Phytoremediation of Mixed Contaminated Soils--Effects of Initial Concentrations

Numerous contaminated sites exist worldwide that contain a mixture of organic and heavy metal contaminants. Very few technologies are proven to be efficient to address the problem of such mixed contamination. Most of these technologies are energy-intensive and expensive and they can disturb the natural ecosystem. Phytoremediation has the potential to be a green and sustainable approach to decontaminate and restore the contaminated sites, maintaining the biological activity and physical structure of the soils. However, its effectiveness for mixed contaminants is not well understood. This study presents a series of laboratory experiments conducted to investigate the effects of initial contaminant concentration on phytoremediation of mixed contaminated soils. A silty clay (typical field soil) was spiked with naphthalene, phenanthrene (representative organic contaminants), lead, cadmium and chromium (representative heavy metals) in different concentrations. Two plant species - specifically, Avena sativa (oat plant) and Helianthus annuus (sunflower) - were grown in these contaminated soils as well as in uncontaminated soil for comparison purposes. Results showed that the increase in contaminant concentrations in the soil negatively influenced the growth and biomass of the plants. Helianthus annuus showed lower germination, survival, growth rates, and biomass under increasing contaminant concentrations compared to Avena sativa.