoextraction data for hyperaccumulators may result in simple models. The objective of this study was to develop a simple model for phytoextraction of heavy metals at multi-contaminated soils. The more preferable input parameters to derive the phytoextraction models were selected by reviewing the literature. Using the published data of Cd and Zn phytoextraction with Thlaspi caerulescens, some reasonable models were derived. The model calculations suggest that phytoextraction using T. caerulescens is not feasible even when the soil is only moderately contaminated with both Cd and Zn.