The antifouling booster biocides are frequently studied for toxic effects on the aquatic ecosystems. The present investigation proposes passive silicone rubber samplers as a collection method for biocides, once these methods can concentrate substances in aqueous matrices at very low levels. Through the passive sampler-water partition coefficient (Ksw) and the analyte chemical nature, we can optimize their extraction from the membrane to apply in the sample medium. We used the co-solvent method to determine the Ksw of three third-generation antifouling biocides, chlorothalonil, dichlofluanid, and dichlorooctylisothiazolinone (DCOIT), with log Ksw = 2.24, 4.01, and 2.38, respectively. Improving extraction also led to a recovery range higher than 70%, determinations were carried out by gas chromatography with an electron capture detector. Biocides concentration in seawater samples from Itaqui port (São Marcos Bay, northern Brazil) ranged from 0.058 to 0.72 µg L-1 for chlorothalonil, 0.001 to 0.008 µg L-1 for dichlofluanid, and 0.018 to 0.64 µg L-1 for DCOIT. ecosystems levels samplerwater sampler water (Ksw nature medium cosolvent co solvent thirdgeneration third generation chlorothalonil dichlofluanid DCOIT, DCOIT , (DCOIT) 224 2 24 2.24 401 4 01 4.01 238 38 2.38 respectively 70 70% detector São Bay Brazil 0058 0 058 0.05 072 72 0.7 L1 L 1 L- 0001 001 0.00 0008 008 0018 018 0.01 064 64 0.6 (DCOIT 22 2.2 40 4.0 23 3 2.3 7 005 05 0.0 07 0. 000 00 06 6 2. 4.

Nanoparticles of TiO2 doped with low amount of Fe were synthesized from natural ilmenite obtained from alluvial gold mine wastes. The obtained TiO2 were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), UV-Vis diffuse reflectance, thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), N2 adsorption-desorption isotherms, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results confirm the formation of mesoporous TiO2 nanoparticles in anatase phase with 0.05 wt.% of iron possibly replacing some titanium places. All the characterizations were performed to the synthesized solid and the reference materials (TiO2 anatase and Degussa P25). The photocatalytic activity of both the synthesized solid and references were evaluated in the photo-oxidation of cyanide in aqueous medium under UV illumination. An experimental design type Box-Behnken was performed choosing three different parameters: the initial concentration of cyanide (50, 150 and 250 ppm) the catalyst load (0.1, 0.5 and 1.0 g L-1) and the oxygen source. The percentage of cyanide conversion was chosen as response in the design obtaining as optimal conditions [CN-]0 = 50 ppm, catalyst load = 0.6 g L-1 and air bubbling. Under these conditions it was reached 32, 32 and 89% of cyanide conversion for Fe-TiO2 synthesized, TiO2 anatase and Degussa P25, respectively. TiO wastes Xray X ray XRD, XRD , (XRD) XRF, XRF (XRF) Fouriertransform Fourier transform FTIR, FTIR (FTIR) UVVis Vis reflectance analysisdifferential analysis differential TGA/DSC, TGADSC TGA/DSC TGA DSC (TGA/DSC) N adsorptiondesorption adsorption desorption isotherms TEM (TEM XPS. XPS . (XPS) 005 0 05 0.0 wt wt. places (TiO P25. P25 P P25) photooxidation photo oxidation illumination BoxBehnken Box Behnken parameters 50, (50 15 25 ppm 0.1, 01 1 (0.1 5 0. 10 1. L1 L source CN0 CN [CN-] 06 6 L- bubbling 3 89 FeTiO2 FeTiO Fe-TiO respectively (XRD (XRF (FTIR (TGA/DSC (XPS 00 P2 (5 2 0.1 (0. [CN- 8 ( (0 [CN

