Pharmaceuticals present
a potential threat to soil organisms, yet
our understanding of their fate and uptake in soil systems is limited.
This study therefore investigated the fate and uptake of 14C-labeled carbamazepine, diclofenac, fluoxetine, and orlistat in
soil–earthworm systems. Sorption coefficients increased in
the order of carbamazepine < diclofenac < fluoxetine < orlistat.
Dissipation of 14C varied by compound, and for orlistat,
there was evidence of formation of nonextractable residues. Uptake
of 14C was seen for all compounds. Depuration studies showed
complete elimination of 14C for carbamazepine and fluoxetine
treatments and partial elimination for orlistat and diclofenac, with
greater than 30% of the 14C remaining in the tissue at
the end of the experiment. Pore-water-based bioconcentration factors
(BCFs), based on uptake and elimination of 14C, increased
in the order carbamazepine < diclofenac < fluoxetine and orlistat.
Liquid chromatography–tandem mass spectrometry and liquid chromatography–Fourier
transform mass spectrometry indicated that the observed uptake in
the fluoxetine and carbamazepine treatments was due to the parent
compounds but that diclofenac was degraded in the test system so uptake
was due to unidentifiable transformation products. Comparison of our
data with outputs of quantitative structure−activity relationships
for estimating BCFs in worms showed that these models tend to overestimate
pharmaceutical BCFs so new models are needed.