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The evaluation of the photocatalytic properties of electrospun TiO2 nanofibres (TiO2-NFs) synthesised in the same experimental conditions using two distinct precursors, tetraisopropyl orthotitanate (TTIP) and tetrabutyl orthotitanate (TNBT), with morphology and crystalline structure controlled by annealing at 460 °C for 3 h is presented. The presence of circular-shaped TiO2-NFs was corroborated by scanning electron microscopy (SEM). By using X-ray photoelectron spectroscopy (XPS), the chemical binding energies and their interactions of the TiO2 with the different incorporated impurities were determined; the most intense photoelectronic transitions of Ti 2p3/2 (458.39 eV), O 1 s (529.65 eV) and C 1 s (284.51 eV) were detected for TTIP and slightly blue-shifted for TNBT. By using energy-dispersive X-ray spectroscopy (EDS), the chemical element percentages in TiO2 were determined. Using X-ray diffraction, it was found that the annealed electrospun TiO2-NFs presented the anatase crystalline phase and confirmed by Raman scattering. Bandgap energies were determined by diffuse reflectance spectroscopy at room temperature. The photocatalytic degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide under exposure to ultraviolet light was studied using the TiO2-NFs obtained with the two molecular precursors. The results showed that the catalyst, prepared with the TTIP precursor, turned out to be the one that presented the highest photocatalytic activity with a half-life time (t1/2) of 28 min and a degradation percentage of 93%. The total organic carbon (TOC) in the solutions resulting from the 2,4-D degradation by the TiO2-NFs was measured, which showed a TOC removal of 50.67% for the TTIP sample and 36.14% for the TNBT sample. Finally, by using FTIR spectroscopy, the final chemical compounds of the degradation were identified as H2O and CO2.

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This work describes characterization and leaching studies of pre-salt drill cuttings from offshore oil and gas exploration in ultradeep waters. The metals Fe, Al, and Ba were present in the highest concentrations in drill cuttings (30000 mg kg-1, 32600 mg kg-1, and 33000 mg kg-1 respectively). The most significant contents of Ba, Al, Fe, Cu, Pb, Mn, Si, and Zn were found in cuttings containing non-aqueous fluids (NADF), but the highest concentrations of Ni and Cr were found in samples containing aqueous fluids (WBDF). The content of total petroleum hydrocarbons (TPHs) in the samples with WBDF fluids ranged from < 5.58 to 15.76 mg Kg-1 while the TPH content of the samples with NADF ranged from 28.46 to 47.16 mg Kg-1. Data on the content of unresolved complex mixtures (UCMs) and sheen tests indicated probable contamination of some cutting samples with oil. Most samples showed some degree of contamination by polycyclic aromatic hydrocarbons (PAHs). The metals present in the highest concentrations in saline and aqueous leachates were Si and Ba. The metals Cd, Cu, Ni, and Zn were present in varied concentrations in the saline leachates, and the metals Si, Ba, Cu, and Zn were found in the aqueous leachates.

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This research has been focused on the removal of two anti-inflammatory drugs, diclofenac (DCF) and ibuprofen (IBU), by a continuous catalytic wet peroxide oxidation (CWPO) process using a lab-synthesized nanomagnetic catalyst (Fe3O4/MWCNTs). The central composite rotatable design (CCRD) method was used to study the effect of DCF and IBU concentration (expressed as theoretical oxygen demand (ThOD) between 0 and 52.5 mg L-1) and of the feed stream pH (from 3 to 7) on the removal of total organic carbon (TOC) and the concentration of aromatic compounds (Arm) and total phenolic compounds (TP) by CWPO. It could be observed that DCF was preferably removed from the DCF-IBU aqueous mixture at pH values ranging from 3 to 5. In addition, feed stream pH had a significant effect on the pollutants removal, as well as on TOC, TP and aromatic compounds removal, observing an increasing in the pollutants degradation when feed stream pH decreased from 7 to 3. Quadratic models predicted for response variable, such as TOC, TP and aromatic compounds removal, and their maximum model-predicted removal values were of 90.0, 80.2 and 90.0%, respectively. Finally, as a proof of concept, three environmentally-relevant aqueous matrices, spiked with DCF-IBU mixture, were treated. In this case, relatively high TOC degradation values were found after 20 h reaction time (ca. 57.7, 73.9 and 54.5% in surface water, WWTP effluent and hospital wastewater, respectively). This work deals the first study about DCF-IBU removal in aqueous solution by CWPO, as well as a continuous study using real wastewater that allow to extend the experimental results to a real scenario.

