Degradation of chlorinated benzoic acid mixtures by plant–bacteria associations

Abstract

AbstractPhytoremediation technologies must tolerate and degrade mixtures of contaminants, as most contaminated sites contain mixtures of compounds. This study assessed the ability of plant–bacteria associations to degrade mixtures of mono‐ and dichlorinated benzoic acids. Sixteen forage grasses and combinations of these grasses with several bacterial inoculants were screened for growth in soil contaminated with various concentrations of mono‐ or dichlorinated benzoic acids. Dahurian wild rye (Elymus dauricus) inoculated with a combination of Pseudomonas aeruginosa strain R75 and Pseudomonas savastanoi strain CB35 reduced 3‐chlorobenzoic acid (3CBA) levels in soil by 74% (i.e., 583 to 149 mg/kg). Meadow brome (Bromus biebersteinii) inoculated with Alcaligenes sp. strain BR60 reduced 2,3‐dichlorobenzoic acid (23diCBA) levels in soil by 56% (i.e., 125 to 55 mg/kg). Altai wild rye (Elymus angitus) inoculated with strains R75 and CB35 reduced 2,5‐dichlorobenzoic acid (25diCBA) levels in soil by 46% (i.e., 211 to 113 mg/kg). Two plant–bacteria associations and uninoculated Dahurian wild rye also degraded mixtures of 3CBA, 23diCBA, or 25diCBA. When 25diCBA was mixed with 23diCBA, uninoculated Dahurian wild rye reduced levels of 25diCBA in soil by 31% and reduced the levels of both 25diCBA and 3CBA by up to 64% when these two contaminants were present in a mixture. Similarly, meadow brome inoculated with BR60 reduced 23diCBA and 3CBA levels by up to 50%. Levels of all three chlorinated benzoic acids were reduced by 53 to 63% by Altai wild rye inoculated with strains R75 and CB35. Our results indicate that plant–bacteria associations can tolerate and degrade mixtures of contaminants in soil but that predictions about phytoremediation of mixed contaminants may not be straightforward.