Spatial patterns of DOC concentration and DOM optical properties in a Brazilian tropical river‐wetland system

Abstract

The Cerrado (savanna) and Pantanal (wetland) biomes of Central Western Brazil have experienced significant development activity in recent decades, including extensive land cover conversion from natural ecosystems to agriculture and urban expansion. The Cuiabá River transects the Cerrado biome prior to inundating large areas of the Pantanal, creating one of the largest biodiversity hot spots in the world. We measured dissolved organic carbon (DOC) and the optical absorbance and fluorescence properties of dissolved organic matter (DOM) from 40 sampling locations spanning Cerrado and Pantanal biomes during wet and dry seasons. In the upper, more agricultural region of the basin, DOC concentrations were highest in the rainy season with more aromatic and humified DOM. In contrast, DOC concentrations and DOM optical properties were more uniform for the more urbanized middle region of the basin between wet and dry seasons, as well as across sample locations. In the lower region of the basin, wet season connectivity between the river and the Pantanal floodplain led to high DOC concentrations, a fourfold increase in humification index (HIX) (an indicator of DOM humification), and a 50% reduction in the spectral slope (SR). Basin‐wide, wet season values for SR, HIX, and FI (fluorescence index) indicated an increasing representation of terrestrially derived DOM that was more humified. Parallel factor analysis identified two terrestrially derived components (C1 and C2) representing 77% of total fluorescing DOM (fDOM). A third, protein‐like fDOM component increased markedly during the wet season within the more urban‐impacted region.

Variação Sazonal Do Carbono Orgânico Dissolvido (Cod) E Propriedades Ópticas Da Matéria Orgânica Em Diferentes Sistemas De Pastagem E De Soja No Estado De Mato Grosso

“…, 2005). This explains the greater bioavailability in the Wetland during the dry season ; (Dalmagro et al, 2017). Four peaks were identified in the Savanna during the dry season, of which the highest represented tryptophan, with a maximum intensity of 0.230.…”

“…The ratios of E 2 :E 3 and E 4 :E 6 did not change significantly between hydrological seasons, but did between ecosystems and land ntative emission and excitation matrices ( , 2005). This explains the greater bioavailability in the Wetland during the dry season ; (Dalmagro et al, 2017).…”

“…This compound is associated with semi-labile dissolved organic matter, which is common in systems under anthropogenic impacts, and is associated with the leaching process within the basin ( , 2005). This explains the greater bioavailability in the Wetland during the dry season ; (Dalmagro et al, 2017). Four peaks were identified in the Savanna during the dry season, of which the highest represented tryptophan, with a maximum intensity of 0.230.…”

“…Recently techniques of optical absorption and fluorescence spectroscopy have been widely used (Singh et al, 2013); (Dalmagro et al, 2017) to evaluate water quality in agricultural river basins (Fellman et al, 2010). The biogeochemical characterization of the dissolved organic matter (DOM) based on fluorescence allows the detection of differences between natural and anthropogenic DOM sources in rivers impacted by agricultural residues ; (Wilson e Xenopoulos, 2008).…”

Streams with Riparian Forest Buffers versus Impoundments Differ in Discharge and DOM Characteristics for Pasture Catchments in Southern Amazonia

“…At each sampling points (distant 50 m from one point to the other), we obtained a sample 0.10 m below the surface from visually well mixed sites in the main thalweg. Water samples were filtered in the field using pre-combusted filters (Whatman GF/F glass fiber filter, 0.7 µm pore size) prior to being stored in 60 mL amber glass vials with Teflon-lined tops previously acid washed [16,39]. Water samples were refrigerated (about 6 • C) and stored in the dark for laboratory testing within 24 hours of collection.…”