Resumen Esta investigación se orienta al tratamiento de la NIC 16 en las empresas comerciales ecuatorianas que vienen aplicando esta normativa desde el año 2011. En la actualidad, no se conoce a ciencia cierta el estado de avance en su aplicación, mismo que se convierte en el objetivo del artículo. El diseño metodológico abarca un enfoque cuantitativo, un tipo de investigación descriptivo con una modalidad bibliográfica - documental y un diseño transeccional descriptivo. Se confeccionó una matriz validada por expertos, elaborada con base en la NIC 16, que fue contrastada con los estados financieros auditados, las notas explicativas y las políticas empresariales de las empresas seleccionadas. Los resultados indican que: las empresas en su gran mayoría utilizan el modelo del costo como medición posterior, todas las empresas analizadas utilizan para cálculo de la depreciación el método de la línea recta y, en la mayoría de las entidades estudiadas, cumplen los requisitos exigidos en la norma en cuanto a información a revelar.

Abstract This investigation is oriented to the treatment of IAS 16 in Ecuadorian commercial companies that have been applying this regulation since 2011. Currently, the state of progress in its application is not well known, which becomes the article's objective. The methodological design encompasses a quantitative approach, a type of descriptive research with a bibliographical-documentary modality, and a descriptive transeccional design. A matrix validated by experts was prepared based on IAS 16, which was contrasted with the audited financial statements, the explanatory notes, and the business policies of the selected companies. The results indicate that: the vast majority of companies use the cost model as a subsequent measurement, all the companies analyzed use the straight-line method to calculate depreciation and, in most of the entities studied, they meet the requirements in the standard regarding information to be disclosed.

Abstract: Objective: To present a new surgical alternative to reduce obstetric hemorrhage in cases of placenta previa-accreta, by means of temporary impingement at the hypogastric arteries, prior to the performance of caesarean-hysterectomy. Material and methods: Seven patients who attended pregnancy control were managed in a third-level care private institution, in whom obstetric ultrasound detected placenta previa accreta, and collecting demographic, clinical and diagnostic data. Results: On average, the gestational age at which the cesarean section-hysterectomy was performed was at 35 weeks with variation between weeks 34.5 and 37; in terms of intraoperative bleeding, in five cases it was 200 mL, one case with 150 mL and one case with 800 mL; surgical times varied from 90 to 106 minutes. In all cases, live products were obtained with Apgar and Silverman-Anderson assessment within the normal ranges; for all patients the hospital stay was two days. Conclusions: Temporary clamping of the hypogastric arteries, prior to caesarean-hysterectomy, shows usefulness in the resolution of cases with placental accreta.

Resumen: Objetivo: Presentar una nueva alternativa quirúrgica a fin de disminuir la hemorragia obstétrica en casos de placenta previa-acreta, mediante el pinzamiento temporal de arterias hipogástricas, precediendo a la realización de cesárea-histerectomía. Material y métodos: Se atendieron siete pacientes que acudieron a control de embarazo en institución privada de tercer nivel de atención, en quienes mediante ultrasonido obstétrico se detectó placenta previa y acretismo placentario, recabando datos demográficos, clínicos y de diagnóstico. Resultados: En promedio, la edad gestacional en que se realizó la cesárea-histerectomía fue a las 35 semanas, con variación entre las semanas 34.5 y 37; en cuanto a sangrado transoperatorio, en cinco instancias fue de 200 mL, un caso con 150 mL y un caso con 800 mL; los tiempos quirúrgicos variaron de 90 a 106 minutos, en todos los casos se obtuvieron productos vivos con valoración de Apgar y de Silverman-Anderson dentro de lo normal; para todas estas mujeres la estancia hospitalaria fue de dos días. Conclusiones: El pinzamiento temporal (clampeo) de las arterias hipogástricas previo a la cesárea-histerectomía muestra utilidad en la resolución de incidencias de acretismo placentario.