Groundwater is considered an important source of water aid for human consumption. However, this water can be contaminated by impurities, such contamination spots that might reach the water tables. The aim of this study was to investigate the quality of shallow groundwater in Flores neighborhood, located in the municipality of Benevides, within Belém metropolitan region, State of Pará, Brazil. Recommendations described in Standard Methods for Examination of Water and Wastewater were followed at the time to determine physical-chemical parameters such as potential hydrogen (pH), electrical conductivity (EC), total dissolved solids (TDS), apparent color, turbidity, total hardness (TH), ions and trace elements. Multivariate statistical analysis has shown that most predictive water-quality parameters set for human consumption are associated with natural events involving weathering and leaching processes. Nevertheless, parameters of nitrate, phosphate, EC, TDS and pH are also influenced by anthropic conditions in the surroundings, mainly phosphate and nitrate ions. Therefore, it can be concluded that shallow groundwaters in Flores neighborhood are unsuitable for human consumption, making it necessary for municipal public authorities to take action to solve the problem of water shortage in the borough, thus preventing the population from use those shallow groundwaters, as their consumption can bring health problems. However impurities tables Benevides region Pará Brazil physicalchemical physical chemical pH, , (pH) EC (EC) TDS, (TDS) color turbidity TH, TH (TH) elements waterquality processes Nevertheless surroundings Therefore borough problems (pH (EC (TDS (TH

The selective separation of precious metals from complex aqueous solutions is important in protecting the environment, aquatic ecosystems, water resources and recycling resources. In this study, cysteine-containing polymeric nanoparticles were synthesized using the molecular imprinting (MIP) technique with the mini-emulsion polymerization method. The basis of the polymer design is inspired by affinity of silver to cysteine in biological systems. The synthesized silver ion imprinted (Ag+-IIP) poly(hydroxyethylmethacrylate-N -methacryloyl-L-cysteine) poly(HEMA-MAC) nanoparticles were characterized by elemental analysis, zeta sizer, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM). The effects of pH, ionic strength and interaction time on adsorption of Ag+ ions were investigated. In experimental studies, the highest adsorption amount (196.9 mg g1 nanoparticle) was reached in a short period of 40 min at pH 5.0 and 150 mg L-1 concentration. Selectivity studies of synthesized Ag+-IIP nanoparticles against silver (Ag+) ions were carried out in the presence of lithium (Li+), barium (Ba2+), mercury (Hg2+) and cadmium (Cd2+) ions. Experimental results indicate that nanoparticles adsorb Ag+ ions with high selectivity. Ag+-IIP nanoparticles have 3.7, 3.1, 2.4, and 2.6 times more selective or higher affinity for Ag+ ions compared to Li+, Ba2+, Hg2+ and Cd2+ ions, respectively, compared to Ag+-non-imprinted (NIP) nanoparticles. environment ecosystems study cysteinecontaining containing MIP (MIP miniemulsion mini emulsion method systems Ag+IIP AgIIP IIP Ag (Ag+-IIP polyhydroxyethylmethacrylateN poly hydroxyethylmethacrylate N methacryloylLcysteine methacryloyl L -methacryloyl-L-cysteine polyHEMAMAC HEMA MAC poly(HEMA-MAC analysis sizer FTIR (FTIR spectroscopy AFM, AFM , (AFM) SEM. SEM . (SEM) investigated 196.9 1969 196 9 (196. g nanoparticle 4 50 5 0 5. 15 L1 1 L- concentration (Ag+ Li Li+ (Li+) Ba2 Ba Ba2+ (Ba2+) Hg2 Hg (Hg2+ Cd2 Cd (Cd2+ selectivity 37 3 7 3.7 31 3.1 24 2 2.4 26 6 2. respectively Ag+nonimprinted Agnonimprinted non NIP (NIP (AFM (SEM 196. 19 (196 (Ag (Li+ (Ba2+ (Hg2 (Cd2 3. nonimprinted (19 (Li (Ba2 (Hg (Cd (1 (Ba (

