Considerações sobre os processos de sedimentação na água preta ácida do rio Negro (Amazônia Central)

The narrow, elongated morphology of the river islands called the Anavilhanas Archipelago, found in the lower Rio Negro, suggests sedimentation processes which differ from other Amazon tributaries, which have lens-shaped river islands. A study of the geochemistry of the water and sediment of the Rio Negro, Rio Branco, and Rio Solimoes suggested that kaolinitic suspended sediments from the Rio Branco were being flocculated by the acid black water of the Rio Negro, due to pH reduction to the zero point of charge of the sediment, and because of the formation of humic-kaolin clay complexes. No sediment flocculation was observed where the Rio Negro combined with the Rio Solimões; as the pH change at this convergence was slight. Sedimentation of flocculates in the lower Rio Negro produces unstratified deposits, which are manifested by elongated islands consisting mainly of silt and clay, and bed sediment of very-high clay content.A morfologia alongada e estreitada das ilhas fluviais chamadas de arquipélago das Anavilhanas, encontrado no baixo rio Negro, sugerem processos de sedimentação que diferem de outros tributários do Amazonas, que têm ilhas fluviais na forma de lentes. Um estudo da geoquímica da água e sedimento do rio Negro, rio Branco e rio Solimões sugere que sedimentos caoliníticos em suspensão do rio Branco estavam sendo floculados pela água preta ácida do rio Negro, face à redução do pH ao ponto zero de carga do sedimento, e à formação de complexos argiloso caulin-húmico. Nenhuma floculação de sedimento foi observada onde o rio Negro se combina com o rio Solimões, uma vez que a mudança de pH nesta convergência era pequena. A sedimentação de floculados no baixo rio Negro produz depósitos não estratificados, os quais são manifestados por ilhas alongadas consistindo principalmente de silte e argila, e sedimento do leito do conteúdo muito alto de argila

A KINETIC AND EQUILIBRIUM STUDY OF THE ADSORPTION OF THE ORGANIC INSECTICIDES CARBARYL AND PARATHION UPON SOME SOIL ORGANIC MATTER SURFACES

Abstract not availabl

Humic Acid: Aggregate, Floc, Macromolecule, Micelle, Polymer, or Supramolecule?

Two humic acids, extracted from an Alfisol forest soil and a lignite mined in Greece, were purified of ash components, size fractionated by membrane dialysis, and polarity fractionated by adsorption chromatography on XAD-8 resin to determine binding mechanisms of humic acid constituents. Humic acids, contained in 12,000 to 15,000 dialysis membranes, were successively dialyzed against 0.1 M HCl, 0.2M HF, 0.1M sodium citrate at pH 10, and 0.1 M NaOH to remove ash components and disaggregate and size fractionate with increasing pH. A part of humic acid did not permeate the dialysis membranes during the acid treatment, while the humic acid that permeated during the sodium citrate and NaOH treatments, was polarity fractionated by a decreasing pH gradient on XAD-8 resin. The resulting fractions were characterized by mass balance, elemental analyses, pH titration, and FT-IR spectrometry. Certain fractions of the lignite humic acid had characteristics very similar to molecular condensates formed by radical coupling of phenolic acid precursors of lignin. Significant differences between the composition and fractionation patterns of the soil and lignite humic acids were interpreted in terms of binding mechanisms within the humic acid precipitates

Water-Resources Investigations Report 82-15

From purpose of study: In January 1980, the u.s. Environmental Protection Agency (EPA) recommended that a ground-water monitoring program for organic constituents be started at the INEL. In response to this recommendation, DOE requested the U.S. Geological Survey to undertake such a program. The purpose of the study was to determine the distribution and extent of organic constituents in the ground water beneath the INEL