Utilizamos la firma de isótopos estables de carbono, medida como δ¹³C, en la materia orgánica de suelo (SOM) como un método de alta resolución espacial para inferir algunos cambios ambientales durante el Pleistoceno tardío y el Holoceno en el valle de Teotihuacán. La interpretación se basa en la diferencia de δ¹³C y preferencias climáticas correspondientes de las plantas referidas como C3, C4 y CAM.Los valores de δ¹³C obtenidos de plantas que crecen en el valle hoy en día difieren claramente entre dos grupos: los de las plantas C3 con un promedio de -27%, y los de C4 y CAM con un promedio cerca de -13%. Los datos obtenidos para los suelos se encuentran en el intervalo de -25.72 a -15.54 %. Las secuencias de suelos Pleistoceno tardío- Reciente del valle alto (posición geomorfológica alta), localizadas en el perfil de Cerro Gordo, se caracterizan por una δ¹³C con poca variabilidad alrededor de -20%, indicando una coexistencia duradera entre las plantas C3 y C4 (y CAM). Las firmas más empobrecidas (-23 ± 2) %, dominadas por carbono derivado de la vegetación tipo C3, corresponden a los suelos de pantano del Pleistoceno tardío en el perfil retrógrado de transición Tepexpan del antiguo lago de Texcoco-Xaltocan. Los paleosuelos en el valle bajo (Pleistoceno tardío - Holoceno medio), incluyendo los de la Pirámide de la Luna, están menos empobrecidos (-17 ± 1) %, o bien, dominados por carbono de plantas C4 y CAM. Los suelos del Holoceno tardío y modernos presentan una disminución (1-2 %) respecto a las δ¹³C de los suelos subyacentes.A partir de las δ¹³C de suelos se estimó la porción relativa de la contribución de las plantas C4 a la materia orgánica del mismo. Nuestros resultados implican un incremento, dependiendo del lugar, de entre 10 y 70%, durante el período de transición entre el Pleistoceno tardío y Holoceno temprano, y un dominio de la vegetación tipo C4 en el ambiente del valle, hasta en un 84%, durante Holoceno medio. Nuestros datos apoyan la idea de un cambio natural de un clima más frío y húmedo durante el último Máximo Glacial y el Pleistoceno tardío a uno más seco y caluroso en el Holoceno medio. Un ligero incremento de humedad y establecimiento de un clima semejante al actual, aún cálido y seco, se infiere del incremento en todo el valle, dependiendo del lugar, de 4 a 10%, de la población de plantas C3. Sugerimos que este último cambio climático pudo favorecer el desarrollo de la antigua agricultura. Nuestra interpretación general de los primeros datos de isótopos estables del carbono concuerda con interpretaciones paleoambientales para el área basadas en registros palinológicos y paleolimnológicos en sedimentos lacustres.

The lakes known as El Sol and La Luna are high mountain water deposits located in Mexico within an inactive volcanic system. These lakes are of ecological importance because they are unique in Mexico. However, currently, the lakes have experienced changes in their shape and an increase in algae blooms, coupled with the degradation of the basin, which has alerted government entities to the need to address the lakes’ problems. To address the environmental status of El Sol and La Luna, a trophic study was conducted during the period of 2021–2023, including an analysis of the influence of climatic variables, lake water quality, and eutrophication conditions. The trophic state was established based on the eutrophication index. The Pearson correlations defined the eutrophication interrelation between the distinct factors influencing the lakes’ status. El Sol registered higher eutrophication conditions than La Luna. El Sol was identified as seasonal eutrophic and La Luna as transitioning from oligotrophic to mesotrophic, showing high levels of chlorophyll, total phosphorus, and total nitrogen and low water transparency. The principal factors altering the eutrophic conditions were water pollution and climatic variables (precipitation and ambient temperature). Eutrophication was the prime factor impacting perimeter loss at El Sol, whereas at La Luna, it was due to a decline in precipitation.

Mexico’s vast archaeological research tradition has increased with the use of remote sensing technologies; however, this recent approach is still costly in emerging market economies. In addition, the scales of prospection, landscape, and violence affect the type of research that heritage-culture ministries and universities can conduct. In Central Mexico, researchers have studied the pre-Hispanic Settlement Pattern during the Mesoamerican Postclassic (900-1521 AD) within the scope of the Aztec Empire and its conquests. There are settlements indications before and during the rule of the central empire, but the evidence is difficult to identify, particularly in the southwest of the capital, in the transition between the Lerma and Balsas River basins and their political-geographical complexities. This research focuses on a Geographic Information System (GIS)-based processing of multiple source data, the potential prospection of archaeological sites based on spatial data integration from Sentinel-2 optical sensors, Unmanned Aerial Vehicle (UAV), Digital Terrain Model (DTM), Normalized Difference Vegetation Index (NDVI) and field validation. What is revealed is the relationship between terrain morphologies and anthropic modifications. A binary map expresses possible archaeological remnants as a percentage; NDVI pixels and the morphometry values were associated with anthropic features (meso-reliefs with a tendency to regular geometries: slope, orientation, and roughness index); they were then interpreted as probable archaeological evidence. Within archaeological fieldwork, with limited resources (time, funding and staff), this approach proposes a robust method that can be replicated in other mountainous landscapes that are densely covered by vegetation.

