Cada año se vierten millones de metros cúbicos de aguas residuales a los cuerpos de agua, las cuales son tratadas de forma inadecuada, siendo estos procedimientos ineficientes para alcanzar lo requerido por la ley o para uso dentro de los procesos industriales. En estos casos, y debido a la escasez del hídrico, se está recurriendo al uso de los procesos de oxidación avanzada como tratamiento alternativo. Estos procesos se basan en procesos fisicoquímicos capaces de producir cambios profundos en la estructura química de los contaminantes, involucrando la generación y uso de especies transitorias de gran poder oxidante, principalmente el radical hidroxilo, el cual puede ser generado por medios fotoquímicos o por otras formas de energía y posee alta efectividad para la oxidación de materia orgánica. Esta revisión tiene como objetivo realizar un análisis de la influencia de los tratamientos en el proceso de descontaminación.

El Paraquat es un herbicida utilizado en la actividad agropecuaria para controlar hierbas, su modo de acción es por medio de contacto y no selectivo. Debido a su alta solubilidad en agua y baja volatilidad representa un riesgo potencial para organismos acuáticos, principalmente los que son cultivados con aguas superficiales que reciben impacto de la actividad agrícola. La tilapia Oreochromis niloticusy el langostino Macrobrachium olfersiison organismos de importancia comercial para la industria acuícola del estado de Veracruz, México.El objetivo de este estudio fue determinar la Concentración Letal Media (CL50) del herbicida Dasurquat® (ingrediente activo Paraquat) a través de un bioensayo de toxicidad aguda (96 horas). Se utilizaron como especímenes de prueba a juveniles de tilapia O. niloticus(peso promedio = 10 mg, longitud total= 8,75 mm) y otro el ensayo fue con poslarvas de langostino M. olfersii(peso promedio = 5 mg, longitud total= 5,72 mm). Se emplearon cinco concentraciones (5, 10, 20, 40 y 80 µl L-1para el bioensayo con juveniles de tilapia; para el bioensayo con poslarvas de langostino las concentraciones fueron 0,1, 0,2, 0,5, 0,7 y 1 µl L-1). El diseño experimental consideró un control negativo, con dos repeticiones y dos réplicas por cada tratamiento. El análisis de datos se realizó con el método Probit para determinar la CL50a 96 horas, se obtuvo un valor para juveniles de O. niloticusde 17,49 µl L-1con intervalo de confianza (95 %) con límite inferior de 13,75 µl L-1y límite superior 22,25 µl L-1, para las larvas de M. olfersiise obtuvo un valor de 0,31 µl L-1con intervalo de confianza (95 %) con límite inferior de 0,26 µl L-1y límite superior 0,35 µl L-1. El análisis de varianza demostró que no existió diferencia estadística significativa (p > 0.05) entre las réplicas de los tratamientos. Se concluye que es necesario continuar con estudios para evaluar su toxicidad en organismos acuáticos debido al amplio uso de este herbicida en la actividad agropecuaria, y determinar su riesgo para otras actividades productivas además de la acuicola.

Farming aquatic plants can be used as an alternative in the treatment of effluents from aquaculture production units and in turn, in the production of biomass plant for feeding terrestrial and aquatic organisms. This research aims to evaluate the efficiency of duckweeds Spirodela sp. and Lemna sp. in the treatment of tilapia effluents (Oreochromis niloticus). The experiment was performed in triplicate and was conducted under natural environmental conditions within the facilities of the Laboratory of Applied Aquaculture Research (LAAR) of the Technological Institute of Boca del Río (ITBOCA). Each treatment contained 230 liters of effluent in each tube, with a water column of 40 cm and a seeding density of 400 g/m2 of vegetative biomass. The evaluation of the efficiency of Spirodela sp. and Lemna sp., in the removal of dissolved nutrients, was performed in 7 monitoring times; 12, 24, 36, 48, 72, 96 and 120 h. The results showed an efficiency in nutrient removal at 120 h of 75, 74 and 66% of N-NH3; 96, 92 and 75% N-NO2; 93, 88 and 75% N-NO3; 75, 72 and 64% N-NTK; 73, 60 and 58% of N-org., and 73, 63 and 68% of P. On the other hand, the removal of TSS and BOD5, during the first 24 h, was 83, 54, 58% and 65, 59, 33%, in the treatments. The efficiency in nutrient removal of both duckweeds, showed that both plants can be used in the treatment of effluents, being a sustainable and economical alternative for the aquaculture industry.

Nitrate nitrogen (N-NO3-), the most common pollutant in groundwater, is a result of the effect of diffuse sources of pollution like agriculture and animal husbandry intensive. The land use for these economic activities is very common in the Los Ríos sub-region in the state of Tabasco, Mexico, where the Los Ríos and Boca del Cerro aquifers are located. The aim of this research was to assess the concentrations of nitrate-nitrogen (N-NO3-) in groundwater, determine the quality in agreement with the maximum permissible limits established by national and international regulations, and the risks to the public health and aquatic life. The spatial distribution of N-NO3- was determined using the inverse distance weighted (IDW) interpolation technique. The average nitrate-nitrogen concentration was 0.76 mg.L-1, while the maximum concentration observed was 3.98 mg.L1. This does not exceed the maximum permissible limit (MPL) established in the national and international normativity for drinking water. However, in 50% of the sampling sites, the concentrations of N-NO3- exceed the MPL established in Mexico for the protection of the life of seawater. Relatively low concentrations of N-NO3- have shown to be toxic to certain aquatic organisms, and the aquifers studied discharge a third of the water to the rivers in the area, which flow into the Laguna de Términos Campeche and the Gulf of Mexico. Laguna de Términos Campeche is one of the most diverse and rich environmental systems on earth, where numerous ecosystems converge such as coastal lagoons, wetlands, mangroves, seagrasses, and coral reefs.

The composition of fish assemblages in the Alvarado Lagoon System was updated with information collected between 1966 and 2008, divided into nine collection periods. A temporal analysis of the variation in species richness, species richness indices, rarity, and composition of ecological and trophic guilds was also carried out. A total of 113 species were recognized, 66 of which were present in most of the collection periods, forming a group with a constant presence in the lagoon system, in which marine and freshwater species predominated. This group showed the highest levels of similarity between collection periods; this was confirmed by the richness and rarity indices. Functionally, the composition of the ecological and trophic guilds did not show significant differences. The composition of the trophic guilds showed a prevalence of invertebrate consumers, macrocrustaceans, and small fish, supporting the fact that migratory marine species were the most numerous, with minor contributions from the other guilds. The contribution of marine or freshwater visitor species was not important in the characteristics of the assemblages. These results suggest that the environmental conditions of the Alvarado Lagoon System have remained without severe changes during the study period, thus allowing both the constancy of the fish community and that of the ecological and trophic guilds.