This study assessed the concentration, bioconcentration, and bioaccumulation of As, Cd, Co, Cr, Cu, Mg, Mn, Ni, Pb, and Zn in juvenile fishes (Acestrorynchus pantaneiro, Brycon orbygnianus, Cyphocharax voga, Megaleporinus obtusidens, Odontesthes bonariensis, Pimelodus maculatus, Prochilodus lineatus, Salminus brasiliensis, and Schizodon borelli) in the Lower Paraná River (Argentina), the most extensive floodplain from the Plata Basin. The floodplain is crucial for the reproduction and growth of various species such as P. lineatus, M. obtusidens, and S. brasiliensis, which complete their life cycle in this environment. In total, 90 individuals were sampled for nitrogen stable isotope, and trace element analysis in muscle tissue, water, and sediment was analyzed. The results show that all the studied species bioaccumulate Cr, Mg, Ni, and Zn. In particular, B. orbygnianus and P. maculatus presented the highest bioaccumulation factor for Cr. A biodilution of Co through the food chain was observed. No positive correlation was found between element concentration and trophic level, but we observed significant differences between trophic guilds (herbivorous, omnivorous, and carnivorous). Our findings suggest that feeding habits determine trace element concentrations. To establish differential behavior between different species within the aquatic web further studies are necessary, particularly in the floodplain of the Paraná, which is a crucial nursery area for most commercially important fishes from the Plata Basin.
The substitution of biogas, an energy source derived from biological feedstock, for fossil natural gas (NG) can mitigate the build-up of greenhouse gases in the atmosphere, making it an attractive renewable energy source in a carbon-constrained future. Although upgraded, pipeline-quality biogas can augment the NG market supply in the United States of America (USA), researchers and energy industry experts have little studied its long-term potential. This report estimates (1) levelized costs of energy for biogas production facilities operating with landfill waste, animal manure, wastewater sludge, and biomass residue feedstocks, (2) feedstock and technology pathway-specific biogas supply functions, and (3) the aggregate national biogas supply potential for the USA by 2040. Under a range of specified assumptions, generation of biogas could be expanded to approximately 3–5 % of the total domestic NG market at projected prices of $5–6/MMBtu, with the largest potential source coming from thermal gasification of agriculture and forest residues and biomass. As market signals have not spurred widespread adoption of biogas in the USA, policy incentives, similar to those used in the European Union (E.U.), may be necessary to increase its production and use. Bioenergy policy in the E.U. and the resulting market penetration achieved there therefore provides important lessons for how biogas markets in the USA can overcome barriers to market expansion and, in doing so, provide substantial climate mitigation benefits. 相似文献
