Problemática del carbono en aerosoles atmosféricos PM2.5

El objetivo general de este proyecto es analizar las variaciones y el aporte de carbono total (TC), carbono orgánico (OC) y carbono elemental (EC) en aerosoles atmosféricos originados por fuentes fósiles (quema de combustibles fósiles) y por quema de biomasa y emisiones biogénicas (emisiones de la naturaleza). Ya que el carbono juega un rol muy preocupante en el cambio climático, salud humana y equilibrio ecológico, debido a sus propiedades físicas y químicas, y sus emisiones descontroladas; además de que, debido a que no existe un monitoreo o registro completo del carbono, no existen normas reguladoras específicas para este contaminante. En este trabajo se observó una ligera disminución de la concentración de PM2.5 en la UNAM, Ciudad de México (CDMX), pero un aumento en el contenido de carbono, debido principalmente al consumo de combustibles fósiles.The general objective of this project is to analyze the variations and the contribution of total carbon (TC), organic carbon (OC) and elemental carbon (EC) in atmospheric aerosols originated by fossil sources (burning fossil fuels) and by burning biomass and biogenic emissions (emissions from nature). Since carbon plays a very worrying role in climate change, human health and ecological balance, due to physical and chemical properties, and uncontrolled emissions; in addition, there is not complete monitoring or registration of carbon, there are not specific regulatory norms for this pollutant. In this work, there was a slight decrease in the concentration of PM2.5 in UNAM, Mexico City (CDMX), but an increase in carbon content, mainly due to fossil fuel consumption

Uso del isótopo ¹⁴C como trazador de fuentes de emisión de CO₂

En la ciudad de México, se capturó CO₂ atmosférico para determinar la concentración de ¹⁴C. Se utilizó una solución alcalina para transportar los átomos de C provenientes del CO₂ atmosférico como material carbonoso, para luego procesarlos hasta extraerlos como grafito, y analizarlos mediante la técnica de Espectrometría de Masas Aceleradora (AMS) para determinar la concentración de ¹⁴C. Fue posible determinar la concentración de CO₂ en ppm y su contenido de ¹⁴C como una fracción del carbono moderno (ƒM). Esto se realizó en diciembre de 2019, durante la temporada seca y fría en un período de 37 días.In Mexico City, atmospheric CO₂ was captured to determine the concentration of ¹⁴C. An alkaline solution was used to transport the C atoms from atmospheric CO₂ as carbonaceous material, to then process them until they were extracted as graphite, and analyzed using the Accelerating Mass Spectrometry (AMS) technique to determine the concentration of ¹⁴C. It was possible to determine the CO₂ concentration in ppm and its ¹⁴C content as a fraction of modern carbon (ƒM). These were carried out in December 2019, during the dry and cold season in a period of 37 days

The Younger Dryas black mat from Ojo de Agua, a geoarchaeologicalsite in Northeastern Zacatecas, Mexico

New explorations in the desert of northeastern Zacatecas, in central-northern Mexico, revealed dozens ofarchaeological and geoarchaeological sites. One of them, Ojo de Agua, contains the remains of a Pleis-tocene spring-fed hydrographic system located at the southeastern end of a large elongated endorheicbasin. The locality yielded a particularly dark, highly organic stratigraphic layer commonly known in theAmericas as Black Mat (BM), exposed on the natural profiles of a creek, but not associated with culturalmaterials. Several radiocarbon assessments confirmed the formation of the Ojo de Agua Black Mat duringthe Younger Dryas chronozone, with ten calibrated results clustering between 12,700e12,100 cal BP. Thismulti-proxy study confirmed the peculiarity of the deposit and found similarities and differences withother contexts of Younger Dryas age. The Ojo de Agua Black Mat (stratum C2) is far richer in charcoalspecks than the related strata, but lacks phytoliths, diatoms or ostracods. No further biological remainswere found in it, except for intrusive capillary roots. Clearly water-lain in a shallow pond, the stratumqualifies as a clayey silt with an acidic-to-neutral pH. Rich in heavy metals and with high contents oftitanium, the Ojo de Agua Black Mat yielded significant indicators of intense wildfires during the YoungerDryas, but produced no carbon spherules or nanodiamonds supposedly linked to the impact theory

Evidence of human occupation in Mexico around the Last Glacial Maximum

The initial colonization of the Americas remains a highly debated topic1 , and the exact timing of the frst arrivals is unknown. The earliest archaeological record of Mexico—which holds a key geographical position in the Americas—is poorly known and understudied. Historically, the region has remained on the periphery of research focused on the frst Americanpopulations2 . However, recent investigations provide reliable evidence of a human presence in the northwest region of Mexico3,4 , the Chiapas Highlands5 , Central Mexico6 and the Caribbean coast7–9 during the Late Pleistocene and Early Holocene epochs. Here we present results of recent excavations at Chiquihuite Cave—a high-altitude site in central-northern Mexico—that corroborate previous fndings in the Americas10–17of cultural evidence that dates to the Last Glacial Maximum (26,500–19,000years ago)18, and which push back dates for human dispersal to the region possibly as early as 33,000–31,000years ago. The site yielded about 1,900stone artefacts within a 3-m-deep stratifed sequence, revealing a previously unknown lithic industry that underwent only minor changes over millennia. More than 50radiocarbon and luminescence dates provide chronological control, and genetic, palaeoenvironmental and chemical data document the changing environments in which the occupants lived. Our results provide new evidence for the antiquity of humans in the Americas, illustrate the cultural diversity of the earliest dispersal groups (which predate those of the Clovis culture) and open new directions of research

Evidence of human occupation in Mexico around the Last Glacial Maximum.

The initial colonization of the Americas remains a highly debated topic1, and the exact timing of the first arrivals is unknown. The earliest archaeological record of Mexico-which holds a key geographical position in the Americas-is poorly known and understudied. Historically, the region has remained on the periphery of research focused on the first American populations2. However, recent investigations provide reliable evidence of a human presence in the northwest region of Mexico3,4, the Chiapas Highlands5, Central Mexico6 and the Caribbean coast7-9 during the Late Pleistocene and Early Holocene epochs. Here we present results of recent excavations at Chiquihuite Cave-a high-altitude site in central-northern Mexico-that corroborate previous findings in the Americas10-17of cultural evidence that dates to the Last Glacial Maximum (26,500-19,000 years ago)18, and which push back dates for human dispersal to the region possibly as early as 33,000-31,000 years ago. The site yielded about 1,900 stone artefacts within a 3-m-deep stratified sequence, revealing a previously unknown lithic industry that underwent only minor changes over millennia. More than 50 radiocarbon and luminescence dates provide chronological control, and genetic, palaeoenvironmental and chemical data document the changing environments in which the occupants lived. Our results provide new evidence for the antiquity of humans in the Americas, illustrate the cultural diversity of the earliest dispersal groups (which predate those of the Clovis culture) and open new directions of research