A High Andean Hydrocolloid Extracted by Microatomization: Preliminary Optimization in Aqueous Stability.

Aqueous suspensions rely on electrostatic interactions among suspended solids, posing a significant challenge to maintaining stability during storage, particularly in the food and pharmaceutical industries, where synthetic stabilizers are commonly employed. However, there is a growing interest in exploring new materials derived from natural and environmentally friendly sources. This study aimed to optimize the stability parameters of a novel Altoandino Nostoc Sphaericum hydrocolloid (NSH) extracted via micro atomization. Suspensions were prepared by varying the pH, gelatinization temperature and NSH dosage using a 23 factorial arrangement, resulting in eight treatments stored under non-controlled conditions for 20 days. Stability was assessed through turbidity, sedimentation (as sediment transmittance), ζ potential, particle size, color and UV-Vis scanning. Optimization of parameters was conducted using empirical equations, with evaluation based on the correlation coefficient (R2), average relative error (ARE) and X2. The suspensions exhibited high stability throughout the storage period, with optimized control parameters identified at a pH of 4.5, gelatinization temperature of 84.55 °C and NSH dosage of 0.08 g/L. Simulated values included turbidity (99.00%), sedimentation (72.34%), ζ potential (-25.64 mV), particle size (300.00 nm) and color index (-2.00), with simulated results aligning with practical application. These findings suggest the potential use of NSH as a substitute for commercial hydrocolloids, albeit with consideration for color limitations that require further investigation.

Examining the source and composition of organic matter through saturated hydrocarbons, δ13C, and δ15N in a subtropical water reservoir.

The sources of organic matter in the sediments of the Passaúna reservoir, an important water supply for the local population, were thoroughly investigated. The objective was to identify the origins of organic matter through the analysis of saturated hydrocarbons, elemental composition (total organic carbon and total nitrogen), and the content of δ13C and δ15N isotopes. This comprehensive approach allowed us to trace the sources of organic matter and discerns indicating heightened primary productivity within the reservoir. To achieve this, two sediment cores spanning a 140-year interval (1880-2020) were retrieved from the reservoir. Core 2 accumulates the majority of sediments, particularly near the dam area. In these parts, sediment deposits can reach up to 1 m above the pre-impoundment soil. Sediments near the area where core 1 was collected contain more sand, resulting in lower thickness compared to core 2. Sediment core 1 primarily reflects terrestrial sources of organic matter, as supported by stable isotope values of δ13C and δ15N. The δ13C values ranged from -23.0 ‰ to -25.7 ‰ in core 1 and from -28.4 ‰ to -29.2 ‰ in core 2. Meanwhile, the δ15N values ranged from 6.6 ‰ to 10.8 ‰ in core 1 and from 3.8 ‰ to 7.6 ‰ in core 2. The distribution of saturated hydrocarbons revealed that organic matter originates from both allochthonous and autochthonous sources. Periods of intense primary productivity were indicated by the presence of n-C16, n-C17, n-C18, and n-C19 alkanes. Additionally, we observed periods characterized by high primary productivity, indicative of elevated nutrient input likely resulting from increased urbanization and industrial activity in the area.

Stability in Aqueous Solution of a New Spray-Dried Hydrocolloid of High Andean Algae Nostoc sphaericum.

There is a growing emphasis on seeking stabilizing agents with minimal transformation, prioritizing environmentally friendly alternatives, and actively contributing to the principles of the circular economy. This research aimed to assess the stability of a novel spray-dried hydrocolloid from high Andean algae when introduced into an aqueous solution. Nostoc sphaericum freshwater algae were subject to atomization, resulting in the production of spray-dried hydrocolloid (SDH). Subsequently, suspension solutions of SDH were meticulously prepared at varying pH levels and gelling temperatures. These solutions were then stored for 20 days to facilitate a comprehensive evaluation of their stability in suspension. The assessment involved a multifaceted approach, encompassing rheological analysis, scrutiny of turbidity, sedimentation assessment, ζ-potential, and measurement of particle size. The findings from these observations revealed that SDH exhibits a dilatant behavior when in solution, signifying an increase in with higher shear rate. Furthermore, it demonstrates commendable stability when stored under ambient conditions. SDH is emerging as a potential alternative stabilizer for use in aqueous solutions due to its easy extraction and application.

