Veterinary Antibiotics in Surface Water and Sediments of Two Rural Streams From the Southeast Pampas

OKADA, ELENA; PÉREZ, DÉBORA JESABEL

Valdivia

Congreso; SETAC Latin America 14th Biennial Meeting. 26 -29 Septiembre 2021. Online.; 2021

There is a lack of information on veterinary pharmaceuticals occurrence in aquatic ecosystems in Latin America. The presence of antibiotics in the environment can be associated with direct animal excretion of feces and urine, point source contamination, or the use of manure as fertilizer. The objective of this work was to study the occurrence in surface water and sediments of two antibiotics, oxytetracycline (OXT) and monensin (MON), commonly used in poultry and cattle production in Argentina. De los Padres stream (S1) is impacted mainly by agricultural land use that encompasses extensive crops and to a certain extent animal husbandry farms (e.g. horses, sheep, cattle). On the other hand, La Tapera stream (S2) basin is greatly impacted by horticultural cropproduction where it is common to apply poultry litter as a soil amendment. Stream water samples (n=51) were taken from January to October 2019 using propylene bottles. Stream sediment samples (n=24) were collected using cylinder samplers. Water pH and EC were measured in situ. Detection and quantification of the compounds was performed by ultra-performance liquid chromatography coupled to a mass spectrometer (UPLC MS/MS). The limit of detection and quantification was 0.1 µg/L in water and 0.1 µg/Kg in sediments. The average pH and EC in surface water were 8.9 ±0.7 and 849 ± 87.6, respectively. OXT was detected in 70.6% of the water samples and 41.7% of the sediment samples. MON was only present in surface water (23.5%) and not in sediment samples. Maximum concentrations in water were 1.2 and 0.7 µg/L for OXT and MON, respectively. We did not find an association between antibiotic presence in the water column and in sediments. Antibiotic distribution in the environment is dependant on the intrinsic properties of the compound and the physico-chemical conditions at the time of sampling. OXT has a high-water solubility, which favors its distribution in the water compartment. However, it also bonds to the particulate organic matter in sediments due to its polar functional groups (phenol, alcohol, amine, and ketone). On the otherhand, MON water solubility is low and its Kow value would suggest a high affinity to the sediment compartment. However, at pH>6 monensin is found in its anionic form, which decreases its sorption to sediment particles. Further studies are needed to understand the source of these compounds in the environment and their impact on aquatic biota.