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Title: Reduction of chlortetracycline residues in manure from therapeutically-treated beef calves

item Rice, Clifford

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/2/2008
Publication Date: 11/13/2008
Citation: Lozano, N., Rice, C., Ramirez, M., Torrents, A. 2008. Reduction of chlortetracycline residues in manure from therapeutically-treated beef calves. Meeting Abstract.

Interpretive Summary: .

Technical Abstract: The heavily-used antibacterials, triclosan (TCS) and triclocarban (TCC) are common contaminants of biosolids that are accumulated and adsorbed into waste-water treatment plants. These compounds are highly persistent because they present high octanol-water partitioning coefficients (log10 Kow of 4.9 for TCC and 4.8 for TCS) and almost show characteristics that turn them into Endocrine Disrupting Chemical group (EDCs). To this day, it is not well known what the fate of these compounds present in the biosolid applied to the land, and which are the biodegradation rates or the possible transformation in bioproducts like methyl triclosan (Me-TCS) metabolite of TCS, that is more lipophilic than its parent compound. In this study, the presence of both compounds (TCS and TCC) were found in the biosolids from a waste-water treatment plant. WWTP-A was studied for two years by collecting samples every two months. Similar concentrations for both compounds were found in a magnitude order of mg/Kg dry weight. The fate of these compounds was studied by applying limed biosolids from the WWTP-A in a small area of 0.242 ha. The application rate was 72.3 ton/ha, and surface samples were collected over a twelve month period following land application of biosolids, except for the last sampling where both surface and deep core samples (down to a depth around 75 cm) were taken. TCS and TCC concentrations were found in a magnitude order of µg/Kg dry weight one year after the application. As lower initial TCC concentrations were applied, the results show that the TCC is more persistent in the soils that contain TCS. Twelve months after application, the TCC concentrations were around six times higher than the TCS ones. In addition, concentrations of Me-TCS were found in the soil samples even one year after application. The results obtained in deep core samples suggest that no migration of TCS and TCC occurs from the surface to the lower soil layers, at least during the first year of application.