Legal aspects and technical alternatives for the treatment of reservoir brines at the Activo Luna oilfield, Mexico.

Deep formation water, extracted as an undesired byproduct from on-shore production wells at the Activo Luna oilfield and processed in adjacent oil fields, are highly enriched in salt minerals, especially in sodium chloride (NaCl) (262 000 mg/L), but also in metals and nonmetals, such as strontium (Sr) (2068 mg/L), bromine (Br) (2034 mg/L), boron (B) (396 mg/ L), iodine (I) (43.4 mg/L), selenium (Se) (3.74 mg/L), and arsenic (As) (0.55 mg/L). Direct reinjection of the brine underground is not possible because of elevated pressure conditions within the petroleum reservoir. The disposal into near shore areas of the Gulf of Mexico without treatment must be rejected because of a) elevated concentrations of some toxic elements, such as B, silver (Ag), thallium (Tl), Se and cadmium (Cd), which exceed permissible limits of environmental legislation for surface discharge (Official Mexican norms NOM-001-ECOL-1998 and CE-CCA-001/89), and b) differences in density that could cause the descent of hypersaline fluid to the ocean floor, potentially affecting the diversity and survival of the benthic ecosystem. Conventional treatment techniques, such as microfiltration or reverse osmosis, are not suitable for the Activo Luna brines because of their extreme mineralization, which will cause pressure conditions exceeding 200 bars across the membrane. As an alternative process, the evaporation of the entire brine volume of approximately 200 m3/day by solar ponds or industrial crystallization plants is suggested. The residual precipitated residuals are composed mainly of chlorine (Cl) (9460 tons/year), sodium (Na) (4230 tons/ year), calcium (Ca) (1028 tons/year), potassium (K) (207 tons/year), and magnesium (Mg) (65.8 tons/year). As an alternative to its disposal on a dumpsite, some special minerals (especially NaCl, Mg, Sr, and Br) could be recovered for its economic value.     

Food resource use in a tropical eastern Pacific tidepool fish assemblage

An understanding of the trophic organization patterns of tropical littoral fish assemblages can contribute to the knowledge of key ecosystem processes while simultaneously assisting to validate large-scale biogeographic patterns (i.e. latitudinal patterns in fish herbivory). In the present study, the diets of eight fish species inhabiting the tide pools of a rocky shore on the western coast of Colombia (tropical eastern Pacific) are documented. A total of 17 prey items were identified, with a major representation (average percent by weight) of crabs and macroalgae items in the guts of all species. Small crustacean prey items (crabs, shrimps, copepods and amphipods) dominated the diets of most species, but consumption of macroalgae and diatoms by a significant number of species was also observed. We identified four significant trophic guilds within the assemblage using multivariate techniques (cluster analysis and nMDS): an omnivorous guild, consisting of Malacoctenus zonifer and the smallest size class of Bathygobius ramosus; a small-prey carnivorous guild, consisting of the intermediate size classes of B. ramosus and the smallest size class of Gobiesox adustus; a large-prey carnivorous guild, consisting of both largest size classes of B. ramosus and G. adustus; and an herbivorous guild consisting of Abudefduf concolor, A. troschelii and Chaenomugil proboscideus. The diet of two species slightly overlapped those of the rest of the assemblage and did not conform to any guild (Echidna nocturna and Halichoeres aestuaricola). It is hypothesised that guild formation may be a consequence of aggregation of species at abundant resources in the intertidal zone rather than a direct consequence of inter-specific competition. Ontogenetic changes in diets were observed in two resident species of the assemblage (B. ramosus and G. adustus). The latitudinal trend for herbivory inside this tropical assemblage is discussed in comparison with similar temperate studies in the eastern Pacific.     

