EGU2017-1992 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

Viena

Congreso; European Geosciences Union General Assembly 2017. Session SSS7.8/BG9.10/HS11.53 The impact of pesticides in life, water, sediment, air and soil resources; 2017

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 reached 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 intensive crop systems upstream (US) and extensive livestock production downstream (DS). It is an optimal site for pesticide monitoring studies since there are no urban or industrial inputs into the system. 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 (>40%) were glyphosate and its metabolite AMPA, atrazine, acetochlor, metolachlor, 2,4-D, metsulfuron methyl, fluorocloridone, imidacloprid, tebuconazole and epoxiconazole. The mean concentrations of ∑CUPs during the sampling period were 1.62 µg/L and 1.66 µg/L in UP site and DN site, respectively. 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. The mass of ∑CUPs showed a direct relation between low base flow and high base flow periods. During high base flow during spring 2014, the stream discharge showed peak of 6.16 mt3/seg and 6.77 mt3/seg, in UP and DN site, respectively; where the total loads of ∑CUPs were 3.7 µg/L and 2.88 µg/L and the associated mass 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 were variable between 1-3 µg/L, but the mass never were higher than 3 µg/seg. The intensive rain during the spring 2014, were the mainly factor that influence the stream flow and pesticide dynamics in the model basin.