An integrative water quality evaluation in two surface water bodies from a tropical agricultural region in Cartago, Costa Rica.

A monitoring study was carried out in two micro-catchments in the Reventazón basin, in Northern Cartago, Costa Rica; pesticide occurrence and water quality were analyzed. Twelve pesticides were detected, five insecticides (chlorpyrifos, carbofuran, cypermethrin, imidacloprid, and oxamyl), four fungicides (carbendazim, imazalil, metalaxyl, and thiabendazole), and three herbicides (diuron, linuron, and terbutryn); eight of them presented risk quotients RQ >1, which implies a high risk for the environment. The water quality evaluation included fourteen physicochemical and microbiological parameters, out of which thermotolerant coliforms, nitrate, and total phosphorus exceeded a selected threshold value in every sample. Five metals were also included in the evaluation, Pb was the most frequent, followed by few detections of Cd, Cu, and Cr. Four water quality indexes (WQIs) were applied, two of them, the CCME WQI, based on physicochemical parameters, and the BMWP-CR WQI, based on benthic macroinvertebrate recount adapted to Costa Rican species, categorized all the sampling points as "bad" and "very bad" quality. This work of monitoring is important in the Latin American region, where there is a lack of information for regulation improvement and management decisions. These results showed poor management of the micro-catchments in this agricultural rural area.

Pesticide occurrence and water quality assessment from an agriculturally influenced Latin-American tropical region.

A monitoring study was carried out in three agriculturally influenced microcatchments in Costa Rica during 2012-2014, for pesticides and water quality parameters. A total of 42 pesticides were analyzed, detecting the following in water samples: two herbicides (oxyfluorfen, diuron), four insecticides (carbofuran, chlorpyrifos, oxamyl, ethion), and two fungicides (thiabendazole, carbendazim); while in sediment samples only the insecticides, chlorpyrifos and cypermethrin were found. Water quality was also assessed by the Canadian Council of Ministers of the Environment Water Quality Index and the National Sanitation Water Quality Index, the first one classified most of the sampling point as marginal and poor quality while the second one classified most of them as good quality, the most affected parameters were nitrate, phosphorous, suspended solids and organic matter content. The results suggest that the water quality in the microcatchments seems to be affected by the nearby agricultural and urban activities in the region.

Pesticide monitoring and ecotoxicological risk assessment in surface water bodies and sediments of a tropical agro-ecosystem.

A pesticide monitoring study including 80 and 60 active ingredients (in surface waters and sediments, respectively) was carried out in a river basin in Costa Rica during 2007-2012. A special emphasis was given on the exceptional ecological conditions of the tropical agro-ecosystem and the pesticide application strategies in order to establish a reliable monitoring network. A total of 135 water samples and 129 sediment samples were collected and analyzed. Long-term aquatic ecotoxicological risk assessment based on risk quotient in three trophic levels was conducted. Short-term risk assessment was used to calculate the toxic unit and prioritization of sampling sites was conducted by the sum of toxic units in both aquatic and sediment compartments. Dimethoate (61.2 µg/L), propanil (30.6 µg/L), diuron (22.8 µg/L) and terbutryn (4.8 µg/L) were detected at the highest concentrations in water samples. Carbendazim and endosulfan were the most frequently detected pesticides in water and sediment samples, respectively. Triazophos (491 µg/kg), cypermethrin (71.5 µg/kg), permethrin (47.8 µg/kg), terbutryn (38.7 µg/kg), chlorpyrifos (18.2 µg/kg) and diuron (11.75 µg/kg) were detected at the highest concentrations in sediment samples. The pesticides carbendazim, diuron, endosulfan, epoxyconazole, propanil, triazophos and terbutryn showed non-acceptable risk even when a conservative scenario was considered. Sum TUsite higher than 1 was found for one and two sampling sites in water and sediment compartments, respectively, suggesting high acute toxicity for the ecosystem. MAIN FINDING OF THE WORK: Exceptional ecological conditions of the tropical agro-ecosystem affect the fate of pesticides in water and sediment environment differently than the temperate one.