Dissolved nitrogen in rivers: comparing pristine and impacted regions of Brazil

• Published in: Brazilian journal of biology Vol. 70; no. 3 Suppl; pp. 709 - 722
• Main Authors: Martinelli, L A, Coletta, L D, Ravagnani, E C, Camargo, P B, Ometto, J P H B, Filoso, S, Victoria, R L
• Format: Journal Article
• Language: English; Portuguese
• Published: Brazil Instituto Internacional de Ecologia 01.10.2010
• Subjects: Amazon basin; BIOLOGY; Brazil; Environmental Monitoring - methods; nitrogen; Nitrogen - analysis; Piracicaba basin; pollution; Population Density; river; Rivers - chemistry; Water Pollutants, Chemical - analysis; Brazil; South America, Amazon R; Brazil, Sao Paulo; bacia Amazônica; Brasil; Amazon basin; poluição; nitrogen; bacia do Piracicaba; Brazil; river; Piracicaba basin; nitrogênio; pollution; rios
• ISSN: 1519-6984; 1678-4375; 1678-4375; 1519-6984
• DOI: 10.1590/S1519-69842010000400003

Riverine nitrogen distribution is increasingly controlled by anthropogenic activities in their watersheds, regardless of spatial scale, climate, and geographical zone. Consequently, modelling efforts to predict the export of nitrogen from rivers worldwide have used attributes such as population density, land use, urbanization and sanitation. These models have greatly enhanced our understanding of the sources and fate of nitrogen added to terrestrial systems and transported to rivers and streams, especially for developed countries of the North temperate zone. However, much of the world's population lives in developing countries of the tropics, where the effects of human activities on riverine N exports are still poorly understood. In an effort to close this gap, we compare riverine nitrogen data from 32 Brazilian rivers draining two contrasting regions in this tropical country in terms of economic development - the State of São Paulo and the Amazon. Our data include nitrogen in different dissolved forms, such as Dissolved Inorganic Nitrogen (DIN) and Dissolved Organic Nitrogen (DON). The results show that nitrogen concentrations decreased as river runoff increased in both study areas, and that concentrations were significantly higher in rivers draining the most economically developed region. The relationships between nitrogen concentrations and fluxes with demographic parameters such as population density were also determined and compared to those in temperate systems. In contrast to temperate watersheds, we found that nitrogen fluxes increased only after population densities were higher than 10 individuals per km².