Risk of agrochemical contamination in a hydrographic basin in the matopiba region in Brazil

The intensive use of agrochemicals has been associated with global human health problems and environmental contamination. Brazil is the world’s largest agrochemical consumer, and this position highlights the growth of agribusiness in the MATOPIBA region (Maranhão, Tocantins, Piauí, and Bahia states). The use of agrochemicals is recurrent in local agricultural practices. However, there is little information on the environmental impacts and risks of contamination regarding river basins in this region. Thus, this study aimed to evaluate the risk of contamination by agrochemicals in the basin area of the Açailândia River in Maranhão. From the multicriteria evaluation, environmental information plans were used to determine the trend of water behavior, infiltration, and runoff, along with agrochemical transportation. The joint evaluation of this information was used to generate the final map of the areas of contamination risk posed by agrochemicals in the region. The hydrographic basin presented high anthropization, with an increase of approximately 27% in land use and occupation by crops in the period from 1984 to 2018. The area of 1087.62 km², corresponding to 35.9% of the basin area, presented a high and extremely high risk of contamination.