Seeking a viable alternative to fossil fuels as the primary energy source, bioethanol has emerged as a promising second-generation fuel derived from lignocellulosic biomass. With Brazil ranking pineapple as the third most produced fruit in temporary crops, this study aims to assess the impact of chemical pretreatment techniques, specifically organosolv and diluted acid, on the residual biomass of Pérola pineapple peel to enhance bioethanol production. Employing an experimental design that incorporates temperature, reaction time, and varying concentrations of organic solvent, the study examines their effects on the susceptibility of the substrate to saccharification for future bioethanol generation. Factors such as alphacellulose, hemicellulose, and lignin were evaluated in triplicate and subjected to statistical analysis using the Tukey test with a confidence level of 95%. Upon application of the pretreatment methods, it was observed that the organosolv solvent approach (utilizing water and ethanol) with sulfuric acid exhibited superior sugar conversion, yielding the highest concentration of xylose at 9.13 g L-1. Additionally, the pretreated biomass contained 1.38 g L 1 of cellobiose, 3.11 g L-1 of arabinose, and 3.76 g L-1 of glucose. This technique demonstrates promising potential for obtaining fermentable sugars crucial for bioethanol production. source secondgeneration second generation crops techniques production temperature time alphacellulose hemicellulose 95 95% methods utilizing ethanol conversion 913 9 13 9.1 L1. L1 1. Additionally 138 38 1.3 cellobiose 311 3 11 3.1 L- arabinose 376 76 3.7 glucose 91 9. 31 3. 37 7

Even though ammonia is a natural component of aquatic environments, elevated concentrations indicate pollution and environmental degradation. Consequently, efficient analytical methods for monitoring ammonia levels are crucial for preserving water quality. Voltammetry offers a sustainable approach for NH3 quantification, combining good analytical performance with low sample and reagent consumption, minimizing waste generation. However, despite these advantages, the voltammetric determination of ammonia remains relatively unexplored. Therefore, this study investigated the electrochemical behavior of NH3 in alkaline solutions using a non-modified Pt electrode and evaluated the performance of differential pulse voltammetry (DPV) and square wave voltammetry (SWV) for NH3 determination. DPV provided superior performance, with limits of detection and quantification of 0.79 µmol L-1 (0.011 ppmN) and 2.6 µmol L-1 (0.036 ppmN), respectively, which comply with the maximum allowable ammonia concentration in natural waters according to Brazilian and European regulations. The voltammetric method successfully quantified ammonia in tap and river water samples, providing results concordant with the established Berthelot spectrophotometric method, at a 95% confidence level. Additionally, it is simple and fully accessible to non-electrochemist since no sophisticated procedures for electrode modification are needed. Finally, the high analytical performance of the proposed method makes it valuable for pollution monitoring in aquatic environments. environments degradation Consequently quality NH consumption generation However advantages unexplored Therefore nonmodified non modified (DPV SWV (SWV 079 0 79 0.7 L1 L 1 L- 0.011 0011 011 (0.01 ppmN 26 2 6 2. 0.036 0036 036 (0.03 ppmN, , respectively regulations samples 95 level Additionally nonelectrochemist electrochemist needed Finally 07 7 0. 0.01 001 01 (0.0 0.03 003 03 9 0.0 00 (0. (0 (

EFFECT OF LIQUID SWINE WASTEWATER DOSES ON PHYSICAL, CHEMICAL AND ELECTROCHEMICAL ATTRIBUTES IN A CERRADO OXISOL. The addition of organic residues enhances soil and plant organic matter and nutrient content. To gauge the impact of varying liquid swine waste (LSW) levels on soil, we studied changes in a clayey Oxisol’s physical, chemical, and electrochemical traits from the Cerrado. LSW doses (0, 50, 150, 450, 600 m3 ha−1) were applied to the 0-0.20 m layer in a randomized design with three replicates. Post a 30-day incubation at 60% field capacity, the soil underwent mineralogical, physical (clay dispersed in water - CDW), chemical (sodium adsorption ratio - SAR, cation exchange capacity - CEC, base saturation - V%), and electrochemical (pH in H2O and KCl, ApH, point of zero charge - PZC, point of zero salt effect - PZSE, surface electric potential - iµo, and electrical conductivity - EC) analyses. The levels of exchangeable Ca, K, Mg, Na, and available P increased with increasing LSW doses. Increasing LSW doses in the soil led to an increase in EC, but soil salinization was not observed at the highest dose. With the application of LSW doses, there was a decrease in pH, ApH, PZSE, and an increase in CEC, PZC and ψo. Despite the increase in ψo, low clay dispersibility was observed. PHYSICAL OXISOL content (LSW Oxisols Oxisol s Cerrado 0, 0 (0 50 150 450 60 ha−1 ha1 ha 1 00.20 0020 0.20 20 0-0.2 replicates 30day day 30 mineralogical CDW, CDW , CDW) sodium SAR CEC V%, V V% V%) pH HO H O KCl ApH PZSE iµo EC analyses Ca K Mg Na dose ψo ( 5 15 45 6 ha− 00 00.2 002 020 0.2 2 0-0. 3 4 00. 02 0. 0-0 0-

