This research describes the application of portable field Raman spectroscopy combined with a statistical analysis of the resulting spectra, employing principal component analysis (PCA) and linear discriminant analysis (LDA), in which we determine that this method provides a high degree of reliability in the early detection of Huanglongbing (HLB) on Sweet Orange, disease caused by the bacteria Candidatus Liberibacter asiaticus. Symptomatic and asymptomatic plant samples of Sweet Orange ( Citrus sinensis), Persian Lime ( C. latifolia), and Mexican Lime ( C. aurantifolia) trees were collected from several municipalities, three at Colima State and three at Jalisco State (HLB presence). In addition, Sweet Orange samples were taken from two other Mexican municipalities, one at San Luis Potosí and the other at Veracruz (HLB absent). All samples were analyzed by real-time PCR to determine its phytosanitary condition, and its spectral signatures were obtained with an ID-Raman mini. Spectral anomalies in orange trees HLB-positive, were identified in bands related to carbohydrates (905 cm ⁻¹ , 1043 cm ⁻¹ , 1127 cm ⁻¹ , 1208 cm ⁻¹ , 1370 cm ⁻¹ , 1272 cm ⁻¹ , 1340 cm ⁻¹ , and 1260–1280 cm ⁻¹ ), amino acids, proteins (815 cm ⁻¹ , 830 cm ⁻¹ , 852 cm ⁻¹ , 918 cm ⁻¹ , 926 cm ⁻¹ , 970 cm ⁻¹ , 1002 cm ⁻¹ , 1053 cm ⁻¹ , and 1446 cm ⁻¹ ), and lipids (1734 cm ⁻¹ , 1736 cm ⁻¹ , 1738 cm ⁻¹ , 1745 cm ⁻¹ , and 1746 cm ⁻¹ ). Moreover, PCA–LDA showed a sensitivity of 86.9 % (percentage of positives, which are correctly identified), a specificity of 91.4 % (percentage of negatives, which are correctly identified), and a precision of 89.2 % (the proportion of all tests that are correct) in discriminating between orange plants HLB-positive and healthy plants. The Raman spectroscopy technique permitted rapid diagnoses, was low-cost, simple, and practical to administer, and produced immediate results. These are essential features for phytosanitary epidemiological surveillance activities that may conduct a targeted selection of highly suspicious trees to undergo molecular DNA analysis.

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.

En el presente artículo se analizan y se presentan las circunstancias físicas, sociales y económicas que en conjunto afectan al panorama y a la problemática actual del abastecimiento de agua potable de la zona metropolitana de la ciudad de San Luis Potosí. Entre los temas que se abordan se encuentra la relación entre la disponibilidad del agua y el incremento de la población, así como la evolución de la extracción de aguas subterráneas. Por otra parte, la investigación muestra un diagnóstico de la situación en que se encuentra actualmente el abasto de agua potable en la ciudad de San Luis Potosí y en las áreas aledañas; también plantea el probable escenario del futuro inmediato.