Interação entre substâncias húmicas aquáticas e elementos metálicos na porção leste do Quadrilátero Ferrífero – MG.

Substâncias húmicas (SH) são compostos que perfazem cerca de metade do carbono orgânico dissolvido (COD) em águas naturais. Elas possuem elevada massa molecular e estrutura química complexa, sendo originadas da degradação da matéria orgânica. Além disso, possuem grande importância ambiental por interferirem na mobilidade e toxidade de metais e outras substâncias liberadas pelo homem. Neste trabalho, substâncias húmicas aquáticas (SHA) foram extraídas de corpos hídricos da porção leste do Quadrilátero Ferrífero/MG (QF), onde também foram determinadas as concentrações de elementos metálicos e suas relações com as condições litológicas regionais. Amostras de água foram coletadas durante a estação seca e a estação chuvosa. Os parâmetros físico-químicos T, pH, ORP, condutividade, resistividade e turbidez foram determinados in situ. Já os parâmetros alcalinidade, sulfatos, cloretos, COD, elementos metálicos maiores Al, Na, Ca, Fe, K, Mg, Mn e Ti; e traço As, Ba, Be, Cd, Co, Cr, Cu, Li, Mo, Ni, P, Pb, S, Sc, Sr, V, Y e Zn foram determinados em laboratório. A média dos valores de COD nas águas coletadas ficou em 2,19 mg/L, sendo que as maiores concentrações foram detectadas nas serras do Caraça e do Itatiaia. As SH foram extraídas das amostras por meio de resinas DAX-8 (que têm a capacidade de adsorver o material húmico em pH ácido) e por evaporação rotativa (que consiste em baixar o ponto de ebulição da água para concentrar o COD). Nos extratos também foram determinados elementos metálicos maiores e traço, além do COD. A fim de entender as dependências entre os compostos húmicos e íons metálicos na área de estudo, todos os dados obtidos foram analisados por meio de uma técnica exploratória multivariada (rede neural de Kohonen). Observou-se que as SH se apresentaram relacionadas com os metais Al, K, Ba, Ca, Cu, Fe, Mn, Sr, Ti e Zn considerando as amostras coletadas. Além disso, foi detectada influência litológica na composição das águas. Constatou-se que o solo pode influenciar na mobilidade de materiais orgânicos, visto que as areias oriundas do intemperismo do quartzito tem menor capacidade de retenção de matéria orgânica. Assim, regiões como as serras do Caraça e do Itatiaia possuíram maior concentração de SH se comparadas com áreas de diferentes litotipos. O baixo teor de argilas nas cabeceiras dos rios dessas áreas facilitaria a liberação de compostos húmicos para as águas. Esse processo é mais ativo em épocas chuvosas, fazendo com que as maiores concentrações de COD fossem observadas no período úmido ou na transição do período chuvoso para o seco. Nos demais pontos analisados com litologias diferentes a maior concentração de carbono se deu na época de transição da estação seca para a estação chuvosa e a menor se deu na estação chuvosa. Considerando os diferentes métodos de isolamento de material húmico, a evaporação rotativa mostrou-se promissora ao poder extrair SH com a possibilidade de minimização de alterações estruturais. Entretanto, ela é uma técnica demorada, sendo inconveniente para grandes volumes. As amostras extraídas com resinas DAX-8 apresentaram uma retenção média de 46,80% de COD nas colunas cromatográficas.Humic substances (HS) are compounds that make up about a half of the dissolved organic carbon (DOC) in natural waters. They are originated from the degradation of organic matter and have high molecular weight and complex chemical structure. They also have great environmental importance for interfering in the mobility and toxicity of metals and other substances released by man. In this work, aquatic humic substances (AHS) were extracted from water bodies of the eastern portion of Quadrilátero Ferrífero (MG/Brazil). Furthermore, concentrations of metallic elements and their relationship with the regional lithological conditions were determined. Water samples were collected during the dry and rainy season. The physico-chemical parameters T, pH, ORP, conductivity, resistivity and turbidity were determined in situ; alkalinity, sulphates, chlorides, DOC, major metal elements Al, Na, Ca, Fe, K, Mg, Mn and Ti; and trace As, Ba, Be, Cd, Co, Cr, Cu, Li, Mo, Ni, P, Pb, S, Sc, Sr, V, Y and Zn were determined in laboratory. The average of the values of DOC in the samples was 2.19 mg/L and the highest values were detected in the mountains of Caraça and Itatiaia. The HS were extracted from samples through DAX-8 resins (that have the ability to adsorb humic material at acidic pH) and by rotary evaporation (that consist in decrease the boiling point of water in order to concentrate the DOC). The DOC and the major and trace metals were also determined in the extracts. In order to understand the dependencies between the humic compounds and metal ions in water bodies in the study area, the data were analysed by an exploratory multivariate analysis (Kohonen neural network). It was observed a relationship between HS and the metals Al, K, Ba, Ca, Cu, Fe, Mn, Sr, Ti and Zn considering the samples collected. It was detected a lithology influence in the composition of waters. It was found that the soil can influence the mobility of organic materials, whereas the sand coming from the weathering of the quartzite has lower ability to retain organic matter. Hence, regions like the mountains of Itatiaia and Caraça contained higher concentrations of HS compared with areas of different types of rocks. The lower presence of clays in the headwaters of these areas would force a greater release of humic compounds to water. This process is most active during rainy season. Consequently the highest levels of DOC were observed during the wet season or in the transition from rainy to dry season. In other points analysed with different lithology the highest concentration of carbon occurred in the period of transition from dry to rainy season and the lowest occurred in the rainy season. Considering the different methods of isolating humic material, the evaporation under vacuum proved to be promising to extracted HS with the possibility of minimizing structural changes. However, it is a time consuming technique and it is inconvenient for large volumes. The samples extracted by DAX-8 resin had an average retention of 46.80% of DOC in the chromatographic columns

