Concentration of potentially toxic elements in soils of an intensively agricultural and industrial watershed.

Soil contamination by potentially toxic elements (PTEs) can alter the structure and functioning of ecosystems and pose risks to public health. In this context, micro.watersheds are important units of analysis, as they integrate natural and anthropogenic processes that influence the distribution of these elements in the environment. In general, environmental agencies establish soil quality guidelines valid for large territorial areas, such as states or countries.However, studies at smaller scales are still limited, especially in micro-watersheds. Our objectives were to quantify the concentrations of arsenic, cadmium, cobalt, copper, chromium, lead, nickel, and zinc in the soils of the Guamium river watershed, located in a Brazilian region with metalwork, boiler making and foundry industries, steel mills, sugarcane and ethanol plants, and the automotive sector; to compare these concentrations with the guidelines established by the Environmental Company of the State of São Paulo; and to establish quality reference values for PTEs in the micro-watershed. Arsenic and cooper presented the highest concentrations, with values equal to or greater than the prevention value established by the environmental agency. The study contributes to the understanding of the natural and anthropogenic variability of PTEs in tropical soils and provides support for environmental monitoring, risk assessment, and the definition of more representative reference values on a regional scale.