Environmental monitoring and risk assessment in a tropical Costa Rican catchment under the influence of melon and watermelon crop pesticides.

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.

Evaluation of a new carbon/zirconia-based sorbent for the cleanup of food extracts in multiclass analysis of pesticides and environmental contaminants.

A novel carbon/zirconia-based material, SupelTM QuE Verde, was evaluated in a filter-vial dispersive solid-phase extraction cleanup of pork, salmon, kale, and avocado extracts for the residual analysis of 65 pesticides and 52 environmental contaminants (flame retardants, polychlorinated biphenyls, polybrominated diphenyl ethers, and polycyclic aromatic hydrocarbons) using low-pressure gas chromatography with tandem mass spectrometry. An amount of 180 mg sorbent per 0.6 mL extract in filter-vial dispersive solid-phase extraction cleanup was found the optimum in terms of achieving satisfactory removal of co-extractives and recoveries of analytes, especially for structurally planar compounds. For analytes partially retained by Verde, normalization to an internal standard resulted in 62-107% recoveries. Addition of Verde to primary secondary amine and C18 in cleanup resulted in 38% more removal of gas-chromatography-amenable co-extractives in avocado, 30% in kale, 39% in salmon, and 50% in pork. The removal efficiency of co-extracted chlorophyll was 93% for kale and 64% for avocado based on ultraviolet-visible absorbance. The developed method was validated at three spiking levels (10, 25, and 100 ng/g), and 70-120% recoveries with ≤20% relative standard deviation were achieved for 96 (83%) out of 117 analytes in pork, 79 (69%) in salmon, 71 (62%) in kale, and 75 (65%) in avocado.

Evaluation of a recent product to remove lipids and other matrix co-extractives in the analysis of pesticide residues and environmental contaminants in foods.

This study demonstrates the application of a novel lipid removal product to the residue analysis of 65 pesticides and 52 environmental contaminants in kale, pork, salmon, and avocado by fast, low pressure gas chromatography - tandem mass spectrometry (LPGC-MS/MS). Sample preparation involves QuEChERS extraction followed by use of EMR-Lipid ("enhanced matrix removal of lipids") and an additional salting out step for cleanup. The optimal amount of EMR-Lipid was determined to be 500mg for 2.5mL extracts for most of the analytes. The co-extractive removal efficiency by the EMR-Lipid cleanup step was 83-98% for fatty samples and 79% for kale, including 76% removal of chlorophyll. Matrix effects were typically less than ±20%, in part because analyte protectants were used in the LPGC-MS/MS analysis. The recoveries of polycyclic aromatic hydrocarbons and diverse pesticides were mostly 70-120%, whereas recoveries of nonpolar polybrominated diphenyl ethers and polychlorinated biphenyls were mostly lower than 70% through the cleanup procedure. With the use of internal standards, method validation results showed that 76-85 of the 117 analytes achieved satisfactory results (recoveries of 70-120% and RSD≤20%) in pork, avocado, and kale, while 53 analytes had satisfactory results in salmon. Detection limits were 5-10ng/g for all but a few analytes. EMR-Lipid is a new sample preparation tool that serves as another useful option for cleanup in multiresidue analysis, particularly of fatty foods.

Influence of rice field agrochemicals on the ecological status of a tropical stream.

Many tropical countries contain a high density of protected ecosystems, and these may often be bordered by intensive agricultural systems. We investigated the chemical and ecological status of a stream connecting an area with conventional rice production and a downstream protected nature reserve; Mata Redonda. Three sites were sampled: 1) an upstream control, 2) in the rice production area and 3) a downstream site in Mata Redonda. We sampled benthic macroinvertebrates and pesticides in water and sediments along with supporting physical and chemical data. Pesticide concentrations in water exceeded current safety thresholds at sites 2 and 3, especially during the rainy season, and sediment associated pesticide concentrations exceeded current safety thresholds in three of six samples. Importantly, the highest predicted pesticide toxicity in sediments was observed at site 3 in the Mata Redonda confirming that the nature reserve received critical levels of pesticide pollution from upstream sections. The currently used macroinvertebrate index in Costa Rica (BMWP-CR) and an adjusted version of the SPecies At Risk index (SPEAR) were not significantly correlated to any measure of anthropogenic stress, but the Average Score Per Taxon (ASPT) index was significantly correlated with the predicted pesticide toxicity (sumTUD.magna), oxygen concentrations and substrate composition. Our results suggest that pesticide pollution was likely involved in the impairment of the ecological status of the sampling sites, including site 3 in Mata Redonda. Based on our results, we give guidance to biomonitoring in Costa Rica and call for increased focus on pesticide transport from agricultural regions to protected areas.

Validation of a GC-MS method for the estimation of dithiocarbamate fungicide residues and safety evaluation of mancozeb in fruits and vegetables.

A sensitive and rugged residue analysis method was validated for the estimation of dithiocarbamate fungicides in a variety of fruit and vegetable matrices. The sample preparation method involved reaction of dithiocarbamates with Tin(II) chloride in aqueous HCl. The CS2 produced was absorbed into an isooctane layer and estimated by GC-MS selected ion monitoring. Limit of quantification (LOQ) was ⩽40µgkg(-1) for grape, green chilli, tomato, potato, brinjal, pineapple and chayote and the recoveries were within 75-104% (RSD<15% at LOQ). The method could be satisfactorily applied for analysis of real world samples. Dissipation of mancozeb, the most-used dithiocarbamate fungicide, in field followed first+first order kinetics with pre-harvest intervals of 2 and 4days in brinjal, 7 and 10days in grapes and 0day in chilli at single and double dose of agricultural applications. Cooking practices were effective for removal of mancozeb residues from vegetables.