Insights into the organic matter composition of soda lakes in the Pantanal, Brazil, through fatty acids analysis in sediments.

We conducted a geochemical analysis on three sediment cores collected from soda and freshwater lakes in the Pantanal region, in Brazil. Our objective was to identify the primary sources of organic matter associated with the Pleistocene-Holocene transition, as previously documented in that area. The Nhecolandia region, located in the Pantanal, encompasses over 10,000 lakes, with approximately 10% of them exhibiting alkaline characteristics. Soda lakes became highly saline and alkaline after ~ 910 cal yr BP, which influences biogeochemistry and aquatic ecology. They have high electrical conductivity and pH can reach 10.5. In contrast to freshwater, soda lakes are absent of surrounding vegetation. Literature suggests a strong influence by the Last Glacial Maximum on the region. We hypothesized that periods of aridity and increased precipitation influenced the composition of organic matter present in sediments and preserved within these cores. Our analysis focused on examining the presence and distribution of fatty acids, organic carbon content, and total nitrogen. In general, the cores exhibited two distinct parts in terms of organic matter sources: the upper sections of the cores were primarily composed by terrestrial sources, identified by the presence of long-chain fatty acids, while the deeper sections were dominated by aquatic sources, therefore short-chain fatty acids. We did not find significant difference among fatty acid profile that could distinguish freshwater from soda lakes, the only remarkable difference was the occurrence of saturated fatty acids, which is lower in freshwater lake. These findings suggest the occurrence of humid and arid periods in the region. The C/N ratio displayed a similar trend to the fatty acid's profiles, exhibiting an abrupt change that was likely induced by climate variations. Although diagenesis can alter the composition of organic matter and, subsequently, the C/N values, it is noteworthy that the abrupt change observed in the Salina da Ponta (soda lake) core corresponds to 3,200 years BP. This coincides with documented climate changes that occurred during the Holocene. Our study revealed the influence of past climatic conditions on the sources and variations of organic matter in sediment cores from the Pantanal's soda and freshwater lakes. Consideration of diagenesis and climate variations is crucial for interpreting sedimentary records.

Detailing the organic matter in suspended sediments as a tool to assess the impact of land occupation in water bodies: a case of Barigui Watershed (Southern Brazil).

Suspended sediments were collected to examine the organic carbon content and n-alkanes in order to assess the impact on water bodies caused by soil and land occupation. For this, samples from distinct areas based on the level of land occupation of the Barigui Watershed and different areas under the influence of human activities were examined. The number of industries increasing along the river was also considered. Twenty-two sediment samples were collected using a time-integrated sediment sampler. Samples were extracted with dichloromethane:methanol (DCM:methanol) (2:1) in an ultrasound bath, treated and injected using gas chromatography coupled with mass spectrometry (GC-MS) for separation and quantification. Twenty-one n-alkanes were identified and were used to track both biogenic and anthropogenic inputs. The concentration of total n-alkanes varied from 38.72 to 222.76 µg g-1, due to the impact of urbanization. Diagnostic indexes indicated high numbers of plants, bacteria and petroleum as n-alkanes sources. The following results were obtained using: carbon preference index (CPI), 1.96-2.22 (rainy season) and 2.12-5.80 (summer season); average chain length (ACL), 30.37-31.17 (rainy season) and 30.05-30.50 (summer season) and terrigenous aquatic ratio (TAR), 0.39-5.47 (rainy season) and 2.98-5.06 (summer season); n-alkanes had two main sources: terrestrial plant and petroleum. It is clear that the source of n-alkanes is different in each season (rainy and dry) demonstrated by n-alkanes occurrence. During the rainy season, there was an increase in organic matter of oil origin which was mainly associated with the increased runoff and rain drainage. Finally, the input of organic matter associated with land occupation and erosion can be distinguished by higher concentration in the most urbanized site (PB).

