http://hdl.handle.net/11627/7 2026-09-08T12:03:56Z 2026-09-08T12:03:56Z Ríos Valenciana, Erika Elizabeth Celis García, Lourdes B. http://hdl.handle.net/11627/6769 2026-06-09T22:37:16Z 2026-01-01T00:00:00Z

Characterization of arsenic biogenic minerals by SEM-EDS and Raman Ríos Valenciana, Erika Elizabeth; Celis García, Lourdes B. The data set contains the SEM-EDS analysis raw data generated to characterize biogenic arsenic sulfides obtained from two arsenate/sulfate-reducing reactors operated in fed- batch mode for 6 cycles (14 d each), fed with simulated groundwater containing 10 mM lactate and 5 mM arsenate, using sediment as the packing material and inoculum. High rates of arsenate (1.9 mmol/L·d) and sulfate (1.0 mmol/L·d) reduction were achieved, reaching 91-99 % arsenic removal efficiencies (last 42 d). Primarily, alacranite (As8S9) and uzonite (As4S5) formed, but once incorporated into the bed, sediment mineralogy masked their signals. The samples analyzed originated at the top of the reactors once yellow precipitates formed, and some solid attached to the glass wall of the reactors was recovered for analysis. The samples consisted of a mixture of sediment and biogenic precipitates and were dried (40 °C) and pulverized in an agate mortar. Finally, the dried samples were characterized by scanning electron microscopy coupled with X-ray Energy-Dispersive Spectroscopy (SEM- EDS) (UHR FEI Helios NanoLab 600, Hillsboro, OR, USA). The data in the CSV files correspond to the signals generated by the Electronic Microscope during the analysis of Zones A and B highlighted in the SEM image file 1ER_SE_0004.tif. The images 1ER_SE_0004_EDS Zona A.tif and 1ER_SE_0004_EDS Zona B.tif correspond to the raw EDS spectra generated for zones A and B, respectively. Files 1 ER_SE_004_EDS Zona A.csv and 1 ER_SE_004_EDS Zona B.csv contain the raw data of the EDS raw X-ray counts of zones A and B, for the yellow precipitate (arsenic sulfide), respectively. To generate the EDS spectrum, it is necessary to graph X-ray intensity on the Y axis against X-ray energy (Kiloelectron volts, keV) on the X axis. Files 1 ER_SE_004_EDS Zona AQ.csv and ER_SE_004_EDS Zona BQ.csv contain the raw data of the weight (wt. %) and atomic (At. %) percentages of the elements detected in the samples for zones A and B, respectively. File 3BP-E_633-2.txt contains the data used to generate the Raman spectrum. A standard Raman spectrum is plotted with Raman Intensity counts on the Y-axis against Wavenumber (cm-1) on the X-axis. Steps to reproduce The dried precipitates formed in biological reactors performing arsenate and sulfate reduction simultaneously were analyzed by SEM-EDS.

2026-01-01T00:00:00Z Treviño Calderón, Katia Karime http://hdl.handle.net/11627/6756 2026-04-16T22:54:03Z 2026-03-19T00:00:00Z