ABSTRACT Soil acidity is one of the main factors that reduces productivity in agricultural crops, and it is corrected with materials that neutralize acidification. Among soils affected by acidity are those of volcanic origin. At least 30 % of agricultural soils in Chile are of volcanic origin, and acidity correction practices must be constantly performed. This study aimed to evaluate the effectively of two materials that may neutralize soil acidification and increase yield production in Chilean volcanic soils. An experiment was conducted during the 2019-2020 season, in which different acidity correction materials derived from the cellulose industry [Ash + Dregs (AD) and Ash + Dregs + Sludge (ADS)] were applied in three volcanic soils cultivated with wheat in southern Chile (Chillán, Temuco, and Osorno). Treatments were a control, CaCO3 at an adjusted rate to reach pH 6.0 and AD and ADS at the same rate as CaCO3 and twice the rate. Results indicated that the application of AD and ADS produced similar effects on pH(H2O), Ca2+, Mg2+, and Al3+ contents, cationic exchange capacity (CEC), and Al saturation compared with CaCO3 at the same rate; the effect was directly proportional to the rate used with each AD and ADS. Wheat production at each location was similar for AD, ADS, and CaCO3 at the same rate; however, it fluctuated between 10.1 and 10.4, 5.4 and 6.5, and 10.0 and 10.3 Mg ha-1 at Chillán, Temuco, and Osorno, respectively. Results indicate that these materials are an alternative to be used as a soil acidity correction amendment.

SUMMARY: The morphological study of the chondrichthyes teeth represents an important taxonomic characteristic used for the classification and identification of different species. The teeth of four different species of selacimorphs (Carcharhinus leucas, Galeocerdo cuvier, Rhizoprionodon longurio and Sphyrna sp.) were diaphonized in order to standardize a dental technique for their transparency. By standardizing the Okumura-Aprile technique applied for the dental diaphonization of humans, an optimal diaphonization was obtained in the four species treated with 7 % HCl where the pulp chamber was clearly observed. Therefore, we may conclude that the OkumuraAprile technique is efficient in shark dental diaphonization.

RESUMEN: El estudio morfológico de la dentadura de chondrichthyes representa un carácter taxonómico importante empleado para la clasificación e identificación de diferentes especies. Se diafanizaron dientes de cuatro especies distintas de selacimorfos (Carcharhinus leucas, Galeocerdo cuvier, Rhizoprionodon longurio y Sphyrna sp.) con la finalidad de estandarizar una técnica dental para su transparentación. Estandarizando la técnica de Okumura-Aprile aplicada para la diafanización dental de humanos, se obtuvo una diafanización óptima en las cuatro especies en tratamiento con HCl al 7 % donde se podía observar con claridad la cámara pulpar, por lo que podemos concluir que la técnica de Okumura-Aprile es eficiente en la diafanización dental de tiburones.

Resumen La anastomosis hepático-yeyuno en Y de Roux se considera la técnica de elección para tratar lesiones quirúrgicas de la vía biliar, como su sección o resección. La pérdida de confluencia de los conductos hepáticos principales derecho e izquierdo es uno de los factores que incrementan la complejidad técnica durante el procedimiento y, en algunos de estos pacientes, se requiere una doble anastomosis hepático-yeyuno para garantizar resultados satisfactorios a largo plazo. Se describen los aspectos técnicos y los resultados posoperatorios del tratamiento quirúrgico empleado, con base en la intervención de una paciente con una lesión quirúrgica de la vía biliar y pérdida de la confluencia de los conductos hepáticos. La evolución de la paciente fue satisfactoria y se mantiene asintomática después de 12 meses de seguimiento. A pesar de ser una técnica compleja, la doble anastomosis hepático-yeyuno en Y de Roux resultó una opción segura de tratamiento en esta paciente.

Abstract Roux-en-Y hepato-jejunostomy (RYHJ) is the technique of choice for the surgical treatment of bile duct injuries (BDI), such as section or resection. The loss of the hepatic confluence (LHC) increases the technical difficulties during the procedure and, in some of these patients, a doble-RYHJ is required to achieve a long term successful result. We report the technical aspects of the surgical technique as well as the results, based on the case of a young female patient with BDI and LHC. The patient shows a satisfactory evolution and remains asymptomatic during the 12 months of follow up. Double RYHJ, although technically demanding, resulted a safe option for treating this patient.