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In this work, the suitability of the UV/H2O2 process for commercial herbicides mixture degradation was studied. Glyphosate, the herbicide most widely used in the world, was mixed with other herbicides that have residual activity as 2,4-D and atrazine. Modeling of the process response related to specific operating conditions like initial pH and initial H2O2 to total organic carbon molar ratio was assessed by the response surface methodology (RSM). Results have shown that second-order polynomial regression model could well describe and predict the system behavior within the tested experimental region. It also correctly explained the variability in the experimental data. Experimental values were in good agreement with the modeled ones confirming the significance of the model and highlighting the success of RSM for UV/H2O2 process modeling. Phytotoxicity evolution throughout the photolytic degradation process was checked through germination tests indicating that the phytotoxicity of the herbicides mixture was significantly reduced after the treatment. The end point for the treatment at the operating conditions for maximum TOC conversion was also identified.

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The rapid, simple and accurate determination of soil quality indicators is fundamental for improvements in precision agriculture and consequently in production efficiency. The objectives of this study were to determine the organic matter (OM) and total organic carbon (TOC) concentrations in agricultural soil and to discriminate soil provenance by energy-dispersive X-ray fluorescence (EDXRF) combined with principal component analysis and partial least square regression. The conventional methods used for the determination of OM and TOC concentrations are the gravimetric and Walkley-Black methods, respectively. Figures of merit such as sensitivity, detection and quantification limits, accuracy and precision were evaluated. Samples were differentiated by their provenance, and the quality of the prediction model shows that EDXRF combined with multivariate analysis is a promising methodology to fulfil the lack of rapid and accurate analytical methods for the assessment of OM and TOC concentrations in agricultural soils.

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This work deals with the degradation of the azo-dye Orange II (OII) by a heterogeneous process with dark Fenton. Natural and purified ilmenites from Colombian soil were used as catalysts. The catalysts have different physicochemical properties and are basically composed of TiO2 and Fe2O3. Ilmenites (FeTiO3), raw materials highly available at low cost, were studied by means of conventional metallography (polished grain mounts), as well as BET, XRD, and XRF in order to determine their possible source area and the factors that influence their use as a catalyst for OII degradation. The pH, the ilmenite amount, the initial CH2O2, and the temperature of the reaction system were studied. Complete degradation of dye was observed within 7 h, while 90 % of OII was removed in 7 h using Cumaribo Ilmenite. Graphical Abstract ᅟ.

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This study investigated long-term (1980-2009) yields and variability of total organic carbon (TOC) from four major coastal rivers in Louisiana entering the Northern Gulf of Mexico where a large-area summer hypoxic zone has been occurring since the middle 1980s. Two of these rivers drain agriculture-intensive (>40%) watersheds, while the other two rivers drain forest-pasture dominated (>50%) watersheds. The study found that these rivers discharged a total of 13.0×10(4)t TOC annually, fluctuating from 5.9×10(4) to 22.8×10(4)t. Seasonally, the rivers showed high TOC yield during the winter and early spring months, corresponding to the seasonal trend of river discharge. While river hydrology controlled TOC yields, land use has played an important role in fluxes, seasonal variations, and characteristics of TOC. The findings fill in a critical information gap of quantity and quality of organic carbon transport from coastal watersheds to one of the world's largest summer hypoxic zones.