Interação entre substâncias húmicas aquáticas e elementos metálicos na porção leste do Quadrilátero Ferrífero – MG.

Substâncias húmicas (SH) são compostos que perfazem cerca de metade do carbono orgânico dissolvido (COD) em águas naturais. Elas possuem elevada massa molecular e estrutura química complexa, sendo originadas da degradação da matéria orgânica. Além disso, possuem grande importância ambiental por interferirem na mobilidade e toxidade de metais e outras substâncias liberadas pelo homem. Neste trabalho, substâncias húmicas aquáticas (SHA) foram extraídas de corpos hídricos da porção leste do Quadrilátero Ferrífero/MG (QF), onde também foram determinadas as concentrações de elementos metálicos e suas relações com as condições litológicas regionais. Amostras de água foram coletadas durante a estação seca e a estação chuvosa. Os parâmetros físico-químicos T, pH, ORP, condutividade, resistividade e turbidez foram determinados in situ. Já os parâmetros alcalinidade, sulfatos, cloretos, COD, elementos metálicos maiores Al, Na, Ca, Fe, K, Mg, Mn e Ti; e traço As, Ba, Be, Cd, Co, Cr, Cu, Li, Mo, Ni, P, Pb, S, Sc, Sr, V, Y e Zn foram determinados em laboratório. A média dos valores de COD nas águas coletadas ficou em 2,19 mg/L, sendo que as maiores concentrações foram detectadas nas serras do Caraça e do Itatiaia. As SH foram extraídas das amostras por meio de resinas DAX-8 (que têm a capacidade de adsorver o material húmico em pH ácido) e por evaporação rotativa (que consiste em baixar o ponto de ebulição da água para concentrar o COD). Nos extratos também foram determinados elementos metálicos maiores e traço, além do COD. A fim de entender as dependências entre os compostos húmicos e íons metálicos na área de estudo, todos os dados obtidos foram analisados por meio de uma técnica exploratória multivariada (rede neural de Kohonen). Observou-se que as SH se apresentaram relacionadas com os metais Al, K, Ba, Ca, Cu, Fe, Mn, Sr, Ti e Zn considerando as amostras coletadas. Além disso, foi detectada influência litológica na composição das águas. Constatou-se que o solo pode influenciar na mobilidade de materiais orgânicos, visto que as areias oriundas do intemperismo do quartzito tem menor capacidade de retenção de matéria orgânica. Assim, regiões como as serras do Caraça e do Itatiaia possuíram maior concentração de SH se comparadas com áreas de diferentes litotipos. O baixo teor de argilas nas cabeceiras dos rios dessas áreas facilitaria a liberação de compostos húmicos para as águas. Esse processo é mais ativo em épocas chuvosas, fazendo com que as maiores concentrações de COD fossem observadas no período úmido ou na transição do período chuvoso para o seco. Nos demais pontos analisados com litologias diferentes a maior concentração de carbono se deu na época de transição da estação seca para a estação chuvosa e a menor se deu na estação chuvosa. Considerando os diferentes métodos de isolamento de material húmico, a evaporação rotativa mostrou-se promissora ao poder extrair SH com a possibilidade de minimização de alterações estruturais. Entretanto, ela é uma técnica demorada, sendo inconveniente para grandes volumes. As amostras extraídas com resinas DAX-8 apresentaram