A field study was carried out in the Metropolitan Area of Monterrey (MAM), the second most populated city in Mexico, characterized by increasing urbanizati

Trace metal concentrations in PM₁₀ were measured in an urban–industrial site in León, Mexico in three different seasons. PM₁₀ were collected in quartz fiber filters of 47 mm diameter using low volume equipment operating with a controlled flow of 5 L min⁻¹ over 24 h. Mass concentrations were gravimetrically determined and it was found that PM₁₀ samples showed values in excess of the Mexican standard and the established values by WHO during cold dry and warm dry seasons. Morphology of selected particles was studied by SEM-EDS analysis, and the elemental composition was determined. Collected samples were analyzed by atomic absorption spectrometry in order to quantify ambient air concentrations of some trace metals (Cu, Co, Zn, Cd, Fe, Mg, and Mn). Median concentrations of trace metals showed the maximum value for iron (3.079 μgm⁻³) and the minimum value for Cd (0.050 μgm⁻³) over the entire period. From the meteorological analysis, it was found that sources located SW and ESE of the sampling site contributed to the levels of trace metals in PM₁₀ in the studied site. The health risk assessment found that the population of León is at increased lifetime risk of experiencing cancer because of exposure to these concentrations of PM₁₀ and their trace metal content.

Levels of BTEX (Benzene, Toluene, Ethylbenzene and p-Xylene) were determined in the ambient air of two urban sites located in the Metropolitan Area of Monterrey (MAM) during two climatic seasons of 2023. The study revealed that BTEX compounds in Santa Catarina and Obispado had the following relative abundance: p-Xylene (20.09 µg m⁻³) > Toluene (19.50 µg m⁻³) > Ethylbenzene (19.34 µg m⁻³) > Benzene (17.39 µg m⁻³). Their concentrations were consistent with global reports, showing diurnal and seasonal variability. Levels were higher during the dry season due to elevated temperatures, low wind speeds, and lack of precipitation, which reduced pollutant dispersion. BTEX concentrations in Santa Catarina (industrial site) and Obispado (urban site) were influenced by local activities like industrial processes, area sources, and vehicular traffic. Wind rose analysis confirmed the influence of local sources, with higher BTEX levels when winds came from the east. This was linked to pollutant transport within MAM and thermal inversions trapping pollutants during the dry season. Benzene/Toluene (B/T) and p-Xylene/Ethylbenzene (X/E) ratios showed that the sampling sites were influenced by vehicular sources and local fresh emissions. Benzene inhalation has an unacceptable lifetime cancer risk, urging MAM authorities to implement stricter regulations to protect public health. While non-cancer risks were within acceptable limits, controlling Benzene and p-Xylene emissions remains critical to improving air quality.

The San Luis Potosí valley is an endorheic basin that contains three aquifers: a shallow unconfined aquifer of alluvial material and two deep aquifers, free and confined. The groundwater contamination documented for the shallow aquifer generates contamination of the deep unconfined type aquifer, from which part of the population’s drinking water needs are met. This study records incipient anthropogenic contamination of two types: biogenic and potentially toxic trace elements. The studied contaminants include fecal coliform bacteria, total coliform, nitrate, and potentially toxic elements such as: manganese ($Mn$), mercury ($Hg$), arsenic ($As$), and cadmium ($Cd$). This contamination in some locations exceeds the permissible limit for human consumption. Some major consequences to health, including severe illness, may be caused by the trace elements. The present results give a first signal about the contamination of the deep unconfined type aquifer due to anthropogenic activity in the valley. This is a priority issue because this aquifer supplies drinking water, and in the short or medium term it will have an effect on public health.

The spatiotemporal distributions of aromatic hydrocarbon levels in the atmosphere were evaluated at ten locations within Monterrey’s Metropolitan Area using passive sampling techniques across three climatic seasons (the rainy season of 2023, the cold front season of 2023, and the dry season of 2024). The observed relative abundance was toluene > p-xylene > benzene > ethylbenzene. The dry season showed the highest concentration values for all measured compounds, and the Santa Catarina site showed the highest average level for toluene (2.79 μg m⁻³). In the rainy season, the highest average concentrations were recorded in Santa Catarina, with toluene at 1.39 μg m⁻³ and p-xylene at 0.99 μg m⁻³. During the cold fronts season, the greatest average concentration of p-xylene (0.98 μg m⁻³) was found in San Bernabe, while Santa Catarina reported the highest average for toluene at 1.55 μg m⁻³. A health risk assessment indicated that cancer risk coefficients exceeded the reference values set by the EPA. These findings suggest that the presence of the alkyl derivatives of benzene (benzene, toluene, ethylbenzene, and p-xylene) in the studied region poses a potential health issue and highlights the need for enhanced control measures regarding their sources.

This study conducts a comparative performance analysis of three different low-temperature solar collector systems: flat plate solar collectors (FPCs), heat pipe evacuated tube solar collectors (HPETCs), and heat pipe flat plate solar collectors (HPFPCs). Key performance parameters, such as heat transfer coefficients, useful heat, and thermal efficiency, are analyzed under varying mass flow rate, fluid temperature, and antifreeze concentration. The objective is to evaluate the thermal performance of these systems using different heat transfer fluids, specifically water, and mixtures of 30% and 50% ethylene glycol and propylene glycol. The performance data indicate that the heat transfer coefficient in the HPFPC diminishes by 28% and 41% when antifreeze is employed at concentrations of 30% and 50%, respectively. Furthermore, the integration of heat pipes with water in a flat plate solar collector results in efficiency enhancements, with respect to FPCs, of up to 13% at a fluid temperature of 30 °C, and up to 21% at 80 °C. At the elevated fluid temperature of 80 °C, an efficiency increase of 13% is observed with a 30% ethylene glycol concentration. The incorporation of heat pipes leads to an efficiency improvement of up to 6.5% in comparison to traditional flat plate solar collectors. This study highlights the significant impact of fluid properties, affecting the convective heat transfer coefficient, on the overall efficiency of solar collectors, emphasizing the importance of optimizing fluid composition and operating conditions for enhanced thermal performance.