Revista Internacional de Contaminación Ambiental
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THERMODYNAMIC AND ELECTROCHEMICAL STUDY OF VANADIUM SOLUTIONS: TOWARDS VANADIUM RECOVERY FROM A SPENT CATALYST
Get PDFDue to the low abundance of vanadium in nature (about 135 g/t), the feasibility to recover it from industrial wastes has highly attracted scientific and technological attention. The main recovery routes reported are associated with chemical or thermochemical processes. However, the electrochemical recovery of vanadium from industrial wastes has been poorly investigated. In this work, a thermodynamic and electrochemical study for the possible vanadium recovery from a spent catalyst generated in the petrochemical industry was conducted. The study was divided into two stages using low vanadium concentrations. In the first stage, the recovery of vanadium was possible in its V4+ state at low reduction potentials, whereas for the second stage, cyclic voltammetry was used to calculate the diffusion coefficient and the heterogeneous velocity coefficient of the V5+/V4+ redox pair. The obtained values are similar to those reported in the literature for aqueous solutions at high vanadium concentrations and would allow the design of the system at large scale. This report aims to set the conditions for the possible vanadium recovery from a spent catalyst by means of electrochemical processes, although the optimization of such conditions must be further explored.Due to the low abundance of vanadium in nature (about 135 g/t), the feasibility to recover it from industrial wastes has highly attracted scientific and technological attention. The main recovery routes reported are associated with chemical or thermochemical processes. However, the electrochemical recovery of vanadium from industrial wastes has been poorly investigated. In this work, a thermodynamic and electrochemical study for the possible vanadium recovery from a spent catalyst generated in the petrochemical industry was conducted. The study was divided into two stages using low vanadium concentrations. In the first stage, the recovery of vanadium was possible in its V4+ state at low reduction potentials, whereas for the second stage, cyclic voltammetry was used to calculate the diffusion coefficient and the heterogeneous velocity coefficient of the V5+/V4+ redox pair. The obtained values are similar to those reported in the literature for aqueous solutions at high vanadium concentrations and would allow the design of the system at large scale. This report aims to set the conditions for the possible vanadium recovery from a spent catalyst by means of electrochemical processes, although the optimization of such conditions must be further explored
PHOTOCATALYTIC SOLAR OXIDATION OF ACESULFAME-K. EFFECT OF INITIAL pH, CATALYST DOSE AND OXIDANT CONCENTRATION
Get PDFAqueous acesulfame-K was oxidized in a pilot solar photocatalytic reactor, equipped with a compound parabolic collector (CPC). The reactor has an area of 0.40 m2 of CPC collectors with geometrical concentration ratio of 1 and a simple mechanical configuration. The experiments of photocatalytic oxidation of acesulfame-K were performed by treating 2 L of water with an initial concentration of 15 mg/L. The photocatalyst used was P25 (Aeroxide TiO2) from Evonik. One of the goals of the research work was to find a set of conditions to efficiently remove this emerging concern pollutant. Results allowed proposing a set of reaction conditions that lead to a high removal of acesulfame-K. In addition, the experimental design allowed determining the effect of initial pH as well as the impact of initial concentrations of photocatalyst and chemical oxidant. The removal efficiency of acesulfame-K and related UV-absorbing species reached values up to 96-99 % and there was not a quantifiable amount of intermediate products (analyzed as UV absorbing species). Despite reaction time was fixed in 3 h for all the experiments, oxidation efficiencies higher than 95 % were reached at 2 h of reaction or even before.Aqueous acesulfame-K