In growing Mexican cities, there are few studies on air pollution, especially on the topic of characterization for the chemical composition of Particulate Matter (PM). This work presents an X-ray Fluorescence (XRF) analysis and Total Carbon analysis of PM_2.5 in a two-year monitoring campaign from 20 May 2017 to 30 July 2018, collecting 96 daily samples in the northeast area of San Luis Potosi city to reconstruct the gravimetric mass and perform a source apportionment study using the Positive Matrix Factorization model (PMF). Concentration differences were due to different yearly seasons. In the year 2017, there was a major influence on heavy metals (V, Cr, Mn, Ni, Cu, Zn, Pb), and for the year 2018, there was a major crustal elements concentration (Na, Al, Si, P). Heavy metal concentrations are higher than any worldwide regulation limit. After applying these methods to the 49 samples collected for the year 2017, the mass reconstruction was nearly 70% of the gravimetric mass. XRF analysis quantified 17 elements (Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn) in addition to Total Carbon (Organic Carbon (OC) + Elemental Carbon (EC)). PMF receptor model was applied to identify possible contribution sources and resolved seven physically interpretable factors that contributed to the ambient particulate pollution at the sampling site: Urban Dust (24.2%), Mobile Sources (22.2%), Chemical industry (18.2%), Oil combustion (16.3%), Smelting Industry (12.4%), Fuel Oil + Ceramic Industry (4.4%), and Braking (2.3%). However, the brick kiln’s emissions may be present in at least four of the emission sources due to several types of combustible employed.

Nevertheless, there is a lot to know about air pollutants in Mexico’s largest cities, like San Luis Potosi City, which is one of the 12 most crowded cities and is expected to grow in the next years; however, there is little information about air pollutant levels mainly particulate matter in their regulated size fractions (PM₁₀ or PM_2.5), and its main component of the Organic fraction: Black Carbon (BC), which is especially important because of its chemical properties and their effects on human health, air pollution, and climate change. This work presents a one-year BC monitoring in the northern part of the city (2018–2019) and another one-year BC monitoring in the southern area (2019–2020) during the health contingency situation due to the SARX-CoV-2 virus to obtain direct equivalent black carbon (eBC) concentrations and their main fractions related to fossil fuel and biomass burning using aethalometer AE-33, as well as other air pollutants concentrations measured at the same periods by the governmental local monitoring network (SEGAM). At the North, BC mass annual average concentration was (1.11 µg m⁻³), divided into seasonal stations, the cold season was the highest with (1.44 µg m⁻³), followed by the dry season (1.23 µg m⁻³), rainy season (0.94 µg m⁻³) and finally warm dry season (0.83 µg m⁻³). In the south, BC annual average concentration was (1.96 µg m⁻³); divided into seasons, the highest was the dry season with (2.73 µg m⁻³), followed by the cold season (2.37 µg m⁻³), dry warm season (1.61 µg m⁻³) and the rainy season (1.28 µg m⁻³). One of the main findings was the dominance of annual mean concentrations of BC originating from fossil fuels (BCff) on the north site in the city was 0.97 and on the south site (BCff) was 0.91 due to some forest fires during the monitoring period. This study presented information from two zones of a growing city in Mexico to generate new air pollutant indicators to have a better understanding of pollutant interactions in the city, to decrease the emission precursor sources, and reduce the health risks in the population.

The sugarcane industry has a high environmental impact. In countries such as Mexico, cultivation and harvesting practices consume and pollute many ecological resources. However, quantifying these impacts is difficult due to their diverse nature and different units of measurement. In this study, an approach with two focuses was taken to assess the environmental costs of the sugarcane industry in San Luis Potosí, México. The first focus is human health costs related to air pollution (black carbon) and the second one is a lifecycle assessment applied to the production phase. In the first case, four scenarios, with different concentrations and populations, were projected. Costs of 516.8 thousand USD were estimated for a scenario in which black carbon concentrations exceeded the WHO reference by one unit for the total population. In the second case, costs of 642 million USD were estimated for the impairment of seven ecosystem-based services. These estimates may vary due to the source and specificity of the information provided, but nevertheless are considered an appropriate approximation of the cost of environmental damage. It is recommended that first-hand information be collected and systematized to improve the certainty of the estimates and that changes to sugarcane agrifood systems be considered to reduce environmental costs.

This work evaluates Black Carbon emissions produced in Ciudad Valles, San Luis Potosí, México, during the harvest 2020–2021 of Ingenio Plan de Ayala and its association with the sugarcane sector in its area of influence. Black Carbon concentrations were measured each hour by the 7-wavelength aethalometer (AE-33) from November 13, 2020, to June 7, 2021, at Tecnológico Nacional de México - Campus Ciudad Valles, located northeast of the city, approximately 1 kilometer from Ingenio and bordered by the sugarcane area. The maximum daily concentration recorded was 4.5 ± 0.072 µg m^− 3 with a daily average of 0.9 ± 0.014 µg m^− 3, enough to increase the mortality of the long-term exposed population by almost 6.0% moreover, according to the World Health Organization, and to cause environmental and productive effects. The burning of fossil fuels represented 62.9% of the total Black Carbon, indicating that contrary to official statistics, Ingenio Plan de Ayala may continue using fuel oil. Likewise, there was a statistically significant difference in Black Carbon concentrations during harvest and no harvest periods, indicating a direct relationship between its emissions and the sugarcane sector of this region. The highest concentrations were in the surrounding area of Ingenio Plan de Ayala and sugarcane lands, which supports the previous theory. With the results obtained, the bottom line is that evaluating other agricultural burning emissions near the growing cities is necessary to minimize adverse effects on human health and reduce CO₂eq emissions.