Analysis and risk assessment of arsenic in the water sources of the cities Cuenca and Azogues, Ecuador

Abstract

Arsenic (As) is a toxic element present in the environment posing a threat to consumers health. To identify the arsenic content in rivers, páramos, and wells in the city of Cuenca, and in rivers in the city of Azogues, two monitoring campaigns in the period August-November 2017 were conducted, respectively during a low and high flow hydrological period. The measurements encompassed physicochemical quality indicators such as pH, color, turbidity, and conductivity. Results show that the páramos and wells are free of As, while this toxic substance is present in surface water with higher levels in periods of high flow. A significant association between the concentration of As and the pH of river water was found. The risk of chronic toxicity from consumption is almost non-existent because the observed As levels exceed only exceptionally the permissible limit established by the Ecuadorian TULSMA (Unified Text of Secondary Environmental Legislation) regulation. The presence of As in surface water is the result of anthropological activities such as the use of pesticides. A permanent monitoring of the quality of water resources for human consumption is necessary, particularly in the rainy season, due to the diffuse and difficult to control pollution processes.