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LUZ OLIVIA LEAL QUEZADA (2011)
The importance of arsenic speciation is being increasingly recognized by the scientific community because intrinsic
arsenic species are known to exhibit differences in mobility, bioavailability and toxicity. A variety of organic and
inorganic species have been identified in environmental and biological samples. The aim of this study was to determine
the optimal operating parameters for chemical speciation of arsenic in human urine samples. HPLC/ICP-MS technique
was employed to determine arsenobetaine (AsB), dimethyl arsenic acid (DMA), monomethyl arsenic acid (MMA),
arsenite [As (III)] and arsenate [As (V)] in human urine samples. The separation was carried out on the Hamilton PRP
X100 column, using two mobile phases: phase A containing 10 mM ammonium carbonate and phase B containing 20 mM
ammonium carbonate at pH 8.83-9.35. The performance of the method was evaluated in terms of linearity, precision,
accuracy and detection and quantification limits. The results demonstrate that the HPLC/ICP-MS methodology proposed
is a sensitive, reproducible and accurate technique for the determination of arsenic species at trace levels in human
Arsenic is a metalloid naturally present in many groundwater sources
destined for human consumption, which entails a public health risk. In Mexico,
reverse osmosis (RO) is the most popular arsenic removal process currently
available. Its greatest limitation is the amount of water that the process rejects
(50%). This feature and its high operation costs make it expensive for many
communities, especially those in rural areas; it is therefore necessary to find
alternatives for efficient arsenic removal. Constructed wetlands (CWs) have
been considered as a possibility for As removal in previous studies. The
objective of the present study was to determine the feasibility of using this
process for the treatment of the water with high arsenic content.
The experiment was performed in three CWS prototypes, operating in
parallel with subsurface flow. Two of the units (CW1 and CW2) were planted
with Eleocharis macrostachya. The third unit was used as a control (CW3),
without plants. The support medium was lime-sand. Two influx arsenic
concentrations (0.1 and 0.4mg/L) were used during this experiment.
Results indicate that CWs prototypes were able to retain an average of 90 to
95% of the arsenic present in feed water. The arsenic retention of the wetland
with no plants was only 23%, which shows the importance of the plants in
arsenic removal. The system as a whole (soil + plants) was able to keep As
concentrations in the treated water under 0.025mg/L (maximum value allowed
for drinking water in Mexico).
"Mobility of Arsenic (As) from metallurgical wastes in Matehuala, Mexico has been accounted for ultra-high concentration of As in water (4.8–158 mg/L) that is used for recreational purposes as well as cultivation of maize. In this study, we (i) measured As concentrations in soils irrigated with this water, (ii) investigated the geochemical controls of available As, and (iii) measured bioaccumulation of As in maize. Water, soil, and maize plant samples were collected from 3 different plots to determine As in environmental matrices as well as water soluble As in soils. Soil mineralogy was determined by X-ray diffraction analysis. Bioaccumulation of As in maize plants was estimated from the bioconcentration and translocation factors. We recorded As built-up in agricultural soils to the extent of 172 mg/kg, and noted that this As is highly soluble in water (30% on average). Maize crops presented high bioaccumulation, up to 2.5 times of bioconcentration and 45% of translocation. Furthermore, we found that water extractable As was higher in soils rich in calcite, while it was lower in soils containing high levels of gypsum, but As bioconcentration showed opposite trend. Results from this study show that irrigation with As rich water represents a significant risk to the population consuming contaminated crops."
ARMANDO QUINTERO CASTAÑEDA (2014)
Arsenic in high concentrations represents a risk to human health and the environment. The Mololoa River, which crosses the city of Tepic, Nayaril, has high concentrations of arsenic. It is also affected by industrial discharges, agricultural, domestic, service and leachate municipal dump open pit "El Ixtete", which causes a serious public health problem. In previous studies carried out on this site, a series of microorganisms with resistance to arsenic and heavy metals such as mercury, chromium, cadmium and antibiotics such as kanamycin, ciprofloxacin, gentamicin and beta-Iactamics have been isolated and identified. These findings suggest the existence of a constant selection pressure in the area. This implies that only the bacteria in whose genome there are genes of resistance to selective agents will survive.
El arsénico en altas concentraciones representa un riesgo para la salud humana y el ambiente. El río Mololoa, que atraviesa la ciudad de Tepic, Nayaril, presenta concentraciones elevadas de arsénico. Además es afectado por descargas industriales, agropecuarias, domesticas, de servicios y lixiviados del tiradero municipal a cielo abierto "El Ixtete", lo que causa un serio problema de salud pública. En estudios previos llevados a cabo en este sitio, se han aislado e identificado una serie de microorganismos con capacidad de resistencia a arsénico y metales pesados como mercurio, cromo, cadmio y a antibióticos como kanamicina, ciprofloxacino, gentamicina y beta-Iactámicos. Estos hallazgos sugieren la existencia de una constante presión de selección en la zona. Ello implica que solo las bacterias en cuyo genoma se encuentren genes de resistencia a agentes selectivos lograrán sobrevivir.