was oxidized in a pilot solar photocatalytic reactor, equipped with a compound parabolic collector (CPC). The reactor has an area of 0.40 m2 of CPC collectors with geometrical concentration ratio of 1 and a simple mechanical configuration. The experiments of photocatalytic oxidation of acesulfame-K were performed by treating 2 L of water with an initial concentration of 15 mg/L. The photocatalyst used was P25 (Aeroxide TiO2) from Evonik. One of the goals of the research work was to find a set of conditions to efficiently remove this emerging concern pollutant. Results allowed proposing a set of reaction conditions that lead to a high removal of acesulfame-K. In addition, the experimental design allowed determining the effect of initial pH as well as the impact of initial concentrations of photocatalyst and chemical oxidant. The removal efficiency of acesulfame-K and related UV-absorbing species reached values up to 96-99 % and there was not a quantifiable amount of intermediate products (analyzed as UV absorbing species). Despite reaction time was fixed in 3 h for all the experiments, oxidation efficiencies higher than 95 % were reached at 2 h of reaction or even before
APLICACIÓN DE DOS METODOLOGÍAS PARA LA EVALUACIÓN DE LA CALIDAD DEL AGUA DE CUERPOS SUPERFICIALES DESTINADOS A LA PESCA EN EL SUR DEL ESTADO DE VERACRUZ, MÉXICO
Get PDFThe evaluation of water quality for protection of aquatic life from surface waters was carried out in 16 sampling points in a region between Jáltipan and Texistepec, Veracruz, Mexico, during a dry season, applying two methodologies. The characterization parameters were pH, temperature, dissolved oxygen (DO), conductivity, turbidity, total dissolved solids (TDS), total suspended solids (TSS), chlorides, hardness, alkalinity, biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total phosphorus, total Kjeldahl nitrogen (TKN), organic nitrogen, ammonium nitrogen (N-NH4+), nitrite nitrogen (N-NO2–) and nitrate nitrogen (N-NO3–). The first methodology is a modification of the proposed by the US National Sanitation Foundation (NSF), which is based on eight parameters: DO, pH, temperature, BOD5, TDS, turbidity, N-NO3 and total phosphorus; while the second is based on the one proposed by CNA, which originally considers 18 parameters (only 13 were contemplated). From the application of both methodologies, water quality indexes were obtained for each point studied, observing that the quality fluctuated from contaminated to excellent. Contrasting with the Ecological Criteria of Water Quality for the protection of aquatic life, the parameters that most affect the quality of water for noncompliance with the recommendations are DO, total phosphorus and N-NH4+. A parameter that is not included in the methodologies used is the COD. According to the Water Quality Criteria from Conagua (less demanding than international regulations), the values reached for COD in the study area classify the water from contaminated to heavily contaminated.Se realizó la evaluación de la calidad del agua para protección de la vida acuática en 16 puntos de muestreo de cuerpos superficiales ubicados en una región entre Jáltipan y Texistepec, Veracruz, México. El estudio se realizó durante el periodo de estiaje y se aplicaron dos metodologías para evaluar la calidad del agua. Se seleccionaron los parámetros de caracterización: pH, temperatura, oxígeno disuelto (OD), conductividad específica, turbidez, sólidos disueltos totales (SDT), sólidos suspendidos totales (SST), cloruros, dureza, alcalinidad, demanda bioquímica de oxígeno (DBO5), demanda química de oxígeno (DQO), fósforo total, nitrógeno total Kjeldahl (NTK), nitrógeno orgánico (N-Org), nitrógeno de amonios (N-NH4+), nitrógeno de nitritos (N-NO2–) y nitrógeno de nitratos (N-NO3–). La primera metodología es una modificación de la propuesta por la National Sanitation Foundation (NSF) de los EU, basada en ocho parámetros: OD, pH, temperatura, DBO5, SDT, turbidez, N-NO3 y fósforo total; la segunda está basada en la propuesta por la CNA. De esta metodología se contemplaron 13 parámetros