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The deposition of organic residues through mechanical harvesting of cane sugar is a growing practice in sugarcane production system. The maintenance of these residues on the soil surface depends mainly on environmental conditions. Nitrogen fertilization on dry residues tend to retard decomposition of these, providing benefits such as increased SOM. Thus, the object of this research was to evaluate the effect of different doses of nitrogen on sugar cane crop residues, as its decomposition and contribution to carbon sequestration in soil. The experiment was conducted in Dourados-MS and consisted of a randomized complete block design. Dried residues were placed in litter bags and the treatments were arranged in a split plot, being the four nitrogen rates (0, 50, 100 and 150 kg ha-1 N) the plots, and the seven sampling times (0, 30, 60, 90, 120, 150 and 180) the spit plots. Decomposition rates of residues, total organic carbon and labile carbon on soil were analysed. The application of increasing N doses resulted in an increase in their decomposition rates. Despite this, note also the mineral N application as a strategy to get higher levels of labile carbon in soil.(AU)

A deposição de resíduos orgânicos através da colheita mecanizada da cana-de-açúcar é uma prática crescente no sistema de produção canavieiro. A manutenção desses resíduos na superfície do solo depende principalmente das condições ambientais. A adubação nitrogenada sobre os resíduos secos tendem a retardar a decomposição desses, proporcionando benefícios como o aumento da MOS. Diante disto, o objetivo da pesquisa foi avaliar o efeito da aplicação de diferentes doses de nitrogênio sobre os resíduos culturais de cana-de-açúcar, quanto a sua decomposição e contribuição para o sequestro de carbono no solo. O experimento foi realizado em Dourados-MS e consistiu de um delineamento experimental em blocos casualizados. Os resíduos secos foram colocados em litter bags e os tratamentos foram arranjados em parcelas subdivididas, sendo as quatro doses de nitrogênio (0,50, 100 e 150 kg ha-1 N) as parcelas, e as sete épocas de coleta (0, 30, 60, 90, 120, 150 e 180 dias) as subparcelas. Foram analisados a taxa de decomposição dos resíduos, carbono orgânico total e carbono lábil no solo. A aplicação de doses crescente de N proporcionou aumento nas suas taxas de decomposição. Apesar disso, destaca-se a aplicação de N-mineral como uma estratégia de manejo para obter maiores teores de carbono lábil no solo.(AU)

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The deposition of organic residues through mechanical harvesting of cane sugar is a growing practice in sugarcane production system. The maintenance of these residues on the soil surface depends mainly on environmental conditions. Nitrogen fertilization on dry residues tend to retard decomposition of these, providing benefits such as increased SOM. Thus, the object of this research was to evaluate the effect of different doses of nitrogen on sugar cane crop residues, as its decomposition and contribution to carbon sequestration in soil. The experiment was conducted in Dourados-MS and consisted of a randomized complete block design. Dried residues were placed in litter bags and the treatments were arranged in a split plot, being the four nitrogen rates (0, 50, 100 and 150 kg ha-1 N) the plots, and the seven sampling times (0, 30, 60, 90, 120, 150 and 180) the spit plots. Decomposition rates of residues, total organic carbon and labile carbon on soil were analysed. The application of increasing N doses resulted in an increase in their decomposition rates. Despite this, note also the mineral N application as a strategy to get higher levels of labile carbon in soil.

A deposição de resíduos orgânicos através da colheita mecanizada da cana-de-açúcar é uma prática crescente no sistema de produção canavieiro. A manutenção desses resíduos na superfície do solo depende principalmente das condições ambientais. A adubação nitrogenada sobre os resíduos secos tendem a retardar a decomposição desses, proporcionando benefícios como o aumento da MOS. Diante disto, o objetivo da pesquisa foi avaliar o efeito da aplicação de diferentes doses de nitrogênio sobre os resíduos culturais de cana-de-açúcar, quanto a sua decomposição e contribuição para o sequestro de carbono no solo. O experimento foi realizado em Dourados-MS e consistiu de um delineamento experimental em blocos casualizados. Os resíduos secos foram colocados em litter bags e os tratamentos foram arranjados em parcelas subdivididas, sendo as quatro doses de nitrogênio (0,50, 100 e 150 kg ha-1 N) as parcelas, e as sete épocas de coleta (0, 30, 60, 90, 120, 150 e 180 dias) as subparcelas. Foram analisados a taxa de decomposição dos resíduos, carbono orgânico total e carbono lábil no solo. A aplicação de doses crescente de N proporcionou aumento nas suas taxas de decomposição. Apesar disso, destaca-se a aplicação de N-mineral como uma estratégia de manejo para obter maiores teores de carbono lábil no solo.

