Phytoremediation of emerging and traditional contaminants in environmentally relevant co-exposure settings: a tool to reduce environmental hazards?

Water bodies are routinely exposed to a mixture of contaminants via various anthropogenic exposure mechanisms. Phytoremediation offers a low-cost nature-based solution to remove contaminants from polluted water bodies. The ability of the aquatic macrophyte, Lemna minor to accumulate both organic [antibiotics, plant protection products (PPPs)] and inorganic contaminants (metals), individually and in co-contaminant mixtures, was evaluated to offer new insights into its potential for phytoremediation in realistic exposure scenarios. When exposed individually, diazinon accumulated to the greatest extent in L. minor, (95.51 ± 2.13%), followed by ciprofloxacin (31.91 ± 6.07%), atrazine (13.04 ± 3.44%), trimethoprim (11.43 ± 5.77%), chromium (4.5 ± 2.74%), and cadmium (3.08 ± 1.36%) These findings highlight that accumulation by L. minor is highly compound specific. Further results revealed that contaminant co-exposure significantly (p = 0.002–0.029) influenced the uptake of selected contaminants. The presence of chromium increased cadmium uptake by a factor of 6.34, while the combination of multiple contaminants (e.g., metals, PPPs, and antibiotics) reduced uptake. Changes in uptake capacity have potential knock-on effects for environmental risk assessments, including an assessment of the potential for antibiotics to contribute to the development of antibiotic resistance. For ciprofloxacin and diazinon, phytoremediation for 72 h was sufficient to reduce the concentration of a single antibiotic below concentrations predicted to result in the development of resistance (PNEC-R) or effects to Daphnia magna. In co-contaminant mixtures a risk was identified with RQ values being a factor of 17 greater than the toxicity threshold for D. magna. Our results support the need for a more comprehensive assessment of the impact of co-contaminant mixtures on L. minor uptake capacity to optimise phytoremediation strategies for improved water quality and reduced environmental risks.