Potential of microalgae in the bioremediation of water with chloride content / Potencial de microalga na biorremediação da água com conteúdo de cloretos

Abstract In this work it was carried out the bioremediation of water containing chlorides with native microalgae (MCA) provided by the Centre for study and research in biotechnology (CIBIOT) at Universidad Pontificia Bolivariana. Microalgae presented an adaptation to the water and so the conditions evaluated reaching a production of CO2 in mg L-1 of 53.0, 26.6, 56.0, 16.0 and 30.0 and chloride removal efficiencies of 16.37, 26.03, 40.04, 25.96 and 20.25% for microalgae1, microalgae2, microalgae3, microalgae4 and microalgae5 respectively. Water bioremediation process was carried out with content of chlorides in fed batch system with an initial concentration of chlorides of 20585 mg L-1 every 2 days. The Manipulated variables were: the flow of MCA3 (10% inoculum) for test one; NPK flow for test two, and flow of flow of MCA3+0.5 g L-1 NPK. Chloride removal efficiencies were 66.88%, 63.41% and 66.98% for test one, two and three respectively, for a total bioprocess time of 55 days.

Resumo Neste trabalho avaliou-se a biorremediação da água com conteúdos de cloretos utilizando microalgas nativas (MCA) fornecidas pelo Centro de Estudos e Pesquisas em Biotecnologia (CIBIOT) da Universidad Pontifícia Bolivariana. As microalgas empregadas apresentaram uma adaptação ao meio de cultura e as condições operacionais avaliadas atingindo uma produção de CO2 em mg L-1 de 53,0, 26,6, 56,0, 16,0 e 30,0 e eficiências de remoção de cloretos de 16,37, 26,03, 40,04, 25,96 e 20,25% para MCA1, MCA2, MCA3, MCA4 e MCA5 respectivamente. A biorremediação da água com conteúdos de cloretos foi realizada em modo batelada alimentada (Feed Batch) com uma concentração inicial de cloretos de 20585 mg L-1. A alimentação foi realizada a cada 2 dias. A variável manipulada foi: ensaio um, uma vazão de MCA3 (10% de inoculo); ensaio dois, uma vazão de NPK e ensaio três, uma vazão de MCA3+0,5 g L-1 NPK. As eficiências de remoção foram 66,88%, 63,41% e 66,98% para os ensaios um, dois e três, respectivamente num tempo do bioprocesso total de 55 dias.

Riesgos potenciales de salud por consumo de agua con arsénico en Colima, México / Potential health risks from consumption of water with arsenic in Colima, Mexico

Resumen: Objetivo: Estimar los riesgos potenciales de salud debidos a la ingestión crónica de arsénico (As) en agua en Colima, México. Material y métodos: Se muestrearon aleatoriamente 36 pozos en 10 acuíferos locales. El análisis se hizo mediante ICP-OES siguiendo estándares internacionales. Se realizó una interpolación geoestadística con ArcGIS, implementando un modelo de ponderación del inverso de la distancia, para estimar la ruta de exposición de consumo en cada localidad. Se calcularon los coeficientes de peligro (HQ) y riesgo carcinogénico (R). Resultados: El HQ promedio ponderado de As para Colima es 2.41. Existen valores de HQ>1 para As que indican efectos adversos no carcinogénicos para la salud por ingestión continua y prolongada de agua; esto podría afectar a 183 832 individuos en el estado. El riesgo calculado de desarrollar cáncer debido a las concentraciones de arsénico en aguas subterráneas (R) es de 1.089E-3; estadísticamente esto podría ocasionar 446 casos de cáncer. Conclusiones: Los niveles actuales de arsénico en el agua de pozo incrementan los riesgos carcinogénicos y no carcinogénicos de salud humana en Colima.

Abstract: Objective: To estimate potential health risks due to chronic ingestion of arsenic from groundwater in Colima, Mexico. Materials and methods: Samples were randomly taken in 36 wells from 10 local aquifers. Analysis was performed by ICP-OES following international standards. Geostatistical interpolation was performed with ArcGIS, implementing a model weighting inverse distance to estimate arsenic routes of exposure and consumption on each locality. The Hazard Quotient Ratio (HQ) and carcinogenic risk (R) for As were estimated. Results: The weighted average HQ for arsenic in Colima is 2.41. There are HQ> 1 values indicating adverse non-cancer health effects by continuous and prolonged intake of water with arsenic, which could affect 183 832 individuals in the state. The risk of developing any type of cancer among the population in this study due to high arsenic concentrations in groundwater (R) is 1.089E-3, which could statistically cause 446 cases of cancer. Conclusions: Current levels of arsenic in groundwater increase carcinogenic and non-carcinogenic human health risks in Colima.