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The no-tillage system (NTS) and more recently, the crop-livestock integration (CLI) are very used for grain production in the Cerrado biome. This, the soil organic matter (SOM) is one of the main components responsible for maintaining the quality of tropical soils. This study aimed to quantify the levels of total organic carbon (TOC), total nitrogen (total N), water soluble carbon (WSC) and carbon of humic fractions in areas with different land use systems in the Cerrado of Goias. The farming systems were used: CLI (brachiaria + corn/beans/cotton/soybean) and NTS (sunflower/millet/soybean/corn) andas a reference, area native Cerrado vegetation (Cerradão). We collected soil samples at 0-10, 10- 20, 20-30 and 30-40 cm. The contents of TOC, total N, WSC, humin fraction carbon (C-HUM), humic acid fraction (C-HAF) and fulvic acid fraction (C-FAF). The area of Cerradão had the highest TOC, total N, C-HUM and C-FAH in the surface layer (0-10 cm). The levels of WSC and humic fractions of SOM showed significant differences between the systems of land use and sampling depths. The highest levels of C-HAF were found in the area of CLI, at 0-10 and 20-30 cm. The CLI systems and NTS did not differ for the TOC and total N except for N in layer 20-30 cm. The system CLI favors the formation of C-HUM compared to the NTS. The CLI system leads to lower levels of WSC and higher C-FAF compared with

O sistema plantio direto (SPD) e mais recentemente, a integração lavoura-pecuária (ILP) são muito utilizados para produção de grãos no bioma Cerrado. Neste, a matéria orgânica do solo (MOS) é um dos principais componentes responsáveis pela manutenção da qualidade dos solos tropicais. Este trabalho objetivou quantificar os teores de carbono orgânico total (COT), nitrogênio total (N-total), carbono solúvel em água (CSA) e carbono das frações húmicas em áreas com diferentes sistemas de uso do solo no Cerrado goiano. Os sistemas agrícolas utilizados foram: ILP (milho+braquiária/feijão/algodão/ soja) e SPD (girassol/milheto/soja/milho) e como referência, área de vegetação nativa de Cerrado (Cerradão). Foram coletadas amostras de terra nas profundidades de 0-10; 10-20; 20-30 e 30-40 cm. Foram determinados os teores de COT, N-total, CSA, carbono da fração humina (C-HUM), fração ácido húmico (C-FAH) e fração ácido fúlvico (C-FAF). A área de Cerradão apresentou os maiores teores de COT, N-total, C-HUM e C-FAH na camada superficial (0-10 cm). Os teores de CSA e das frações húmicas da MOS apresentaram diferenças significativas entre os sistemas de uso do solo e as profundidades de amostragem. Os maiores teores de C-FAH foram encontrados na área de ILP, nas camadas de 0-10 e 20-30 cm. Os sistemas de ILP e SPD não apresentaram diferenças para o COT e N-Total, exceto para N na camada de 20-3

