Residue and risk assessment of veterinary antibiotics in manure-based composts and agricultural soils

While veterinary antibiotics are used only in a part of the dose administered, the rest are excreted as urine or feces. Residual antibiotics enter the adjacent agricultural environments by spraying manure-based composts on farmlands and lead to secondary pollution. Therefore, it is necessary to develop the technique for post management such as regulatory levels of antibiotics in the agricultural environments. This study was conducted to compare by different matrices the amount of residual antibiotics such as tetracyclines and sulfonamides, which are known to be frequently used in Korea and to practice risk assessment by different antibiotics in soils before and after application of composts. Pre-treatment with modified typical method using buffer and solid phase extraction showed the recovery of composts and soils was more than 70% at ppb level and the limits of detection were 0.13-0.46 and 0.05-0.25 µg/kg, respectively. Analysis of manure-based composts revealed concentrations from 5.38 to 196.0 µg/kg for tetracyclines, from below the detection of limit (BDL) to 259.0 µg/kg for sulfonamides. In case of agricultural soils, residual concentrations of selected veterinary antibiotics were ranged 0.30-53.3 µg/kg, BDL-4.16 µg/kg respectively and the concentration level of tetracyclines, which had higher soil distribution coefficient (Kd) values, was higher than that of sulfonamides. There was a difference in human risk assessment by different antibiotics in soil before and after application of composts. But, it was indicated that detection values of all of 5 antibiotics were very safe on the basis that Hazard Quotient was safe below 1.