Versatilidad metabólica de una comunidad arseniato reductora bajo condiciones reductoras y oxidantes Treviño Calderón, Katia Karime "El arsénico es un metaloide tóxico para todos los seres vivos, en humanos puede causar daños severos a la salud. Para la biorremediación de sitios contaminados con arsénico se pueden usar bacterias con capacidad de respirar arsénico, que usan arseniato como aceptor final de electrones para transformarlo en arsenito, en combinación con bacterias que reducen sulfato a sulfuro. El arsenito y el sulfuro al alcanzar la saturación precipitan como sulfuros de arsénico (biominerales) y de esta forma separan el arsénico de la corriente acuosa para su confinación, disposición o reúso. Sin embargo, se ha perdido de vista que existe el riesgo de que el arsénico de los sulfuros de arsénico se movilice nuevamente por la acción de bacterias quimiolitótrofas capaces de usar arsenito como donador de electrones para la fijación de CO2 mediante la reducción de oxígeno o nitrato. Actualmente no hay investigación sobre dicho tema. El objetivo de este proyecto fue evaluar la capacidad de un consorcio especializado en arseniato reducción para movilizar arsénico de sulfuros de arsénico biogénicos, al oxidar arsenito en condiciones aerobias o anóxicas. En primer lugar, se evaluaron las cinéticas de reducción de arseniato y la posterior oxidación del arsenito producido en ensayos de microcosmos en lote por triplicado conteniendo 10 mM de arseniato. Los resultados mostraron que tanto la reducción de arseniato como la oxidación de arsenito fueron llevadas a cabo por el mismo consorcio anaerobio que se usó como inóculo en los ensayos. Dicho consorcio había sido previamente enriquecido y usado exclusivamente para llevar a cabo la reducción de arseniato y sulfato con lactato como donador de electrones en condiciones anaerobias. En otro conjunto de ensayos, se usaron precipitados de sulfuros de arsénico para evaluar la capacidad de la comunidad para movilizar nuevamente el arsénico a la fase acuosa. En este caso se encontró que la capacidad de oxidar arsenito fue 7 veces menor que en los ensayos con arsénico soluble. El consorcio microbiano con el que se realizaron los ensayos estaba compuesto por géneros como Desulfomicrobium, Desulfobulbus y Desulfosporosinus. Después de la etapa de oxidación, la diversidad disminuyó entre 38.8 y 68.2% para experimentos inoculados y endógenos, respectivamente; mientras que géneros como Thauera y Pseudomonas se enriquecieron entre 55- 83% y 85-95%, respectivamente. Estos resultados demuestran que los consorcios microbianos arseniato reductores poseen dualidad metabólica y son capaces de realizar el proceso contrario (oxidación de arsenito). Por lo tanto, los bioprecipitados de sulfuros de arsénico obtenidos mediante un proceso de biorremediación anaerobio podrían perder su estabilidad al encontrarse bajo condiciones fluctuantes en el ambiente (óxicas/anóxicas)."; "Arsenic is a toxic metalloid for all living organisms; in humans it can cause severe health damage. For the bioremediation of arsenic-contaminated sites, bacteria with the ability to respire arsenic can be used, which use arsenate as the final electron acceptor to transform it into arsenite, in combination with bacteria that reduce sulfate to sulfide. When arsenite and sulfide reach saturation, they precipitate as arsenic sulfides (biominerals), and in this way arsenic is separated from the aqueous stream for confinement, disposal, or reuse. However, it has been overlooked that there is a risk that arsenic from arsenic sulfides may become mobilized again by the action of chemolithotrophic bacteria capable of using arsenite as an electron donor for CO₂ fixation through oxygen or nitrate reduction. Currently, there is no research on this topic. The objective of this project was to evaluate the capacity of an arsenatereducing specialized consortium to mobilize arsenic from biogenic arsenic sulfides by oxidizing arsenite under aerobic or anoxic conditions. First, the kinetics of arsenate reduction and the subsequent oxidation of the produced arsenite were evaluated in triplicate batch microcosm assays containing 10 mM arsenate. The results showed that both arsenate reduction and arsenite oxidation were carried out by the same anaerobic consortium used as inoculum in the assays. This consortium had been previously enriched and used exclusively to carry out arsenate and sulfate reduction with lactate as electron donor under anaerobic conditions. In another set of assays, arsenic sulfide precipitates were used to evaluate the community’s ability to mobilize arsenic again into the aqueous phase. In this case, it was found that the capacity to oxidize arsenite was 7 times lower than in assays with soluble arsenic. The microbial consortium used in the assays was composed of genera such as Desulfomicrobium, Desulfobulbus, and Desulfosporosinus. After the oxidation stage, diversity decreased between 38.8 and 68.2% for inoculated and endogenous experiments, respectively; while genera such as Thauera and Pseudomonas were enriched between 55–83% and 85–95%, respectively. These results demonstrate that arsenate-reducing microbial consortia possess metabolic duality and can perform the opposite process (arsenite oxidation). Therefore, arsenic sulfide bioprecipitates obtained through an anaerobic bioremediation process could lose their stability when found under fluctuating environmental conditions (oxic/anoxic)."