Abstract Nitrogen (N) gaseous losses have environmental and economic implications. Ammonia (NH3) volatilization and nitrous oxide (N2O) emissions from a volcanic soil were concurrently quantified using intact lysimeters, after application of the equivalent to 100 kg N ha-1 with and without urease (NBPT) and nitrification (DCD) inhibitor: Urea, Urea+NBPT, Urea+DCD, Dairy slurry and Dairy slurry+DCD. A control treatment (-N) was also included. Treatments were distributed on a randomized block design and evaluated during 28 days. Ammonia was analyzed for NH4 by colorimetry, while N2O was estimated by gas chromatography. Total emissions were estimated by addition of daily fluxes, and results were analyzed by ANOVA. Ammonia was the main N loss, with 35 to 43% and 5% to 16% of the total N applied in Urea and Dairy slurry (P<0.01), respectively, with and without inhibitors (P>0.05). The use of DCD reduced N2O emissions by 44 and 8% in the same treatments, respectively (P<0.05). Results suggest that DCD has a potential as a mitigation option in grassland volcanic soils reducing N2O losses. The use of NBPT did not reduce NH3 losses and N2O emissions when applied with urea. Concurrent N gasses losses from soil showed that indirect N2O losses following NH3 volatilization might be more relevant in volcanic soils than direct N2O losses.

This work presents the characterization of ZnTe nanolayers grown on GaAs and GaSb (100) substrates by the Atomic Layer Deposition (ALD) regime. Under certain conditions, the alternating exposition of a substrate surface to the element vapours makes possible the growth of atomic layers in a reactor where the atmosphere is high-purity hydrogen. ZnTe was grown simultaneously on GaAs and GaSb at the same run, allowing, a comparison between the effects produced by the superficial processes due to the different used substrates, thereby eliminating possible unintended changes of growth parameters. Nanolayers on GaSb maintained their shiny appearance even at temperatures near 420°C. It was found that for exposure times below 2.5 s there was not growth on GaAs, while for GaSb the shortest time was 1.5 s at 385°C. By HRXRD the peak corresponding to (004) diffraction plane of ZnTe was identified and investigated, the FWHM resulted very wide (600-800 arcsec) indicating a highly distorted lattice mainly due to mosaicity. Raman scattering shows the peak corresponding to LO-ZnTe, which is weak and slightly shifted in comparison with the reported for the bulk ZnTe at 210 cm-1. Additionally, the measurements suggest that the crystalline quality have a dependence with the growth temperature.

Abstract There are some situations when it is necessary to weigh, with high accuracy and high precision, a required amount of material using heterogeneous and irregular pieces. As an example, in the laboratory, when preparing a liquid phase epitaxial growth, each of the materials that constitute the liquid phase must have an exact weight, within micrograms, given by the phase diagrams. The sources of the materials usually are small polycrystalline pieces of irregular shapes and random weights. Normally the weighing is done by interchanging the small irregular pieces of different sizes according to the criteria of the operator until the given weight is obtained. This is a long and tedious process and since each liquid solution requires several components, and a different liquid phase is needed for each layer, very often weighing it takes several hours. This operative process is prone to errors. To ease this kind of processes, a vision-assisted system has been developed. It consists of a webcam, an analytical balance and a PC. To use this assembly the operator only needs to put sequentially the pieces of the material in the analytical balance. When the required weight can be obtained by a combination of some of the pieces added to the analytic balance, the PC notifies the operator and signals the selected pieces in the screen. With the help of this system, the weighing accuracy has been improved and the time required to accomplish the process has been dramatically reduced.

A small card used for detecting hydrogen gas in a crystal growth system by the liquid phase epitaxy technique was designed and built. The small size of the card enables its portability to other laboratories where leakage detection of hydrogen or other flammable gas is required. Card dimensions are approximately 10 cm long and 5 cm wide enabling easy transportation. The design is based on a microcontroller which reads the signal from the hydrogen sensor and internally compares the read value with preset values. Depending on the signal voltage a red, yellow or green LED will light to indicate the levels of concentration of the flammable gas. The card is powered by a 9 V battery.

