Modelo Pesticide Water Calculator para previsão do potencial de contaminação por agrotóxicos na bacia hidrográfica do ribeirão Espírito Santo JF- MG

Abstract

Pesticides are compounds widely used in agriculture and when present in water, even in low concentrations, they can impart toxic characteristics to the environment, offering ecological and health risks, especially when detected in water for human consumption. Brazil is one of the largest consumers of pesticides in the world, which raises great concerns regarding the possibility of contamination from non-target organisms. In this sense, modeling is an important tool, capable of representing real systems, estimating the potential for contamination of natural resources, through studies that predict the behavior and fate of chemical products in the environment, helping to make environmental decisions. The USEPA PWC (Pesticide Water Calculator) model stands out, capable of predicting the risk of contamination of surface and underground water sources, emerging as an important tool. In this context, the study aimed to use the PWC model to estimate the potential for contamination by pesticides in the Espírito Santo river basin (BHRES), in Juiz de Fora (MG), which is aimed at the municipality's public water supply. To this end, the corn crop was used, as it is the most representative for the region. The pesticides evaluated were the seven most sold in the State, and some of their metabolites: glyphosate and AMPA, 2,4-D, atrazine and DEA, mancozeb and ETU, chlorothalonil, acephate and methamidophos, chlorpyrifos. Three simulations were evaluated: the standard USEPA lagoon (L) and reservoir (R) models, as well as the parameterization (P) for the basin under study. Scenarios were proposed in order to investigate more and less critical contamination situations. The results showed that the pesticides of most concern for BHRES were atrazine + DEA, acephate + methamidophos and mancozeb + ETU, in that order. The main way of transporting the contaminant to the water body was through erosion, and metabolism was the main mechanism for degrading the pesticide in the environment. In general, the PWC proved to be efficient for the purposes of this study and it is believed that the model can be an important management tool, especially in water treatment plants. However, some observations must be made, mainly with regard to the difficulty of obtaining data to feed the model, and the unavailability of scenarios that represent in a more realistic way the country's climatic, hydrological and pedological particularities.