This study used chemometric tools and a Geographic Information System (GIS) to determine the influence of organic matter and anthropogenic activity on the distribution of metal species between two major communities of the Middle Negro River Basin-AM. Higher concentrations of metal species were determined in flooded regions. The chemometric analysis showed the affinity of organic matter for potentially toxic metals, indicating its selectivity. GIS spatial analysis has shown that proximity to urban areas is a variable that is likely to influence the pattern of concentration of organic matter, and consequently the distribution of metal species between flooded and non-flooded areas.

As elevadas concentrações de mercúrio em diferentes matrizes ambientais na Amazônia têm sido atribuídas a atividades mineradoras. Entretanto, altas concentrações de mercúrio também estão presentes no solo e na água em locais como a Bacia do médio Rio Negro, distantes de fontes emissoras antropogênicas. A região Amazônica é caracterizada por dois diferentes regimes sazonais, bem definidos em períodos de cheias e vazantes. O objetivo deste trabalho foi investigar as influências sazonais na interação entre mercúrio e substâncias húmicas aquáticas (AHS), que são os principais complexantes orgânicos naturais. Os resultados obtidos por análise estatística multivariada dos dados mostraram que as substâncias húmicas possuem diferentes características estruturais, dependendo do período sazonal. A capacidade das substâncias húmicas em formar complexos com Hg(II) não está diretamente relacionada ao seu teor de carbono, mas sim natureza e disponibilidade dos grupos funcionais presentes em sua estrutura. Os grupos funcionais carboxílicos e aromáticos estão diretamente relacionados maior capacidade de complexação de AHS por íons mercúrio.

High mercury concentrations in different environmental matrices in the Amazon have been attributed to mining activities. However, high concentrations of mercury are also present in the soil and water in places like in the middle of the Negro River Basin, which is far away from any anthropogenic emission sources. The Amazon region is characterized by two different regional seasons, with well-defined flood and low water periods. The objective of this work was to investigate the seasonal influences of the interaction between mercury and aquatic humic substances (AHS), which are the main agents of the natural organic complexation capacity. The results of the multivariate statistical analysis of the data showed that the humic substances had different structural characteristics, depending on each season. The ability of humic substances to form complexes with Hg(II) is not directly related to their carbon content, but to the nature and availability of the functional groups present in its structure. The functional groups are carboxylic and aromatic directly related to the higher complexation capacity of AHS by mercury ions.

The aim of this work was to study the contamination by chromium in the sediments of the Monte Alegre stream and in the larvae of Odonata and the possible impact caused by them on the stream macroinvertebrates community. It was found that chromium contaminated the sediments and the aquatic biota. Although, the stream macroinvertebrates community structure did not appear to be modified.

The region of Aracá River (Middle and Upper Rio Negro-AM) has peculiar characteristics, having soils with atypical profile and high organic matter contents in great deep. The levels of aluminum and iron in the soil samples increased as a function of depth and concentrations of mercury ranged from 0.097 to 0.964 µg g-1. Statistical analysis showed the degree of similarity between soil samples collected. The highest concentrations of mercury in soil samples are directly related to soil higher content of organic matter, directly influencing the fate and bioavailability of mercury species to the environment.

Streams located in areas of sugar cane cultivation receive elevated concentrations of metal ions from soils of adjacent areas. The accumulation of metals in the sediments results in environmental problems and leads to bioaccumulation of metal ions by the aquatic organisms. In the present study, bioaccumulation of the metals ions Al, Cd, Cr, Cu, Fe, Mg, Mn and Zn in aquatic insects in streams impacted by the sugar cane was evaluated. The results pointed out that the insects were contaminated by the sediment and that the collector organisms as Chironomus species accumulated higher concentration of metals than the predator organisms.

The work reported here involved the characterization of sludges produced at water treatment plants in Jaboticabal-SP using FeCl3 as flocculant, and in Taquaritinga-SP and Manaus-AM using Al2(SO4)3 as flocculant. An evaluation was also made of the interaction of organic matter extracted from the sludges with different metal species. The results indicated that all the sludges produced at water treatment plants have an important agricultural potential and that their use depends on the characteristics of the raw water and the type of flocculant employed in conventional treatment. The humic substances extracted from the sludges showed different affinities for metal species, favoring eventual exchanges between potentially toxic metals and macro- and micronutrients. An alternative for the use of sludge in agriculture is to pretreat it to remove potentially toxic metals and enrich it with micro- and macronutrients that can be released to the plant.

