## 3 Results and Discussions
### VAs Accumulation and Bio-Concentration  
In this study, only the active compounds of SDZ and OTC were extracted from the plant samples (Figure 1). However, STR antibiotics could be successfully extracted from soil (Table 4), indicating the failure of test plants to absorb and translocate the antibiotic. Interestingly all three test plants absorbed SDZ and OTC but not STR antibiotics, which can be explained based on the differences in adsorption coefficients (K\({}_{\text{d}}\)) of these antibiotics in soil. STR is a strongly basic antibiotic known to form strong complexes with the soil components, especially clay, making it highly unavailable [25]. Since the soil used in this study was sandy clay loam with 30.73% clay content, STR can quickly form strong complexes with clay. Another explanation is the higher molecular weight of STR antibiotics (728.69 g mol\({}^{-1}\)), almost double the mass of SDZ and OTC molecule. Such a large molecule can't be taken up by plants easily, both in mass flow (transpiration) or as active uptake. Similar conclusions have been drawn from a previous study where stylosin antibiotic with a large molar mass of 916.1 g mol\({}^{-1}\) was not taken up by green onion, cabbage, and corn plants [6]. On the contrary, all three plants (lettuce, carrot, and pepper) absorbed SDZ and OTC antibiotics (Figure 1). The active molecules of SDZ and OTC were recovered from all the plant parts examined. The amount of SDZ and OTC extracted, from the plant parts, increased with increasing concentration of the VAs in the soil-manure mixture, indicating a higher absorption of VAs by plants as the amount of VAs increases in the soil-manure mix. The maximum amount of SDZ and OTC was extracted from carrot plants, followed by lettuce and pepper. The highest plant-tissue concentration was found in the carrot and lettuce plant, followed by pepper (Figure 1). The concentration of SDZ extracted from lettuce, carrot, and pepper tissues were \(\approx\) 0.2%, 0.4%, and 0.1% of the amount applied to the soil through manure. On the other hand, OTC concentration in lettuce, carrot, and pepper tissues was \(\approx\) \begin{table}
\begin{tabular}{c c c c} \hline \hline
**VAs (mg kg\({}^{-1}\))** & **Lettuce (mg kg\({}^{-1}\))** & **Carrot (mg kg\({}^{-1}\))** & **Pepper (mg kg\({}^{-1}\))** \\ \hline
**Control** & 0.00 \(\pm\) 0.00 & 0.00 \(\pm\) 0.00 & 0.00 \(\pm\) 0.00 \\ \hline
**SDZ 10** & 1.19 \(\pm\) 0.829 d  & 1.41 \(\pm\) 0.069 d  & 1.97 \(\pm\) 0.001 d  \\
**SDZ 50** & 3.31 \(\pm\) 1.797 c  & 3.84 \(\pm\) 2.214 b  & 4.41 \(\pm\) 0.057 b [FONOTE:b]Footnote d: footnotemark: [ENDFOOTNOTE] \\
**SDZ 100** & 12.47 \(\pm\) 3.173 a  & 14.34 \(\pm\) 1.681 a [FONOTE:a]Footnote a: footnotemark: [ENDFOOTNOTE] & 16.88 \(\pm\) 0.047 a  \\ \hline
**OTC 10** & 0.43 \(\pm\) 0.649 e  & 0.39 \(\pm\) 0.049 e  & 0.23 \(\pm\) 0.058 e  \\
**OTC 50** & 1.19 \(\pm\) 0.741 d [FONOTE:d]Footnote d: footnotemark: [ENDFOOTNOTE] & 2.03 \(\pm\) 0.237 c [FONOTE:c]Footnote e: footnotemark: [ENDFOOTNOTE] & 1.72 \(\pm\) 0.784 d [FONOTE:d]Footnote d: footnotemark: [ENDFOOTNOTE] \\
**OTC 100** & 4.95 \(\pm\) 0.794 b [FONOTE:b]Footnote d: footnotemark: [ENDFOOTNOTE] & 3.84 \(\pm\) 0.343 b  & 3.51 \(\pm\) 0.402 c [FONOTE:c]Footnote e: footnotemark: [ENDFOOTNOTE] \\ \hline
**STR 10** & 0.07 \(\pm\) 0.049 f  & 0.08 \(\pm\) 0.784 f [FONOTE:f]Footnote f: footnotemark: [ENDFOOTNOTE] & 0.09 \(\pm\) 0.851 f [FONOTE:f]Footnote f: footnotemark: [ENDFOOTNOTE] \\
**STR 50** & 0.41 \(\pm\) 0.649 e  & 0.33 \(\pm\) 0.049 e  & 0.41 \(\pm\) 0.058 e [FONOTE:e]Footnote e: footnotemark: [ENDFOOTNOTE] \\
**STR 100** & 1.29 \(\pm\) 2.262 d  & 1.17 \(\pm\) 4.275 d [FONOTE:d]Footnote d: footnotemark: [ENDFOOTNOTE] & 1.57 \(\pm\) 3.627 d  \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Concentration of veterinary antibiotics extracted from the soil planted with lettuce, carrot, and pepper plants at the end of the experimental period. 0.1%, 0.2%, and 0.05%, respectively. A higher accumulation of VAs in the roots than in aerial parts was evident.