de los 18 originales. Se obtuvieron índices de calidad del agua para cada punto estudiado, observándose que la calidad fluctuó de contaminada a excelente de acuerdo con los resultados alcanzados. En comparación con los Criterios Ecológicos de Calidad del Agua para protección de la vida acuática, los parámetros que más afectan la calidad del agua por incumplir las recomendaciones son OD, fósforo total y N-NH4+. Un parámetro que no se incluye en las metodologías utilizadas es la DQO; si se considera la Escala de Clasificación del Agua de Conagua conforme a la DQO, la cual es menos exigente que la normatividad internacional, los valores alcanzados por este parámetro en la zona de estudio clasifican al agua de contaminada a fuertemente contaminada
INVESTIGATION OF METALS RELEASED FROM IMPORTED COOKWARE COLLECTED FROM A LOCAL MARKET IN RIYADH, SAUDI ARABIA
Get PDFMonitoring the presence of heavy metals in cookware intended for use by both humans and animals is of interest, because of their toxic effects. In this report, a study has been conducted to determine the heavy metals released from 46 items of metallic cookware purchased from a local market in Riyadh. Mn, Fe, Cu, Cr, As, Zn, Ni, Al, Cd and Pb, were analyzed using an inductively coupled plasma-optical emission spectrometer. The order of concentration of essential and toxic elements in all samples showed the following trend: Mn > Al > Pb = As > Fe > Zn > Cu = Ni = Cd > Cr. This study highlighted the importance of the metal release monitoring from cooking utensils in order to protect people from the dangers posed by toxic metals.Monitoring the presence of heavy metals in cookware intended for use by both humans and animals is of interest, because of their toxic effects. In this report, a study has been conducted to determine the heavy metals released from 46 items of metallic cookware purchased from a local market in Riyadh. Mn, Fe, Cu, Cr, As, Zn, Ni, Al, Cd and Pb, were analyzed using an inductively coupled plasma-optical emission spectrometer. The order of concentration of essential and toxic elements in all samples showed the following trend: Mn > Al > Pb = As > Fe > Zn > Cu = Ni = Cd > Cr. This study highlighted the importance of the metal release monitoring from cooking utensils in order to protect people from the dangers posed by toxic metals
CRITERIOS DE SELECCIÓN PARA UN SITIO DE DISPOSICIÓN FINAL DE RESIDUOS SÓLIDOS NO PELIGROSOS. REVISIÓN DE NORMAS AMBIENTALES LATINOAMERICANAS Y SU CONTRASTE CON LA NORMA ECUATORIANA
Get PDFIn Latin America, landfill sites as a final disposal technology are configured as highly problematic areas from a socio-environmental perspective, attributable to inefficient technical, administrative and political processes that the region experiences in a generalized way. Furthermore, being a potential source of pollution, generate citizen opposition because of its implications for public health and natural resources. Due to the large amounts of waste generated by lack of empowerment in the reuse and recycling processes, it is imperative for developing countries to have sanitary landfills in greater numbers and areas. In this context, each country in the region has developed legal bodies anchored to their respective public policies, where they establish minimum criteria to be met for implementation of a final disposal site. Considering the former, this article carries out a systematic review of 14 Latin American standards and compares them with the Ecuadorian regulations, in order to establish opportunities for improvement, from a technical and legal perspective, which contributes to a sustainable development of Ecuador.En Latinoamérica, los sitios de emplazamiento de un relleno sanitario como tecnología de disposición final, se configuran como zonas altamente conflictivas desde una perspectiva socioambiental, lo que pudiera ser atribuible a los ineficientes procesos técnicos, administrativos y políticos que experimenta la región de forma generalizada. Además, al ser fuentes de contaminación en potencia generan una gran oposición ciudadana por las