Preparation and Chemical and Physical Characteristics of an Edible Film Based on Native Potato Starch and Nopal Mucilage.

Edible films prepared from biological materials are being massively used. This study aimed to prepare edible films from native potato starch of the Allcca sipas variety (Solanum tuberosum subsp. Andigena), nopal mucilage (Opuntia ficus indica), and glycerol. Twelve edible films were prepared with starch, mucilage, and glycerin in different proportions by thermosynthesis. It was observed that mucilage and glycerol have a significant direct effect on film solubility and an inverse effect on aw, while the effect of starch is the opposite. The aw ranged from 0.562 to 0.639. The FTIR analysis showed the interaction of the components in the films being considerably influenced by the addition of mucilage. The TGA/DTA analysis reported low thermal stability in the films, retaining water around 100 °C, and showing a tendency to lose weight when the content of starch is high, while the opposite occurred with the addition of mucilage; it was also observed that around 310 °C, the maximum weight loss was observed between 53.6 and 86.1%. SEM images showed uniform films without cracks. The results are promising and show the possibility of preparing edible films from native potato starch and mucilage.

Bacia hidrográfica do rio balsas: diagnóstico físico e avaliação qualitativa de áreas suscetíveis à erosão / Balsas river basin: physical diagnosis and qualitative presentation of erosion-susceptible areas

RESUMO Conhecer o comportamento geomorfológico de bacias hidrográficas é fundamental para a elaboração de políticas públicas de conservação dos recursos naturais, para subsidiar a ocupação humana de forma que os processos erosivos sejam minimizados. Considerando-se as escassas informações sobre a bacia hidrográfica do Rio das Balsas, no sul do estado do Maranhão, este estudo teve como objetivos realizar o diagnóstico físico e apresentar as áreas suscetíveis à erosão por meio de classificação qualitativa. Para tanto, utilizaram-se informações das bases de dados da Agência Nacional de Águas, Companhia de Pesquisa de Recursos Minerais e United States Geological Survey (modelo digital de elevação, hidrografia, solos e geologia). Por rotinas de geoprocessamento, foram delimitadas a bacia e as sub-bacias e obtidos os dados para o cálculo dos índices morfométricos. Além disso, foi feita a reclassificação das áreas suscetíveis a erosão, baseada no curve number, método que avalia o potencial de escoamento superficial por tipo de solo e respectivo uso. A reclassificação em quatro classes de suscetibilidade possibilitou elaborar o mapa de áreas suscetíveis à erosão. As características morfogenéticas encontradas na área mostram que são necessárias ações de manejo adequado, já que alguns tipos de solos combinados com 45% de declividade (44% da área) são as áreas mais vulneráveis aos processos erosivos. Com isso, conclui-se que o planejamento do uso e ocupação da bacia são extremamente importantes para que as características físicas da região não interfiram de maneira negativa no futuro da sua expansão, no que concerne tanto às atividades agrícolas quanto às urbanas.

Abstract Knowledge of the geomorphological behavior of watersheds is fundamental for the elaboration of public policies for the conservation of natural resources, to subsidize human occupation in a way that minimizes erosion processes. Considering the lack of information about the Balsas river basin, located in the south of the state of Maranhão, Brazil, this study aimed to make a physical diagnosis and indicate areas susceptible to erosion through qualitative classification. To that end, it drew on information from National Water Agency (ANA), the Geological Survey of Brazil (CPRM) and the United States Geological Survey (USGS) databases (digital elevation model, hydrography, soils and geology). Through geoprocessing routines, the basin and sub-basins were mapped and data was obtained for the calculation of morphometric indices. In addition, the areas susceptible to erosion were reclassified based on the curve number method, which assesses surface runoff potential by soil type and use. Reclassification into four susceptibility classes made it possible to map erosion susceptible areas. The morphogenetic characteristics found in the area show the need for appropriate management actions, since some types of soils, combined with 45% slope (about 44% of the area), are the most vulnerable to erosive processes. The conclusion reached was that planning of the use and occupation of the basin is extremely important to prevent the physical characteristics of the basin interfering negatively in the future of the region, as its agricultural as well as urban activities expand.