2026-03-19T00:00:00Z Gonzalez-Vera, Andrea Susana http://hdl.handle.net/11627/6712 2026-08-28T18:45:45Z 2025-09-01T00:00:00Z

Synthesis, Purification, Photoluminescence Mechanisms and Energy Applications of Biomass-Derived Carbon Dots Gonzalez-Vera, Andrea Susana La generación de puntos de carbono (CDs) a partir de biomasa es una gran oportunidad para aprovechar los residuos de biomasa mediante metodologías sencillas y económicas, sin embargo, la estructura química y los mecanismos de fotoluminiscencia de este tipo de nanopartículas aún no se encuentran completamente descritos y siguen siendo objeto de debate en la comunidad científica. En este estudio, se sintetizaron CDs mediante un proceso hidrotermal asistido por microondas a partir de la fracción lignocelulósica de cáscara de naranja colectada en San Luis Potosí. Los CDs se purificaron mediante un proceso de separación secuencial con membranas de distinta porosidad (0.22 µm, 0.1 µm, 100, 50 y 5 kDa), el cual fue diseñado específicamente para este material con base a estudios de la descomposición de la lignina y la celulosa y a la estimación del peso molecular de los CDs en correspondencia con el diámetro de partícula esperado. Las suspensiones derivadas de cada etapa de purificación se caracterizaron mediante distintas técnicas (FTIR, TPD-MS, DLS, UV-Vis, y espectroscopía de fotoluminiscencia), lo que permitió evidenciar la presencia de subproductos y su influencia en las características fisicoquímicas, coloidales y ópticas de los CDs. Adicionalmente, se analizaron a mayor profundidad las características texturales, de química superficial y el comportamiento coloidal en función de la concentración del material en suspensión de la fracción más purificada de los CDs. Dichos análisis, en conjunto con la caracterización de la emisión de fotoluminiscencia de suspensiones de CDs a distintas concentraciones y la deconvolución de los espectros correspondientes, permitieron explicar los procesos de interacción y transferencia de energía que ocurren entre las partículas en suspensión. Finalmente, los CDs generados demostraron su capacidad para sensibilizar celdas solares de tercera generación. La presencia de CDs en el fotoánodo de las celdas incrementó su eficiencia en comparación con aquellas construidas con fotoánodos prístinos de FTO-TiO2.; The generation of carbon dots (CDs) from biomass is a great opportunity to take advantage of biomass waste using simple and economical methodologies. However, the chemical structure and photoluminescence mechanisms of this type of nanoparticles have not yet been fully described and remain under debate in the scientific community. In this study, CDs were synthesized using a microwave-assisted hydrothermal process from the lignocellulosic fraction of orange peel collected in San Luis Potosí. The CDs were purified using a sequential separation process with membranes of different porosity (0.22 µm, 0.1 µm, 100, 50, and 5 kDa), which was specifically designed for this material based on studies of lignin and cellulose decomposition and the estimation of the molecular weight of CDs in correspondence with the expected particle diameter. The suspensions derived from each purification stage were characterized using different techniques (FTIR, TPD-MS, DLS, UV-Vis, and photoluminescence spectroscopy), which revealed the presence of by-products and their influence on the physicochemical, colloidal, and optical characteristics of the CDs. In addition, the textural characteristics, surface chemistry, and colloidal behavior were deeply analyzed as a function of the concentration of the material in suspension (for the most purified fraction of the CDs). These analyses, together with the characterization of the photoluminescence emission of CDs suspensions at different concentrations and the deconvolution of the corresponding spectra, allowed us to explain the interaction and energy transfer processes that occur between the particles in suspension. Finally, the CDs generated demonstrated their capacity to sensitize third-generation solar cells. The presence of CDs in the photoanode of the cells increased their efficiency compared to those constructed with pristine FTO-TiO2 photoanodes.

