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Keywords: Sedimento;  Matéria Orgânica;  Lignina;  Rio Paraíba do Sul;  Bacia de Campos;  Sediment;  Organic Matter;  Lignin;  Paraiba do Sul River;  Campos Basin
Issue Date: 28-Feb-2013
Abstract: The Campos basin is the largest domestic oil producer, located in the southeastern portion of Brazil (20-24 ° S, 39-42 ° W) is bounded on the north by the Espirito Santo basin and south by the arc of Cabo Frio. The basin suffers intense pressure by environmental industrial-urban disordered growth, and fine transport of organic material in the continent-ocean interface seems to influence the region's ecosystem. In this design, to evaluate the influence of ocean currents and the the contribution of continental Paraíba do Sul river basin to Campos (RJ), lignins were used as geochemical tracers of allochthonous organic matter origin and reactivity. For a macroevaluation of the Campos basin, on a regional scale, 59 samples of surface sediments (0-2 cm) were collected from May to July 2008. The sampling points were distributed along the topographical features within five transects (A, E, G, H, I) and two canyons (Almirante Câmara and Grussaí), distributed on: shelf (25 to 150 m), slope (400 to 1300 m) ocean floor (1900 to 3000 m) and canyons (400-1300 m). In the canyons and at stations located on the slope and ocean floor there was the predominance of silt + clay, with a contribution of more than 80%, whose isobaths between 700 and 1300 m showed surface areas from 15.0 to 28.5 m2 g-1. In the continental shelf a greater heterogeneity in grain size was observed, with a predominance of the sand fraction (69 %) and surface areas below 10 m2 g-1. The highest concentrations of TOC and variations occurred and NT to the slope, ranging from 0.65 to 1.77 % and 0.11 to 0.33 %, respectively. Moreover, the shelf was responsible for greater variation in the ratio (C: N) (5.31 to 15.6), with a median higher for canyons (8.58). The isotopic signatures of C were similar -23.0 to -21.0 . The highest values of 13C occurred to the canyons and shallow areas north of the basin (shelf). The isotope ratio of N showed the following distribution decreasing from the following median values: floor (5.67 ) > slope (5.54 ) > canyons (4.98 ) > shelf (4.39 ). The greater isotopic variability of C and N was present on the shelf with amplitudes of -27.4 to -20.8 , and 2.68 to 6.55 , respectively. The highest concentrations of total lignin (L8) were observed on the shelf, shallow areas of the south (1.2 mg 100mgCorg-1) and North (1.0 mg 100mgCorg-1). In canyons and slope distribution L8 was homogeneous with a median of approximately 0.2 mg 100mgCorg-1. The distribution of phenolic groups along transects and canyons was as follows: vanilil (V) > syringyl (S) > cinnamyl (C). The ratio (Ac/Ad)v was greater than 0.4 in 97% of samples, the indications phenols were strongly degraded by diagenetic processes in the basin. The study showed variability in the qualitative and quantitative distribution of organic matter along the different topographic features (shelf, slope, and canyon floor), predominantly associated to the autochthonous phytoplankton primary production and depositional processes of microbial degradation of MO.
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