Fluxos de carbono orgânico dissolvido e de nitrato em duas microbacias sob diferentes usos

The impacts of human activities on watersheds can alter the quality and possible uses of water resources. In this context, the objective of this study was to evaluate the flows of dissolved organic carbon (DOC) and nitrate (NO3) in the surface waters of two mini-watersheds with different anthropic impacts. Water samples were collected in two mini-watersheds with different soil use (regenerated savanna and an agricultural area) from January 2014 to April 2015. In the rainy season, the samples were collected every 15 days and in the dry period every month. The composite samples were collected by an automatic sampler in the stream. The water flow monitoring was performed with a sensor that measured the hydraulic load on the sill of the triangular spillway installed in each of the mini watershed. The DOC and NO3 contents were analyzed in a UV-Vis spectrophotometer. The flow was estimated with the values of flow and concentrations of DOC and NO3. COD concentrations are higher in the cerrado mini watershed, but there was no difference in NO3 concentrations. In both watersheds there is a significant increase in the concentration of DOC and NO3 on rainy days, with this increase being greater in the agricultural watershed. COD and NO3 flows are higher in the mini-watershed with cerrado vegetation in the presence of rainfall, but there was no difference in the absence of rainfall.