Arsenic and mercury uptake and accumulation in oilseed sunflower accessions selected to mitigate co-contaminated soil coupled with oil and bioenergy production

Abstract

Thirty-seven accessions of oilseed sunflower were evaluated under natural field conditions for growth performance, ligno-cellulosic mass production of bioenergy, and metal uptake potential during the remediation of arsenic and mercury-contaminated soil. Significant variations were observed in the ligno-cellulosic components of plant stems at maturity, decreasing the following order: total sugars > cellulose > hemicellulose > lignin > ash. A significant difference was also noted in metal uptake among the different accessions. The highest concentrations in the above-ground parts were 14.08 and 0.40 mg/kg, respectively for As and Hg. In rhizosphere soil concentrations of inorganic As species (arsenate: 69.73 mg/kg, arsenite: 4.41 mg/kg) were higher, as compared organic As (dimethyl arsenic: 0.22 mg/kg); mono-methyl arsenic: 0.02 mg/kg). Arsenate concentration (3.72 mg/kg) was higher in root, whereas arsenite concentration (0.47 mg/kg) was higher in the shoots. Many accessions showed good oil production (26–45.6%), with the highest percentage of oleic (75%) and linoleic acids (37.6%). These results suggest that some oilseed sunflower cultivars could be adopted as crop plants for effective remediation of lightly to moderately As-/Hg-contaminated soils, coupled with agro-production.