In situ measurement of solution concentrations and fluxes of sulfonamides and trimethoprim antibiotics in soils using o-DGT
2015
(Kevin C.),
Techniques, such as Diffusive Gradients in Thin-films (DGT), which either minimally disturb the soil or perturb it in a controlled way are most likely to provide information relevant to toxicity. Herein, we report the first use of DGT for organics (o-DGT) in soil systems to gain insight into the mobility and lability of four antibiotics—sulfamethoxazole (SMX), sulfamethazine (SMZ), and sulfadimethoxine (SDM), trimethoprim (TMP) in soil. In experiments where the same known amount of antibiotics were spiked into the soil, which was then further modified with NaOH, NaCl or dissolved organic matter, directly measured soil solution concentrations (Csoln) of these antibiotics were in the order: SMX>SMZ≈SDM>TMP. The R values (ratio of concentrations measured by o-DGT and directly in solution) were 0.56, 0.41, 0.40 and 0.28, respectively, indicating that the removal of these antibiotics from the solution can be to some extent resupplied by release from the solid phase. The nonlinearity of the relationship between o-DGT fluxes and the reciprocal of diffusive layer thickness (Δg) also suggested that soil solution concentrations were only partially sustained by the solid phase. The potential fluxes of these antibiotics in this soil were 5.4, 3.6, 2.4, and 1.2pg/cm²/s for SMX, SMZ, SDM, and TMP, respectively. o-DGT is a promising tool for understanding the fate and behaviour of polar organic chemicals in soil, and it potentially provides an in situ approach for assessing their bioavailability.
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