2025-09-01T00:00:00Z ESQUIVEL-ARRIAGA, GERARDO http://hdl.handle.net/11627/6677 2025-05-12T20:42:58Z 2025-04-22T00:00:00Z

Social-ecological participatory observatory sites in arid northern Mexico: co-definition of shared space and future challenges of drought under climate change ESQUIVEL-ARRIAGA, GERARDO Drylands social-ecological systems are one of the most extensive, diverse, yet highly vulnerable social–ecological systems of our planet Earth. Aridity and drought patterns cause increasing pressure on land and water resources and are some of the largest global and local environmental and social change problems and thus are a challenge for science and society. Drylands cover approximately 65% of the Mexican territory; over 60% of the total population inhabit these areas. Recent scientific consensus suggests that to potential solutions to land degradation need to be identified and implemented within the context of local environmental, social, economic and political conditions. At the same time, the complexity of drought risk demands cross-sectoral policies accounting for regional diversity, leveraging local knowledge and promoting communities' engagement. In this research, our study sites, the Social-ecological participatory observatories (OPSEs) lie along a west–east transect in northern Mexico drylands. The OPSEs are a social-ecological innovation and provide a space for the consolidation of formal and informal alliances for sustainability through learning communities that share diverse knowledge, technologies, and innovations. As a result of a survey applied to actors of various sectors linked to the OPSEs, priority issues were defined, including climate change, drought, and water scarcity. In this research, the general objective was to analyze the social-environmental value linked to shared land by multiple stakeholders as a basis to co-define the spatial boundaries of social-ecological systems and analyze potential future changes in precipitation and the potential occurrence of droughts under climate change conditions in the context of the OPSE network divided in three chapters. Chapter one showed that the valuation of land by multiple stakeholders by identifying and mapping different meaningful places in the OPSE Mapimí can be integrated to generate socio-economic variables that are not available in vectorial format and combined with biophysical variables allowed the spatial delineation of a Social-ecological system and the estimation of social-ecological units within the OPSE Mapimí. This delineation is dynamic and flexible and subject to updates and re-evaluations, as it is based on the perception, intuition, experience, interest, knowledge and judgment of different stakeholder groups, which are highly experienced and knowledgeable about the local and current social-environmental conditions. Chapter 2 highlights that for an adequate characterization of drought conditions, good quality precipitation data are indispensable. This chapter examined how the rainfall gauge network in Mexico’s drylands that is highly heterogeneously distributed and frequently with incomplete datasets, can be compensated by information derived from global precipitation datasets. Based on the performance of five global precipitation datasets, we suggest using CHIRPS and AgERA5 climatic data to fill gaps of observational rain gauge information. Chapter 3 examined the occurrence (frequency, severity and duration) of historical (1981-2010) and future (2041-2100) meteorological droughts at time scale of 12 months for the OPSEs network using the Standardized Precipitation Index (SPI). Likewise, the perception of the concept of drought and adaptation measures were analyzed in the OPSE Mapimí. Results suggest that in the near (2041-2070) and far (2071-2100) future, an increase in the average annual precipitation is projected for the OPSE network. In general, drought conditions at the 12-months time scale for the near future, presented less frequent events with a decrease in its duration. In the OPSE Mapimí, the drought concept mostly found to be linked with issues related to rainfall (no rain) and vegetation (no forage). The years 1951, 1953, 1970, 1972, 1977, 1978, 1984, 1986, 1988, 1989, 1990, 1995, 1997, 1998, 2001, 2002, 2008, 2011, 2012 and 2019 were identified as the most important drought events since they affected their living conditions. The years 1958, 1987, 1990 and 2010 were identified as the wettest years, causing flooding in the ejido Laguna de Palomas. Changes in the weather were generally recognized by the respondents (more heat and less rain), if not expressed as “climate change”. Adaptation measures to face drought in case of cattle raising include selling some animals to maintain the remaining animals or cutting and burning prickly pear as an alternative food source for livestock. The salt producers and ecotourism people were temporarily employed or received economic support from relatives. One of the innovations of this research is that the process promotes an exchange of information (scientific and non-scientific) and is approached from two different perspectives: one based on observation and measurement (e.g., relief morphometry, land use/cover, etc.) and a phenomenological one, based mainly on people's experiences (mapping of significant places from valuations of space by multiple sectors and the deep understanding of the concept drought. Hence, this research represents a transferable and replicable approach. The OPSE model, in a time frame of 4-5 years (to be defined), is observed to have important implications for future transdisciplinary research that could focus on collaborative social-environmental governance with the important focus on water governance, climate modeling, community resilience and novel questions that could lead to the development of more sustainable approaches for the adaptive and integral management of Mexico’s drylands.

2025-04-22T00:00:00Z