Assessing the prevalence of veterinary antibiotics and associated potential ecological risk in dryland soil, manure, and compost: A case study from Saudi Arabia

Application of manure and compost can result in the accumulation of veterinary antibiotics in soil, subsequently posing ecological risks. The occurrence and potential ecological risk assessment of nine antibiotics (4 tetracyclines, 3 sulfonamides, and 2 macrolides) residues in soil, manure, and compost samples collected from Al-Kharj, Saudi Arabia are reported in this study. A total of 36 samples (20 soil, 8 manure, and 8 compost) were collected and their physiochemical characteristics were analyzed. Large variabilities were observed in organic matter, pH, electrical conductivity, and nutrient status. In the soil samples obtained, three textural groups were identified: sandy loam, loamy sand, and loam. Overall, the mean concentrations of all detected antibiotics measured were lower (<50 μg kg−1) in all matrices (soil, manure, and compost). However, the mean concentrations of tetracycline (TC), doxycycline (DC), oxytetracycline (OT), and sulfamethoxazole (SMZ) were 97.96, 183.29, 101.24, and 69.58 μg kg−1, respectively, in manure samples, and 49.59, 93.26, 74.21, and 18.32 μg kg−1, respectively, in compost samples. The concentrations of antibiotics were highest in manure samples, then compost, and finally soil. The calculated risk quotient (RQ) values for the majority of the studied antibiotics were