11 research outputs found
Mixture Effects on Biodegradation Kinetics of Hydrocarbons in Surface Water: Increasing Concentrations Inhibited Degradation whereas Multiple Substrates Did Not
Most
biodegradation tests are conducted using single chemicals
at high concentrations, although these chemicals are present in the
environment as mixtures at low concentrations. A partitioning-based
platform was recently developed for biodegradation testing of composed
mixtures of hydrophobic chemicals at ng/L to ÎĽg/L concentrations.
We used this platform to study the concentration and mixture effect
on biodegradation kinetics. Biodegradation tests were conducted in
20 mL vials using environmental water samples as inocula. Passive
dosing was applied (1) to vary initial test concentrations of individual
test compounds and (2) to vary the number of mixture components between
1 and 16. Automated solid-phase microextraction coupled to gas chromatography–mass
spectrometry was used to measure substrate depletion relative to abiotic
controls. The number of mixture components had no or only a limited
effect on the biodegradation half times for three compounds when tested
at environmentally relevant concentrations. In contrast, longer lag
phases and half lives were observed for single compounds when tested
at higher concentrations that approached aqueous solubility. The obtained
results support that simultaneous testing of multiple chemicals at
low concentrations can accelerate the generation of biodegradation
kinetic data, which are more environmentally relevant compared with
data from tests conducted with single chemicals at much higher concentrations