Layered double hydroxides (LDHs) and related materials have been studied for a long time and their application in catalytic processes remain attractive due to the tuned properties, morphologies and metal-support interactions obtained from a variety of composition and synthesis route. In this mini-review, some important reactions, such as photocatalysis, electrocatalysis, reduction, carbon-carbon cross-couplings and water-gas shift will be emphasized along with the role of LDHs as catalysts, co-catalysts or catalytic precursors when it was clearly indicated. (LDHs properties metalsupport metal support route minireview, minireview mini review, review mini-review reactions photocatalysis electrocatalysis reduction carboncarbon carbon crosscouplings cross couplings watergas water gas catalysts cocatalysts co indicated

RESUMO Objetivo: Identificar e caracterizar a população de casos pediátricos encaminhados para o nosso centro de oxigenoterapia hiperbárica. Métodos: Estudo retrospetivo e observacional, que incluiu doentes pediátricos tratados com oxigenoterapia hiperbárica, de 2006 a 2021, no centro de referência de medicina hiperbárica do norte de Portugal. As variáveis de interesse foram extraídas dos processos clínicos eletrônicos. Resultados: O nosso estudo incluiu 134 casos. Os motivos de encaminhamento mais frequentes foram intoxicação por monóxido de carbono (n=59) e surdez súbita neurossensorial (n=41). Em 75 casos (56%) o tratamento foi iniciado em contexto de urgência. Os sintomas de apresentação à admissão variaram entre os diferentes casos, sendo os mais frequentes cefaleias e náuseas/vômitos. No que diz respeito à intoxicação por monóxido de carbono, as fontes mais comuns foram o aquecedor, lareira/braseiro e caldeira. Com relação aos efeitos adversos, foram identificados um caso de intoxicação por oxigênio e quatro casos de barotrauma do ouvido médio. Conclusões: A causa mais frequente de encaminhamento foi a intoxicação por monóxido de carbono. Todos os pacientes evoluíram favoravelmente e foram registrados poucos efeitos adversos, o que enfatiza a segurança desta terapia. Uma vez que a maioria dos pediatras pode não estar informada sobre os potenciais benefícios da oxigenoterapia hiperbárica, é de extrema importância promovê-los para que esta técnica seja cada vez mais implementada. Objetivo Métodos observacional 200 2021 Portugal eletrônicos Resultados 13 n=59 n59 n 59 (n=59 n=41. n41 n=41 . 41 (n=41) 7 56% 56 (56% urgência náuseasvômitos náuseas vômitos náuseas/vômitos aquecedor lareirabraseiro lareira braseiro caldeira adversos médio Conclusões terapia promovêlos promovê los implementada 20 202 1 n=5 n5 5 (n=5 n4 n=4 4 (n=41 (56 2 n= (n= (n=4 (5 (n (