Use of fatty acids as tracer of organic matter input associated with level of land urbanization.

Suspended sediments (SSs) were examined regarding the content of fatty acids (FAs) to associate them with sources of soil entry into the river. The source of organic matter was traced through fatty acid distribution, as well as erosion. Also, TOC, TN, and TOC/NT were used to support the results of FAs. For this, a tropical river was chosen to understand the main source of input considering the level of land occupation along the river. The Barigui river, in southern Brazil, was segmented in four distinct areas regarding the soil occupation (P1, P2, P3, and P4). Nine sampling campaigns were conducted from Nov/2014 to Nov/2015 using a time-integrated sampler. Site P1 has the lowest level of urbanization and showed the lowest concentration of FAs (16.35 µg-1). In contrast, site P4, the most urbanized, showed the highest content of fatty acids, including those associated with erosion, 378.53 µg g-1, specifically those with long chains. The mean concentrations of the saturated fatty acids (FAs) was 283.40 µg g-1, monounsaturated fatty acids (MUFAs) was 79.46 µg g-1, and polyunsaturated fatty acids (PUFAs) was 15.66 µg g-1. Twenty-seven fatty acids were examined, nevertheless C15:0, C16:0, C18:0, and C18:1ω9 prevailed in all samples. Generally, those acids indicate sewage inputs. Statics analyses were used to find the relation between the source of organic matter (autochthonous, allochthones, and anthropogenic) and FAs. Finally, the input of organic matter is associated with land occupation, which can be distinguished by FA distribution.

Water quality dynamic during rainfall episodes: integrated approach to assess diffuse pollution using automatic sampling.

Diffuse pollution caused by rainfall events potentially affects water quality in rivers and, therefore, must be investigated in order to improve water quality planning and management recovery strategies. For these, a quali-quantitative approach was used to monitor the water quality parameters in a river located in a semi-urban watershed area based upon automatic sampling. Thirteen water quality parameters were measured during five rainfall events. Events ranged from 2.3 to 56.8 mm and water peak flows from 3.3 to 4.5 m3/s. The pollutographs measured showed a standard pattern for total suspended solids (TSS). However, for the other chemical parameters, as total phosphorous (TP) and dissolved organic carbon (DOC), the dilution effects were more evident. It was possible to observe the rainfall influence mainly for physical parameters indicating a mass transport pattern for diffuse pollutants, which increased, for example, the amount of TSS in the river. Furthermore, hydrological characteristics were relevant considering the pollutant behavior. Antecedent dry periods, ranging from 1.3 days to 21.4 days, and critical time, from 2.0 to 10.4 h, are determinants to evaluate non-traditional water quality impacts in the river. In general, each rainfall episode has its own characteristics, which produces distinct mass contribution and temporal behavior, being challenging in making generalization. Therefore, the results indicate that diffuse pollution has to be considered to establish future decision-making strategies to water resources management.

Use of n-alkanes to trace erosion and main sources of sediments in a watershed in southern Brazil.

Erosive processes can transport sediments containing nutrients, heavy metals and contaminants of organic and inorganic origin into bodies of water, therefore affecting the local ecosystem and the population that benefits from the water sources. In order to better understand the origin of sediment sources and establish mitigation measures, the use of the sediment fingerprinting technique has been highlighted. Thus, the present work had as objective to apply n-alkanes in order to trace and understand the main sources of organic matter in sediments and associate the results with land and soil occupation. The study area is located in the municipality of Rio Negrinho - Brazil, in the Saci river basin. Soil samples were collected and classified according to their use and occupation, as well as and samples of local vegetation to be used as reference. The distribution of n-alkanes in the sediments was compared with the distribution found in the vegetation and soil. Previously, a distribution pattern of n-alkanes had been identified in all major vegetation used to trace the source of organic matter and hence the soil. The concentrations of total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP) and granulometry were also analyzed in the soil and sediment samples. Indexes between n-alkanes were used and applied to assess the source together with statistical analysis (PCA). In sum, the results showed that the sediments are mainly composed of Pinus taeda reforestation soils, as well as soil from the abandoned roads used to transport the cut trees, while the contribution of autochthonous sediments was found to be minimal. In this way, the fingerprint technique served as an auxiliary tool in order to establish measures for the good management of a river basin, bringing important information about the contributing sources of sediment to water bodies.

