Fluorescence characteristics in the deep waters of South Gulf of México.

Vertical profiles of deep-water fluorescence determined by the chlorophyll sensor, polycyclic aromatic hydrocarbons, biomarkers, and other miscellaneous parameters measured in the southern Gulf of Mexico are reported. In the course of the survey, unexpected deep fluorescences were recorded (>1100m depth) in half of the 40 stations studied, a novel finding in this area of the Gulf. Currently, the deep-water fluorescence phenomenon is not completely understood, however we observe linear correlation between the fluorescence intensity and chlorophyll-α concentrations and coincidence of higher number of hydrocarbonoclastic bacteria in samples collected precisely in the deep-water fluorescence. This information is particularly interesting in relation to the Deepwater Horizon oil spill in 2010, in view that the aftermaths of the spill can be observed till today as oil plumes trapped in deep water layers that may disturb the natural water ecosystem.

Long-term effects of discharges of produced water the marine environment from petroleum-related activities at Sonda de Campeche, Gulf of México.

Produced water from offshore oil platforms is a major source of oil and related chemicals into the sea. The large volume and high salinity of produced water could pose severe environmental impacts upon inadequate disposal. This study is based on direct field sampling of effluents released into the ocean in the years 2003 and 2013 at the Sonda de Campeche located in the southern part of the Gulf of Mexico. Metals and hydrocarbons were characterized in water, sediments, and fish tissues at the discharge site and compared with those obtained at two reference sites. Chemicals that exceeded risk-based concentrations in the discharge included the metals As, Pb, Cd, and Cr, and a variety of compounds polycyclic aromatic hydrocarbon (PAHs), including naphthalene, fluorenes, and low molecular weight PAHs. The values of low to high molecular weight polycyclic aromatic hydrocarbon (PAHs), and carbon preference index indicate that hydrocarbons in sediments of the discharge zone are originated from the produced water and combustion sources. Fish tissues at the discharge zone and reference site are contaminated with PAHs, dominated by 2- and 3-rings; 4-ring accounted for less than 1% of total PAHs (TPAHs) in 2003, but increased to 7% in 2013. Results suggest that, from 2003 to 2013, discharges of produced water have had a non-negligible impact on ecosystems at a regional level, so the possibility of subtle, cumulative effects from operational discharges should not be ignored.

Application of the positive matrix factorization approach to identify heavy metal sources in sediments. A case study on the Mexican Pacific Coast.

During the last two decades, sediments collected in different sources of water bodies of the Tehuantepec Basin, located in the southeast of the Mexican Pacific Coast, showed that concentrations of heavy metals may pose a risk to the environment and human health. The extractable organic matter, geoaccumulation index, and enrichment factors were quantified for arsenic, cadmium, copper, chromium, nickel, lead, vanadium, zinc, and the fine-grained sediment fraction. The non-parametric SiZer method was applied to assess the statistical significance of the reconstructed metal variation along time. This inference method appears to be particularly natural and well suited to temperature and other environmental reconstructions. In this approach, a collection of smooth of the reconstructed metal concentrations is considered simultaneously, and inferences about the significance of the metal trends can be made with respect to time. Hence, the database represents a consolidated set of available and validated water and sediment data of an urban industrialized area, which is very useful as case study site. The positive matrix factorization approach was used in identification and source apportionment of the anthropogenic heavy metals in the sediments. Regionally, metals and organic matter are depleted relative to crustal abundance in a range of 45-55 %, while there is an inorganic enrichment from lithogenous/anthropogenic sources of around 40 %. Only extractable organic matter, Pb, As, and Cd can be related with non-crustal sources, suggesting that additional input cannot be explained by local runoff or erosion processes.

Weighing the evidence of ecological risk from PAHs contamination in the estuarine environment of Salina Cruz Bay, México.

Results of bulk-phase chemical measurements, toxicological tests combined with bioaccumulation measures in fishes, were used to evaluate the toxicity of the 16 USEPA priority polycyclic aromatic hydrocarbons from the sediment collected from eight stations of the Ventosa Estuarine System, located close to the main center of processing oil in the Mexican Pacific coast. Levels of the sum of polycyclic aromatic hydrocarbons varied from 22 to 6,850 microg kg(-1) dry weight. Based on sediment quality guidelines, the compounds with high environmental priority were acenaphtylene, acenaphtene, and phenanthrene. Acute toxicity tests with Vibrio fischeri and Daphnia magna as well as chronic toxicity with Panagrellus redivivus were performed. The quantification of hepatic ethoxyresorufin O-deethylase activity was used to assess the induction of the mixed function oxygenase system of brown trout. However, because it is often difficult to blend the results from such very different assays into a unified decision about the potential for impacts, a weight-of-evidence (WOE) approach to sediment quality investigations was followed. These assays provided measurement endpoints that could be used to develop an overall evaluation of the potential for environmental impacts from the oil processing operations. WOE provides a valuable tool for assessing the results of environmental investigations because it provides a framework for considering the strengths and weaknesses of environmental measurements, an approach for addressing uncertainty in the measurements, and documentation of the evaluation and its assumptions.

Nickel and vanadium concentrations and its relation with sediment acute toxicity.

Sediments from Pánuco River historically have contained elevated levels of numerous contaminants that may pose risks to ecological receptors and humans. Sediments were sampled and characterized to determine the acute sediment toxicity and its relationship with contaminants. Results demonstrated that toxicity was significantly correlated with fitness index (r = 0.82, p < 0.001), TOC (r = 0.55, p < 0.5), Ni (r = 0.95, p < 0.001), and V (r = 0.93, p < 0.001), but not with PAHs (r = 0.20, p < 0.5) during rainy and dry seasons. Although a great heterogeneity exists, the river outlet presents the biggest problems, due to dredging allow the metal desorption from solid to water phase, increasing the metal bioavailability.

Polyaromatic hydrocarbons (PAHs) and metal evaluation after a diesel spill in Oaxaca, Mexico.

Pollution in the marine environment due to a diesel spill takes days to months to complete natural remediation owing to its low volatility. Metal and PAH contamination caused by an accidental diesel spill were studied. V, Ni and Hg levels increased immediately after the spill, while PAH levels decreased after 1 month (79.4-7.6 microg kg(-1)). At the diesel spill point, fluoranthene exceeded acute and chronic levels, although most of the PAHs were within the range of low effects. In fish body burden, the highest bioaccumulation factor (2.63 for naphthalene) was related to the lower molecular weight PAHs.