implicaciones en la salud pública y en los recursos naturales. Como consecuencia de las grandes cantidades de desechos que se generan por falta de empoderamiento en procesos de reutilización y reciclaje, para los países en vías de desarrollo aún es imperante contar con rellenos sanitarios en mayor número y superficie. En este contexto, cada país de la región ha desarrollado cuerpos legales anclados a sus respectivas políticas públicas, en donde establecen los criterios mínimos a cumplir para la implementación de un sitio de disposición final. El presente artículo realiza una revisión sistemática de 14 de estas normas latinoamericanas y su posterior comparación con las variables de la regulación ecuatoriana, con el fin de establecer oportunidades de mejora desde una perspectiva técnica y legal, que contribuyan a un desarrollo sustentable del Ecuador
FIRST EVIDENCE OF POTENTIAL TOXIC CYANOBACTERIA IN THE WATER-SEDIMENT INTERFACE OF A TROPICAL DRINKING WATER RESERVOIR
Get PDFThe Nostocales and Chroococcales cyanobacteria can produce potent cyanotoxins and survive in deep zones of aquatic ecosystems by the formation of morphologically distinguishable resistance structures and temporarily latent colonies in sediments. The purpose of this study was to determine the presence and density of Nostocales and Chroococcales with toxic potential in the water-sediment interface. During four samplings in three locations of the drinking water reservoir Riogrande II, some physical and chemical variables and chlorophyll a concentration of different spectral groups were measured, density of cyanobacteria was established by conventional microscopy, and mcyD and mcyE genes were detected by PCR. The environmental factors correlated with the abundance of cyanobacteria in the water-sediment interface were pH, total phosphorus, and iron. The highest chlorophyll concentration was provided by Chlorophyceae, while chlorophyll from the cyanobacteria spectral group fluctuated between 0.07 and 3.6 mg/L in field samples. About 86 % of the total cells number corresponded to the Microcystis complex while the Nostocales represented just 3.35 %. It was possible to find evidence for cyanobacteria with toxic potential in the three sampling points through the detection of the mcyD and mcyE genes. The presence of these cyanobacteria is possibly related to their life cycle and the resuspension processes caused by the way river water enters the reservoir. Additionally, this is the first evidence that demonstrates the importance of the water-sediment interface as a reservoir of cyanobacteria with toxic potential, since they can recolonize the water column in ecosystems that supply drinking water. The Nostocales and Chroococcales cyanobacteria can produce potent cyanotoxins and survive in deep zones of aquatic ecosystems by the formation of morphologically distinguishable resistance structures and temporarily latent colonies in sediments. The purpose of this study was to determine the presence and density of Nostocales and Chroococcales with toxic potential in the water-sediment interface. During four samplings in three locations of the drinking water reservoir Riogrande II, some physical and chemical variables and chlorophyll a concentration of different spectral groups were measured, density of cyanobacteria was established by conventional microscopy, and mcyD and mcyE genes were detected by PCR. The environmental factors correlated with the abundance of cyanobacteria in the water-sediment interface were pH, total phosphorus, and iron. The highest chlorophyll concentration was provided by Chlorophyceae, while chlorophyll from the cyanobacteria spectral group fluctuated between 0.07 and 3.6 mg/L in field samples. About 86 % of the total cells number corresponded to the Microcystis complex while the Nostocales represented just 3.35 %. It was possible to find evidence for cyanobacteria with toxic potential in the three sampling points through the detection of the mcyD and mcyE genes. The presence of these cyanobacteria is possibly related to their life cycle and the resuspension processes caused by the way river water enters the reservoir. Additionally, this is the first evidence that demonstrates the importance of the water-sediment interface as a reservoir of cyanobacteria with toxic potential, since they can recolonize the water column in ecosystems that supply drinking water
