Objective: The objective of this study was to determine the water quality of the lower basin of the Usumacinta River, based on its physicochemical and microbiological characteristics. Design/methodology/approach: There were taken 11 monthly samplings of surface water during the rainy season, from June to December, 2017 and in the dry season, from April to May, 2018, in three different sites. The parameters of temperature, pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Total Suspended Solids (TSS), total phosphorus (TP) and Nitrogen nitrate (N-nitrate) were evaluated. Significant statistical differences (p≤0.05) between seasons and between sites were determined. Results: The results obtained were compared with Mexican regulations and Ecological Criteria for water quality. The parameters such as EC, TDS, TSS and total phosphorus showed substantial differences among seasons. The temperature, pH, EC and N-nitrate, did not exceed the maximum permissible limits for the use of irrigation water, urban public use and protection of aquatic life. However, the presence of E. coli and total coliforms from 530 to> 24 196 MPN/100 ml was recorded throughout the study period. Findings/conclusions: Parameters under study did not show significant differences between sites. The rainy season had an important effect on the increase in concentrations of TSS, TP, N-nitrate and total coliforms. Also, that maximum concentrations were recorded during the study period in the sampling sites of Boca del Cerro (R1) and Puente Chablé (R2).

Coastal lagoons have undergone changes due to anthropogenic activities, the presence of wastewater discharges, and unsustainable practices that alter water quality, favoring the presence of pathogenic microorganisms such as Vibrio. This study identified the presence of the genes for zinc metalloproteinase (HA) Vibrio sp. and choleric toxin (ctx) Vibrio cholerae, associated with the sources of contamination in the Mandinga Coastal Lagoon (MCL). During 2017, samplings were carried out in which sources of contamination associated with anthropogenic activities were identified. At the same time, water samples were collected from which DNA was extracted and the presence/absence of the HA and ctx genes was detected with a PCR analysis. The HA gene was identified in the three seasons of the year, while the ctx gene was only present in the dry and rainy seasons. The prevalence of both genes in the study area was independent of the presence of the pollution sources identified in the area. The absence of the ctx gene during the northern season is associated with the variability of the physicochemical parameters typical of the season.

Microplastics (MP) are emerging pollutants found in the Veracruz Reef System National Park (PNSAV). They are widely distributed in the aquatic environment and are ingested by organisms either accidentally or because they are mistaken for food. In this article, the author analyses the physicochemical characteristics of reef sediments using visual identification, Nile Red (NR), scanning electron microscopy (SEM), and Energy Dispersive Spectroscopy (EDS) of microplastics found in sediments adjacent to reefs; this allowed us to determine their distribution within the PNSAV. A total of 687 microplastics per kilogram of dry sediment were quantified, including fibres (98.5%), films (1.4%), and fragments (0.01%). The predominant colour was transparent (60.2%), followed by blue (16%) and red (12%). Based on their MP distribution, the sites were classified into two groups: north and south. The sampling stations with the highest concentrations of MP are located in the group of reefs south of the PNSAV, with the Anegadilla Reef being the most affected station. SEM/EDS analyses revealed elemental spectra dominated by carbon and oxygen, which is consistent with the expected elemental composition of polymeric materials. Peaks of chlorine were detected in some MP particles, suggesting the possible presence of chlorinated polymers, such as polyvinyl chloride (PVC). In addition, elements such as titanium, silicon, and nickel were identified, which could be associated with inorganic particles adhering to the surface or with additives commonly incorporated during the manufacture of plastics such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and polyethylene terephthalate (PET). The presence of elements such as titanium and nickel were detected; these are found in additives used in the manufacturing of polymers.

Agro-industrial residues, derived from cereals, fruits, and vegetables, comprise non-consumable byproducts, including stems, leaves, peels, and seeds. Globally, approximately 3,045 million tons of such material is generated annually. In Mexico, the industrial crops coffee (Coffea spp.) and sugarcane (Saccharum spp.) yield residues rich in structural components, including lignin, cellulose, and hemicellulose. This study determined the physicochemical characteristics of cellulose isolated from these residues to formulate biodegradable polymers. Cellulose isolation was performed through chemical bleaching treatments, alkaline hydrolysis, and acid hydrolysis, yielding high-purity α-cellulose at 88.8% for coffee husks and 83.3% for sugarcane bagasse, with yields of 32.8% and 29.4%, respectively. Two biopolymers were developed: (A) 100% coffee husk cellulose and (B) a composite of 75% sugarcane bagasse fiber and 25% coffee husk cellulose. Biopolymer A demonstrated superior physicochemical properties, including moisture content, water vapor permeability, and solubility. Biodegradability assessments confirmed that both biopolymers were compostable within 110 days, exhibiting degradation extents of 84.4% (A) and 77.5% (B), primarily converting into organic matter and CO₂. These findings indicate that coffee and sugarcane agro-industrial residues are viable feedstocks for sustainable biopolymer production.