Air pollution exceedances are important air quality events for its associated effects on public health. Chemical transport models are frequently used for estimating pollution concentrations, especially in areas with limited monitoring capacity. Even though their performance may be improved by combining observations from different platforms through data assimilation, in Mexico these applications are limited, especially those aiming to assimilate chemical composition observations. In this study, surface observations of O3, CO and NO2 from the local monitoring network (RAMA) together with conventional global meteorological observations, were assimilated over the Mexico City Metropolitan Area (MCMA) using the WRFDA-Chem v4.5.2 assimilation system and the 3DVAR algorithm. The global observations were obtained in PREPBUFR format and consisted of upper-air and surface weather reports collected worldwide. The observations included pressure, temperature, dew point, wind speed and direction, from several platforms including surface, radiosondes, and aircraft reports. Two sets of experiments focusing on the impact of the chemical initial and boundary conditions were conducted. One experiment used default chemical initial and boundary conditions provided. In the experiment denoted by “default”, the WRF-Chem model was initialized through predetermined NALROM (NOAA Aeronomy Lab Regional Oxidant Model) ideal profiles that are included in the model. These profiles represent a northern-hemispheric, mid-latitude, relatively clean atmospheric composition and provide values for species such as O3, CO, NOx. (WRF-Chem user guide). The other experiment, denoted by “global”, the NALROM ideal profile was replaced with external chemical fields obtained from the global chemical transport model WACCM (Whole Atmosphere Community Climate Model). These fields provide spatially and temporally varying initial and boundary conditions that reflect realistic large-scale chemical distributions rather than a static climatology. Results showed that chemical data assimilation corrected pollutants concentrations. Regarding CO and NO2, differences between model results and observations were rather small, suggesting the need of tuning the background error covariance matrix parameters for these pollutants. However, for ozone, using global model outputs to initialize the model, tended to better represent regional maximum concentration, whilst using default conditions tended to better represent regional average concentration. However, both setups estimated similar daily ozone peaks. This suggests that using default chemical conditions cycled over a long period may optimize storage and computing resources.
En este estudio se llevó a cabo la investigación hidrogeofísica del acuífero de San Agustín Texcaltitlán, municipio de Tenancingo Estado de México, para determinar los parámetros intrínsecos como la porosidad (n) y la conductividad hidráulica vertical (Kv) por análisis granulométrico; se midió la variación del nivel del agua en norias y se determinó el espesor (h) de los estratos de la zona no saturada y saturada empleando el método del Sondeo Eléctrico Vertical (SEV) y el arreglo Schlumberger de resistividad eléctrica (ρ). El objetivo consistió en determinar y zonificar la vulnerabilidad intrínseca a la contaminación del agua subterránea por fuentes antropogénicas con el método AVI, que define la resistencia hidráulica (C) y la capacidad protectora del acuífero con el método ICE, a partir de la conductancia longitudinal unitaria (S), con el método geoeléctrico del SEV. Ambos métodos solo requieren de dos parámetros, la Kv y el espesor h de las capas que constituyen la zona no saturada (ZNS), respectivamente. Los datos de 20 SEV adquiridos se interpretaron con el programa de computadora iterativo Interpex IX1D. Los resultados obtenidos indican que la porosidad de la ZNS es de 0.36-0.40 y la conductividad hidráulica vertical de 6-15 m/d, obtenida con la fórmula empírica de Slitcher. De 20 SEV realizados, se detectaron de 5 a 7 capas para el sistema acuífero con valores de la resistividad de 10-3,600 ohm-m y espesores variables, que se utilizaron para calcular las variaciones de la resistencia hidráulica (C), dando valores de 0.4-6.0 (días) indicando baja a alta vulnerabilidad, la conductancia longitudinal (S) y la resistencia transversal (R), conocidos como parámetros de Dar Zarrouk, arrojaron valores de 0.2-6.0 (Ω-1), indicando baja a alta capacidad de protección, y de 1,000-26,000 (ohm-m2), indicando zonas de baja a alta capacidad de infiltración, respectivamente. Finalmente, se elaboró el modelo conceptual de funcionamiento hidrogeológico del sistema acuífero de Texcaltitlán.