Volcanic activity in ancient Mesoamerica was decisive for many populations since it influenced daily life and the way of understanding the world. Eruptive events can provoke the total or partial abandonment of the sites, changes in the social organization, and, inclusively, changes in the pedogenesis with alteration of the natural resources. The impact of volcanic activity can be detected easily. However, it can also be “hidden” among the soil and archaeological materials; consequently, its identification and analysis are essential to understanding archaeological stratigraphy. To document the above, this work presents the results obtained at two sites in western Mexico: Cerro del Teúl in Zacatecas (ca. 100-1531 d.C.) and El Pitayo in Michoacán (200- 600 d.C.). In the case of Cerro de Teúl, the construction fills were analyzed in two stratigraphic profiles: the Patio Hundido (PH21) and the Main Plaza (P2M80). In El Pitayo, construction fills and soil horizons were analyzed in two profiles located in a trench with an E-W orientation (East Trench and South Trench). The main objective was to identify the impact of volcanic activity on the archaeological stratigraphy and the transformations of volcanic materials as a consequence of natural and anthropogenic processes, using colorimetric, granulometric, and micromorphological analyses. In addition, the chemical composition (by X-ray fluorescence) and the petrography of the volcanic ash found in the sites were determined and compared with that from surrounding volcanoes. According to the results, the ash observed in Cerro Teúl originated from the Jala eruption of the Ceboruco volcano, dated 990-1020 AD. This eruption did not produce the site abandonment, as the site was rapidly re-occupied, and the ash was left between the construction fills. In the case of El Pitayo, according to archaeological evidence (the ages of the abandoned artifacts and the absence of volcanic glass on the lower floors of the construction), it is probable that the landslide was emitted during the first half of the 6th century and the site contin- ued developing after the event. The geochemical and mineralogical composition of the volcanic materials found in the excavations has an intermediate-acid affinity, which contrasts with the monogenetic volcanism in the area; however, as the material is reworked, it is probable that the original mineralogical composition has been modified by transport and erosional processes, or diluted by the mixture with more acid sources, as evidenced by the domain of volcanic glass with heterogeneous textures and morphologies. Until now, there is a possible source of emission of the volcanic material associated with that found in the “black earth” at the site of El Pitayo, which is the El infiernillo volcanic event, located south of Michoacán and which has a date of 1500- 1370 BC (Mahgoub et al., 2017). However, the “black earth” that covered the site is after this dating, so chronologically it would not correspond to an eruption that occurred during the occupation of the site, but it allows us to associate it as a product of a landslide from Cerro El Arco, since that the geochemical characterization of the volcanic glass shows a very close affinity to this El Infiernillo event.

This study examines the impact of physicochemical and geological factors on radon concentrations in groundwater throughout the Mexican Altiplano. Geological diversity, uranium deposits, seismic zones, and geothermal areas with high heat flow are all potential factors contributing to the presence of radon in groundwater. To move beyond local-scale assessments, this research employs spatial prediction methodologies that incorporate geological and geochemical variables recognized for their role in radon transport and geogenic potential. Certain properties of radon enable it to serve as an ideal tracer, viz., short half-life, inertness, and higher incidence in groundwater than surface water. Twenty-five variables were analyzed in samples from 135 water wells. Geostatistical techniques, including inverse distance weighted interpolation and kriging, were used in conjunction with multivariate statistical analyses. Salinity and geothermal heat flow are key indicators for determining groundwater origin, revealing a dynamic interplay between geothermal activity and hydrogeochemical evolution, where high temperatures do not necessarily correlate with increased solute concentrations. The occurrence of toxic trace elements such as Cd, Cr, and Pb is primarily governed by lithogenic sources and proximity to mineralized zones. Radon levels in groundwater are mainly influenced by geological and structural features, notably rhyolitic formations and deep hydrothermal systems. These findings underscore the importance of site-specific groundwater examination, combined with spatiotemporal models, to account for uranium–radium dynamics and flow paths, thereby enhancing radiological risk assessment.