Influence of sediments and tungsten traces on the skeletal structure of Pseudodiploria: a reef building scleractinian coral from the Veracruz Reef System National Park, Mexico / Influencia de los sedimentos y trazas de tungsteno en la estructura del esqueleto de Pseudodiploria un coral escleractinio constructor de arrecifes del Parque Nacional Sistema Arrecifal Veracruzano, México

Abstract:Coral reefs are under intense conditions of stress caused by the anthropogenic activities in coastal areas and the increase of human population. Water effluents from urban and industrial areas carry large amounts of sediments and pollutants affecting corals populations, inducing bioerosion, increasing diseases and promoting the development of algae that compete for space with corals. In the Veracruz Reef System National Park (VRSNP) coral reefs are strongly affected by human activities carried out in the area. Gallega and Galleguilla reefs are among the most affected by wastewater discharges from the industrial (petrochemical and metallurgical) and urban areas in their vicinity. To assess the potential impact of this contamination on corals in the VRSNP, a chemical composition and morphology study of 76 Pseudodiploria colonies collected in reefs Gallega, Galleguilla, Isla Verde and Isla de Enmedio, was performed. Fragments of ~10 cm2 were collected and boric acid at 0.5 % was used to remove tissue from the skeleton; once clean, the morphology of each sample was determined with a scanning electron microscope (SEM). Subsequently, to test the chemical composition, an energy dispersion spectroscopy of X-ray chemical microanalysis (EDSX) was performed in the SEM. We found that corals from Gallega and Galleguilla reefs, located closer to human populations, presented high levels of tungsten and the skeleton exhibited multiple perforations. In contrast, corals from the farthest offshore reefs (Isla Verde and Isla de Enmedio) exhibited lower levels of tungsten and fewer perforations in their skeleton. These results demonstrated that anthropogenic activities in the NPVRS are affecting corals skeleton, highly damaging and promoting their bioerosion. The presence of traces of tungsten in the skeleton of corals is an evidence of the damage that waste discharges are causing to coral reefs. Discharges of large amounts of contaminants promoted the growth of harmful species that grow and develop into the corals skeleton, causing its bioerosion, and making them susceptible to disease and physical damage. This study is the first evidence of the effects of contamination on these species; therefore, further studies are necessary to determine the impact of pollution on their biology and survival. Rev. Biol. Trop. 64 (3): 1077-1089. Epub 2016 September 01.

ResumenLos arrecifes de coral se encuentran bajo condiciones intensas de estrés causado por las actividades antropogénicas y el incremento de las poblaciones humanas en las zonas costeras. Las descargas de aguas de origen urbano e industrial transportan sedimentos y contaminantes que afectan a las poblaciones de corales, induciendo la bioerosion, el aumento de enfermedades en los corales y promueven el desarrollo de algas que compiten por espacio con los corales. En el Parque Nacional Sistema Arrecifal Veracruzano (NPVRS) los arrecifes de coral son afectados fuertemente por las actividades humanas que se llevan a cabo en la zona. Los arrecifes Gallega y Galleguilla son de los más afectados por las descargas de aguas residuales provenientes de la industria (petroquímica y metalúrgica) y de áreas urbanas que desembocan sus aguas en las proximidades de los arrecifes. Para evaluar el posible impacto de las descargas de aguas en los corales del NPVRS, se realizó un estudio de la composición química y morfología de 76 colonias de Pseudodiploria en los arrecifes Gallega, Galleguilla, Isla Verde e Isla de Enmedio. Se recolectaron fragmentos de ~10 cm2, el tejido del esqueleto fue removido utilizando ácido bórico al 0.5 %. Una vez limpia la muestra, la morfología fue analizada con un microscopio electrónico de barrido (SEM), posteriormente, para analizar la composición química de las muestras, realizamos una espectroscopia de dispersión de energía o micro-análisis químico de rayos X (EDSX) en el SEM. Encontramos que los corales de los arrecifes Gallega y Galleguilla que se encuentran ubicados cerca de poblaciones humanas, presentan altos niveles de tungsteno y el esqueleto exhibe múltiples agujeros. En contraste, los corales de los arrecifes más lejanos (Isla Verde e Isla de En medio) mostraron niveles más bajos de tungsteno y un menor número de agujeros en su esqueleto. Nuestros resultados demuestran que las actividades antropogénicas en el NPVRS, están afectando el esqueleto de los corales y promueven la bioerosión. Las descargas de grandes cantidades de contaminantes hacia las zonas costeras, promueven el crecimiento de especies dañinas que crecen y se desarrollan dentro del esqueleto de los corales, causando bioerosión del esqueleto, haciéndolos susceptibles a enfermedades y daños físicos. Debido a que este estudio es la primera evidencia de los efectos de la contaminación sobre esta especie de corales, son necesarios más estudios para determinar el impacto de la contaminación sobre su biología y la supervivencia de los corales.

