Assessment of Veterinary Antibiotics, Hormones, and Pathogens in Animal Wastes and Their Fate and Transport in Tropical Soils
USDA-Cooperative State Research, Education, and Extension Service
08/23/06 – 09/14/08
In animal husbandry, antibiotics and hormones need to be used for efficient and economical production. Administration of these chemicals is more common for animals raised in confined animal feeding operations. Residual antibiotics and hormones are typically present in animal wastes, especially in wastewaters from lagoons or in fresh manures. Lagoon effluents and manures also contain various bacteria, viruses, and protozoa. Since land application is the primary means of disposal of manure, lagoon effluent and sludge, their leaching to underlying ground water could be cause for concern.
Although there are documented cases of ground water contamination near unlined lagoons and land application sites in temperate climates, literature on the fate and transport of antibiotics and pathogens in tropical soils is scarce. In a recent study, we found that metal oxide rich soils of Hawaii are excellent sinks for pathogens. Mobility of bacteria and viruses was limited to the top few inches. Besides the metal oxides, these soils provide ample surface area because of their clay content and the soil solution pH is low, favoring adsorption. As a result, we hypothesized that the oxidic soils of the tropics reduce the potential of ground water contamination from pathogens. Similarly, many pharmaceutical compounds can be cationic, anionic, or non-ionic depending on ambient pH. The kaolinitic soils of Hawaii are found to carry net positive charges below the top organic layer. This may have positive impact in retaining many ionic compounds in low pH.
In this study, we examined the transport behavior of several antibiotic and pharmaceutical compounds of veterinary importance and selected bacteria and viruses in tropical soils from Hawaii and Puerto Rico and examined if there is potential for these compounds or bacteria/viruses to breakthrough soils taken from various depths. This information is useful to researchers, stakeholders, and the regulating agencies in evaluating the degree of ground water contamination potential near these sources.
Dr. Chittaranjan Ray
Water Resources Research Center
University of Hawaii at Manoa