The chemical and spectroscopic characteristics of soil organic matter (SOM) isolated from Amazonian dark earth (ADE) and surrounding soil (SR) were evaluated according to the soil depth. The results showed opposite trends for the soils. While ADE featured SOM with a greater aromatic condensation degree and greater hydrophobicity in the top layer, the SR showed more aliphatic and polar SOM. The SOM arrangement from ADE was less hydrophobic, aromatic, and more polar in depth. In contrast, the SOM from SR showed an increase in molecular weight and hydrophobicity. Besides the aromatic protection in the SOM from ADE, there was organo-mineral protection through binding to soil minerals. This suggested that the SOM from ADE was protected by its hydrophobicity and interaction with minerals compared with that from the SR, thereby showing that the combination of both characteristics is important to create new technologies for soil carbon storage.

The Amazon rainforest presents one of the greater biodiversity in the world and a huge and dynamic carbon reservoir, both in the vegetation and in the soil pools, so it is an attractive subject of study. In the present paper, humic acids from a toposequence of an Oxisol-Spodosol system associated with kaolin was studied using fluorescence emission-excitation matrix combined with parallel factor analysis. The combined techniques allowed to assess the intensities of the two different fluorophores associated with humic acid with core consistency diagnoses of 84.2%. The results for the Humiluvic Spodosol seem to corroborate the model of the supramolecular structure of humic acid, because the intensity ratio of fluorophores does not remain in the profile. Therefore, the use of these combined techniques can provide information about the transformation processes of humic substances in soils, becoming an interesting analytical tool for studying these substances of different soils.

Este estudo teve como objetivo principal avaliar a influência das SHA obtidas a partir de uma área de cultivo de cana de açúcar sobre a influência das espécies de crômio (Cr(III) e Cr(VI)). Foi estudada a capacidade de complexação (CC) das SHA com as espécies de crômio e estas foram caracterizadas por espectrofotometria de UV/Vis, fluorescência molecular, análise elementar e infravermelho. SHA com e sem fracionamento apresentou maior grau de aromaticidade e predominância de ácidos húmicos, e as razões E4/E6 e E2/E4 sugerem a presença de anéis aromáticos e maior contribuição das plantas e lignina. As maiores CC foram observados para a SHA fracionadas, sendo as frações com tamanho molecular < 10 kDa e 10-30 kDa as que apresentaram as maiores capacidades para complexar os íons Cr(III) e Cr(VI), respectivamente. Estes resultados corroboram com os dados de C/H/N e UV/Vis, permitindo concluir que as SHA sem fracionamento têm em sua estrutura maior grupos aromáticos e uma predominância de ácidos húmicos.

This study had as main objectiveto evaluate the influence of AHS obtained from an area under sugarcane cultivation on the dynamics of chromium species (Cr(III) and Cr(VI)). Was studied complexing capacity (CC) with the AHS of chromium species and these were characterized using UV/Vis spectrophotometry, molecular fluorescence, elemental analysis and infrared. AHS with and without fractionation showed a greater aromaticity degree and a predominance of humic acids, and the E4/E6 and E2/E4 ratios suggested aromatic rings and a greater contribution from plants, which indicates lignin structures. The highest CCs were observed for the AHS fractionated, being fraction with molecular-size < 10 kDa and 10-30 kDa showed the highest ability to complex Cr(III) and Cr(VI) ions, respectively. These results are corroborating with C/H/N and UV/Vis data, where we can conclude that the AHS without fractionation had the greatest aromaticity and a predominance of humic acids in their structure.

Este estudo teve como principal objetivo determinar a capacidade de complexação da Matéria Orgânica (MO) de regiões tipicamente agrícolas e urbanas, com os íons de cobre e níquel. As amostras foram coletadas durante as estações de seca e chuva e submetidas ao estudo da capacidade de complexação e da constante de estabilidade condicional da MO com os íons Cu(II) e Ni(II) usando um Espectrofluorímetro de Luminescência e o Sistema de Ultrafiltração de Fluxo Tangencial. Os valores da constante de estabilidade condicional (log Kc) da MO com o íon cobre variaram de 0,04 a 1,35 sendo o maior valor obtido para o local com maior carbono orgânico dissolvido (COD 2,73-2,43 mg L-1) e o menor para local de menor COD, corroborando com o grau de aromaticidade. Conclui que a Matéria Orgânica Dissolvida (MOD) de rios de áreas agrícolas e urbanas continha um número menor de sítios de ligação, quando comparado com outros locais.

This study had as main objective to determine the complexing ability of the Organic Matter (OM) from typical agricultural areas and from urban areas with copper and nickel ions. The samples were collected during the dry and rainy seasons and were subjected to study the complexing capacity and OM conditional stability constant with Cu(II) and Ni(II) ions using a luminescence spectrofluorometer and tangential flow ultrafiltration system. The conditional stability constant values (log Kc) of OM with the copper ion varied from 0.04 to 1.35 with the highest value obtained for the place with the largest dissolved organic carbon (DOC 2.73-2.43 mg L-1) and the lowest for the smallest site DOC, corroborating the degree of aromaticity. We can conclude that the Dissolved Organic Matter (DOM) of the bodies of water in agricultural and urban areas contained a lower number of binding sites when compared with other locations.

This work aims to study spatial and seasonal variability of some chemical-physical parameters in the Turvo/Grande watershed, São Paulo State, Brazil. Water samples were taken monthly, 2007/07-2008/11, from fourteen sampling stations sited along the Turvo, Preto and Grande Rivers and its main tributaries. The Principal Component Analysis and hierarchical cluster analysis showed two distinct groups in this watershed, the first one associated for the places more impacted by domestic effluent (lower levels of dissolved oxygen in the studied region). The sampling places located to downstream (Turvo and Grande rivers) were discriminate by diffuse source of pollutants from flooding and agriculture runoffs in a second group.