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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, fve 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. Universidad de Costa Rica/[802-B5-400]/UCR/Costa Rica UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro en Investigación en Contaminación Ambiental (CICA)

A monitoring network was established in streams within a catchment near the Costa Rican Pacific coast (2008–2011) to estimate the impact of pesticides in surface water (84 samples) and sediments (84 samples) in areas under the influence of melon and watermelon production. A total of 66 (water) and 47 (sediment) pesticides were analyzed, and an environmental risk assessment (ERA) was performed for four taxa (algae, Daphnia magna, fish and Chironomus riparius). One fungicide and seven insecticides were detected in water and/or sediment; the fungicide azoxystrobin (water) and the insecticide cypermethrin (sediments) were the most frequently detected pesticides. The insecticides endosulfan (5.76 μg/L) and cypermethrin (301 μg/kg) presented the highest concentrations in water and sediment, respectively. The ERA revealed acute risk in half of the sampling points of the melon-influenced area and in every sampling point from the watermelon-influenced area. Safety levels were exceeded within and around the crop fields, suggesting that agrochemical contamination was distributed along the catchment, with potential influence of nearby crops. Acute risk was caused by the insecticides chlorpyrifos, cypermethrin and endosulfan to D. magna, fish and C. riparius; the latter was the organism with the overall highest/continuous risk. High chronic risk was determined in all but one sampling point, and revealed a higher number of pesticides of concern. Cypermethrin was the only pesticide to pose chronic risk for all benchmark organisms. The results provide new information on the risk that tropical crops pose to aquatic ecosystems, and highlight the importance of including the analysis of sediment concentrations and chronic exposure in ERA. Universidad de Costa Rica/[802-A8-016]/UCR/Costa Rica Universidad de Costa Rica/[802-B7-508]/UCR/Costa Rica Organismo Internacional de Energía Atómica/[RLA5/050]/IAEA/Austria Organismo Internacional de Energía Atómica/[RLA5/053]/IAEA/Austria Organismo Internacional de Energía Atómica/[RLA5/061]/IAEA/Austria Unión Europea/[690918 H2020-MSCA-RISE-2015]/UE/Paises Bajos UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro en Investigación en Contaminación Ambiental (CICA)

Knowledge of pesticides fate in tropical soils and how it could be affected by pyrolyzed biomass as amendment is limited. Combining conventional and radiotracer methods, as well as risk assessment tools, the effects of several charred agrowastes on the sorption, persistence, and ecological risk of the herbicides bromacil (BMC) and diuron (DRN) were evaluated in a tropical agricultural soil under laboratory conditions. Pineapple stubble (PS), palm oil fiber (PF), and coffee hull (CH) were charred at 300 (torrefied) and 600 °C (biochar) and applied to the soil at 10 and 20 t ha−1 rates. The sorption coefficients (Koc) in unamended soil for BMC and DRN were 18.4 and 212.1 L kg−1, respectively. The addition of torrefied PS and PF caused a 3 to 4-fold increment in BMC sorption and a 3 to 6-fold change in DRN's sorption. The only biochar that affected the sorption was PS that increased DRN's sorption 3.5 times. The application of coffee hull materials had no significant effect. In terms of degradation (half-life, DT50), for unamended soil BMC's degradation (300 days) was limited compared to DRN (73 days). Alternatively, biodegradation (mineralization half-life time, MT50) was 1278 d for BMC and 538 for DRN. While only PF and CH torrefied increased BMC's persistence, all the torrefied affected DRN's persistence. However, despite the observed effects, the predicted ecological risk was not mitigated. Our results highlight the need for scientific evidence on the use of pyrolyzed organic amendments to assess potential benefits and prevent unintended impacts in tropical agroecosystems.

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. UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro en Investigación en Contaminación Ambiental (CICA)

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.

Constructed wetlands (CWs) and biopurification systems (BPS) present two low-cost approaches for the removal of pesticides from waters of agricultural origin. Both strategies were tested in the treatment of the herbicide terbuthylazine, a triazine of worldwide use. Three horizontal subsurface flow (HSF) CW systems were operated continuously for one year; the planted CWs (containing either Phragmites australis or Typha latifolia) were able to remove up to 73.7% and 58.4% of the pesticide, respectively, and exhibited a markedly superior performance compared to the unplanted CW. However, by the end of the treatment period, some symptoms of phytotoxicity were observed in the plants of the CWs, which are related to high terbuthylazine concentrations in plant material. A coconut fiber-containing biomixture was used in BPS which was able to rapidly remove terbuthylazine, with an estimated half-life of 8.1 d, the fastest so far reported in these systems. However, the biomixture failed to detoxify the matrix, according to ecotoxicological tests of seed germination. The current data suggests that coupled/hybrid configurations comprising CWs and BPS in series could provide increased effectiveness and a low-cost technology to remove terbuthylazine from highly contaminated water.

Environmental contamination with neonicotinoid insecticides represents an issue of wide concern due to their negative effects on pollinators. The goal of this work was to evaluate the potential use of biomixtures employed in biopurification systems (BPS) to remove two neonicotinoid pesticides, imidacloprid and thiamethoxam, from wastewater of agricultural origin. The removal was assayed by quantification of the parent compounds and the detection of putative transformation products of imidacloprid by means of LC-MS/MS, and mineralization of radiolabeled imidacloprid. Two biomixtures (B1, B2) were prepared using coconut fiber, compost and two soils pre-exposed to imidacloprid (volumetric composition 50:25:25). After spiking of neonicotinoids and 228 days of treatment, the removal ranged from 22.3%–30.3% and 38.6%–43.7% for imidacloprid and thiamethoxam, respectively. Transformation products imidacloprid-urea, desnitro-imidacloprid and desnitro-olefin-imidacloprid were detected in both biomixtures. The mineralization of 14C-imidacloprid revealed DT50 (mineralization half-lives) values of 3466 and 7702 days in the biomixtures B1 and B2, respectively, markedly lower than those in the soil used in their preparation (8667 and 9902 days, respectively). As demonstrated by these findings, the high persistence of these compounds in the BPS suggests that additional biological (or physicochemical) approaches should be explored in order to decrease the impact of neonicotinoid-containing wastewater of agricultural origin.

The use of antibiotics in agriculture produces residues in wastewaters. The disposal of such wastewaters in biopurification systems (BPS) employed for the treatment of pesticides could result in the inhibition of the degrading capacity of the biomixtures used in the BPS. We assayed the effect of two commercial formulations of antibiotics used in agriculture, one containing kasugamycin (KSG) and the other oxytetracycline plus gentamicin (OTC+GTM), on the biomixture performance. Doses from 0.1mgkg-1 to 1000mgkg-1 of KSG increased the respiration of the biomixture, and low doses enhanced the mineralization rate of the insecticide 14C-chlorpyrifos. On the contrary, OTC+GTM depressed the respiration of the biomixture and the initial mineralization rate of 14C-chlorpyrifos; nonetheless, the antibiotics did not decrease overall mineralization values. The application of both formulations in the biomixture at a relevant concentration did not harm the removal of the fungicides carbendazim and metalaxyl, or their enhanced degradation; on the other hand, the biomixture was unable to dissipate tebuconazol or triadimenol, a result that was unchanged during the addition of the antibiotic formulations. These findings reveal that wastewater containing these antibiotics do not affect the performance of BPS. However, such a response may vary depending on the type of pesticide and microbial consortium in the biomixture.