Samples of soil, water and sediment were collected and analyzed in order to evaluate chromium contamination due to deposition of tannery residues onto soils under different management regimes. The results showed that soils used for sugar cane cultivation were not adversely impacted. However, in the case of mango plantations, variable concentrations of chromium were measured in the soil profile, with 22.2% of values being higher than permitted legal limits, and 38.9% being at levels requiring remediation. Concentrations of bioavailable chromium were lower than the detection limit of the method (0.01 mg of chromium kg-1 of soil), indicating that all of the chromium present in the samples was either complexed or in an insoluble form. Chromium concentrations measured in samples of water and sediments were indicative of low mobility of the metal in soils. The main cause of differences found between soil samples obtained from different cultivations was the type of soil management.

Neste trabalho substâncias húmicas (SH) extraídas de solos não alagáveis (Araçá) e alagáveis (Iara) foram caracterizadas com cálculos de estabilidade e energias de ativação associadas com a desidratação e decomposição térmica de SH utilizando TGA and DTA, ressonância paramagnética eletrônica (EPR) e razões atômicas C/H, C/N e C/O. Para SH extraídas de solos alagáveis, existe evidências da influência da umidade sobre o processo de humificação da matéria orgânica. Observações do comportamento térmico, com análise elementar, indicaram a presença de fósseis de carbono orgânico nas partículas de argila, o que só decompõe acima de 800 ºC. Essa característica pode explicar as diferentes estabilidades térmicas e energias de ativação requeridas na pirólise para amostra Iara comparada a amostra Araçá.

In this work humic substances (HS) extracted from non-flooded (Araçá) and flooded (Iara) soils were characterized through the calculation of stability and activation energies associated with the dehydration and thermal decomposition of HS using TGA and DTA, electronic paramagnetic resonance and C/H, C/N and C/O atomic ratios. For HS extracted from flooded soils, there was evidence for the influence of humidity on the organic matter humification process. Observations of thermal behaviour, with elemental analysis, indicated the presence of fossilized organic carbon within clay particles, which only decomposed above 800 ºC. This characteristic could explain the different thermal stability and pyrolysis activation energies for Iara HS compared to Araçá HS.

Soils play an important role in the biogeochemical cycle of mercury as a sink for and source of this metallic species to atmospheric and hydrological compartments. In the study reported here, various types of soil were evaluated to ascertain the influence of parameters such as pH, organic matter content, Fe, Al, sand, silt, clay, C/H, C/N, C/O atomic ratios, and cation exchange capacity on the distribution of Hg in Amazonia's mid-Negro River basin. The data obtained were interpreted by multivariate exploratory analyses (hierarchical cluster analysis and principal component analysis), which indicated that organic matter plays an important role in mercury uptake in the various soils studied. The soils in floodable areas were found to contain 1.5 to 2.8-fold higher Hg concentrations than those in non-floodable areas. Since these soils are flooded almost year-round, they are less available to participate in redox processes at the soil/atmosphere interface. Hence, floodable areas, which comprise humic-rich soils, accumulate more mercury than non-floodable soils, thus playing an important role in the biogeochemical cycle of Hg in Amazonia's mid-Negro River basin.

A capacidade de complexação de substâncias húmicas extraídas de amostras de turfa coletadas na região do Rio Mogi em Ribeirão Preto, SP, Brasil, foi determinada utilizando Al(III), Pb(II), Cr(VI) e Cd(II). A seguinte ordem de afinidade foi observada: Cr(VI)< Cd(II)<Pb(II)<Al(III). O teste toxicológico LD50 mostrou que as substâncias húmicas não são tóxicas até a concentração máxima de 512 mg kg-1. Esses resultados reforçam a possibilidade do uso das substâncias húmicas como agente desintoxicante de metais.

The complexation capacity of humic substances extracted from peat samples taken from the Mogi River in Ribeirao Preto, SP, Brazil, was determined using metal ions (Al(III), Pb(II), Cr(VI) and Cd(II)), yielding the following order of affinity: Cr(VI)< Cd(II)<Pb(II)<Al(III). An oral LD50 test showed that these humic substances are nontoxic up to a maximum concentration of 512 mg kg-1. These findings reinforce the possibility of using humic substances as a metal detoxicant.

O objetivo deste trabalho foi comparar a complexação de substâncias húmicas (SH) e alfa-aminoacidos (metionina, metionina sulfoxido e cloridrato de cisteína) por elementos traço de interesse biológico (Al, Cu, Pb, Mn, Zn, Cd e Ni). Sistema de ultrafiltração tangencial foi utilizado para diferenciação entre os complexos SH-metal e alfa-aminoácidos-metal. As determinações de metal foram feitas utilizando ICP-OES. Os resultados mostraram que as SH podem ser consideradas agentes complexantes seletivos com alta capacidade de complexação a Al, Cu e Pb, podendo ser clinicamente importante.