[Adsorption of arsenic [III] on a natural lignocellulosic residue valued activated carbon - such cores dates]

The objective of this study, is the removal of arsenic [three] from contaminated water, by adsorption on activated carbon, prepared from a lignocellulosic natural waste in fact "the dates stones". The effectiveness of adsorption was evaluated for the carbonized raw material at 600[degree]C and after its activation at 900[degree]C. Results of the adsorption capacity tests were found to be 21mg/g for the activated carbon and barely 2mg/g before activation. The satisfactory operating conditions are carried out with pH bordering neutrality and an ambient temperature of 20[degree]C. This result is similar to that found in the litterature but for other biosorbents. The optimal adsorption of arsenic [three] follows the Langmuir and Freundlich models. The kinetics of adsorption is slow, of the second order, with a value of adsorption constant k[ads] equal to 1,16.10[-2] h[-1].

Flocculation of Cu, Mn, Ni, Pb, and Zn during estuarine mixing [Caspian Sea]

During estuarine mixing of fresh water with saline water and due to the flocculation process, a portion of dissolved metals come into particulate phase, and the dissolved load decreases. This process plays an important role in self-purification of heavy metals in rivers. In this study, flocculation of Cu, Mn, Ni, Pb and Zn during mixing of Cheshme-Kileh River water with Caspian Sea water has been investigated. Salinity and electrical conductivity are the governing factors for the flocculation of Mn and Cu. Zn and Ni are governed by pH. Dissolved oxygen is a governing factor for the flocculation of Pb. Rapid flocculation occurs in the earlier stages of mixing. The final flocculation rates of metals are in the following order: Mn [68.79%] > Pb [45.45%] > Ni [26.32%] > Cu [23.08%] > Zn [21.21%]. In addition, electro-flocculation [EF] is investigated. The results reveal that EF had adverse effect on flocculation rates of heavy metals. General pattern of EF of metals is like the following: Mn [57.89%] > Pb [40.9%] > Cu [23.08% > Ni [22.37%] > Zn [15.15%]. Furthermore, the effect of decreasing pH level on flocculation of heavy metals is studied. Except for Mn, decreasing the pH increased the flocculation rates of heavy metals. Maximum flocculation of Ni, Cu, Pb, and Zn occur at pH about 7.5. Due to the flocculation of trace metals during the estuarine mixing about 51.6, 7.8, 5.5, 3.9, and 3.6 ton/year of Mn, Ni, Zn, Pb, and Cu, respectively, are removed from the river water

[Producing activated carbon from scrap tires by thermo-chemical method and evaluation its efficiency at removal racid black1 dye]

The disposal of waste tires has become an increasingly important issue worldwide in recent years. Tires not only take up large amounts of valuable landfill space, but also create fire hazards and provide a refuge for disease- carrying creatures. The goal of this study was to produce activated carbon from scrap tires .Adsorption of Acid Black1 [AB1] in aqueous solution as a pollutant by the activated carbon was also investigated. Activated carbon was prepared from scrap vehicle tires using a thermo-chemical activation method. The chemical composition and solid structure of prepared activated carbon were analyzed using Scanning Electron Microscopy [SEM] coupled with energy dispersive spectrometry [EDS] and Nitrogen Sas. Micro pore volumes of the sample were determined by the application of the BET and BJH. Predominant composition of prepared activated carbon was C [83.274%] and with area surface of 44.226 and 35.747 m2/gr observed by BET and BJH methods, respectively. Mean pore diameter was 52 nm. The result of this study showed that increasing of initial dye concentration and pH would lead to decrease of adsorption/removal of dye but by increasing of sorbent dosage and contact time, adsorption/removal of dye increased. As the results of present study it can be concluded that the production of the activated carbon from scrap tires, can provide a two-fold environmental and economic benefit; a recycling path is created for scrap tires of vehicles, and a new suitable adsorbent is produced for pollutants removal

