Baseline survey on water and sediments: Agrochemicals, Hydrocarbons and Heavy metals in an emergent mixed production area.

DUFILHO, A.C.; INDACO, M. M.; SMICHOWSKY, P.; MONZA, L.B.; LATINI, L.A.; LONDONIO, A.; MACCHI, P.A.; PECHEN, A.M.; LOEWY, R.M.

San José de Costa Rica

Workshop; 6° Latin American Pesticide Residues Workshop; 2017

universidad de Costa Rica

The aim of the present study is to assess the ecological condition of the middle and lower basin of the Neuquen river, addressing three main aspects: hydromorphology, biology and chemical status. This hydrographic basin is extremely important as it comprises the major water resource for agriculture, agroindustrial, mining and drinking water (app. 400.000 inhabitants). There is a great public concern about the enlargement of the agricultural border with a wide crop diversification and, also, about the exploitation of new tight gas, shale gas and shale oil fields. It is necessary to run independent studies providing baseline information, before the expected productive development occurs. The studied area embraces an extension of 120 km including two dams, a regulated section and the river after the water restitution. 28 sampling sites were selected in the river, in the dams, and in farm drainages. Water and sediments samples were taken along 4 sampling campaigns. Organochlorine pesticides and pyrethroids (GC-µECD); organophosphate pesticides and carbamates (GC-NPD, GC-MS), heavy metals (ICP-OES, ICP-MS), AHs and PAHs (GC-FID, GC-MS) were analyzed. At the same time, benthic macroinvertebrates were sampled using the multi habitat method. Basic physicochemical, hydrological and habitat data were measured in situ. The results show that traces of organophosphate pesticides were detected in drainages nearby the agricultural area. In a drainage sediment a high chlorpyrifos level was measured (23 µg/kg), besides detections in some river sites of pp´DDE (from 13 µg/kg to 54 µg/kg) exceeding the guidelines for aquatic life protection (CCME, 2015) probably due to historical applications.PAHs were not detected and the AHs distribution patterns denote a biogenic source. No differences were observed in the structure and composition of macroinvertebrates assemblies. With reference to heavy metals, the obtained values are below the TEL or between the TEL and PEL. From the hydromorphology point of view, there is an alteration of the natural river course, especially in the regulated section (app 12 m3/s). As a preliminary conclusion the ecological status of the water body can be classified as good (DIRECTIVE 2000/60/CE) with very minor anthropogenic alterations from those normally associated with undisturbed conditions. This is an initial recognition programme from which an ordinary monitoring program is strongly recommended.