EVALUACIÓN DEL CRECIMIENTO Y TOXIGENICIDAD DE Microcystis EN AGUAS ENRIQUECIDAS CON NUTRIENTES
Get PDFThe growth of several harmful cyanobacteria (Microcystis) has increased worldwide as a result of numerous and rapid environmental alterations. In this study, the toxigenic cyanobacterium Microcystis was isolated from a water body in Mexico City (Pista Olímpica de Remo y Canotaje Virgilio Uribe) with the aim to investigate: (1) the influence of increasing nitrogen (N) and phosphorus (P) on the growth of Microcystis and (2) the potential toxigenicity of Microcytis using mortality bioassays of Artemia sp. In 2017, two clonal strains (Mc17C2 y Mc17C3) of Microcystis were established in monoculture under controlled laboratory conditions. Microcystis strains were grown in a culture chamber in vitro with irradiance 19.6 µmol/m2/s with a 12 h light:12 h dark photoperiod, and at room temperature (~ 24 ± 2 ºC). Artemia sp. was cultured and juvenile organisms were used and feed on different quantities of Microcystis strains. Increasing N and P concentrations lead to higher growth rates of Microcystis; however, its optimum growth rate did not match with the highest nutrient concentrations in the cultures. Microcystis ingestion by juvenile Artemia caused 50 to 100 % of mortality in 48-72 h, when fed on abundance between 3 × 105 y 3 × 106 cells/ml. In general, Artemia was not susceptible to Microcystis ingestion within a time of 24 h. In conclusion, higher availability of dissolved nutrients in the water leads to increasing growth rates of Microcystis which may cause potential effects on zooplankton.El crecimiento de diversas cianobacterias nocivas (Microcystis) se ha intensificado a nivel mundial como resultado de numerosas y rápidas alteraciones ambientales. En este estudio la cianobacteria Microcystis fue aislada de la Pista Olímpica de Remo y Canotaje Virgilio Uribe de la Ciudad de México y se investigaron: 1) la influencia del aumento de nitrógeno (N) y fósforo (P) en el crecimiento de Microcystis y 2) la toxigenicidad potencial de Microcystis mediante bioensayos de mortalidad de Artemia sp. En 2017, dos cepas clonales de Microcystis (Mc17C2 y Mc17C3) se establecieron en condiciones controladas de laboratorio. Dichas cepas crecieron en una cámara iluminada con irradianza de 19.6 µmol/m2/s con un fotoperiodo de 12 h luz:12 h oscuridad a temperatura ambiente (~ 24 ± 2 ºC). Se cultivó Artemia sp. y se seleccionaron juveniles del crustáceo para alimentarlos con diferentes concentraciones de Microcystis. El aumento en la concentración de N y P se asoció con mayores tasas de crecimiento de Microcystis; sin embargo, su crecimiento óptimo no coincidió con los niveles más altos de nutriente en los cultivos. La ingestión de Microcystis por juveniles de Artemia causó mortalidad del 50 al 100 % en un lapso de 48-72 h cuando la abundancia fluctuó entre 3 × 105 y 3 × 106 cel/mL. En general, Artemia sp. no mostró sensibilidad al consumo de Microcystis en las primeras 24 h. Se concluye que el incremento y la disponibilidad de nutrientes disueltos conducen a mayores tasas de crecimiento de Microcystis con efecto potencial sobre el zooplancton
HEAVY METALS BIOACCUMULATION AND RISK ESTIMATION IN EDIBLE FRESHWATER FISH FROM PEDROSO RESERVOIR (MAYABEQUE, CUBA)
