RESUMO
Glyphosate-based herbicides can be harmful to the environment and human health. Especially in developing countries, these herbicides are often used indiscriminately in agricultural and urban areas. Here, we optimized a simple and efficient flow injection-based spectrophotometric method to monitor environmentally relevant glyphosate concentrations in surface waters. The method was then used to assess the environmental mobility of glyphosate in Southeast Brazil by monitoring surface runoff from experimental agricultural soil plots that received glyphosate applications in 2015. Further, water samples from low-order streams were collected in five agricultural, urban, and natural areas, as well as from the 5th-order Rio das Mortes during the rainy season. Finally, 20 drinking water sources were sampled in urban, rural, and agricultural areas. Runoff from reference plots without glyphosate application showed concentrations below the method's detection limit of 0.49 mg.L-1, whereas runoff from plots with standard glyphosate application had concentrations between 1.24 and 6.1 mg.L-1. Similarly, concentrations in natural stream water were below the detection limit, whereas agricultural streams had concentrations of up to 3.7 mg.L-1 (average: 0.97 mg.L-1). In an agricultural stream monitored weekly, concentration peaks were observed after glyphosate applications by farmers, and concentrations were correlated to stream discharge. Urban streams had concentrations of up to 5.8 mg.L-1 (average: 2.6 mg.L-1), but samples from the catchment's major river were mostly below detection limits, illustrating the dilution of urban and agricultural runoff in high-order rivers. In the sampled drinking water resources, glyphosate pollution occurred mainly in the rainy season, with detectable concentrations between 0.5 and 8.7 mg.L-1 in 80% of the sampled drinking water sources. In conclusion, our results suggest considerable environmental mobility of glyphosate in the studied Southeast Brazilian catchment. Substantial pollution, well above national and international limits, was detected in surface runoff, stream water, and drinking water resources.
Assuntos
Água Potável , Herbicidas , Poluentes Químicos da Água , Humanos , Brasil , Poluentes Químicos da Água/análise , Monitoramento Ambiental , Herbicidas/análise , GlifosatoRESUMO
Analysis that link hydrological processes with oceanographic dispersion offer a promising approach for assessing impacts of land-based activities on marine ecosystems. However, such an analysis has not yet been customised to quantify specific pressures from mining activities on marine biodiversity including those from spillages resulting from tailing dam failure. Here, using a Brazilian catchment in which a tailing dam collapsed (Doce river) as a case study, we provide a modelling approach to assess the impacts on key ecosystems and marine protected areas subjected to two exposure regimes: (i) a pulse disturbance event for the period 2015-2016, following the immediate release of sediments after dam burst, which witnessed an average increase of 88% in sediment exports; and (ii) a press disturbance phase for the period 2017-2029, when impacts are sustained over time by sediments along the river's course. We integrated four components into impact assessments: hydrological modelling, coastal-circulation modelling, ecosystem mapping, and biological sensitivities. The results showed that pulse disturbance causes sharp increases in the amount of sediments entering the coastal area, exposing key sensitive ecosystems to pollution (e.g. rhodolith beds), highlighting an urgent need for developing restoration strategies for these areas. The intensity of impacts will diminish over time but the total area of sensitive ecosystems at risk are predicted to be enlarged. We determined monitoring and restoration priorities by evaluating and comparing the extent to which sensitive ecosystems within marine protected areas were exposed to disturbances. The information obtained in this study will allow the optimization of recovery efforts in the marine area affected, and valuation of ecosystem services lost.