The role of suspended sediments in the metabolism and nutrient concentrations in river waters of Rondonia.
Michelle
Cristine
Cogo, CENA - Centro de Energia Nuclear na Agricultura, mccogo@esalq.usp.br
(Presenting)
Alexandra
Ayres
Montebelo, CENA - Centro de Energia Nuclear na Agricultura, nandaymo@bol.com.br
Alex
Vladimir
Krusche, CENA - Centro de Energia Nuclear na Agricultura, alex@cena.usp.br
Anthony
K
Aufdenkampe, Stroud Water Research, aufdenkampe@stroudcenter.org
In the last decade there was a significant increase on the land cover transformations of forests into pastures in the State of Rondonia. These transformations can lead to an increase in the load of materials carried by the rain in the erosive process. Presuming that rivers are integrators of processes occurring in the watershed, these alterations interfere directly in their physical and chemical parameters. The objective of this study is to evaluate the controlling mechanism of respiration rates in rivers and possible changes in nutrient concentrations in two paired watersheds of Rondonia. The study was conducted at Igarap¨¦ Boa Vista in areas of forest and pasture. Samples were collected with a submersible pump, a plankton sieve and a Millipore ultra-filtration system equipped with 0.1¦Ìm membranes, the coarse and fine sediments present in these waters were concentrated 4 to 7 times. The concentrated solutions were added to bottles containing in natura samples from the rivers, and incubated in the dark for 24 and 48 hours. The respiration rates were calculated from oxygen consumption in these incubations. The concentrations of dissolved oxygen were determined by Winkler titration. Also, the following concentrations were analyzed: respiration rates, nitrate, nitrite, ammonium, and phosphate. Preliminary results exhibit an alteration on respiration rates and concentrations of these compounds from the addition of fine and coarse suspended sediment. Therefore, it is possible that the adsorbed elements in the sediments, such as carbon and other nutrients, are determinant factors of respiration rates of these aquatic ecosystems.
Submetido por Michelle Cristine Cogo em 17-MAR-2004
Tema Científico do LBA: SH (Hidrologia e Química das Águas)