Sphingomyelinases (SMases) catalyze the hydrolysis of sphingomyelin to ceramide and phosphorylcholine. Sphingolipids are recognized as diverse and dynamic regulators of a multitude of cellular processes mediating cell cycle control, differentiation, stress response, cell migration, adhesion, and apoptosis. Bacterial SMases are virulence factors for several species of pathogens. Whole cell extracts of Mycobacterium tuberculosis strains H37Rv and CDC1551 were assayed using [N-methyl-14C]-sphingomyelin as substrate. Acidic Zn2+-dependent SMase activity was identified in both strains. Peak SMase activity was observed at pH 5.5. Interestingly, overall SMase activity levels from CDC1551 extracts are approximately 1/3 of those of H37Rv. The presence of exogenous SMase produced by M. tuberculosis during infection may interfere with the normal host inflammatory response thus allowing the establishment of infection and disease development. This Type C activity is different from previously identified M. tuberculosis SMases. Defining the biochemical characteristics of M. tuberculosis SMases helps to elucidate the roles that these enzymes play during infection and disease.

Las esfingomielinasas (SMasas) catalizan la hidrólisis de esfingomielina a ceramida y fosforilcolina. Los esfingolípidos son reconocidos como reguladores diversos y dinámicos de una multitud de procesos celulares que median en el control del ciclo celular, la diferenciación, la respuesta al estrés, la migración celular, la adhesión y la apoptosis. Las esfingomielinasas bacterianas son factores de virulencia reconocidos en varias especies de patógenos. En este trabajo se analizaron los extractos de células enteras de las cepas de Mycobacterium tuberculosis H37Rv y CDC1551 utilizando [N-metil-14C]-esfingomielina como sustrato. Se identificó actividad de SMasa-ácida dependiente de zinc en ambas cepas. La actividad máxima se observó a pH 5.5. Curiosamente, los niveles de actividad de SMasa generados a partir de extractos de la cepa CDC1551 son aproximadamente un tercio de los de la cepa H37Rv. La presencia de una SMasa exógena producida por M. tuberculosis durante la infección puede interferir con la respuesta inflamatoria del huésped, permitiendo así el establecimiento de la infección y el desarrollo de la enfermedad. Esta actividad tipo C es distinta de las actividades previamente reportadas para M. tuberculosis. Definir las características bioquímicas de las esfingomielinasas de M. tuberculosis ayudará a dilucidar el papel que desempeñan estas enzimas durante la infección y la enfermedad.

Biotinidase deficiency is an autosomal recessive metabolic disorder that affects the cleavage of biotin. Family studies of the index case found that both parents are usually carriers and siblings have the altered gene, but only homozygotes have manifestations that vary depending on the deficiency grade. Mothers may have moderate deficiency and be asymptomatic; biotin deficiency in pregnant women causes defects in children. In a study, using human cells exposed to biotin deficiency, cell growth decreased contributing to the development of cleft palate. In newborns, biotinidase deficiency has been associated with VACTERL syndrome and annular pancreas. The case of an infant with biotinidase deficiency and congenital defect of the vascular ring is presented. This defect surrounds and compresses the trachea and esophagus, disturbing swallowing and breathing. Infant was supplemented with biotin and surgically intervened with excellent results.

La deficiencia de biotinidasa es una alteración metabólica autosómica recesiva, que afecta la escisión de biotina disminuyendo su reciclado. Estudios en familiares del caso índice encontraron que generalmente ambos padres son portadores y los hermanos presentan el gen alterado; solo los homocigotos tienen síntomas que varían según el grado de deficiencia. Las madres pueden tener deficiencia moderada y mantenerse asintomáticas. En un estudio que utiliza células humanas expuestas a deficiencia de biotina, disminuyó el crecimiento celular y contribuyó al desarrollo de paladar hendido. La deficiencia de biotina en embarazadas ocasiona malformaciones en los productos. En recién nacidos, la deficiencia de biotinidasa se ha relacionado con síndrome VACTERL y páncreas anular. Se presenta el caso de una lactante con deficiencia de biotinidasa y defecto congénito de anillo vascular que rodea y comprime tráquea y esófago, alterando la deglución y la respiración. La niña fue suplementada con biotina e intervenida, con excelentes resultados.