Contamination assessment and prediction of 27 trace elements in sediment core from an urban lake associated with land use.

A sediment core was sampled in an urban lake in southern Brazil, and the presence of 27 trace elements was assessed. The geochronology showed that the core corresponds to the period from 1914 to 2012. Accumulation of metals and the level of pollution was measured by the geoaccumulation index (Igeo) and enrichment factor (EF). According to Igeo and EF, the lake showed a high concentration of Ag, Se, Na, Au, S, Ca, Mg, Ba, Sb, Bi, and Sr with 5 ≤ EF ≤ 45 and Igeo class = 2-6. The EF to Au = 45 and Ag = 40. In contrast, Fe, Al, As, Cr, Ga, La, Sc, and Th do not represent pollution (Igeo ≤ 0 and EF ≤ 1.6). A principal component analysis and Spearman correlation showed a first group composed of Ca, Mg, P, Ba, Sr, Na, K, Ag, Bi, Au, Mo, sand, silt, and total organic carbon with positive correlation ≥ 0.70 and > 0.95 to Sr, Ag, sand, and silt. These were negatively correlated ≥- 0.70 with Fe. The second group: Fe, La, Ga, Ti, V, Cr, As, Al, Th from lithogenic source. Prediction models for the concentration for Mg, Na, P, Sr, Fe, Ga, and total organic carbon to years 2020-2050 were obtained with R2 > 0.65. In the anthropogenic source analyses, a watershed land use map indicates multiple uses of the land, with 53% urban area, 14.6% agriculture, and 14.5% forest.

PAHs in Water, Sediment and Biota in an Area with Port Activities.

The study reports concentration of 16 PAHs in sediment, water, plankton and in muscle and liver of sampled fishes from Paranagua Bay in Southern Brazil. According to the range of PAHs concentration found in sediments (ΣPAHs 15.33-133.61 µg g-1) and water (ΣPAHs 51.20-162.37 µg L-1), the area was characterized as slightly polluted. In contrast, significant concentration of PAHs was found in fish and plankton, ranging from 26.52 to 2055.00 µg g-1 and 175.41 to 2096.10 µg g-1, respectively. The concentrations were 15 times more than in sediments. Even though the concentration of PAHs in water and sediments are low, the concentration in fish tissues are alarmingly. The hypothesis of bioaccumulation is not discharged. Accumulation levels of PAHs in the biota were used to calculate biota-sediment accumulation factor (BSAF) and bioaccumulation factor (BAF). For example, fish sampled from site 11 had a BAF of 49 and BSAF of 2.3, whereas for plankton the BAF was 16.3 and BSAF 0.7. Mean values of BAF and BSAF were higher in plankton samples. It is known that PAHs are enzymatically metabolized by organisms, thus the lower BSAF in fish might have resulted from biochemical transformation. Statistical analysis indicates no significant correlation between total PAHs concentration in fish tissues and total lipid content in fishes (p > 0.1).Accumulation in tissues is controlled by lipid content, although factors, such as spatial distribution of compounds, trophic level, and behavior of each species in the environment, must be considered. Besides, size and nutritional conditions can affect both absorption as well as metabolic process and excretion. A positive and significant correlation was found between total PAHs and trophic positions obtained from FishBase data (r2 = 0.784; p < 0.05). Thus, it seems that the area, with great influence of urban and industrial activities, and the bioaccumulation compounds, such as PAHs, depend on others factors, as well as resuspension of sediments and releasing of compounds for biota.

Tracking capybara (Hydrochoerus hydrochaeris) feces contribution method in aquatic environments using sterols.