RESUMO

The no-tillage system (NTS) and more recently, the crop-livestock integration (CLI) are very used for grain production in the Cerrado biome. This, the soil organic matter (SOM) is one of the main components responsible for maintaining the quality of tropical soils. This study aimed to quantify the levels of total organic carbon (TOC), total nitrogen (total N), water soluble carbon (WSC) and carbon of humic fractions in areas with different land use systems in the Cerrado of Goias. The farming systems were used: CLI (brachiaria + corn/beans/cotton/soybean) and NTS (sunflower/millet/soybean/corn) andas a reference, area native Cerrado vegetation (Cerradão). We collected soil samples at 0-10, 10- 20, 20-30 and 30-40 cm. The contents of TOC, total N, WSC, humin fraction carbon (C-HUM), humic acid fraction (C-HAF) and fulvic acid fraction (C-FAF). The area of Cerradão had the highest TOC, total N, C-HUM and C-FAH in the surface layer (0-10 cm). The levels of WSC and humic fractions of SOM showed significant differences between the systems of land use and sampling depths. The highest levels of C-HAF were found in the area of CLI, at 0-10 and 20-30 cm. The CLI systems and NTS did not differ for the TOC and total N except for N in layer 20-30 cm. The system CLI favors the formation of C-HUM compared to the NTS. The CLI system leads to lower levels of WSC and higher C-FAF compared with

O sistema plantio direto (SPD) e mais recentemente, a integração lavoura-pecuária (ILP) são muito utilizados para produção de grãos no bioma Cerrado. Neste, a matéria orgânica do solo (MOS) é um dos principais componentes responsáveis pela manutenção da qualidade dos solos tropicais. Este trabalho objetivou quantificar os teores de carbono orgânico total (COT), nitrogênio total (N-total), carbono solúvel em água (CSA) e carbono das frações húmicas em áreas com diferentes sistemas de uso do solo no Cerrado goiano. Os sistemas agrícolas utilizados foram: ILP (milho+braquiária/feijão/algodão/ soja) e SPD (girassol/milheto/soja/milho) e como referência, área de vegetação nativa de Cerrado (Cerradão). Foram coletadas amostras de terra nas profundidades de 0-10; 10-20; 20-30 e 30-40 cm. Foram determinados os teores de COT, N-total, CSA, carbono da fração humina (C-HUM), fração ácido húmico (C-FAH) e fração ácido fúlvico (C-FAF). A área de Cerradão apresentou os maiores teores de COT, N-total, C-HUM e C-FAH na camada superficial (0-10 cm). Os teores de CSA e das frações húmicas da MOS apresentaram diferenças significativas entre os sistemas de uso do solo e as profundidades de amostragem. Os maiores teores de C-FAH foram encontrados na área de ILP, nas camadas de 0-10 e 20-30 cm. Os sistemas de ILP e SPD não apresentaram diferenças para o COT e N-Total, exceto para N na camada de 20-3

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Identificar os mecanismos de estabilização da matéria orgânica (MO) que atuam com maior eficiência em solos hidromórficos é essencial para compreender e avaliar a dinâmica da MO nestes agroecossistemas. O objetivo deste estudo foi avaliar a agregação, o teor de carbono orgânico total (COT) do solo e de carbono nas frações físicas da MO, em Planossolo Háplico Eutrófico solódico, sob diferentes sistemas de manejo; além de caracterizá-la por Infravermelho com Transformada de Fourier (FTIR). O presente estudo foi realizado na Estação Experimental de Terras Baixas da Embrapa Clima Temperado, Capão do Leão, RS. A área experimental foi implantada em 2003. Em novembro de 2007, foram amostradas duas camadas (0,000 - 0,025 m e de 0,025 - 0,075 m) de solo em áreas sob preparo convencional (PC), plantio direto (PD) e campo nativo (CN). A qualidade estrutural na camada superficial do solo sob PC e PD foi afetada nas classes de agregados de 4,76 a 0,50 mm. O PC e o PD apresentaram reduções nos teores de COT do solo, carbono da fração grosseira, fração leve livre (FLL) e fração leve oclusa (FLO). Em curto período de tempo (quatro anos), os sistemas de manejo não influenciaram a fração pesada (FP). As proporções das frações físicas da MO em relação ao COT aumentaram na ordem FLL