The aim of this paper is to evaluate the vulnerability of groundwater to contamination by adapting aquifer vulnerability index (AVI) approach, based mainly on the hydraulic conductivity (K) of the aquifer and overburden layers' thickness (h). The technique of vertical electrical sounding (VES) with the configuration of Schlumberger was applied to model the Quaternary aquifer and its overburden layers in the Khanasseer Valley area in Northern Syria. According to AVI classification, 5.88% of the study area is hugely polluted, 67.00% highly polluted, 23.53% moderately polluted, and 2.94% lowly polluted. Several hydro-geoelectrical parameters which affect the Aquifer Vulnerability Index (AVI) (such as anisotropy (lambda) of the subsurface hydrogeological layers, thickness (hOverb), resistivity (rho Overb), hydraulic conductivity (K), and hydraulic resistance (C) of the protecting layers) are statistically analyzed. Different mutual empirical relationships between the above parameters are established through analyzing their statistical correlation matrix. The derived empirical relationships highlight the mutual hydrological processes and the lithological connectivity nature between the study Quaternary aquifer and its overlaying layers. The obtained results highlighted the importance of safeguarding groundwater resources, and outlined resource allocation to protect the aquifer zones, for decision-makers. This was the first time that AVI approach is applied in Syria, and can be consequently extended to other Syrian aquifers. AVI can be also applied worldwide to estimate the conditions dominating the aquifer's protectivity in semi-arid regions.
In order to investigate the particle size distribution pattern of atmospheric suspended particles in Tehran, simultaneous sampling was conducted at six stations located in the western (ST1 to ST3) and eastern (ST4 to ST6) halves of the city. Mass concentrations were measured across nine size fractions ranging from particles larger than 11 µm to those smaller than 0.4 µm. The results indicated that at the western stations, the highest mass concentrations were mainly observed in the coarser particle fractions (11-7 µm and ≥11 µm), with maximum values of 19.6 and 16.3 µg.m-3 recorded at ST2 and ST1, respectively. This pattern suggests the dominance of mechanical sources and road dust resuspension in the western part of the city. In contrast, the eastern half of Tehran exhibited an increasing trend in concentration within the finer fractions (less than 2.1 µm), with the highest value measured at ST6 in the <0.4 µm fraction (18.7 µg.m-3). Additionally, in the 0.7-0.4 µm and 2.1-1.1 µm ranges, eastern stations showed higher concentrations compared to the western stations. This shift in size distribution pattern-from coarse-particle dominance in the west to fine-particle dominance in the east-may be attributed to differences in land use, traffic density, combustion-related sources, as well as topographic conditions and prevailing wind patterns across Tehran. Overall, the findings indicate a greater contribution of combustion-related and secondary fine particles in the eastern half, whereas the western half appears to be more influenced by primary sources and coarse particle resuspension. These results highlight the importance of region-specific management strategies for effective control of particulate matter pollution in the megacity of Tehran.
The subsidence of the East Coast of Lake Maracaibo-COLM in Zulia state in Venezuela is a geological event of anthropic cause with almost a century of existence. We wanted to know the current state of this event with the use of the Interferometric Synthetic Aperture Radar-InSAR technique, for this, we emphasized the need to mitigate atmospheric delays in the data, for which the ERA5 climate model with PyAPS was applied. In order to obtain accurate subsidence measurements in three oil fields located in the COLM (Tia Juana, Lagunillas and Bachaquero), whose cumulative subsidence process is approximately 5 meters between 1926 and 1986. For this study, subsidence values were estimated, for the period from 2018 to 2020, using a dataset of 157 interferometric Sentinel-1 images (79 from ascending orbits and 78 from descending orbits), which allowed the calculation of the values of displacements along the line of sight-LOS for both orbits, the tropospheric delay contribution, and the east-west and vertical components values, extracted from representative pixels with high coherence and with spatial and temporal average, having random noise component reduced, obtaining displacement values for Tia Juana, Lagunillas and Bachaquero fields respectively of: -6.4 +/- 0.8 cm/y; -7.9 +/- 1.0 cm/y and; -7.1 +/- 0.8 cm/y, for ascending mode. From 1.2 +/- 0.5 cm/y; -4.1 +/- 0.5 cm/y and; -1.8 +/- 0.3 cm/y, for descending mode. Also, by selecting representative pixels, we estimated reliable values for contribution from tropospheric delay, obtaining: -0.2 cm/y and -0.6 cm/y; -0.3 cm/y and -0.5 cm/y and; -0.4 cm/y and -0.5 cm/y. And the east-west (dE) and vertical (dU) components for the three fields, with: -6.79 cm/y and -2.94 cm/y; -3.27 cm/y and -5.19 cm/y and; -5.92 cm/y and -6.29 cm/y respectively, minimizing the risk that geometric projection errors will amplify underlying noise.