The aim of the present work was to carry out experimental comparison between humic substances (HS) and representative alpha-amino acids (methionine, methionine sulfoxide and cysteine hydrochloride) in relation to the complexation of biologically active trace elements (Al, Cu, Pb, Mn, Zn, Cd and Ni). A mobile time-controlled tangential-flow UF technique was applied to differentiate between HS-metal and alpha-aminoacids-metal complexes. Metal determinations were conventionally carried out using a ICP-OES. The results showed that HS may be considered as a selective complexing agents with higher metal bonding capability in relation to Al, Cu and Pb, the fact that may be clinically important.

Estudou-se a distribuição de Cr, Ni, Cu, Cd e Pb em frações de substâncias húmicas (SH) de diferentes tamanhos moleculares. As SH foram extraídas de amostras de água (SHA) e de sedimentos de superfície (SHSS), interface/água (SHSI) e fundo (SHSF) coletados no reservatório de captação de água superficial Anhumas, localizado no município de Araraquara-SP. Para a extração das SH utilizaram-se os procedimentos recomendados pela Sociedade Internacional de Substâncias Húmicas. Após purificação por diálise, as SH foram fracionadas com base no tamanho molecular utilizando-se sistema de fracionamento seqüencial por ultrafiltração e fluxo tangencial. O fracionamento das amostras de SHA permitiu caracterizar uma distribuição de massa relativamente uniforme dentre as frações de diferentes tamanhos moleculares, com valores maiores nas frações F2 (20,8%) e F4 (23,8%). Exceto para os íons Pb(II) e Cu(II) os quais apresentaram concentrações relativamente mais altas nas frações F2 e F4, respectivamente, de maneira geral, crômio, níquel, cádmio e chumbo têm distribuições similares nas cinco frações com tamanhos moleculares maiores e médios (F1 a F5). Quanto às distribuições de massa nas diferentes frações de substâncias húmicas extraídas de amostras de sedimento de superfície (SHSS), sedimento interface/água (SHSI) e sedimento de fundo (SHSF), as três amostras apresentaram 42-48% das SH nas frações com maiores tamanhos moleculares (F1 e F2), 29-31% nas frações intermediárias (F3 e F4) e 13-20% nas frações com menores tamanhos moleculares (F5 e F6). De modo geral, caracterizaram-se para os íons metálicos, distribuições similares dentre as respectivas frações F1 a F6. Exceções para Pb(II) e Ni(II) em sedimento de superfície com concentrações relativamente menores nas frações F2 e F4, respectivamente.

In this work was studied the distribution of Cr, Ni, Cu, Cd and Pb in humic fractions with different molecular size. The HS were extracted from waters (AHS), surface sediments (HSSS), interface water sediment (HSIS) and bottom sediment (HSBS) collected in the Anhumas surface water collection reservoir, located in the district of Araraquara - São Paulo/State - Brazil. The humic substances were extracted by procedures recommended by International Humic Substances Society (IHSS). After purification by dialysis, the humic substances were fractionated using a multistage tangential flow ultrafiltration system. The fractionation patterns of HS characterized a mass distribution relatively uniform among the fractions with different molecular sizes, with larger values in the fractions F2 (20,8%) and F4 (23,8%). Except for the ions Pb(II) and Cu(II), which presented relatively higher concentrations in the fractions F2 and F4, respectively. In general, chromium, nickel, cadmium and lead have similar distributions in the five fractions with larger and medium molecular sizes (F1 to F5). With relation to the mass distributions in the different humic substances fractions extracted from sediment samples collected at three depth, they presented 42-48% of HS in the fractions with larger molecular sizes (F1 and F2), 29-31% in the middle fractions (F3 and F4) and 13-20% in the fractions with smaller molecular sizes (F5 and F6). In general, the metallic ions presented distributions similar among the respective fractions F1 to F6. Exceptions for Pb(II) and Ni(II) in surface sediment with concentrations relatively smaller in the fractions F2 and F4, respectively.

The aquatic humic substances (AHS) investigated in this study were conventionally isolated from Rio Negro waters - Amazonas State/Brazil by means of the collector XAD 8. A special five-stage tangential-flow ultrafiltration device was used for analytical fractionation of AHS. The fractionation patterns (6 fractions each) showed that metal traces remaining in AHS after their XAD 8 isolation have different size distributions. For instance, the major percentage of traces of Ni, Cu, Zn, Cd and Pb (determined using ICP-AES) was preferably complexed by molecules with relatively high molecular size (30-100 kDa) and the following complexation order was characterized: F2 >> F1 = F4 = F5 > F3 > F6. Moreover, the species formed between AHS and metals prepared by spiking, showed distribution patterns changing as a function of the complexation time (ageing process), indicating a slow transformation process and an inner rearrangements in the binding sites within the AHS molecules.