[Evaluation of powdered activated carbon efficiency in removal of dissolved organic carbon in water treatment]

Powdered Activated-carbon is known as a suitable absorbent for organic materials. The aim of this research is evaluation of Powdered Activated-Carbon [PAC] efficiency in removal of Dissolved Organic Carbon [DOC] in water treatment in Isfahan. The increase of PAC for DOC reduction has done in three paths in the Isfahan water treatment plant [WTP]. These paths including: 1] Intake up to entrance of WTP 2] Intake to exit of WTP 3] Between entrance and exit of waterworks. The paths were simulated by the Jar test system. Then DOC and UV[254] absorption were analyzed and SUVA parameter for samples and activated-carbon adsorption isotherm was calculated. The injected PAC doses of 20,40,60,80 and 100 mg/l caused decreasing in DOC and UV [254] absorption in every sample in all paths. The average of this decrease, from intake to WTP.s exit [second path] was the greatest 69.8 +/- 3.9% and the common WTP process had capability of removing 35% of DOC. The first path also showed that PAC can reduce 33 +/- 2% DOC of raw water by itself. Activated-carbon absorption results were adhered from Freundlich adsorption isotherm. In the third path there was less DOC removal efficiency than excepted when Activated-Carbon injected in rapid mixed basin with coagulant. Powdered activated carbon porosity reduction due to effect of coagulant can be the reason for this issue. Also according to different paths, the point of intake is more suitable for powdered activated carbon addition

Removal of lead from aqueous effluents by adsorption on coconut shell carbon.

The application of adsorption for removal of heavy metals is quite popular and activated carbon is universally used as an adsorbent. However, high cost of its preparation and regeneration has led to a search for alternative sorbents, especially in the developing countries. A number of sorbents are used to remove metals by adsorption from industrial effluents, which include insoluble starch, xanthates, modified cotton and wool, tree barks, activated carbon, plant leaves and agricultural products. Therefore, as an alternative, coconut shell carbon (CSC), a low cost sorbent derived from organic waste material, was used in the present work, for removal of lead from aqueous effluents. The results of the batch sorption studies indicated that the efficiency of lead removal by coconut shell carbon is comparable to that of commercially available activated carbon. From the kinetic and equilibrium studies, the sorptive capacity of coconut shell carbon for lead was found to be 30 mg/g. Desorption and subsequent recovery of the metal from the surface of the sorbent was successfully demonstrated. Parameters affecting the sorption were evaluated.

2, 4 dichlorophenol (2, 4-DCP) sorption from aqueous solution using granular activated carbon and polymeric adsorbents and studies on effect of temperature on activated carbon adsorption.

Adsorption equilibrium, kinetics and thermodynamics of 2,4-dichlorophenol (2,4-DCP), one of the most commonly used chlorophenol, onto bituminous coal based Filtrasorb-400 grade granular activated carbon, were studied in aqueous solution in a batch system with respect to temperature. Uptake capacity of activated carbon found to increase with temperature. Langmuir isotherm models were applied to experimental equilibrium data of 2, 4-DCP adsorption and competitive studies with respect to XAD resin were carried out. Equilibrium data fitted very well to the Langmuir equilibrium model. Adsorbent monolayer capacity 'Q0, Langmuir constant 'b' and adsorption rate constant 'k(a)' were evaluated at different temperatures for activated carbon adsorption. This data was then used to calculate the energy of activation of adsorption and also the thermodynamic parameters, namely the free energy of adsorption, deltaG0, enthalpy of adsorption, deltaH0 and the entropy of adsorption deltaS0. The obtained results showed that the monolayer capacity increases with the increase in temperatures. The obtained values of thermodynamic parameters showed that adsorption of 2,4 DCP is an endothermic process. Synthetic resin was not found efficient to adsorb 2,4 DCP compared to activated carbon. The order of adsorption efficiencies of three resins used in the study found as XAD7HP > XAD4 > XAD1180.

