We have over 12,000 students, from over 100 countries, within one of the safest campuses in the UK


93% of Lancaster students go into work or further study within six months of graduating

Home > Research > Publications & Outputs > Desorption kinetics of sulfonamide and trimetho...
View graph of relations

« Back

Desorption kinetics of sulfonamide and trimethoprim antibiotics in soils assessed with diffusive gradients in thin-films

Research output: Contribution to journalJournal article


Journal publication date4/04/2014
JournalEnvironmental Science and Technology
Number of pages7
Original languageEnglish


Although sorption/desorption of antibiotics in soils affects their mobility and availability, with consequences for risks to the surrounding environment, the dynamics of these processes are not well-known. In this study, diffusive gradients in thin-films devices suitable for measuring polar organic compounds (o-DGT) were deployed in two soils for a range of times (5 h to 20 d) to measure the distribution and rates of exchange between solid phase and solution of three sulphonamides (SAs; sulfamethoxazole, SMX; sulfamethazine, SMZ; and sulfadimethoxine, SDM) and trimethoprim (TMP). o-DGT continuously removes antibiotics to a XAD gel layer after passage through a well-defined diffusion layer and therefore perturbs their concentration in the adjacent soil solution. This induces a remobilization flux from the solid phase, which is related to the concentration of antibiotics in the soil solution, their diffusional supply, and the exchange kinetics between dissolved and sorbed antibiotics. A dynamic model of solute interactions called DIFS (DGT induced fluxes in soils) was used to derive distribution coefficients for labile antibiotics (Kdl) and the rate constant for supply of antibiotics from solid phase to solution, expressed as a response time (Tc). Larger labile solid phase pools were observed for TMP than for SAs. The soils could resupply TMP so rapidly that in one soil, where Tc = 2 min, supply was controlled by diffusion. Response times for SAs were generally longer (>27 min), particularly for SDM (>3 h), implying that the supply of SAs to o-DGT samplers was limited by the desorption release rate. A wider implication of this study is that similar solid phase release kinetics may control the uptake of antibiotics by biota.