A range of technologies is available to reduce greenhouse gas emissions from agricultural systems. Among these, applying N transformation inhibitors is promising in reducing nitrous oxide (N2O) emissions in both arable and pastoral soils. A randomized complete block design with six replicates was used to quantify the effect of urease (UI) and nitrification (NI) inhibitors on N2O emissions and pasture production from permanent pasture in an Andisol after autumn-applied urea. The N2O emissions were measured periodically for 8 wk with PVC stationary chambers. Mineral N, DM yield, N concentration, and N uptake were analyzed. Our results show that adding fertilizer (40 kg N ha-1) significantly increased N2O emissions by 281% over the control treatment (P < 0.05) and adding N inhibitors to fertilizer N resulted in a 10%-29% reduction in emissions. Both inhibitors initially reduced nitrate-N production in the Andisol (Osorno series) either by slowing urea hydrolysis or the nitrification process. Increases in pasture yield (8%-13%), N concentration (7%-9%), and N uptake (46%-56%) were measured by adding N inhibitors with urea. Emission factors, measured under field conditions in Chile after autumn- applied urea and N inhibitors (applied alone or combined), were very low (0.052%-0.114%) compared with values reported in the literature and the Intergovernmental Panel on Climate Change (IPCC) default value (1%). Using these technologies could contribute to Chile’s nationally established goal of a 20% reduction in greenhouse gas emissions by 2020.

Una gama de tecnologías están disponibles para reducir las emisiones de gases de efecto invernadero desde sistemas agrícolas. Entre éstas, la aplicación de inhibidores de transformación del N es considerada prometedora para reducir emisiones de oxido nitroso (N2O) en suelos de cultivo y praderas. Un diseño de bloques completos al azar con seis repeticiones se utilizó para cuantificar el efecto de inhibidores de ureasa (UI) y nitrificación (NI) sobre emisiones de N2O y producción de pradera permanente sobre un Andisol después de la aplicación otoñal de urea. Las emisiones de N2O se midieron periódicamente durante 8 semanas en cámara estacionaria de PVC. Se analizaron N mineral, rendimiento de MS, concentración de N, y absorción de N. Los resultados muestran que la aplicación de fertilizante (40 kg N ha-1) aumentó significativamente las emisiones de N2O en 281% sobre el tratamiento control (P < 0,05) y generó 10-29% de reducción de emisiones. Ambos inhibidores redujeron la producción de N-nitrato en el Andisol serie Osorno por detener la hidrólisis de urea o el proceso de nitrificación. Se midieron aumentos en producción (8-13%), concentración N (7-9%) y absorción N (46-56%) con la adición de inhibidores del N con urea sobre el tratamiento control. Los factores de emisión medidos bajo condiciones de campo en Chile por la aplicación otoñal de urea e inhibidores del N (aplicados solos o combinados) fueron muy bajos (0,052-0,114%) en comparación con los valores reportados en literatura y valores por defecto del Panel Intergubernamental para el Cambio Climático (IPCC) (1%). El uso de estas tecnologías puede contribuir al objetivo establecido a nivel nacional de reducir las emisiones de gases de efecto invernadero en un 20% para el año 2020.

This paper presents the first inventory of ammonia emissions from livestock production in Los Lagos and Los Ríos Regions of Chile. The inventory was focused in this area because is where cattle production is concentrated. This study aimed to quantify the amount of N losses due to ammonia volatilization from livestock production in these regions of the country, and to provide its spatial representation identifying their main sources. Calculations have been carried out for 1997 and 2007, and also projections to 2017 and 2027 were obtained. Calculated emissions were 6097 and 6206 t NH3-N for 1997 and 2007, respectively. Major sources of NH3-N emissions were cattle accounting for more than 85%, followed by horses and pigs. Farm management practices as grazing, housing, manure storage and land spreading of manure accounted for 87%, 9%, 3%, and 2%, respectively, of total annual emissions. Projections suggest that emissions could increase up to 6344 and 6516 t NH3-N for 2017 and 2027, respectively. Emissions are much lower than those reported for developed European countries. However, intensification of cattle production systems may lead to an increase of ammonia emissions which could impact the temperate forest of Southern Chile characterized by low nutrient fluxes.