Evaluation of adsorption potential of adsorbents: a case of uptake of cationic dyes.

Adsorption potential of a commercial activated carbon (FS300) has been evaluated for the uptake of cationic dyes namely methylene blue (MB) and rhodamine B (RB). Though, there are numerous studies in literature which report the sorption of MB (more than 40 studies) and RB (more than 10), however none of these use a common parameter to report the capacity of the sorbent. A protocol, based on the equilibrium dye concentration has been proposed to measure the sorption potential of a sorbent. The Langmuir model can very well describe the experimental equilibrium data for both dyes (coefficient of correlation > 0.999). MB (Qm = 312.5 mg g(-1)) is more adsorbable than the RB (Qm = 144.9 mg g(-1)). Molecular weight and chemical structure of dye molecules seem to affect the dye uptake. The effect of pH on dye uptake has also been evaluated by varyingpH from 3 to 11. Uptake of MB increases with pH, wherein RB removal decreases with pH. Dyes could not be desorbed either by distilled water (0.06 and 0.11% for MB and RB respectively), or by 0.1 NHCl (0.136 and 3.0% for MB and RB respectively) indicating, chemical adsorption type of adsorbent-adsorbate interactions.

Molecular size as a limiting characteristic for bioconcentration in fish.

The relationships between the bioconcentration factor (BCF) of chemicals in fish and their size, as characterized by molecular weight (MW), effective cross sectional diameter (Deff), and maximum diameter (Dmax) have been investigated using an experimental data set of 737 new and 441 existing chemicals monitored by the Japanese Chemical Substances Control Law (CSCL). Substances with BCF > or = 5000 (very high bioconcentration potential) typically have MW < 550, Deff < 1.1 nm and Dmax < 2.0 nm, respectively and the substances with BCF > or = 1000 (high bioconcentration potential) have MW < 550, Deff < 1.4 nm and Dmax < 2.9 nm, respectively Therefore, the previously suggested threshold values for Deff (0.95 nm) and Dmax (1.5 nm) used for discriminating between bioconcentrative and non-bioconcentrative substances were found to be somewhat small. We found that many substances with BCF > or = 1000 and Dmax > or = 1.5 nm have Deff < 0.95 nm.

Treatment of municipal landfill leachate by solar photocatalytic method using fixed titanium dioxide.

Treatment of municipal landfill leachate by fixed TiO2 photocatalytic method was investigated in the present study using sunlight as light source. Indigenous TiO2 was immobilized with white cement. The leachate used in the study was collected from Kodungaiyur dumpsite in Chennai. Optimization of pH, catalyst dose and exposure time were carried out. Chemical Oxygen Demand (COD) was used to determine the degradation efficiency. The degradation efficiency of leachate was found to be 85% with a batch flat reactor under optimum condition. Fixed catalyst was found to be reusable for 5 times without any reduction in the efficiency. The degradation process was found to follow pseudo first order kinetics.

Remediation of lead from lead electroplating industrial effluent using sago waste.

Heavy metals are known toxicants, which inflict acute disorders to the living beings. Electroplating industries pose great threat to the environment through heavy load of metals in the wastewater discharged on land and water sources. In the present study, sago processing waste, which is both a waste and a pollutant, was used to adsorb lead ions from lead electroplating industrial effluent. Two types of sago wastes, namely, coarse sago waste and fine sago waste were used to study their adsorption capacity with the batch adsorption and Freundlich adsorption isotherm. The parameters that were considered for batch adsorption were pH (4, 5 and 6), time of contact (1, 2 and 3 hrs), temperature (30, 37 and 45 degrees C) and dosage of the adsorbent (2,4 and 6 g/L). The optimal condition for the effective removal of lead was found to be pH 5, time of contact 3 hrs, temperature 30 degrees C and dosage 4 g/L with coarse sago waste than fine sago waste.

Vinasse biodegradation by Phanerochaete chrysosporium.