To identify the mechanisms of stabilization of organic matter (OM) that act more efficiently in hydromorphic soils is essential to understand and to assess OM dynamics in these ecosystems. The aim of this study was to evaluate the aggregation, the total organic carbon (TOC) in the soil and in the physical fractions of OM, to characterize them by Fourier Transform Infrared (FTIR), and to identify the mechanisms of protection in an Albaqualf soil under different management systems. This study was conducted at the Lowlands Experimental Station of Embrapa Temperate Climate, in Capão of Leão municipality, Rio Grande do Sul State. The experimental area was established in 2003. In November 2007, soil was sampled in two layers (0.000 - 0.025 m and 0.025 - 0.075 m depth) under conventional tillage (CT), no tillage (NT) and native pasture (CN) areas. The structural soil quality under CT and NT, in the surface layer, was affected in the aggregate of diameter classes from 4.76 to 0.50 mm. The CT and the NT showed reductions in levels of soil TOC, C from the coarse fraction, free light fraction (FLF) and occluded light fraction (OLF). In a short period of time (four years), the management systems did not affect the heavy fraction (HF). The proportions of physical fractions of OM in relation to the COT increased in the order FLL

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A dinâmica da matéria orgânica do solo (MOS) pode ser melhor compreendida após identificadas suas frações lábeis (> 53 µm) e estáveis (< 53 µm). Diante da importância crescente do uso de técnicas de fracionamento físico da MOS, torna-se necessário avaliar se a recuperação de carbono nessas frações é influenciada pelos métodos utilizados para sua determinação. O objetivo deste trabalho foi avaliar os teores de carbono, por três métodos, em diferentes frações da matéria orgânica, num Latossolo Vermelho-Amarelo distrófico sob consórcio milho-forrageiras e em sistema solteiro. Foram determinados os teores de carbono das frações: (i) particulada da matéria orgânica (COP) e naquela (ii) associada aos minerais da matéria orgânica (COM). Determinou-se ainda, o teor de (iii) carbono orgânico total do solo (COT) na matéria orgânica não fracionada. Três métodos de determinação do carbono orgânico do solo foram utilizados: (i) Walkley & Black modificado, (ii) Mebius modificado, e (iii) combustão via seca, em analisador elementar (CHN). Foram utilizadas amostras de solos de três sistemas de manejo dispostos em delineamento em blocos casualizados, com três repetições para determinação do carbono orgânico do solo: (i) milho solteiro; (ii) milho consorciado com capim colonião (Panicum maximum cv. Aruana); e (iii) milho consorciado com braquiária (Brachiaria humidicola). As amostras de solo foram coletadas na profundidade de 0 ­ 5 cm. O método Walkley & Black apresentou menores valores de COT em relação ao CHN nos sistemas de manejo milho/braquiária e milho solteiro, e mostrou valores de COP semelhantes àqueles obtidos pelo CHN nos sistemas de manejo milho solteiro e milho/braquiária. Valores de COT, COP e COM obtidos pela metodologia de Mebius modificado foram semelhantes àqueles obtidos pelo analisador elementar, para todos os sitemas de manejo. O COP, quando avaliado pelas metodologias de Mebius e CHN, mostrou-se significativamente mais sensível às alterações de manejo em relação ao COT e COM.