ABSTRACT Objective: To identify and characterize the population of Pediatric patients referred to our hyperbaric oxygen therapy center. Methods: Retrospective and observational study, including pediatric patients treated with hyperbaric oxygen therapy, from 2006 to 2021, at the hyperbaric medicine reference center in the north of Portugal. Variables of interest were extracted from electronic medical records. Results: Our study included 134 patients. The most frequent reasons for referral were carbon monoxide poisoning (n=59) and sudden sensorineural hearing loss (n=41). In 75 cases (56%), treatment was initiated in an urgent context. Symptom presentation at Emergency Department varied among patients, the most frequent being headache and nausea/vomiting. Concerning carbon monoxide poisoning, the most common sources were water heater, fireplace/brazier, and boiler. Regarding adverse effects, it was identified one case of intoxication by oxygen and four cases of middle ear barotrauma. Conclusions: The most frequent cause for referral was carbon monoxide poisoning. All patients evolved favorably, with few side effects being reported, emphasizing the safety of this therapy. While most pediatricians may not be aware of the potential benefits arising with hyperbaric oxygen therapy, it is of upmost importance to promote them, so that this technique is increasingly implemented. Objective Methods 200 2021 Portugal records Results 13 n=59 n59 n 59 (n=59 n=41. n41 n=41 . 41 (n=41) 7 56%, 56 56% , (56%) context nauseavomiting nausea vomiting nausea/vomiting heater fireplacebrazier fireplace brazier fireplace/brazier boiler barotrauma Conclusions favorably reported them implemented 20 202 1 n=5 n5 5 (n=5 n4 n=4 4 (n=41 (56% 2 n= (n= (n=4 (56 (n (5 (

Iron is an important ion that regulates many metabolic functions in the human body, and its deficiency or overload can cause serious health problems. In view of this, the development of tools that can quantify iron in aqueous media is quite valuable. A new material based on a metal-organic framework (MOF) and a calixarene derivative (CALIX), here named CALIX@UiO-66-NH2, was successfully prepared and used as a luminescent sensor for iron ions in a water matrix containing various metal ions. The post-synthetic modification was demonstrated to be efficient on the MOF (UiO-66-NH2) modification, leading to a hybrid platform. The effect of the combination of both components (MOF and CALIX) led to a platform more sensitive to iron detection than the independent compounds. The CALIX@UiO-66-NH2 sensor shows a linear response toward Fe3+ ions with satisfactory linearity (R2 = 0.994) within the concentration range of 6.74 × 10−6−1.72 × 10−5 mol L−1. The limit of detection was determined to be as low as 1.6 mg L−1. The data demonstrate that CALIX@UiO-66-NH2 is an excellent probe for detecting Fe3+, as confirmed by almost complete fluorescence suppression. body problems this valuable metalorganic organic CALIX, CALIX , (CALIX) CALIX@UiO66NH2, CALIXUiO66NH2 CALIXUiONH CALIX@UiO 66 NH2, UiO NH2 NH postsynthetic post synthetic UiO66NH2 UiONH (UiO-66-NH2 compounds CALIX@UiO66NH2 CALIX@UiO-66-NH Fe3 Fe R2 R (R 0.994 0994 0 994 674 6 74 6.7 106172 10 1 72 10−6−1.7 105 5 10− L1 L L−1 16 1. suppression (CALIX CALIXUiO CALIXUiO66NH UiO66NH (UiO-66-NH CALIX@UiO66NH 0.99 099 99 67 7 6. 10617 10−6−1. L− 0.9 09 9 1061 10−6−1 0. 106 10−6− 10−6