uma retenção média de 46,80% de COD nas colunas cromatográficas.Humic substances (HS) are compounds that make up about a half of the dissolved organic carbon (DOC) in natural waters. They are originated from the degradation of organic matter and have high molecular weight and complex chemical structure. They also have great environmental importance for interfering in the mobility and toxicity of metals and other substances released by man. In this work, aquatic humic substances (AHS) were extracted from water bodies of the eastern portion of Quadrilátero Ferrífero (MG/Brazil). Furthermore, concentrations of metallic elements and their relationship with the regional lithological conditions were determined. Water samples were collected during the dry and rainy season. The physico-chemical parameters T, pH, ORP, conductivity, resistivity and turbidity were determined in situ; alkalinity, sulphates, chlorides, DOC, major metal elements Al, Na, Ca, Fe, K, Mg, Mn and Ti; and trace As, Ba, Be, Cd, Co, Cr, Cu, Li, Mo, Ni, P, Pb, S, Sc, Sr, V, Y and Zn were determined in laboratory. The average of the values of DOC in the samples was 2.19 mg/L and the highest values were detected in the mountains of Caraça and Itatiaia. The HS were extracted from samples through DAX-8 resins (that have the ability to adsorb humic material at acidic pH) and by rotary evaporation (that consist in decrease the boiling point of water in order to concentrate the DOC). The DOC and the major and trace metals were also determined in the extracts. In order to understand the dependencies between the humic compounds and metal ions in water bodies in the study area, the data were analysed by an exploratory multivariate analysis (Kohonen neural network). It was observed a relationship between HS and the metals Al, K, Ba, Ca, Cu, Fe, Mn, Sr, Ti and Zn considering the samples collected. It was detected a lithology influence in the composition of waters. It was found that the soil can influence the mobility of organic materials, whereas the sand coming from the weathering of the quartzite has lower ability to retain organic matter. Hence, regions like the mountains of Itatiaia and Caraça contained higher concentrations of HS compared with areas of different types of rocks. The lower presence of clays in the headwaters of these areas would force a greater release of humic compounds to water. This process is most active during rainy season. Consequently the highest levels of DOC were observed during the wet season or in the transition from rainy to dry season. In other points analysed with different lithology the highest concentration of carbon occurred in the period of transition from dry to rainy season and the lowest occurred in the rainy season. Considering the different methods of isolating humic material, the evaporation under vacuum proved to be promising to extracted HS with the possibility of minimizing structural changes. However, it is a time consuming technique and it is inconvenient for large volumes. The samples extracted by DAX-8 resin had an average retention of 46.80% of DOC in the chromatographic columns

Characterization and treatability of wastewater from a dying hood of a furniture industry.