Este artículo presenta el primer inventario de emisiones de amoníaco de la producción pecuaria de las Regiones de Los Lagos y Los Ríos de Chile, porque esta área concentra la producción chilena de ganado bovino. Este estudio tuvo como objetivos cuantificar las pérdidas de N por volatilización de amoníaco emitidas desde la producción animal en estas regiones del país, y proveer su representación espacial identificando las principales fuentes de emisión. Los cálculos fueron realizados para 1997 y 2007; y desde el año base se proyectaron emisiones para los años 2017 y 2027. Las emisiones calculadas fueron 6097 y 6206 t NH3-N para 1997 y 2007, respectivamente. Las principales fuentes de emisión fueron los bovinos con más del 85% de las emisiones, seguido por equinos y porcinos. Prácticas de manejo de las explotaciones pecuarias como el pastoreo, la estabulación de ganado, el almacenamiento y la aplicación de desechos aportaron el 87%, 9%, 3% y 2%, respectivamente, del total de las emisiones anuales. Las proyecciones sugieren que las emisiones pueden alcanzar las 6344 y 6516 t NH3-N para el 2017 y 2027, respectivamente. Estas emisiones son mucho menores que las reportadas por algunos países europeos desarrollados. Sin embargo, la intensificación de los sistemas productivos ganaderos puede conllevar al aumento en las emisiones de amoníaco, las cuales pueden provocar un impacto en los bosques templados del sur de Chile caracterizados por bajos flujos de nutrientes.

Amebiasis caused by Entamoeba histolytica is a problem of public world health. The most frequent clinical presentation are the dysentery and the amebic liver abscess. Fifty millions of cases and more than 100.000 deaths for this disease are reported annually worldwide. The life cycle of E. histolytica has two phases: trophozoite and cyst. Trophozoites are the causal agent of disease. The effective treatment for the amebiasis includes drugs with serious collateral effects. Ivermectin is a macrolid with activity against endoparasites and ectoparasites causing strongiloidosis, filariasis, oncocercosis, scabiasis and pediculosis. The use of ivermectin has been extended almost worldwide; it is recognized as a safe drug. The main objective of this study was to determine in vitro sensibility of trophozoites of E. histolytica was to the treatment with ivermectin. To determine the sensibility of the parasites to the drug, E. histolytica was cultivated in PEHPS medium. During its logarithmic growth phase the trophozoites were exposed to different concentrations of ivermectin. As controls other antiparasitic drugs were used. For each drug, serial dilutions were prepared, and mixed in culture tubes with parasites (2 x 10(4) cells/ml). They were incubated for 72 h and then the percentage of growth inhibition was calculated by Probit analysis. Ivermectin showed activity against trophozoites of E. histolytica. The 50% of growth inhibition of ivermectin was 6.40 mg/ml. This dose was higher than for other anti parasitic drugs. Its activity in vivo in animal models remains to be demonstrated.

La amibiasis producida por Entamoeba histolytica es un problema de salud pública. Las formas clínicas más frecuentes son la disentería y el absceso hepático amibiano. En el mundo se notifican anualmente 50 millones de casos y más de 100 000 muertes por esta enfermedad. El ciclo de vida de E. histolytica tiene dos fases: trofozoíto y quiste. Los trofozoítos son los responsables de producir enfermedad. El tratamiento actual para la amibiasis incluye medicamentos con efectos colaterales serios. La ivermectina es un macrólido con actividad contra endoparásitos y ectoparásitos causantes de strongiloidosis, filariasis, oncocercosis, sarna y pediculosis. Su uso está extendido a casi todo el mundo y se lo reconoce como un medicamento seguro. El objetivo de este trabajo fue determinar la sensiblidad in vitro de trofozoítos de E. histolytica al tratamiento con ivermectina. Para determinar su sensibilidad a la droga, se utilizaron trofozoítos de E. histolytica cultivados en medio PEHPS. Durante su fase de crecimiento logarítmico se expusieron a diferentes concentraciones de ivermectina. Como controles se usaron otras drogas antiparasitarias. Se prepararon diluciones seriadas de cada droga, luego se agregaron a tubos con parásitos (2 x 10(4) células/ml). Se incubó por 72 h y luego se determinó el porcentaje de inhibición de crecimiento calculado por análisis Probit. La ivermectina tiene actividad contra trofozoítos de E. histolytica. La dosis de ivermectina que produjo el 50% de inhibición de crecimiento fue de 6.40 mg/ml. Esta dosis fue mayor a la encontrada con otras drogas antiparasitarias. Falta demostrar su actividad in vivo en modelos animales.