Vinasse is a colored recalcitrant wastewater of the distillery industry. The aim of this work was to study the use of Phanerochaete chrysosporium for the vinasse degradation under two different growth conditions. Vinasse was treated by P. chrysosporium in a liquid inoculum form, during 32 days at room temperature (approximately 25 degrees C) and at 39 degres C. Chemical oxygen demand (COD), total phenol concentration and color removal were measured and there8 was a decrease in COD, phenolic concentration and color of 47.48%, 54.72% and 45.10% respectively, at room temperature and a decrease in 54.21%, 59.41% and 56.8 1% respectively at 39 degrees C.

Ozonation of exhausted dark shade reactive dye bath for reuse.

Exhausted reactive dye bath of dark shades were collected from cotton knit wear dyeing units in Tirupur. Ozonation was conducted in a column reactor system fed with ozone at the rate of 0.16 g/min to assess its efficiency in reducing the color, chemical oxygen demand and total organic carbon. The potential of the decolorized dye bath for its repeated reuse was also analyzed. The results from the reusability studies indicate that the dyeing quality was not affected by the reuse of decolorized dye bath for two successive cycles. Complete decolorization of the effluent was achieved in 60 minutes contact time at an ozone consumption of 183 mg/L for Red, 175 for Navy Blue and 192 for Green shades respectively. The corresponding COD removal was 60%, 54% and 63% for the three shades while TOC removal efficiency was 59%, 55% and 62% respectively. It is concluded that ozonation is efficient in decolorization of exhausted dye bath effluents containing conventional reactive dyes. However, the corresponding removal of COD from the textile effluent was not significant.

Photocatalytic degradation of reactive dyes and simulated dyebath wastewater.

The study related to photocatalytic degradation of three reactive dyes, namely, Reactive Red 141 (RR141), Reactive Orange 16 (RO16) and Reactive Violet 13 (RV13) was carried out. Further, two simulated textile dyebath wastewaters were prepared and examined for photocatalytic degradation. Three dyes were subjected to photodegradation in a batch annular immersion well photoreactor equipped with a 400W Medium Pressure Mercury Lamp (MPML). The UV illuminated TiO2 containing aqueous suspensions found to remove colour as well as chemical oxygen demand (COD). The photocatalytic activity was monitored by measuring the rates of decolorization and COD removal as a function of concentration of the dye and treatment time. The photodegradation efficiency of these three reactive dyes was found in the order of RR141 > RO16 > RV13. The first order rate constant (k(app)) for decolorization was 3-9 times higher than the k(app) for COD removal. The rate constants for degradation of simulated wastewater were also of the similar order of magnitude. These results suggest that TiO2/UV photocatalysis may be envisaged as a method for treatment of diluted coloured wastewaters not only for decolourization, but also for polishing of the COD parameter.

Scavenging of Ni(II) metal ions by adsorption on PAC and babhul bark.

The removal of toxic nickel metal ions by adsorption, using powder activated charcoal (PAC) and non-conventional adsorbent modified Indian powder babhul bark (PBB), was studied at room temperature. The adsorption isotherms were obtained in a batch reactor. It is observed that, the process of uptake followed first-order adsorption rate expression and obeyed Langmuir and Freundlich models of adsorption. Effects of variations in parameters such as pH, contact time, adsorbent dose, initial Ni(II) concentration and particle size were also studied.

Studies on fluoride removal using adsorption process.

Batch adsorption studies were undertaken to assess the suitability of commercially available activated charcoal to remediate fluoride-contaminated water. The effects of some of the major parameters of adsorption, viz. pH, dose of adsorbent, rate of stirring, contact time and initial adsorbate concentration on fluoride removal efficiency were studied and optimized. The optimum sorbent dose was found to be 2.0 g/100 mL, equilibrium was achieved in 120 minutes and enhanced adsorption was obtained at pH 2. Maximum fluoride removal was observed to be 94% at optimum conditions. Freudlich as well as Langmuir isotherms were plotted and kinetic constants were determined.

The use of testa of groundnut shell (Arachis hypogea) for the adsorption of Ni(II) from the aqueous system.

This paper presents the use of testa of groundnut shell for the removal of nickel from dilute aqueous solutions at laboratory scale. The adsorption isotherm of Ni(II) on the testa of groundnut shell was carried out by the batch adsorption process. Various parameters such as initial concentration, pH and amount of the adsorbent doses were studied. The experimental adsorption data obtained followed both Langmuir as well as Freundlich isotherms. Maximum adsorption (85%) was observed at pH 6. The monolayer adsorption capacity was found to be 18.79 mg/g, which is greater than most of the low-cost adsorbents reported.

