Dynamics of current-use pesticides in the agricultural model basin.

PÉREZ, DÉBORA JESABEL; OKADA, ELENA; DEGERÓNIMO EDUARDO; APARICIO, VIRGINIA; MENONE, MIRTA LUJÁN; COSTA, JOSE LUIS

Córdoba, Capital

Congreso; VI Congreso Argentino de la Sociedad de Toxicología y Química Ambiental, Capítulo Argentina.; 2016

Society of Environmental Toxicology and Chemistry

The southeast of the Pampas plains is a zone with intensive agricultural activities. This zone is highly irrigated by wetlands, rivers and many streams. The stream flow dynamics are strongly related to the regional humidity, mainly given by runoff water and phreatic surface level, and can change dramatically during storm events. In this sense, it is important to study the fluctuations in the loads and mass of current-use pesticide (CUPs) to examine the influence of hydrologic and seasonal variability on the response of pesticide levels. The objective of this work was to determine the maximum loads of ∑CUPs and mass of CUPs associated with the flow dynamic in surface waters of ?El Crespo? stream. ?El Crespo? stream is only influenced by farming activities, with an intensive crop system upstream (US) and an extensive livestock production downstream (DS). Water samples were collected monthly from October 2014 to October 2015 in the UP and DN sites using 1 L polypropylene bottles and stored at -20°C until analysis. The samples were analyzed using liquid chromatography coupled to a tandem mass spectrometer (UPLC-MS/MS). The stream flow was measured during the sampling times in both sites, covering low base-flow and high base-flow periods. The most frequently detected residues were glyphosate, atrazine, acetochlor, metolachlor, 2,4-D, metsulfuron methyl, fluorocloridone, imidacloprid, tebuconazole and epoxiconazole. The mean concentrations of ∑CUPs during the sampling period were ~ 1.6 µg/L in both sites. The highest levels of ∑CUPs were 4.03 µg/L in UP site during spring 2014 and 2.53 µg/L in DN site during winter 2014. During high base flow (spring 2014), the stream discharge showed a peak of 6.16 mt3/seg and 6.77 mt3/seg, in UP and DN sites, respectively; where the total loads of ∑CUPs were 3.7 µg/L and 2.88 µg/L and the associated masses were 22.74 and 19.54 µg/seg, in UP and DN site, respectively. During low base flow the discharge were lower than 1 mt3/seg and the total loads of ∑CUPs varied between 1-3 µg/L, while the mass did not reach more than 3 µg/seg. A storm event during winter 2015 causes an intense runoff and the ∑CUPs in UP site were ~ 11 µg/L. The rainfall regime was the main factor that could influence the streamflow and pesticide dynamics in this basin. This is the first study in which the streamflow is associated with pesticide levels in Argentina and the data generated could be used in future regulation guidelines for wetlands.