O objetivo deste trabalho foi caracterizar os efluentes gerados em cabines de pintura de uma indústria moveleira e avaliar a eficiência de sistemas biológicos (anaeróbio e aeróbio) para o seu tratamento. O efluente industrial apresentou elevado teor de matéria orgânica (DQO total de 634 a 2.790 mg.L-1; DBO5 total de 360 a 972 mg.L-1) e baixos teores de macronutrientes (NTK de 1,9 mg.L-1 e Ptotal de 0,5 mg.L-) e metais tóxicos. Os ensaios de tratabilidade em reator UASB (~25°C e tempo de detenção hidráulica − TDH = 10 horas), indicaram uma eficiência máxima de remoção de matéria orgânica de 90% na composição volumétrica 70:30 (efluente industrial:esgoto sanitário). A alimentação do reator UASB só com efluente industrial resultou em acúmulo de ácidos graxos voláteis e inibição microbiana, mas o uso de pós-tratamento aeróbio (TDH = 96h) garantiu elevada eficiência global (~88%) de remoção de matéria orgânica.The main objective of this work was to characterize the wastewater from the dying hood of a woven furniture industry, and to assess the efficiency of biological processes (anaerobic and aerobic) for its treatment. The physical-chemical characterization of the industrial wastewater showed a high organic matter content (total COD from 634 to 2,790 mg.L-1; total BOD5 from 360 to 972 mg.L-1), low content of macronutrients (NTK of 1.9 mg.L-1 and P of 0.5 mg.L-1) and toxic metals. The anaerobic degradation tests in a bench-scale UASB reactor (25°C and hydraulic retention time − HRT = 10 hours) showed that a maximum removal efficiency of 90% was obtained when the reactor was fed with 30% raw sewage and 70% industrial wastewater. The feeding of UASB reactor with only industrial wastewater resulted in volatile fatty acids accumulation and microbial inhibition; however, the use of aerobic post-treatment (HRT = 96 hours) granted a high (~88%) organic matter removal efficiency

Effects of Fe(III) and quality of humic substances on As(V) distribution in freshwater : use of ultrafiltration and Kohonen neural network.

Humic substances (HS) are ubiquitous organic compounds able to affect mobility and availability of arsenic (As) in aquatic systems. Although it is known that associations between HS and As occur mainly via iron (Fe)-cationic bridges, the behaviour and distribution of this metalloid in HS- and Fe-rich environments is still not fully understood. In this paper, the quality of HS from different rivers in Brazil and Germany and its influence on the behaviour of As(V) under different Fe(III) concentrations were investigated. HS were extracted from four different rivers (Cascatinha, Holtemme, Selke and Warme Bode), characterised and fractionated into different molecular weight sizes (10, 5 and 1 kDa). Complexation tests were performed using an ultrafiltration system and 1 kDa membranes. All data was analysed using the Kohonen neural network (SOM e Self organising maps). All samples, except Selke, exhibited similar results of free As (<1 kDa). The results suggested that associations between HS, Fe and As were dependent on nitrogen (N)earomatic carbon (C), amount of sulphur (S) and the molecular size of the HS. Although all HS appeared to be similar after looking at most variables analysed, the SOM could discriminate them into three different groups. Characterisation of the HS indicated that they had terrestrial material (from C3 plants) as precursor material. Most of the As and Fe was distributed in the fractions of higher (>10 kDa) and lower (<1 kDa) size. HS quality is an important factor to take into account when studying the behaviour of As in HS-rich environments

Distribution and bioavailability of arsenic in natural waters of a mining area studied by ultrafiltration and diffusive gradients in thin films.

The distribution of metals and metalloids among particulate, dissolved, colloidal, free, and labile forms in natural waters is of great environmental concern since it determines their transportation behaviour and bioavailability. Organic matter can have an important role for this distribution process, since it is an important complexing agent and ubiquitous in the aquatic environment. We studied the distribution, mobility and bioavailability of Al, As and Fe in natural waters of a mining area (Quadril atero Ferr?fero, Brazil) and the influence of organic matter in these processes. Water samples were taken from 12 points during the dry and rainy seasons, filtrated at 0.45 mm and ultrafiltrated (<1 kDa) to separate the particulate, colloidal and free fractions. Diffusive gradients in thin films (DGT) were deployed at 5 sampling points to study the labile part of the elements. Total and dissolved organic carbon and the physicochemical parameters were measured along with the sampling. The results of ultrafiltration (UF) and DGT were compared. The relationship among the variables was studied through multivariate analysis (Kohonen neural network), which showed that the seasonality did not impact most of the samples. Fe and Al occurred mainly in the particulate fraction whereas As appeared more in the free fraction. Most of the dissolved Fe and Al were inert (colloidal form) while As was more labile and bioavailable. The results showed that sampling points with a higher quantity of complexed Fe (colloidal fraction) showed less labile As, which may indicate formation of ternary complexes among organic matter, As and Fe