Phytoremediation in lead-contaminated agricultural soil using Annual Ryegrass (Lolium multiflorum)

Abstract

The contamination of agricultural soils by heavy metals such as lead (Pb), resulting from the proximity of industrial activities to croplands, poses a significant issue in Ecuador. An underexplored alternative in the country is phytoremediation, an environmentally friendly, efficient, and cost-effective method. This study aims to assess the lead remediation capacity in synthetic solutions and contaminated agricultural soil using annual Ryegrass (Lolium multiflorum). The removal of lead in the water-plant system, using synthetic solutions with 5 mg L^-1 of Pb after 5 days of treatment, reached 87.9%. Meanwhile, in the water-plant-soil system, employing agricultural soil from the Machachi area (Pichincha province) contaminated with 200 mg Kg^-1 of lead over a 7-week period, a removal efficiency of 55.3% was achieved, with plant mortality and withering rates below 5%. In both cases, post-treatment lead concentrations were below 0.5 mg.L^-1, which is the maximum permissible limit for lead discharge into the public sewer system defined by the TULSMA standard. For agricultural soils, the maximum permissible Pb value is 100 mg.Kg^-1, as per soil restoration criteria. This study highlights the potential of phytoremediation as an effective method for mitigating lead contamination in agricultural settings in Ecuador.