A green supramolecular vortex-assisted microextraction employing a mixture of 1-decanol and tetrahydrofuran (THF) was developed for the simultaneous extraction of pesticides from different classes (insecticides, fungicides, and herbicides) from water and flour samples, followed by their determination in high-performance liquid chromatography with diode array detector (HPLC-DAD). The most favorable results were achieved at pH 6.0 in the presence of 4% (m/v) NaCl, utilizing a low volume of 1-decanol and THF (75 and 400 µL, respectively), a short vortex-assisted extraction time (120 s), and centrifugation time (120 s). These conditions yielded high preconcentration factors ranging from 50.1 to 90.3 and low limits of quantification (LOQs) ranging from 1.3 to 27.3 µg L-1. The intraday (n = 10) and interday (n =1 0) precision, assessed as the percentage of relative standard deviation (RSD), varied from 4.4 to 12.4%. The optimized method was successfully applied to determine the pesticides in water and flour samples, with recoveries ranging from 81 to 111%. vortexassisted vortex assisted 1decanol decanol 1 (THF insecticides, insecticides (insecticides fungicides herbicides samples highperformance performance HPLCDAD. HPLCDAD HPLC DAD . (HPLC-DAD) 60 6 0 6. 4 m/v mv m v (m/v NaCl 75 (7 40 µL respectively, respectively , respectively) 120 (12 s, s s) s. 501 50 50. 903 90 3 90. LOQs (LOQs 13 1. 273 27 27. L1. L1 L L-1 n 10 precision RSD, RSD (RSD) 44 4. 124 12 12.4% 8 111 111% (HPLC-DAD 7 ( (1 5 9 2 L- (RSD 12.4 11 12.

Phosphate species can affect aquatic ecosystems, as excess of this nutrient can cause eutrophication, generating environmental impacts. Lamellar double hydroxides have shown promise in removing phosphate at low concentrations (10-50 mg L 1). In this context, lamellar double hydroxides were synthesized interspersed with nitrates and humic substances, searching for a new product that favors phosphorus adsorption. X-ray diffraction showed the presence of characteristic peaks of lamellar double hydroxides and thermogravimetric analysis showed the decomposition behavior of lamellar structure. The adsorption capacity occurred quickly (< 30 min), being more efficient for lamellar double hydroxides with NO3. The maximum adsorption capacity showed results of 35.03 and 44.20 mg g 1 for lamellar double hydroxides with humic substances and lamellar double hydroxides with NO3, respectively. The complexation capacity showed that pH directly influences complexation, being greater for lamellar double hydroxides with humic substances at pH 6.5. Thus, nanostructured materials with humic substances are promising for use in contaminant remediation and adsorption can be a fast and efficient technique for use in soil and water. ecosystems eutrophication impacts 1050 10 50 (10-5 1. . 1) context Xray X ray structure < ( 3 min, min , min) NO3 NO 3503 35 03 35.0 4420 44 20 44.2 respectively 65 6 5 6.5 Thus water 105 (10- 350 0 35. 442 4 2 44. 6. (10 (1

Nanocomposites of GO/γ-Fe2O3 were used for magnetic dispersive solid-phase microextraction (m-d-μ-SPE) of six pesticides from river water samples, followed by the determination using high performance liquid chromatography-diode array detection. The synthesis of the nanocomposites is described and characterized using Fourier transform-infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. A central composite design was used to optimize the extraction time, sample solution pH, and adsorbent amount. The solvent type and volume for desorption and the effect of the ionic strength for adsorption were also investigated. The optimum adsorption conditions were achieved at 84 min of extraction time, pH 5.4, 115 mg of absorbent, and 1% (m/v) of NaCl, while the desorption solvent selected was 1.0 mL of methanol-acetic acid (9:1, v/v). The limits of detection ranged from 0.1 to 0.9 μg L-1, and a good precision was achieved with relative standard deviation (RSD) lower than 7.6% (n = 10). The accuracy of the method was accessed by recovery tests ranging from 82 to 117% (n = 3, RSD < 8%). GO/γFe2O3 GOγFe2O3 GOγFeO GO/γ Fe2O3 GO γ Fe O GO/γ-Fe2O solidphase solid phase mdμSPE m d μ SPE (m-d-μ-SPE samples chromatographydiode chromatography diode transforminfrared transform infrared spectroscopy Xray X ray diffraction microscopy time amount investigated 8 54 5 4 5.4 11 absorbent 1 m/v mv v (m/v NaCl 10 0 1. methanolacetic methanol acetic 91, 91 9 1, (9:1 v/v. vv v/v . v/v) 01 0. 09 L1, L1 L L-1 (RSD 76 7 6 7.6 n 10. 10) 117 3 8%. 8% 8%) γFe2O3 γFe GO/γFe2O GOγFe GOγFe2O GOγ FeO Fe2O 5. (9: L- 7. γFeO γFe2O (9 (

