Composition of particulate and dissolved organic matter in a disturbed watershed of southeast Brazil (Piracicaba River basin)

Abstract

The elemental and isotopic composition of particulate and dissolved organic matter was investigated in the Piracicaba River basin, S* ao Paulo State, Brazil. Comparison of riverine organic matter from the Piracicaba River basin, a region where rivers and streams receive urban sewage and industrial effluents, with data reported for the pristine Amazon system revealed significant differences associated with anthropogenic impacts. One important difference was N enrichment in the particulate organic material of the Piracicaba basin rivers, due to (a) urban and industrial effluents, and (b) enhanced phytoplankton growth, which results from the combination of nutrient enrichment and damming of sections of the rivers. Radiocarbon concentrations were overall more depleted (older 14 C age) in the Piracicaba basin rivers than in the Amazon, which may reflect the importance of soil erosion in the former. Analyses of stable and radioactive carbon isotopes and lignin-derived compounds indicated that coarse particulate organic material is composed of a mixture of soil particles and degraded organic matter from C3 and C4 vascular plants. Fine particulate organic material was composed mainly of soil particles and phytoplankton cell remains, the latter especially during low water. Ultrafiltered dissolved organic matter was the most degraded fraction according to its lignin oxidation products, and showed the greatest influence of C4 plant sources. r

Riverine Organic Matter Composition as a Function of Land Use Changes, Southwest Amazon

“…Secondly, the Ji-Paraná size fractions plotted near the Amazon River particles, suggesting that both systems have similar organic-matter sources. The organic degradation stages of the size fractions in the Ji-Paraná Basin also appear to be similar to what has been found in other Amazonian and South American rivers , Hedges et al 2000, Devol and Hedges 2001, Krusche et al 2002. The coarse fraction of the Ji-Paraná River appears to be the least degraded and resembles the remains of tree leaves (Fig.…”

“…7 and 9). This characteristic was also found in other rivers of the Amazon (Hedges et al 2000) and also in rivers of southeast Brazil (Krusche et al 2002). This N enrichment is probably due to the fact that nitrogenous organic matter selectively accumulates in the fine fractions with time by preferential sorption on soil minerals before they are eroded into aquatic systems (Hedges et al 2000, Aufdenkampe et al 2001).…”

Water quality, pollutant loads, and multivariate analysis of the effects of sewage discharges into urban streams of Southeast Brazil

“…The results were also compared with those obtained in previous studies of streams in the Piracicaba river basin (Machado et al 2018;Medeiros et al 2013;Silva et al 2012;Medeiros et al 2009;Filoso et al 2003;Daniel et al 2002;Krusche et al 2002;Martinelli et al 1999;Ometo et al 2000).…”

“…Based on the land use in the micro-basins monitored, where there was no significant agricultural activity, it could be inferred that Pinorg and Ntotal were mainly influenced by point source pollution from the discharge of domestic sewage, particularly in the case of the Recanto stream. In other streams of the Piracicaba river basin, located in regions of intensive sugar cane cultivation, the levels of nitrogen are associated with the use of chemical fertilizers, as reported by Krusche et al (2002) and Filoso et al (2003).…”

“…This affects the quality of life of the population and the resilience of aquatic ecosystems of the PRB (Machado et al 2018;Botelho et al 2013;Meche et al 2010;Jardim et al 2008;Salomão et al 2008;Fostier et al 2005;Krusche et al 2002;Ometo et al 2000).…”