Dissolved inorganic carbon dynamics in a highly seasonal river in Southwestern Amazonia: Upper Purus River
Salimon, universidade federal do acre, email@example.com
Sousa, UFPA/EMBRAPA, firstname.lastname@example.org
Alin, University of Washington, email@example.com
In order to broaden our knowledge of the spatial variability and also of seasonal patterns of dissolved inorganic carbon dynamics, we have studied the Upper Purus river in Acre State, Brazil; which is one of the major tributaries of the Solimões river. Our objectives were to (1) characterize the seasonal patterns of physical and chemical parameters such as pH, water temperature, dissolved oxygen and water electrical conductivity, (2) determine the seasonal variation in DIC concentration and the contribution of each of its components (CO2, HCO3,- and CO3--).
The seasonal patterns for the physical and chemical parameters were inversely related to precipitation. Dissolved oxygen, pH and water electrical conductivity present higher values during the dry season (from may to October), and the highest values were observed in the month of September 2005, where pH, dissolved oxygen and electrical conductivity were 8.61, 104% and 385 µS cm-1, respectively. During the rainy season these values decrease (from November to March), and the lowest values were observed in February 2005 (6.84, 30.5% e 79µScm-1, for pH, dissolved oxygen and electrical conductivity respectively.
Dissolved inorganic carbon also presented a very seasonal pattern, with highest concentration in october 2004 in the dry season (3,460 µM) and the lowest concentration was in January 2005 (1,194 µM). In the driest months, when pH is more basic, CO2 partial pressure (pCO2) is lower (780±152 ppm) and the pattern reverts during the rainy months when pH is lower (pCO2 4029±511 ppm).
From these results, we conclude that seasonality has a major impact in dissolved inorganic carbon dynamics in upper Purus.