Maternal serum levels of total activin-A in first-trimester trisomy 21 pregnancies

Maternal serum total activin-A concentration was measured in 45 pregnancies affected by trisomy 21 and 493 control unaffected pregnancies at 10–14 weeks of gestation. In the trisomy 21 pregnancies total activin-A concentration was significantly higher (1.36 MoM of the unaffected pregnancies) and in 16% of cases the level was above the 95th centile of normal. The log₁₀ SD for the control group and the trisomy 21 group were 0.17 and 0.22, respectively. The median pregnancy associated plasma protein-A (PAPP-A) in this trisomy 21 series was 0.49 and for free β-hCG was 2.05. In the trisomy group there were significant positive associations between total activin-A and PAPP-A (0.6071) and free β-hCG (0.4255). The low median difference and the high overlap in values between trisomic and unaffected pregnancies make total activin-A of little practical use in first-trimester screening for trisomy 21. Copyright © 2001 John Wiley & Sons, Ltd.     

Organic persistent toxic substances in soils, waters and sediments along an altitudinal gradient at Mt. Sagarmatha, Himalayas, Nepal

Persistent Organic Pollutants (POPs) and Polycyclic Aromatic Hydrocarbons (PAHs) are important classes of compounds of serious environmental concern. These compounds were measured in waters, sediments and soils from several high altitude sites in the Sagarmatha National Park (Nepal) and included in the Himalayan ridge.In water samples, low-level substituted PCBs and PBDEs, along with more volatile PAHs, were the most common contaminants. In sediment and soil samples, the PCB profile was mainly composed of medium-level chlorinated congeners and significantly correlated with altitude. The PAH profile for water and soil samples showed the main contribution of pyrogenic PAHs due to emissions of solid combustion, whereas the profile for sediments indicated the main contribution of pyrogenic PAHs from gasoline emissions. The PAH levels measured in Himalayan samples must be considered as low to medium contaminated, whereas the regarded Himalayan stations can be considered undisturbed remote areas concerning PCB, PBDE and OC compounds.     

Hidden demographic impacts of fishing and environmental drivers of fecundity in a sea turtle population

Fisheries bycatch is a critical threat to sea turtle populations worldwide, particularly because turtles are vulnerable to multiple gear types. The Canary Current is an intensely fished region, yet there has been no demographic assessment integrating bycatch and population management information of the globally significant Cabo Verde loggerhead turtle (Caretta caretta) population. Using Boa Vista island (Eastern Cabo Verde) subpopulation data from capture–recapture and nest monitoring (2013–2019), we evaluated population viability and estimated regional bycatch rates (2016–2020) in longline, trawl, purse-seine, and artisanal fisheries. We further evaluated current nesting trends in the context of bycatch estimates, existing hatchery conservation measures, and environmental (net primary productivity) variability in turtle foraging grounds. We projected that current bycatch mortality rates would lead to the near extinction of the Boa Vista subpopulation. Bycatch reduction in longline fisheries and all fisheries combined would increase finite population growth rate by 1.76% and 1.95%, respectively. Hatchery conservation increased hatchling production and reduced extinction risk, but alone it could not achieve population growth. Short-term increases in nest counts (2013–2021), putatively driven by temporary increases in net primary productivity, may be masking ongoing long-term population declines. When fecundity was linked to net primary productivity, our hindcast models simultaneously predicted these opposing long-term and short-term trends. Consequently, our results showed conservation management must diversify from land-based management. The masking effect we found has broad-reaching implications for monitoring sea turtle populations worldwide, demonstrating the importance of directly estimating adult survival and that nest counts might inadequately reflect underlying population trends.     

Preparation and Properties of Chitosan–PVA Fibers Produced by Wet Spinning

Chitosan fibers were prepared by wet spinning in three stages. Initially, a polymer solution of chitosan and polyvinyl alcohol (PVA) was solidified in a mixture of potassium hydroxide and ethanol. The polymers were then crosslinked with sodium tripolyphosphate (TPP) or glutaraldehyde, and finally dried in methanol or acetone. The effect of these conditions was evaluated based on scanning electron microscopy images, water-holding capacity, and swelling and mechanical properties. The miscibility of the mixture was evaluated using Fourier Transform Infrared spectroscopy and differential scanning calorimetry. The results obtained showed that chitosan fibers containing 45% (v/v) PVA and crosslinked using TPP have properties similar to those of commercial sutures prepared using other biomaterials.