Soil organic matter alterations can be better understood when it is fractionated for the identification of its labile (> 53 µm) and stable (< 53 µm) fractions. Because of the increasing and important use of soil organic matter fractionation techniques, it becomes necessary to evaluate if the carbon recovery in these fractions is influenced by methods used for its determination. The aim of this work was to evaluate the content of organic carbon in soil organic matter fractions, by three different methods, under maize-grass intercropping and sole maize in a dystrophic Red-Yellow Latosol (Oxisol). The following carbon contents were determined from the fractions: (i) of the particulate soil organic matter (POM) and from that (ii) of mineral-associated soil organic matter (MOC). The content of total organic carbon (TOC) was also determined in the non-fractionated soil organic matter. Three methods for the determination of soil organic carbon were used: (i) Walkley & Black modified, (ii) Mebius modified, and (iii) dry combustion in a CHN elemental analyzer. The experimental design was a randomized block design with three replications. Soil samples were collected from three management systems: (i) sole corn; (ii) maize-Panicum maximum intercropping; and (iii) maize- Brachiaria humidicola intercropping. Soil samples were collected from the depth of 0 ­ 5 cm. Lower TOC were found in the Walkley & Black method in relation to the CHN elemental analyzer, under the management systems sole maize and maize-Panicum maximum intercropping. However, the Walkley & Black method showed similar POM in relation to CHN analyzer method, under the management systems sole maize and maize-Brachiaria humidicola intercropping. TOC, POM and MOC obtained from the Mebius modified method were similar to those obtained from the elemental analyzer, under the three management systems. The POM when evaluated by the Mebius and CHN methods, showed to be more sensible to soil management alterations.

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La técnica de análisis por combustión y detección por infrarrojo no dispersivo (IRND) fue validada para la determinación de materia orgánica en agua, cuantificada como carbono orgánico total (COT). Previamente se optimizó la eliminación del carbono inorgánico (CI) de la muestra con un tiempo óptimo de 1,5 min y una relación ácido de 5%. Se estableció un rango dinámico lineal (RDL) entre 3 y 20 mg/L de COT, en el cual la recta de regresión cumplió con los parámetros que acreditaron su linealidad según el análisis por el método de los mínimos cuadrados, mostrando un coeficiente de correlación de 0,9994. La sensibilidad expresada por la pendiente de la recta de regresión indicó una variación de aproximadamente 5 unidades en la respuesta del detector por cada mg/L de COT. Los límites de detección y cuantificación obtenidos a partir de la recta de regresión fueron 0,517 y 1,722 mg/L de COT, respectivamente. La precisión de la técnica, teniendo como meta un 5% en coeficiente de variación (CV), fue mejor en el agua potable y en concentraciones cercanas a ésta (aprox. 7 mg/L de COT), mientras que las mayores desviaciones se presentaron en concentraciones cercanas a los límites inferior y superior del RDL. Las recuperaciones de concentraciones conocidas sobre muestras reales adicionadas fueron del 85% con baja adición y del 83% con adición alta, valores que sugieren una reevaluación del desempeño de la técnica con respecto a su exactitud, no obstante se alcanzó la meta de recuperación comprendida entre el 70 y el 130%. La técnica así establecida es por tanto apta para el análisis de aguas crudas, potables y residuales y es viable su utilización en el seguimiento a procesos de oxidación avanzada aplicados en el tratamiento de agua para consumo humano.

The technique of combustion analysis and detection by non-dispersive infrared (NDIR) was validated for the determination of organic matter in water, quantified as total organic carbon (TOC). Previously optimized the elimination of inorganic carbon (IC) of the sample with an optimum time sparge of 1.5 min and an acid ratio of 5%. It established a linear dynamic range (LDR) between 3 and 20 mg/L of TOC, in which the regression line that met the parameters credited its linearity as analyzed by the method of least squares, showing a correlation coefficient of 0,9994. The sensitivity expressed by the slope of the regression line indicated a variation of about 5 units in the detector response for each mg/L of TOC. The detection and quantification limits obtained from the regression line were 0.517 and 1.722 mg/L of TOC, respectively. The precision of the technique, aiming at 5% coefficient of variation (CV) was better in the drinking water at concentrations close to it (about 7 mg/L of TOC), whereas larger deviations were presented at concentrations near the lower and upper limits of LDR. The recoveries of known concentrations of actual samples of 85% additions were low addition and 83% with high added values that suggest a reevaluation of the performance of the technique with respect to its accuracy, however the goal was reached between recovery 70 to 130%. The technique is well established thereby capable of analyzing raw water, drinking and waste and feasible to use in monitoring advanced oxidation processes applied in the treatment of drinking water.

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