Aquileo Gabriel Hernández-Ramírez

This study evaluates microplastic contamination within critical agricultural infrastructure by examining the Anzaldúas and Rodhe irrigation canals in Reynosa, Mexico. To ensure geographical representativeness while managing analytical throughput, we implemented an in situ composite sampling design, pooling field triplicates across four strategic locations. We processed the resulting matrices through vacuum filtration onto microstructured silicon nitride nanomembranes, followed by hydrophobic staining with Nile Red fluorophore and automated fluorescence imaging under a TRITC optical channel. Image processing utilized a customized digital watershed segmentation macro to isolate, count, and morphologically classify individual synthetic particles. Our findings reveal a pronounced spatial heterogeneity in pollutant loading, establishing a clear decreasing contamination gradient: Rodhe Internal (RI) > Rodhe External (RE) > Anzaldúas Internal (AI) > Anzaldúas External (AE). The Rodhe Canal emerged as the primary vector for microplastic transport; the internal site (RI) exhibited the highest contamination profile (55.73 particles/mL; 2.99 µg), followed by the external site RE (19.64 particles/mL; 1.52 µg). Conversely, the Anzaldúas Canal displayed substantially lower incidence, yielding 2.61 particles/mL (0.48 µg) at the internal site (AI) and a baseline minimum of 1.31 particles/mL (0.09 µg) at the external site (AE). Morphological analysis identified fragments and fibers as the predominant particle types. Crucially, all sites exceeded laboratory blanks by 13.05 to 557.3 times, demonstrating persistent anthropogenic alteration. This work establishes the first regional quantitative baseline within this vital agricultural corridor, validating an efficient, high-throughput diagnostic tool to guide targeted water management policies in northeastern Mexico.

Fluvial sediment analysis and water quality assessment are useful to identify anthropic and natural sources of pollution in rivers. Currently, there is a lack of information about water quality in the Pixquiac basin (Veracruz state, Mexico), and this scarcity of data prevents authorities to take adequate measures to protect water resources. The basin is a crucial territory for Xalapa, the capital city of Veracruz state, as it gets 39% of its drinkable water from it. This research analyzed 10 physicochemical parameters and 12 metal concentrations in various rivers and sources during two seasons. Dissolved metals presented average concentrations (µg/L): Al (456.25) > Fe (199.4) > Mn (16.86) > Ba (13.8) > Zn (7.6) > Cu (1.03) > Pb (0.27) > As (0.12) > Ni (0.118) (Cd, Cr and Hg undetectable). Metals in sediment recorded average concentrations (ppm): Fe (38575) > Al (38425) > Mn (460) > Ba (206.2) > Zn (65.1) > Cr (29.8) > Ni (20.9) > Cu (16.4) > Pb (4.8) > As (2.1) (Cd and Hg undetectable). During the rainy season, Water Quality Index (WAWQI) classified stations P17 and P18’s water as “unsuitable for drinking” with values of 110.4 and 117.6. Enrichment factor (EF) recorded a “moderate enrichment” of Pb in sediment in P24. Pollution was mainly explained by wastewater discharges in rivers but also because of erosion and rainfall events. Statistical analysis presented strong relationships between trace and major metals which could explain a common natural origin for metals in water and sediment: rock lixiviation.

The Valsequillo reservoir is a Ramsar wetland due to its importance as a point of convergence of migratory waterfowl. It is located in Central Mexico and is currently endangered by the constant spill of municipal and industrial discharges from Puebla city. On this context, we evaluated thirteen potential toxic metals (PTMs) in water, Water hyacinth (E. crassipes) plants and sediments at this site. A combined number of 31 samples were collected from the study area. The degree/extent of metal contamination in sediments was assessed through different geochemical indexes, namely: Geoaccumulation index (I_geo), Enrichment Factor (EF) and Potential Ecological Risk Index (PERI). The ability of Water hyacinth plants residues as a phytodepurator in the Ramsar site was tested in terms of the bioaccumulation factor (BF) and the translocation factor (TF). The results concerning sediments showed that Pb, Cu and Hg pose a threat to the aquatic environment since I_geo and EF indicate sediments ranging from moderately contaminated to contaminated. Moreover, PERI pointed out Hg as the main contributor to the ecological risk in sediments, especially in the part of the reservoir covered by E. crassipes. Water hyacinth plants displayed good capacity to absorb PTMs from the water, since the content of Co, Zn, As, Ni, Cu, Pb, Ti, Cr, Ba, Mo and V in the total plant was (all values in mg/kg of dry weight) 21 ± 9, 408 ± 300, 12 ± 6, 93 ± 21, 93 ± 69, 53 ± 29, 1067 ± 643, 78 ± 55, 362 ± 39, 14 ± 0.6 and 96 ± 35, respectively. Metal content in sediments resembles to that of E. crassipes; especially in the roots, suggesting a constant deposition of plants at the bottom of the reservoir, which contributes to the eutrophication of the water. The present work encourages the need for a sustainable management of Water hyacinth plants in the Ramsar site, since they represent a plague and a natural phyto-depurator at the same time.

The present work aims to elucidate the possibility of injecting ozone into surface waters combined with urban wastewaters in order to improve the water quality of the High Atoyac Sub-basin (HAS) in Central Mexico. For this purpose, twenty physicochemical parameters, eight heavy metals, seven organic compounds, and one biological indicator were assessed in water from different sites of the studied area (the Alseseca River, the Atoyac River and the Valsequillo Reservoir). Results demonstrated that O₃ injection led to the decrease of the aromatic fraction of organic molecules since the Spectral Absorption Coefficient at 254 nanometers (SAC₂₅₄) reduction was found to be 31.7% in the Valsequillo Reservoir water samples. Maximum Chemical Oxygen Demand (COD) removal was observed to be 60.2% from the Alseseca River with a 0.26 mg O₃/mg initial COD dose. Among all the phthalates studied in the present work, Di(2-ethylhexyl) phthalate (DEHP) exhibited the highest concentration (5.8 μg/L in the Atoyac River). Treatment with O₃ was not effective in eliminating fecal coliforms (FC) in waters that host high organic matter (OM) loads as opposed to waters with low OM. After the injection of 4.7 mg O₃/mg COD in the VO₃-AT water sample, a 90% removal of Iron (Fe) and Aluminum (Al) was registered; while Manganese (Mn), Nickel (Ni), Zinc (Zn), and Cooper (Cu) showed a 73%, 67%, 81%, and 80% removal, respectively; Chromium (Cr) registered the highest removal (~100%). The present work demonstrated that while finding a suitable O₃ dose to improve the quality of water in the HAS, the 5-days Biochemical Oxygen Demand (BOD₅)/COD ratio (i.e., biodegradability) is more important than the overall OM removal percentage proving that O₃ injection is a feasible process for the treatment of eutrophic waters from HAS.