The aim of this study was to effectively remove Fe2+ by using ozone microbubbles in bottled mineral water to prevent sediment from occurring during storage and increase shelf life. By considering the characteristics of mineral water with low solubility of ozone and high CO2 content, a suitable ozone injection step was chosen and a new mineral water treatment method using microbubbles was proposed. As a result of the treatment of the bottled mineral water with ozone microbubbles, the concentration of the iron ion was reduced from 0.14 to 0.01 mg L-1, and the shelf life increased to 360 days. During the treatment, the concentrations of K+ and Na+ were almost unchanged, and the deposition time was reduced to one-third compared to the natural oxidation. Fe2 Fe CO content proposed 014 0 14 0.1 001 01 0.0 L1, L1 L 1, 1 L-1 36 days K Na unchanged onethird one third oxidation 0. 00 L- 3

Abstract Introduction: Various anthropic pressures affect the aquatic ecosystems of the foothills of Colombia. The response to environmental stressors is still unknown in bioindicator organisms such as Leptohyphidae. Objective: To determine the diversity of Leptohyphidae nymphs of the Quenane-Quenanito river, in two contrasting hydrological periods and its relationship with some physicochemical variables. Methods: In December (2014) and February (2015), organisms were collected with a Surber net at six stations along the current. Alpha and beta diversity was analyzed and redundancy analysis and generalized linear model were applied to establish the relationship between taxa and environmental variables. Results: Were identified 369 organisms belonging to four genera (Amanahyphes, Traverhyphes, Tricorythopsis, and Tricorythodes), two species, and eight morphospecies. Amanahyphes saguassu is reported for the first time for the Meta department. High diversity of Leptohyphidae nymphs was recorded in the transition to drought season and greater abundance in drought. Beta diversity indicated that the configuration of the assemblage changes spatially and temporally. Conclusions: Leptohyphidae organisms prefer fast habitats, particularly in the dry period where they find food (leaf litter, detritus) and shelter to establish themselves successfully; anthropic activities such as urbanization notably affect diversity. The high diversity recorded in this small river in the foothills of the plains reflects the need to increase this type of works and collection efforts of study material in the region.

Resumen Introducción: Varias presiones antrópicas sufren los ecosistemas acuáticos del piedemonte llanero en Colombia. La respuesta a estresores ambientales aún se desconoce en organismos bioindicadores como Leptohyphidae. Objetivo: Determinar la diversidad de ninfas de Leptohyphidae del río Quenane-Quenanito, en dos periodos hidrológicos contrastantes y su relación con algunas variables fisicoquímicas. Métodos: En diciembre (2014) y febrero (2015) se recolectaron organismos con red Surber en seis estaciones a lo largo del río. Se analizó la diversidad alfa y beta y se aplicó análisis de redundancia y modelos lineales generalizados con el fin de establecer la relación entre los taxones y las variables ambientales. Resultados: Se identificaron 369 organismos pertenecientes a cuatro géneros (Amanahyphes, Traverhyphes, Tricorythopsis y Tricorythodes), dos especies y ocho morfoespecies. Se reporta por primera vez para el departamento del Meta Amanahyphes saguassu. Se registró la mayor diversidad de ninfas en la transición a la sequía y la mayor abundancia en sequía. La diversidad beta señaló que la configuración del ensamblaje cambia a nivel espacial y temporal. Conclusiones: Los organismos de Leptohyphidae prefieren hábitats de corrientes, particularmente en el periodo de sequía, donde hallan alimento (hojarasca, detritos) y refugio para establecerse exitosamente; actividades antrópicas como la urbanización afectan notablemente la diversidad. La alta diversidad registrada en este pequeño río de piedemonte llanero refleja la necesidad de incrementar este tipo de trabajos y esfuerzos de recolección de material de estudio en la región.