# Retention of the Antibiotic Cofruoxime onto Agricultural and Forest Soils
## 4 Conclusions  
In the agricultural soils included in this study, the adsorption of the antibiotic cefuro-ime (CFX) was dependent on the pH of the soil, with the highest adsorption corresponding to those soils having higher pH values. In the case of forest soils, which had a very acidic pH, their high organic matter contents would explain the high CFX adsorption obtained. Regarding desorption, it was below 1% in most cases, indicating the low reversibility of the \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**C\({}_{0}\) (\(\mu\)mol L\({}^{-1}\))**} \\ \hline
**Soil** & **2.5** & **5** & **10** & **20** & **30** & **40** & **50** \\ \hline M1 & 0 (0) & 0.37 (1.5) & 0.37 (0.8) & 0.39 (0.8) & 0.51 (0.7) & 0.51 (0.5) & 0.53 (0.4) \\ M2 & 0 (0) & 0.36 (3.0) & 0.35 (1.4) & 0.36 (0.7) & 0.39 (0.5) & 0.36 (0.4) & 0.48 (0.4) \\ M3 & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0.11 (2.7) \\ M4 & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) \\ M5 & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) \\ M6 & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) \\ M7 & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) \\ \hline VO1 & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) \\ VO2 & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) \\ VO3 & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) \\ VO4 & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) \\ VO5 & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) \\ \hline VP1 & 0.39 & 0.41 & 0.43 & 0.50 & 0.49 & 0.59 & 0.59 \\  & (6.64) & (3.35) & (1.77) & (1.02) & (0.67) & (0.60) & (0.48) \\ VP2 & 0.38 & 0.38 & 0.41 & 0.46 & 0.66 & 0.65 & 0.73 \\  & (6.45) & (3.15) & (1.67) & (0.92) & (0.89) & (0.66) & (0.59) \\ VP3 & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) \\ VP4 & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) \\ VP5 & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) & 0 (0) \\ VP6 & 0 (0) & 0 (0) & 0.37 & 0.34 & 0.47 & 0.42 & 0.49 \\  & (1.55) & (0.69) & (0.64) & (0.43) & (0.40) \\ VP7 & 0.44 & 0.42 & 0.39 & 0.33 & 0.27 & 0.30 & 0.51 \\  & (7.98) & (3.07) & (1.66) & (0.67) & (0.37) & (0.33) & (0.40) \\ VP8 & 0.36 & 0.35 & 0.33 & 0.11 & 0.32 & 0.31 & 0.46 \\  & (6.27) & (2.90) & (1.34) & (0.23) & (0.43) & (0.31) & (0.37) \\ \hline FP & 0.14 & 0.33 & 0.73 & 1.13 & 1.22 & 0.41 & 0 (0) \\  & (3.12) & (3.22) & (3.33) & (2.53) & (1.81) & (0.47) & 0 (0) \\ FE & 0.11 & 0.26 & 0.58 & 1.17 & 0.96 & 0.66 & 0.49 \\  & (2.32) & (2.42) & (2.58) & (2.54) & (1.38) & (0.72) & (0.42) \\ FC & 0.15 & 0.35 & 1.05 & 1.87 & 0.77 & 0.58 & 0.33 \\  & (3.53) & (3.50) & (4.85) & (3.79) & (1.11) & (0.64) & (0.29) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: CFX desorption, expressed in \(\mu\)mol kg\({}^{-1}\) (and in a percentage, between brackets), from the various studied soils, as a function of the concentration of antibiotic added (C\({}_{0}\), in \(\mu\)mol L\({}^{-1}\)). M, maize (corn) soils; VO, vineyard soils (Ourense province); VP, vineyard soils (Pontevedra province); F, forest soils. Average values (\(n=3\)), with coefficients of variation always \(<5\%\). adsorption process, especially in soils with a higher proportion of clay. Adsorption data fitted better to the Freundlich than to the Linear and Langmuir models. The correlations of [PERSON]'s \(K_{F}\) parameter and the \(K_{d}\) parameter of the Linear model with soil characteristics indicate that the most important factors in adsorption are pH and the concentrations of exchangeable Ca and Mg, probably due to their influence on the electric charges of colloids and the formation of cationic bridges. These results can be considered relevant in terms of the evaluation of the possible evolution of the antibiotic CFX when it reaches the soil as a contaminant, affecting its retention/release. Therefore, there is a probability that it will be mobilized into water bodies or absorbed by plants, entering the food chain, with have consequent environmental and public health repercussions.