No abstract

Levels of barium, cadmium, chromium, copper, mercury and vanadium were determined by plasma emission spectroscopy in sediments and oysters (Crassostrea virginica) in the Palizada, Chumpán and Candelaria rivers, which flow into the Términos Lagoon, state of Campeche, Mexico. The relation between the condition index of the oyster and the detected elements were determined as well. Significant relations were observed between copper (r = -0.825, p \ 0.05) and chromium (r = -0.787, p \ 0.05), which indicates the oysters' affectation by ingesting both elements; concurrently, the results confirm that oysters present high tolerance to heavy metals. The average concentration of cadmium (2.05 lg/g), chromium (1.82 lg/g) and copper (115.55 lg/g) in rainy-season climate exceeded the limits for marine mollusks regarding different health standards. It was found that the rainy season, the sediment characteristics and organic matter content have a great influence on the transport and availability of heavy metals.

Some heavy metals and trace metals reach aquatic ecosystems from natural and anthropogenic sources, and are considered some of the most important environmental contaminants due to their toxicity, persistence and tendency to accumulate in aquatic organisms. Thus, their study is needed due to the environmental risk they pose. Concentrations of Cu, Cd, Mg, Fe and Mn in recent sediments of the deltaic lagoon-river system of the Palizada river, Campeche, Mexico were determined for three climatic seasons on the 2010 annual cycle. The results confirmed that the climatic season has great influence over the results variability. The highest levels of Cu, Fe and Mn were found during dry season, which may suggest significant evaporation phenomena in the area. Both Fe and Mn are abundant elements in the Earth crust; their concentrations could be related to the study area's characteristics, given the conjunction of two sedimentary provinces: terrigenous in the western portion and carbonated in the eastern. On the other hand, the results suggest a high relationship of Fe-Mn (r = 0.5131), Fe-clay (r = 0.5978), Cu-Mn (r = 0.8707), Cu-clay (0.8501) and Mn-clay (0.9311). The latter confirms the high dependence of these elements and the great affinity of some metallic elements for finer sediments. In conjunction, the climatic season and the sediment's characteristics are essential for metal mobilization and transport. Likewise, the Cd and Cu levels reported are lower than international parameter, indicating value ranges that could cause effects in exposed organisms.

Atmospheric levels of benzene, toluene, ethylbenzene, and xylenes (BTEX) were measured in an urban site located in Nuevo Leon, Mexico, during summer and autumn 2013. A total of 60 samples were collected using carbon-packed cartridges at 0900, 1200, and 1500 h and then analyzed using gas chromatography with flame ionization detector. Meterological parameters and criteria air pollutants were measured and correlated with BTEX by a principal component analysis (PCA). The relative abundance of BTEX followed the order: benzene > toluene > ethylbenzene > p-xylene with mean concentrations of 55.24 μg m−3, 22.24 μg m−3, 6.94 μg m−3, and 4.17 μg m−3, respectively, during summer. Mean concentrations during autumn were 21.079 μg m−3 for benzene, 3.648 μg m−3 for toluene, 2.521 μg m−3 for ethylbenzene, and 2.115 μg m−3 for p-xylene. All measured BTEX showed clear diurnal and seasonal patterns. The highest mean levels for benzene were obtained during the midday. Toluene, ethylbenzene, and p-xylene showed the highest levels during afternoon period. BTEX levels were higher when wind blew from NE and ESE during summer and from ESE during autumn. The municipalities of Apodaca and Guadalupe are located in these directions where important industries, high traffic volume, many oil and gas service stations, and the biggest airport in this region are found. These sources could contribute to the BTEX concentrations measured during the sampling period

Amazon sailfin catfish (Pterygoplichthys pardalis) is considered one of the greatest threats to the biodiversity of continental aquatic systems, causing serious economic and environmental problems in the regions. In this work, the production of biodiesel from Amazon sailfin catfish biomass oil is studied. The physical and chemical properties of biofuel produced were evaluated under the specifications of the European standard EN-14214 by using gas chromatography-mass spectrometry, infrared spectroscopy, and atomic absorption spectrometry analyses. The results show that the biodiesel complies with all the specifications of the standard, except the content of polyunsaturated methyl esters. The yields obtained from oil and biodiesel were 9.67 and 90.71% (m/m), respectively. The methyl ester concentrations study identified 17 components where 47.003% m/m corresponded to methyl esters with saturated chains, whereas 34.394% m/m was attributed to monosaturated methyl esters and the remaining (18.624% m/m) to polysaturated methyl esters. Finally, mineral analysis by atomic absorption showed the absence of heavy metals Cd, Ni, and Pb, as well as low concentrations of Ni, Fe, Cu, and Zn, demonstrating that the quality of the fuel is not compromised. The study indicates the feasibility of manufacturing biodiesel using Amazon sailfin catfish biomass oil as a low-cost raw material. It represents an environmental option to mitigate a global problem of atmospheric pollution, and at the same time, it shows a commercial alternative to reduce the ecological impact caused by this fish in the diverse ecosystems to which it has spread. In addition, the great adaptability of this fish provides the possibility of a profitable process to have very high rates of reproduction and growth, allowing the generation of large amounts of biomass for the production of biodiesel.