Impact of multiwall carbon nanotubes on the accumulation and distribution of carbamazepine in collard greens (Brassica oleracea)†
Pre-existing pharmaceutical residues in agricultural soils may encounter engineered nanomaterials, resulting in poorly understood co-contamination interactions. In this study, the bioaccumulation and translocation of the pharmaceutical residue carbamazepine (100 μg L−1) in collard greens (Brassica oleracea) was evaluated upon concurrent exposure to pristine or carboxyl-functionalized multiwall carbon nanotubes (pCNTs or cCNTs) at 50 mg L−1 under hydroponic exposure and at 500 mg kg−1 in soil-grown conditions. B. oleracea toxicity was more evident under hydroponic exposure, with growth inhibtion dependent on carbamazepine concentrations; however, biomass enhancement was noted in cCNTs-treated plants. Without CNTs, B. oleracea accumulated and translocated significant amounts of carbamazepine; up to 2500 μg kg−1 in the leaves and 300 μg kg−1 in the roots, depending on growth condition. The co-exposure of carbon materials notably suppressed carbamazepine accumulation in both hydroponic and soil systems. Specifically, root carbamazepine content in soil-grown plants was suppressed 29%, 53% and 89% by pCNTs, cCNTs and AC, respectively. Generally, the adsorption capacity of the carbon materials correlated well with the suppression of carbamazepine accumulation. The results also suggest that functionalization of CNTs enhanced carbamazepine translocation potential and significantly affected nanomaterial/co-contaminant interactions as compared to its pristine analog. These findings show that the CNTs in the environment may significantly affect the bioavailability and translocation pattern of coexisting organic contaminants.