LUZ OLIVIA LEAL QUEZADA (2009)
The levels of arsenic and mercury of fish samples collected in the water reservoirs El Granero, Las Virgenes y La Boquilla
were determinate by atomic absorption spectrometry with hydride generator. The accuracy of the method was determinate
by certified reference material (NRCC-DOLT-3 Dogfish Liver). Three factors were studicd and their infiuence
on the concentrations of arscnic and mercury in fish: water reservoir, spccies and tissue. The data were analyzed using
analysis of variante (ANOVA) considering the sources of variation caused by the factors and their interactions, making
comparison of means tests using Tukcy's test when significant di fferences were detected by ANOVA.
"In this study, bimetallic nanoparticles (BMNPs) with different mass ratios of Cu and Fe were evaluated. The influence of the morphology on the removal of pollutants was explored through theoretical and experimental studies, which revealed the best structure for removing arsenate (As(V)) in aqueous systems. To evidence the surface characteristics and differences among BMNPs with different mass proportions of Fe and Cu, several characterization techniques were used. Microscopy techniques and molecular dynamics simulations were applied to determine the differences in morphology and structure. In addition, X-ray diffraction (XRD) was used to determine the presence of various oxides. Finally, the magnetization response was evaluated, revealing differences among the materials. Our cumulative data show that BMNPs with low amounts of Cu (Fe0.9Cu0.1) had a non-uniform core-shell structure with agglomerate-type chains of magnetite, whereas a Janus-like structure was observed in BMNPs with high amounts of Cu (Fe0.5Cu0.5). However, a non-uniform core-shell structure (Fe0.9Cu0.1) facilitated electron transfer among Fe, Cu and As, which increased the adsorption rate (k), capacity (qe) and intensity (n). The mechanism of As removal was also explored in a comparative study of the phase and morphology of BMNPs pre- and post-sorption."
"The aim of this research was to estimate the risk of human exposure to arsenic due to sporting activities in a private soccer club in Mexico, where arsenic-contaminated water was regularly used for irrigation. For this purpose, the total concentration in the topsoil was considered for risk assessment. This was accomplished through three main objectives: (1) measuring arsenic concentrations in irrigation water and irrigated soils, (2) determining arsenic spatial distribution in shallow soils with Geographical Information Systems (GIS) using geostatistical analysis, and (3) collecting field and survey data to develop a risk assessment calculation for soccer activities in the soccer club. The results showed that the average arsenic concentrations in shallow soils (138.1 mg/kg) were 6.2 times higher than the Mexican threshold for domestic soils (22 mg/kg). Furthermore, dermal contact between exposed users and contaminated soils accounted for a maximum carcinogenic risk value of 1.8 × 10−5, which is one order of magnitude higher than the recommended risk value, while arsenic concentrations in the irrigation water were higher (6 mg/L) than the WHO’s permissible threshold in drinking water, explaining the contamination of soils after irrigation. To the best of our knowledge, this is the first risk study regarding dermal contact with arsenic following regular grass irrigation with contaminated water in soccer pitches."
En el presente trabajo se llevó a cabo el desarrollo del uso de pellets, provenientes de resi-duos lignocelulósicos, para el tratamiento de aguas contaminadas con arsénico de las comu-nidades del municipio de Xichú, Gto., México. Las muestras de agua, n = 72, se evaluaron con base en la NOM-127-SSA1-1994. La concentración más alta de arsénico fue arriba de los límites permisibles, 0.2 mg.L–1 ± 0.04 mg.L–1. Los pellets utilizados fueron a partir de aserrín, paja de trigo, agave y sorgo. Se optimizó la rampa de temperatura para la mejor consistencia de los pellets. Se realizaron varios diseños experimentales con los pellets, n = 162, a diferentes condiciones, para desarrollar el proceso de activación y tratamiento con Fe (III). Los pellets obtenidos fueron colocados en muestras de agua contaminadas con ar-sénico por 24 h. Se logró una remoción de arsénico a pH entre 6.5 a 7, del 98.50% ± 1.2%.
Present work was carried out development of use of pellets from lignocellulosic waste for arsenic-contaminated waters treatment in communities of the municipality of Xichu, Guanajuato, Mexico. Water samples, n = 72, were evaluated based on NOM-127-SSA1-1994.
The highest concentration of arsenic was above permissible limits, 0.2 mg.L–1 ± 0.04 mg.L–1. Pellets used were from sawdust, wheat straw, agave and sorghum. Temperature ramp to the best consistency of pellets is optimized. Several experimental designs with pellets were
performed,n = 162, in different conditions to develop activation process and treatment with Fe (III). Pellets obtained were placed in water samples contaminated with arsenic 24 h. Arsenic removal at pH between 6.5 to 7, of 98.50% ± 1.2% was achieved.
Technologies currently available for the remediation
of arsenic-contaminated sites are expensive and environmentally
disruptive. Rhizofiltration, a strategy
of phytoremediation that uses plants to clean up contaminated
water, has been successfully applied in
this study to remove arsenic from contaminated water.
Proper plant selection is key to ensuring the success
of rhizofiltration as a water cleanup strategy.
Therefore, the aim of this study was to analyze the
behavior of Eleocharis Macrostachya in the removal
of arsenic from water. The experiment was performed
by duplicate in constructed wetland prototypes.
Results indicate that E. Macrostachya was
able to tolerate and accumulate in its roots significant
amounts of arsenic from water (47mg-kg-1 dry
weight). The number of individual plants doubled
during the experiment, showing that the presence of
the metalloid had no effect on growth. The removal
efficiency of arsenic from water in the system
ranged from 90 to 99% for an input concentration of
0.1 and 0.5 mg-L-1, respectively.