The monitoring of fecal contamination (human and animal) is an incessant challenge. In this approach, microbiological methods play an important role, though with substantial limitations. Organic compounds, such as sterols, are often used to trace fecal contamination. Although the fecal sterols profiles of some animals are already known, capybara, a typical mammal from South America, is a significant contributor to aquatic fecal contamination because of its water dependence; and still there is no one way, scientifically speaking, to trace its fecal contribution. The aim of the present study was to provide a tool to measure the temporal fecal contribution of capybara in aquatic systems. We examined the sterol content of capybara feces and compared with another species (sheep, cow, horse, pig, hen, duck, cat, dog, opossum, and human). From numerical relationships among fecal sterols, 6 ratios were delineated and tested to assess their potential to identify the capybara feces contribution in contaminated environments. Statistical analysis showed that 3 ratios were able to differentiate capybara feces from other sources. Such ratios were applied in samples of a sediment core from an urban area in south Brazil with a large capybara population. The temporal trend showed a significant contribution of capybara feces in the last 100 yr. Environ Toxicol Chem 2018;37:353-361. © 2017 SETAC.

Critical aggregates concentration of fatty esters present in biodiesel determined by turbidity and fluorescence.

Biodiesel for combustible engine is available as mixture of fossil diesel and fatty esters obtained by transesterification of vegetable oils. The use of biodiesel reduces the amount of SOx, mainly. However, it was already observed that biodiesel has a different behavior in environment in cases of accidental spill and groundwater contamination. It was noticed that the biodegradation of hydrocarbons (cyclic and aliphatic) in the presence of biodiesel are speeded, although the mechanism is still unclear. Considering the chemical structure of fatty esters, it was investigated the formation of aggregates in water solution by fatty esters present in commercial biodiesel. In Brazil, biodiesel is composed by 95% of fossil diesel and 5% of fatty esters mixture. In this work, fatty esters were treated as neutral surfactant, i.e., it was treated as a molecule with polar and non-polar part. Turbidity and fluorescence were used to determine the critical aggregates concentration (CAC). Water solutions containing fatty esters were examined exploiting changes in turbidity and fluorescence intensity of pyrene. Abrupt changes were attributed to aggregates formation, following the same behavior of traditional amphiphilic compounds. It was determined the CAC for ethyl palmitate, ethyl stearate, ethyl oleate, and ethyl linoleate. The values of CAC for fatty esters varied from 1.91 to 4.27 µmol/L, while CAC for the mixture of esters (biodiesel) was 2.01 for methyl esters and 1.19 for ethyl esters, both prepared using soybean oil. The aggregates formation was also determined by fluorescence measurements considering the changes in intensity of peaks I and III of pyrene. Pyrene senses the changes in environment polarity. The values found of CAC by fluorescence for individual ethyl esters varied from 1.85 to 3.21 µmol/L, while mixtures of ethyl esters was 2.23 and 2.07 µmol/L for mixture of methyl esters. The results clearly showed that fatty esters form aggregates and might be responsible for speed degradation of compounds by accommodation of them in inner part of aggregates.

Characterization of quality of sediments from Paranaguá Bay (Brazil) by combined in vitro bioassays and chemical analyses.

The present study characterizes the quality of sediments from the Paranaguá Estuarine Complex (South Brazil). Polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs) were determined in sediment samples together with a series of different in vitro bioassays. The fish hepatoma cell line (PLHC-1) was used to determine the presence of cytotoxic compounds and CYP1A- and oxidative stress-inducing agents in sediment extracts. Ovarian microsomal fractions from sea bass (Dicentrarchus labrax) were used to detect the presence of endocrine disrupters that interfered with the synthesis of estrogens (ovarian CYP19). Despite the relatively low levels of pollutants and no evidence of negative effects based on guideline levels, sediments collected close to harbors were enriched with CYP1A-inducing agents and they showed higher cytotoxicity. In contrast, sediments from internal areas inhibited CYP19 activity, which suggests the presence of endocrine disrupters at these sites. Overall, the selected bioassays and the chemistry data led to the identification of potentially impacted areas along the Paranaguá Estuarine Complex that would require further action to improve their environmental quality. Environ Toxicol Chem 2017;36:1811-1819. © 2016 SETAC.

