Compost assisted phytoremediation in agricultural acid soil contaminated by heavy metals

At an agricultural site contaminated by heavy metals, phytoremediation, preferred by stakeholders as remediation technology, appeared of difficult applicability due to the acidic nature of the soil that promoted a very high bioavailability of the metals thus inducing phytotoxicity effects in plants with a strong reduction of growth and of biomass production. The soil chemical environment was modified to decrease metal solubility in order to promote an increase in biomass production, allowing in the meantime a significant uptake of metals. Different strategies were evaluated: pH increase by lime treatment, addition of organic matter (compost) and inorganic material (zeolites) with adsorptive properties for metals. Microcosm Experiments with Brassica juncea, Poa annua and Helianthus annuus were performed in the three different situations. the effects of the treatments on biomass production were positive with an increase for all the plant species. The addition of compost produced the most favorable condition for the growth of plants, probably also due to the beneficial effects caused by the increase in fertility elements such as carbon, nitrogen and phosphorous in the contaminated soil.