Efecto de sedimentos naturales enriquecidos con zinc, en modelos aislados y en microcosmos, sobre tres especies de invertebrados bentónicos / Effect of zinc-enriched sediments, in open and isolated systems, on three species of benthonic invertebrates

Availability of toxics in aquatic bodies is limited by the physicochemical characteristics of sediments and water, as well as by the interactions between the different xenobiotics and inhabits species. The aim of this work was to relate the effect produced by zinc (Zn) spiked in sediments of the Ignacio Ramirez dam (PIR), in isolated and microcosms models, on ATP concentration of three benthic organisms with the metal biodisponibility. The selected species were a crustacean, an annelid and a mollusk: Hyalella azteca (Amphipoda: Hyalellidae), Limnodrilus hoffmeisteri (Oligochaeta: Tubificidae) and Stagnicola attenuata (Basommatophora: Lymnaeidae), species that are found at high proportions in the reservoir and use different spaces in the benthos. Samples of sediments and organisms were collected from the PIR during the dry season (February of 1999). Metal concentration (Zn, Fe, Cu and Ni), pH, texture, particle size, total nitrogen and organic matter were determined in sediments. Sublethal studies were carried out using two types of static systems (organisms isolated and in microcosms). Both models contained PIR sediments enriched with Zn (nominal concentration of 0.8129 mg/kg) and synthetic water in a proportion of 1:4. The test organisms were added to the systems once the equilibrium was reached (2 hr) considering the biomass quantity with respect to volume (1.0 g of organism by each 100 ml of water:sediment). After 0, 12, 24, 36, 48 and 72 hr of exposure, samples of sediment and hydrobionts were taken, and Zn content was quantified by atomic absorption. ATP concentration was also determined in organisms. The effect produced by natural sediments spiked with Zn is increased by the presence of more than one specie in the system (microcosm). With respect to Zn levels, two of the organisms tend to lose this metal in isolated and microcosm models, probably as a regulation strategy in its accumulation, as well as Fe presence in the reservoir sediments. Therefore...

En los cuerpos acuáticos la disponibilidad de los tóxicos es limitada por las características fisicoquímicas de los sedimentos y agua, así como por las interacciones entre los diversos xenobióticos y entre las especies que los habitan. Por lo anterior, el objetivo del presente trabajo fue relacionar el efecto producido por el zinc (Zn) sembrado en sedimentos del embalse Ignacio Ramírez (PIR), en modelos aislados y en microcosmos, sobre el ATP de res organismos bentónicos con la biodisponibilidad del metal. Las especies seleccionadas fueron: Hyalella azteca, Limnodrilus hoffmeisteri y Stagnicola attenuata, dado que se encuentran en altas proporciones en el embalse y ocupan espacios diferentes en el bentos. Las muestras de sedimentos y organismos se colectaron en la estación de sequía (febrero de 1999). A los primeros se les determinó el pH, textura, tamaño de partícula, nitrógeno total, materia orgánica y concentración de metales (Zn, Fe, Cu y Ni). Posteriormente se realizó un estudio de toxicidad subletal utilizando dos tipos de sistemas estáticos (organismos aislados y en microcosmos). Ambos modelos contenían sedimentos de la PIR enriquecidos con Zn (concentración nominal de 0.8129 mg/kg) y agua sintética en una proporción de 1:4. Los organismos de prueba fueron adicionados una vez alcanzado el equilibrio (2 hr) considerando la cantidad de biomasa con respecto al volumen (1.0 g de organismo por cada 100 ml de agua:sedimento). Después de 0, 12, 24, 36, 48 y 72 hr de exposición se tomaron muestras del sedimento y de los hidrobiontes, a los cuales se les cuantificó el contenido de Zn por absorción atómica. A los organismos también se les determinó la concentración de ATP. Los resultados obtenidos muestran que el efecto producido por los sedimentos naturales enriquecidos se ve potenciado por la presencia de más de una especie en el sistema (microcosmos). Con respecto a los niveles de Zn, dosde los organismos (L. hoffmeisteri y S. attenuata) tienden a...