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Abstract: A field study was carried out in the Metropolitan Area of Monterrey (MAM), the second most populated city in Mexico, characterized by increasing urbanization, high traffic density, and intense industrial activity. These characteristics commonly present high concentrations of air pollutants leading to the degradation of air quality. PM2.5 was analyzed for heavy metals at two urban sites located within the MAM (Juarez and San Bernabe) in order to determine sources, health risk, morphology, and elemental content during the COVID-19 pandemic (autumn 2020 and spring 2021). Twenty-four-hour samples of PM2.5 were collected at each site during 30-day periods using high-volume equipment. Gravimetric concentrations and 11 metals were measured (Ca, Cd, Co, Cu, Fe, K, Mg, Mn, Ni, Cr, and Pb) by different analytical techniques (flame atomic absorption spectroscopy, graphite furnace atomic absorption spectroscopy, and inductively coupled plasma optical emission spectroscopy). Selected samples were analyzed by scanning electron microscopy-energy-disperse spectroscopy in order to characterize their morphology and elemental content. PM2.5 concentrations exceeded the Mexican standard and WHO guidelines in Juarez during spring 2021. Cu, Cd, and Co were highly enriched by anthropogenic sources, and Ni, K, Cr, and Pb had a moderate enrichment. Mg, Mn, and Ca were of crustal origin. Bivariate statistics and PCA confirmed that alkaline metals originated from crustal sources and that the main sources of trace metals included traffic emissions, resuspension from soil/road dust, steel industry, smelting, and non-exhaust emissions at both sites. Lifetime cancer risk coefficients did not exceed the permissible levels established by EPA and WHO, implying that local residents are not at risk of developing cancer. Non-carcinogenic risk coefficients revealed that there is a possible risk of suffering cardiovascular and respiratory diseases due to inhalation of cobalt at the study sites. Supplementary Information: The online version contains supplementary material available at 10.1007/s11869-023-01372-7.

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The negative synergistic effects of air pollution and sensible heat on public health have been noted in numerous studies. While separate, simplified, and public-facing indices have been developed to communicate the risks of unhealthful levels of air pollution and extreme heat, a combined index containing elements of both has rarely been investigated. Utilizing air quality, meteorology, and mortality data in Monterrey, Mexico, we investigated whether the association between the air quality index (AQI) and mortality was improved by considering elements of the heat index (HI). We created combined indices featuring additive, multiplicative, and either/or formulations and evaluated their relationship to mortality. Results showed increased associations with mortality for models employing indices that combined the AQI and the HI in an additive or multiplicative manner, with increases in the interquartile relative risk of 3-5% over that resulting from models employing the AQI alone.

Asunto(s)

Contaminantes Atmosféricos , Contaminación del Aire , Contaminantes Atmosféricos/análisis , Contaminación del Aire/efectos adversos , Contaminación del Aire/análisis , Calor , México/epidemiología , Material Particulado/análisis , Riesgo

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Trajectory models are frequently used to characterize the atmospheric transport pathways for airborne gases and aerosols. Users of these models must specify a starting elevation for their calculations. The variation of wind with altitude causes trajectory models to be sensitive to the starting elevation, particularly when single trajectories rather than Lagrangian particle dispersion simulations are used to characterize atmospheric transport. In this work we systematically investigate and quantify the sensitivity of single trajectory calculations to the starting elevation. The analysis was based on an eight-year database of daily, 48-h back-trajectories calculated for ten sites. Trajectories were calculated at four different starting elevations, and the horizontal difference between endpoints was determined for five upwind travel times. Trajectory model calculations were found to be strongly sensitive to starting elevation. A 500 m difference in starting elevation leads to an average horizontal separation of 326 km after 48 h. Mean horizontal separations of 627 km and 886 km were found for starting elevation differences of 1000 m and 1500 m, respectively. A seasonal dependence of the sensitivity was found, with the smallest separations occurring during the summer, the largest during winter, and intermediate values during the fall and spring. A linear relationship was observed between trajectory model sensitivity and difference in starting elevation. Empirical equations were presented to approximate this relationship.

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The Monterrey Metropolitan Area (MMA) is the third largest city in Mexico. Few studies have been carried out regarding its air pollution. The aim of this study was to analyze the temporal behavior of PM10 (particulate matter < or =10 microm in aerodynamic diameter). Data reported by the "Sistema Integral de Monitoreo Ambiental" (Integrated Environmental Monitoring System) network from 2006 to 2008 were used. PM10 levels were compared among the stations by year, season, and day of week. A bootstrap technique was used to obtain subsamples to which Student's t test and ANOVA were applied. PM10 levels were high and exceeded the annual limit of 50 microg/m3 set up by the Mexican standard Norma Oficial Mexicana NOM-025-SSA1-1993. These levels could have serious health effects. The southwest zone of MMA had the highest levels of PM10 during the period studied. Winter was the most polluted season, and summer was the least polluted season. Thursday and Friday were the most polluted days, and Sunday was the least polluted day. The hours with the highest levels of PM10 were 8:00 to 10:00 a.m., whereas nighttime hours were the cleanest.

Asunto(s)

Contaminantes Atmosféricos/análisis , Contaminación del Aire/análisis , Exposición por Inhalación/prevención & control , Material Particulado/análisis , Contaminación del Aire/prevención & control , Monitoreo del Ambiente , Humanos , México , Tamaño de la Partícula , Material Particulado/toxicidad , Estaciones del Año , Factores de Tiempo , Salud Urbana

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Black carbon (BC) from biomass and fossil fuel combustion alters chemical and physical properties of the atmosphere and snow albedo, yet little is known about its emission or deposition histories. Measurements of BC, vanillic acid, and non-sea-salt sulfur in ice cores indicate that sources and concentrations of BC in Greenland precipitation varied greatly since 1788 as a result of boreal forest fires and industrial activities. Beginning about 1850, industrial emissions resulted in a sevenfold increase in ice-core BC concentrations, with most change occurring in winter. BC concentrations after about 1951 were lower but increasing. At its maximum from 1906 to 1910, estimated surface climate forcing in early summer from BC in Arctic snow was about 3 watts per square meter, which is eight times the typical preindustrial forcing value.

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Air trajectory and particle scattering data (bsp) for the period 1984-1989 are used to determine the relationship between atmospheric transport and visual air quality at the Grand Canyon National Park. Using cluster analysis, 72-hour back-trajectories arriving four times per day were grouped into distinct transport patterns. Northwesterly and southerly/southwesterly flow dominate in the winter and summer seasons, respectively. Comparisons of bsp values accompanying different transport patterns showed a clear relationship between air flow pathway and light scattering due to small particles during the non-summer months only. An index is defined which describes the percentage of annual trajectories belonging to specific transport routes delivering predominantly clear air to the GCNP.