Get PDFThis work is a validation of the second step of a heavy metal monitoring procedure in Cuba fluvial ecosystems. Concentrations of seven heavy metals were measured by ICP-MS in water samples collected from the Pedroso reservoir (Mayabeque province, Cuba) and its main tributaries, as well as in edible muscle of three locally consumed fish species: Oreochromis spp., Tinca tinca and Clarias gariepinus. The results show a high concentration of Pb in areas near a paint factory (85.5 μg/L), an asphalt factory and a high traffic area (345.8 μg/L). Metal content (in mg/kg ww) in fish fillet ranged as follows: Cr (0.01-0.58), Co (0.01-0.58), Cu (0.23-88.16), Zn (4.9-29.9), As (0.01-0.86), Cd (0.02-2.93) and Pb (0.01-1.23). According to Cuban regulations, concentrations of Cd in muscle are not safe in 37.5 to 44.0 % of the studied fishes, while Pb is high in 14.0 to 20.0 %. Non-carcinogenic risk (HI) is present when daily intake is above 81 g/day. Carcinogenic risk (ELCR) is calculated to be 5.8 × 10–4 according to the US-EPA methodology. Fishermen families are the most sensitive population sector. Local authorities were informed and different measures were taken to avoid polluted fish consumption and the reduction of pollutant sources.This work is a validation of the second step of a heavy metal monitoring procedure in Cuba fluvial ecosystems. Concentrations of seven heavy metals were measured by ICP-MS in water samples collected from the Pedroso reservoir (Mayabeque province, Cuba) and its main tributaries, as well as in edible muscle of three locally consumed fish species: Oreochromis spp., Tinca tinca and Clarias gariepinus. The results show a high concentration of Pb in areas near a paint factory (85.5 μg/L), an asphalt factory and a high traffic area (345.8 μg/L). Metal content (in mg/kg ww) in fish fillet ranged as follows: Cr (0.01-0.58), Co (0.01-0.58), Cu (0.23-88.16), Zn (4.9-29.9), As (0.01-0.86), Cd (0.02-2.93) and Pb (0.01-1.23). According to Cuban regulations, concentrations of Cd in muscle are not safe in 37.5 to 44.0 % of the studied fishes, while Pb is high in 14.0 to 20.0 %. Non-carcinogenic risk (HI) is present when daily intake is above 81 g/day. Carcinogenic risk (ELCR) is calculated to be 5.8 × 10–4 according to the US-EPA methodology. Fishermen families are the most sensitive population sector. Local authorities were informed and different measures were taken to avoid polluted fish consumption and the reduction of pollutant sources
EFECTO DEL TAMAÑO DE PARTÍCULA DE DIÓXIDO DE TITANIO INMOVILIZADO EN LA OXIDACIÓN FOTOCATALÍTICA DE PÚRPURA DE BROMOCRESOL
Get PDFPollution of sewage water with organic matter and aromatic compounds is a complex problem that is constantly in need of more efficient systems for its treatment. The objective of this works is to evaluate the effect of TiO2 particle size in the photocatalytic oxidation of bromocresol purple, used as a model of organic polluter. TiO2 was immobilized on a borosilicate substrate through the coating by immersion technic and was characterized by atomic force microscopy (AFM) to evaluate the morphology of the obtained surface. The anatase crystalline structure of TiO2 was confirmed by X ray diffraction (DRX) and its particle size was evaluated by dynamic light scattering (DSL). The effects of 25- and 300- nm TiO2 particles on the degradation of bromocresol purple at 5, 10, 20 and 30 ppm concentrations were evaluated. Kinetics of the bromocresol purple (PBC) degradation reaction was pseudo first order, consistent with the Langmuir model for low concentrations of this dye. The photodegradation in 25-nm TiO2 particles was more efficient than in 300 nm, due to the greater number of grains formed on the surface, thus promoting a greater number of available active sites.La contaminación de agua residual con materia orgánica y compuestos aromáticos es un problema cada vez más complejo que demanda sistemas de tratamiento más eficientes. El objetivo de este trabajo es evaluar el efecto del tamaño de partícula de TiO2 en la oxidación fotocatalítica del púrpura de bromocresol usado como modelo de contaminante orgánico. El TiO2 se inmovilizó sobre un sustrato de borosilicato mediante la técnica de revestimiento por inmersión y se caracterizó por microscopia de fuerza atómica (AFM, por sus siglas en inglés) para evaluar la morfología de la superficie obtenida. La estructura cristalina anatasa del TiO2 se confirmó mediante difracción de rayos X (DRX) y el tamaño de partícula se determinó mediante dispersión de luz dinámica (DSL). Se evaluaron los efectos de partículas de 25 y 300 nm de TiO2 sobre la degradación del púrpura de bromocresol en concentraciones de 5, 10, 20 y 30 ppm. La cinética de la reacción de degradación de púrpura de bromocresol (PBC) fue de pseudoprimer orden, congruente con el modelo de Langmuir para concentraciones bajas de este colorante. La fotodegradación en partículas de 25 nm de TiO2, resultó más eficiente que la de 300 nm, debido al mayor número de granos formados en la superficie, el cual promovió un mayor número de sitios activos disponibles
