Abstract
Chlorobenzoic acids (CBA) are intermediate products of the aerobic microbial degradation of PCB and several pesticides. This study explores the feasibility of using basket willows, Salix viminalis, to remove 4-CBA from polluted sites, which also might stimulate PCB degradation. The removal of 4-CBA by willow trees was investigated with intact, septic willow trees growing in hydroponic solution and with sterile cell suspensions at concentrations of 5 mg/L and 50 mg/L 4-CBA. Nutrient solutions with different levels of ammonium and nitrate were prepared to achieve different pH levels. The concentration of 4-CBA was tracked over time and quantified by HPLC. At the low level of 4-CBA (5 mg/L), willows removed 70% (pH 4.2) to 90% (pH 6.8), while 48% (pH 4.2) to 52% (pH 6.8) of the water was transpired. At the high 4-CBA level (50 mg/L), the pH varied between 4.4 and 4.6, and 10% to 30% of 4-CBA was removed, but only 5% to 9% of the water. In sterile cell suspensions, removal of 4-CBA by fresh biomass was much higher than removal by dead biomass. The results indicate that 4-CBA is toxic to willow trees at 50 mg/L. The removal of 4-CBA from solution is by both passive processes (uptake with water, sorption to plant tissue) and metabolic processes of the plants. Plants, such as willow trees, might assist in the degradation of PCB and their degradation products CBA.
Highlights
Polybrominated diphenyl ethers (PBDEs) have been widely used as flame retardants in consumer products
The transport of BDE-47 and BDE-99 indicates in utero exposure to these congeners
Our study demonstrates fetal exposure to PBDEs, which should be included in risk assessment of PBDE exposure of women of child-bearing age
Summary
Polybrominated diphenyl ethers (PBDEs) have been widely used as flame retardants in consumer products. Polybrominated diphenyl ethers (PBDEs) have been widely used as flame retardant additives in a variety of products of everyday use, e.g. electric equipment, textiles and furniture upholstery. As they are not chemically bound to the polymers, they can be emitted during the product's life cycle and accumulate in the environment. Biotransformation of BDE-209 in fish and rodents results in lower brominated congeners, for example hexaBDEs [6,7] with further debromination possible. The lower brominated congeners are more toxic and bioaccumulative than BDE209 [8,9]. The two US producers of BDE-209 and the largest US importer recently announced to phase out BDE-209 by the end of 2013 [14]
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