Modelo condutométrico para determinação da concentração de dióxido de carbono dissolvido no Reservatório Vossoroca, Brasil / Conductometric model for the determination of dissolved carbon dioxide concentration in Vossoroca Reservoir, Brazil

RESUMO: Um modelo condutométrico foi desenvolvido como uma técnica menos dispendiosa para determinar a concentração de dióxido de carbono dissolvido em reservatórios e foi aplicado no Reservatório Vossoroca, Brasil. A parte principal do Reservatório Vossoroca está localizada na Área de Proteção Ambiental de Guaratuba e foi construída para regular os fluxos de uma usina hidrelétrica, considerada uma forma limpa e renovável de exploração; no entanto, há evidências de que reservatórios de hidrelétricas poderiam ser potenciais emissores de gases de efeito estufa. O modelo utiliza como parâmetros a condutividade elétrica, a temperatura e o pH da água do reservatório. Foi possível observar nos resultados as estratificações térmica e química que ocorrem no reservatório por meio dos parâmetros temperatura (18º a 25ºC), pH (5,9 a 8,4), oxigênio dissolvido (com o limite superior de 8 mg.L-1) e condutividade elétrica (0,04 a 0,2 mS.cm-1). Os resultados das campanhas apresentaram bons coeficientes de determinação (R2), acima de 0,9, para todas as campanhas para a determinação da concentração de dióxido de carbono dissolvido obtido por titulação alcalimétrica, também feita no local do estudo, e pelo modelo condutométrico (com o limite superior de cerca 250 mg.L-1), mas em profundidades próximas ao leito do reservatório foram encontradas diferenças. O teste de significância estatística (Student) não apresentou diferença significativa entre os valores obtidos por titulação alcalimétrica e pelo modelo condutométrico.

ABSTRACT: A conductometric model was developed as a less costly technique to determine the dissolved carbon dioxide concentration in reservoirs and was applied in Vossoroca Reservoir, Brazil. A main portion of Vossoroca Reservoir is located in the Environmental Protection Area of Guaratuba and was built for regulate flows to a hydroelectric power plant, considered a clean and renewable form of exploitation; however, there is evidence that hydroelectric reservoirs could be potential emitters of greenhouse gases. The model uses parameters as electrical conductivity, temperature and pH of the water reservoir. It was possible to observe in the results the thermal and chemical stratification that occurs in the reservoir through the parameters temperature (18º to 25ºC), pH (5.9 to 8.4), dissolved oxygen (with upper limit of 8 mg.L-1) and electrical conductivity (0.04 to 0.2 mS.cm-1). The campaign results showed good determination coefficients (R²), above 0.9, for all campaigns for the determination of dissolved carbon dioxide concentration obtained by alkalimetric titration, also made on the study site, and by the conductometric model (with upper limit of approximately 250 mg.L-1), but at depths close to the bed of the reservoir discrepancies were found. The statistical significance test (Student) did not show significant difference between the values obtained by alkalimetric titration and by the conductometric model.

Assessment of historical fecal contamination in Curitiba, Brazil, in the last 400 years using fecal sterols.

A 400-year sedimentary record of the Barigui River was investigated using fecal biomarkers and nutrient distribution. The temporal variability in cholesterol, cholestanol, coprostanol, epicoprostanol, stigmastanol, stigmasterol, stigmastenol, sitosterol, and campesterol between 1600 and 2011 was assessed. Anthropogenic influences, such as deforestation and fecal contamination from humans and livestock, were observed from 1840. The sterol ratios exhibit evidence of hens, horses, cows, and an unknown herbivore, which may be a capybara (Hydrochoerus hydrochaeris), from 1820 and has been observed more markedly from 1970 onward. Human fecal contamination was detected from 1840 and was observed more markedly from 1930 due to population growth. Thus, the sanitation conditions and demographic growth of Curitiba seemed to be the main factors of human sewage pollution, as the coprostanol concentration over time was strongly correlated with the population growth (r=0.71, p<0.001) although diagenetic processes have also been observed.(1.)

