Ocurrence and spatial-temporal trends of monensin in a mixed-uses watershed in Argentina.

MENONE, MIRTA LUJÁN; PÉREZ, DÉBORA JESABEL; DEGERÓNIMO EDUARDO; CANTÓN, GERMÁN

Sacramento, Californa

Congreso; SETAC North America 39th Annual Meeting; 2018

Society of Environmental Toxicology and Chemistry

Occurrence and potential ecological risk of veterinary medicines in aquatics ecosystem of South America, is for our knowledge not well reported. This work attempts to generate relevant data about the occurrence, levels and spatial-temporal trends of monensin (MON) in a mixed-uses watershed of Argentina. El Pantanoso is a first-order stream located in the southeast of the Buenos Aires Province, with a catchment area of 476 km2. This watershed is influenced by urban and farming activities. There is a Constructed Channel (CC) that receives the wastewater discharge of Balcarce City and some effluents of livestock production and it is coupled to the stream in the main channel. Water samples were collected from 11 sampling sites in August and November 2017 cover the high flow and low flow periods, respectively. Sampling sites were chosen to cover from the headwaters to the end of stream in the floodplain contemplating different possible points of pollution by veterinary medicines. Samples was collected by triplicate using 1 L polypropylene bottles and stored at -20°C until analysis. Samples were analyzed using liquid chromatography coupled to a tandem mass spectrometer. The limit of detection (LOD) was set in 0.01 µg/L and the limit of quantification was estimated similarly to the LOD. In August and November MON was detected in 90% and 100% of the samples, respectively. In August, at headwaters were detected minimum levels (0.2 ± 0.03 µg/L) associated with the farming activities. Highest levels were detected associated with cattle slaughter waste water effluent (2.6 ± 0.74 µg/L). In the CC, the levels varied from no detected at the beginning with urban and periurban impact to 1.0 ± 0.1 µg/L downstream to the wastewater plant treatment and 0.6 ± 0.03 µg/L downstream to the livestock production. In November, the levels no surpass 0.02 µg/L. Monensin occurrence was become an ubiquitous emergent contaminant in this watershed. Cattle slaughter was the main point source pollution of MON and the wastewater plant treatment discharge result the secondary source of impact. The highest concentrations found in August close to the cattle slaughter could be explained for the intense rains during this period that induced a strong drainage from the treatment lagoon to the stream, because the distance between both sites is less than 0.5 km. This is the first report for our knowledge that describes the presence of monensin in surface water of Argentina.