Se realizaron muestreos mensuales (set 2002-set 2003) de aguas en ocho estaciones en los ríos Areo, Morichal Largo, Uracoa y Yabo, a fin de estudiar el comportamiento estacional de las variables físico-químicas de estos ríos Morichales. Los parámetros pH, O2 disuelto y conductividad fueron determinados in situ, mientras que las concentraciones de algunos nutrientes (NO3-, NH4+, N total y P total), iones mayoritarios disueltos (Cl-, Na, K, Ca, Mg) y elementos trazas (Fe y Al) fueron medidas en el laboratorio. Todas las especies evaluadas mostraron mayores concentraciones durante el período de lluvias, lo que indica que en estos ecosistemas acuáticos, el proceso de aporte de elementos por las lluvias y el lavado de los suelos es más eficiente que el proceso de dilución por aumento de caudal. Algunos elementos tales como Na, Mg y cloruros son aportados principalmente por las precipitaciones, mientras que P total, Fe, Al y gran parte del Ca disuelto son aportados por el sustrato. El pH se relaciona positivamente con el Ca disuelto proveniente del sustrato. Las relaciones encontradas entre N total, Fe y Al indican que las solubilidades de ambos metales se incrementan por la presencia de materia orgánica soluble rica en N. Los resultados revelan que la composición química de las aguas de los ríos Morichales está condicionada por la naturaleza arenosa de los suelos, la cercanía a zonas costeras y el tipo de vegetación presente en estos ecosistemas acuáticos.

Monthly (Sept 2002-Sept 2003) water samples were collected in eight stations at the Areo, Morichal Largo, Uracoa and Yabo rivers, to determine the seasonal behavior of some physicochemical variables in these "Morichales" rivers. Parameters such as pH, dissolved O2 and conductivity were measured in situ, whereas concentrations of nutrients (NO3-, NH4+, total N and total P), dissolved major ions (Cl-, Na, K, Ca, Mg) and dissolved trace elements (Fe and Al) were measured in the laboratory. All the evaluated species showed higher concentrations in the wet season, indicating that, in these aquatic ecosystems, the contribution by rains and the washing of soils prevails over the dilution by river flow increase. Elements such as Na, Mg, and chlorides are principally provided by rainfall, whereas Fe, Al, total P and most of the dissolved Ca are leached from the substratum. The pH values correlated positively with dissolved Ca provided from the substratum. The relationships found between Fe, Al and total N indicate that their solubilities increase due to the presence of soluble N-rich organic matter. The results show that the water chemistry of these rivers is controlled by the sandy nature of the soils, the distance from the sea and the kind of vegetation found in these aquatic ecosystems.

O objeto principal deste trabalho foi determinar o comportamento estacional das variáveis físico-químicas dos rios Morichales tomando mostras mensais das águas entre setembro 2002 e setembro 2003 em oito (8) estações distribuídas entre os rios Areo, Morichal Longo, Uracoa y Yabo. Os parâmetros pH, oxigênio disolto e condutividade foram determinados in situ, enquanto as concentrações de alguns nutrientes (NO3-, NH4+, nitrogênio total e fósforo total), íons majoritários dissolvidos (Cl-, Na, K, Ca, Mg) e elementos traça (Fe e Al) foram medidas no laboratório. Todas as espécies químicas determinadas mostraram suas maiores concentrações durante o período de chuva, o que indica que nestes ecossistemas aquáticos, a contribuição de elementos pelas chuvas e a lavagem dos solos é mais eficiente que o processo de diluição por aumento de volume. Alguns elementos como o Na, o Mg e os cloretos são aportados principalmente pelas precipitações, enquanto o fósforo total, o Fe, o Al e grande parte o Ca dissolvido são aportados pelo substrato. Os valores o pH relacionam-se positivamente com o Ca dissolvido aportado pelo substrato. As relações encontradas entre o nitrogênio total, o Fe e o Al indicam que a presença destes elementos se encontra associada à presença de matéria orgânica dissolvida rica em compostos nitrogenados. Os resultados obtidos revelam que a composição química das águas dos rios Morichales se encontra associada à natureza arenosa dos solos, à cercania às zonas costeiras e a o tipo de vegetação presente nestes ecossistemas aquáticos.