Sedimentary record of PAHs in the Barigui River and its relation to the socioeconomic development of Curitiba, Brazil.

Concentrations of polycyclic aromatic hydrocarbons (PAHs) were determined in a sediment core collected from the Barigui River, in Curitiba, South Brazil. The USEPA's 16 priority PAH concentrations ranged from 39ng g(-1) to 2350ng g(-1) of dry sediment over a period that corresponds temporally to between ca. 1855 and 2011. The concentrations and patterns of PAH distribution changed over this time period and may be associated with several episodes in the Curitiba's history. Two major PAHs concentration peaks occurred in approximately 1910 and 1970, which might reflect population increases due to immigration programs in the 1890s and the sudden economic development that occurred in Brazil from 1960 to 1980, "The Economic Miracle Period", respectively. Isomeric ratios revealed that the PAHs had predominantly pyrolytic sources. The population, number of highways and electric energy consumption of Curitiba, as indices of socioeconomic development, were positively correlated with PAH deposition in the sediment core from 1855 to 1970, indicating the influence of socioeconomic development on the environmental load of sedimentary PAHs.

Evaluation of potential sewage contamination by fecal sterol biomarkers adsorbed in natural biofilms.

The use of biofilms for adsorption of sterols was investigated for the first time to evaluate sewage contamination in the Barigüi River, Curitiba (Brazil). The characteristics of a biofilm that favor its use in monitoring include the relatively rapid development of biofilms and their capacity to sorb hydrophobic compounds. Some fecal sterols considered to be biomarkers for human and animal feces have relatively high octanol-water partitioning coefficients (log KOW); thus, sterols were expected to be readily sorbed in the biofilms. The biofilms were developed on glass plates (0.48 m(2)) previously coated with a fine layer of stearic acid and supported by a PVC tube that was submersed in the river 20 cm above the river bottom. After a certain period of incubation time, the biofilm growth was scraped from the plates and analyzed for the following fecal steroids: coprostanol (5ß-cholestan-3ß-ol), epicoprostanol (5ß-cholestan-3α-ol), cholesterol (5,6-cholesten-3ß-ol), cholestanol (5α-cholestan-3ß-ol), stigmastanol (24ß-ethyl-5α-cholestan-3ß-ol) and coprostanone (5ß-cholestan-3-one). Six samples were collected between March 2012 and June 2012. All analyzed compounds were detected, and in general, cholesterol was present in high amounts (23 160-41.9 ng g(-1) dry biofilm). Variation among campaigns was observed in the distribution of sterols, with cholestanol showing the least variation among the samples. Sterol ratios that are commonly used for evaluating sewage contamination were calculated; these ratios indicated some periods of potential sewage influence. However, these sterol ratios are intended to be applied primarily for sediments and not for biological compartments; thus, the results must be carefully interpreted. Biofilms developed under natural conditions can be a tool for monitoring some important sterols that are used as biomarkers of fecal pollution.

Occurrence of selected estrogens in mangrove sediments.

This paper presents results related to the occurrence and distribution of estrogens along the Brazilian coast. Three mangrove areas were chosen to evaluate the presence of estrogens in surface sediments of mangrove forests. The presence of estrogens was observed in all studied sites. 17-α-Ethinylestradiol (EE2), a synthetic estrogen, was the most common and has been found in higher concentration (0.45-129.78 ng/g) compared to 17-ß-estradiol (E1) and estrone (E2) (both being natural estrogens). The concentrations of E1 and E2 ranged from 0.02 to 49.27 ng/g and 0.03 to 39.77 ng/g, respectively. Theoretically, under anaerobic conditions EE2 can be reduced to E1 even in environments such as sediments of mangrove forests, which are essentially anaerobic. Even if the concentrations of estrogens seem to be insignificant in some samples, the effects remain uncertain.