Despite their ability to mitigate climate change by efficiently absorbing atmospheric carbon dioxide (CO₂) and acting as natural long-term carbon sinks, mangrove ecosystems have faced several anthropogenic threats over the past century, resulting in a decline in the global mangrove cover. By using standardized methods and the most recent Bayesian tracer mixing models MixSIAR, this study aimed to quantify source contributions, burial rates, and stocks of organic carbon (C_org) and explore their temporal changes (∼100 years) in seven lead-210 dated sediment cores collected from three contrasting Mexican mangrove areas. The spatial variation in C_org burial rates and stocks in these blue carbon ecosystems primarily depended on the influence of local rivers, which controlled C_org sources and fluxes within the mangrove areas. The C_org burial rates in the cores ranged from 66 ± 16 to 400 ± 40 g m^-2 yr^-1. The C_org stocks ranged from 84.9 ± 0.7 to 255 ± 2 Mg ha^-1 at 50 cm depth and from 137 ± 2 to 241 ± 4 Mg ha^-1 at 1 m depth. The highest C_org burial rates and stocks were observed in cores from the carbonate platform of Yucatan and in cores with reduced river influence and high mangrove detritus inputs, in contrast to patterns identified from global databases. Over the past century, the rising trends in C_org burial rates and stocks in the study sites were primarily driven by enhanced inputs of fluvial-derived C_org and, in some cores, mangrove-derived C_org. Despite their decreasing extension, mangrove areas remained highly effective producers and sinks of C_org. Ongoing efforts to enhance the global database should continue, including mangrove area characteristics and reliable timescales to facilitate cross-comparison among studies.

Sediment cores maintain a historical record of the various sources of polycyclic aromatic hydrocarbons (PAHs). In 2020, one sediment core was collected within the oyster farming area of the Pom–Atasta lagoon system and the Terminos lagoon. A total of 16 PAH compounds were analyzed to identify the historical patterns of PAH inputs and the relationship with sediment materials. The core was classified into three strata at depths of 0.0–0.2 m, 0.2–0.6 m, and 0.6–1.1 m, in which the high content of silt–sand, organic matter, and carbonates indicates a system of high energy and productivity. The hydrology and characteristics of the sediment suggest a free access of adsorbed PAHs to the study area, mainly of pyrolytic origin. The concentration of ∑PAHs decreases from the surface (527.0 ng g⁻¹ dw) to a greater depth (75.7 ng g⁻¹ dw), which corresponds to 60% of the HMW (high molecular weight) of the total PAHs as combustion products at low temperatures, while LWM-PAH (low molecular weight) inputs are from discharges of petroleum products. The core sediments showed a low probability of toxicity quotient of 9%. The analysis of the carcinogenic toxic equivalent (TEQ^carc) in each section of the core was variable, decreasing with the depth from 107.91 ng TEQ g⁻¹ dw to 57.65 ng TEQ g⁻¹ dw, with the compounds benzo(a)pyrene (53.55 ng TEQ g⁻¹ dw) and dibenzo(a,h) anthracene (29.2 ng TEQ^carc g⁻¹ dw) having the highest TEQ^carc. The anthropogenic activities around the study area may increase the carcinogenic and mutagenic risk to human health. However, in the present study, the low toxic carcinogenic equivalents (TEQ_BaP) and mutagenic equivalents (MEQ_BaP) indicate a low probability of sediment toxicity. The ecosystem could be under constant threat from increasing anthropogenic activity; therefore, monitoring programs for the conservation of these ecosystems and oyster farms should be considered.

Sedimentary processes, ecological risks, and historical trends of mercury (Hg) contamination were assessed through ²¹⁰Pb-dated sediment cores and sediment traps (period 2017-2019) in Términos Lagoon (TL), a critical coastal ecosystem in the southern Gulf of Mexico. Hg natural background levels in TL cores widely varied (7-153 ng g^-1), and Hg concentrations were higher in the cores (median 32 ng g^-1, range 6-4240 ng g^-1) than in the sediment traps (median 54 ng g^-1, range 44-1311 ng g^-1). In most cores, enrichment factors ranged from null to moderate, except for very severe levels found in core LT01, indicating the presence of an Hg hotspot. Enrichments (minor to severe) were confined to river discharge areas in the sediment traps. Low to very high ecological risks were observed across the sampling areas. The factor analyses, for the core and trap samples, indicated fine-grained terrigenous sediments and high organic matter content as major drivers of Hg accumulation, with river discharges playing a central role. The sediment records displayed increasing Hg fluxes after the 1970s, coinciding with the local urban-industrial boom, while peak values in recent decades corresponded with population growth around the lagoon. Sediment trap data suggested that Hg fluxes are somewhat independent of rainfall, as peak values were observed during dry and winter storm seasons. These findings highlight the interplay of natural and anthropogenic factors promoting Hg accumulation in TL, offering insights to mitigate the effects of global change in one of Mesoamerica's most important coastal ecosystems.

Los indicadores de sustentabilidad permiten evaluar los impactos ambientales relacionados con la estrategia del desarrollo sustentable. En este estudio realizado en Ciudad del Carmen, Campeche considerada una isla de barrera que se localiza al sureste de México. El municipio canaliza la disposición final de los residuos sólidos urbanos (RSU) a través de un relleno sanitario el cual se encuentra ubicado en una zona de manglar, teniendo un impacto negativo en el medio ambiente lo que incide negativamente en el desarrollo sustentable. Mediante el análisis sedimentológico del subsuelo, se obtuvieron resultados que identificaron la dominancia de arenas carbonatadas, lo que permitió definir un rango de porosidad del 20,2 al 40,1%, y permeabilidad de ±10-2-10-4 m/s darcys, es decir, los sedimentos presentan una buena porosidad y una permeabilidad alta. Por su parte, mediante un análisis de la calidad del agua, se detectaron concentraciones de Demanda Bioquímica de Oxígeno (DBO5) y Demanda Química de Oxígeno (DQO) de 63,06 y 1,338.13 mg/L, respectivamente, así como la presencia de concentraciones traza de algunos metales pesados. Estos valores permitieron clasificarlo como un cuerpo de agua fuertemente contaminado.

The study evaluates the performance of a proposed mold [utility model MX 4516] for the artisanal production of concrete bricks with nominal dimensions of 24 × 10.1 × 6.2 cm. Dimensional measurements exhibit variations lower than 3%, complying with standard NMX-C-404. Using a cement-to-sand ratio of 1:5 and a water–cement ratio of 0.6, the bricks achieve average compressive strengths close to 109 kg/cm², exceeding the structural requirements of NMX-C-441. It is demonstrated that 5 × 5 × 5 cm cubic specimens adequately represent the material behavior of the full unit for compressive strength testing, facilitating quality control and process standardization in artisanal or laboratory-scale production.