ARSENIC AND LEAD BIOACCESSIBILITIES MEASURED WITH A NOVEL REACTOR SYSTEM USING THE MEXICAN STANDARD AND PBET METHODS: COMPARISON WITH IN VIVO AND IN VITRO REPORTED DATA
Get PDFContaminated soils can become exposure routes of elements toxic to human beings. The health risk of a toxic element by ingestion depends on its bioavailability in the gastrointestinal system, measured in vivo or in vitro. This study aimed to use a novel, versatile reactor (gastrointestinal simulation reactor system to determine bioaccessibility -GSRSB-) to measure lead and arsenic bioaccessibility in the gastric and intestinal phases by applying a modified physiologically based extraction test (PBET). Three composite samples of polluted soils with As (0.50 - 3.25%) and Pb (0.02 - 0.10%) and the certified reference material NIST 2710 were analyzed with this GSRSB-PBET method and the NOM-147 Mexican standard method, which uses an end-over-end shaker. All results were compared to one another. The NIST 2710 results were contrasted with those reported in vivo and in vitro by 14 laboratories. The (GSRSB-PBET) gastric phase ranges were 35.9-55.1 % (As) and 59.6-96.1 % (Pb), while (NOM-147) gastric phases were 35.8-60.4 % (As) and 61.0-70.7 % (Pb). The (GSRSB-PBET) intestinal phase ranges were 39.5-46.9 % (As) and 19.9-31.5 % (Pb). The As and Pb compounds and the stirring technique seem to influence bioaccessibility. On the other hand, the comparison of NIST 2710 results with those reported in vitro and in vivo indicated that As and Pb gastric bioaccessibility obtained with GSRSB-PBET falls into the in vivo results range, while NOM-147 results are higher and fall outside the in vivo range, possibly overestimating the risk. Thus, the proposed method is adequate for modifying the current Mexican Standard Method (NOM-147), which only allows the calculation of Pb gastric bioavailability in vitro.Contaminated soils can become exposure routes of elements toxic to human beings. The health risk of a toxic element by ingestion depends on its bioavailability in the gastrointestinal system, measured in vivo or in vitro. This study aimed to use a novel, versatile reactor (gastrointestinal simulation reactor system to determine bioaccessibility -GSRSB-) to measure lead and arsenic bioaccessibility in the gastric and intestinal phases by applying a modified physiologically based extraction test (PBET). Three composite samples of polluted soils with As (0.50 - 3.25%) and Pb (0.02 - 0.10%) and the certified reference material NIST 2710 were analyzed with this GSRSB-PBET method and the NOM-147 Mexican standard method, which uses an end-over-end shaker. All results were compared to one another. The NIST 2710 results were contrasted with those reported in vivo and in vitro by 14 laboratories. The (GSRSB-PBET) gastric phase ranges were 35.9-55.1 % (As) and 59.6-96.1 % (Pb), while (NOM-147) gastric phases were 35.8-60.4 % (As) and 61.0-70.7 % (Pb). The (GSRSB-PBET) intestinal phase ranges were 39.5-46.9 % (As) and 19.9-31.5 % (Pb). The As and Pb compounds and the stirring technique seem to influence bioaccessibility. On the other hand, the comparison of NIST 2710 results with those reported in vitro and in vivo indicated that As and Pb gastric bioaccessibility obtained with GSRSB-PBET falls into the in vivo results range, while NOM-147 results are higher and fall outside the in vivo range, possibly overestimating the risk. Thus, the proposed method is adequate for modifying the current Mexican Standard Method (NOM-147), which only allows the calculation of Pb gastric bioavailability in vitro