1,721,141 research outputs found
Benthic communities of a Thyrrenian sea coastal area (Agropoli, Salerno)
No full textA contribution to the knowledge of the coastal benthic fauna of a Thyrrenian sea area is the aim of this work. Hard and mobile sea bed taxa, living either on an antitrawling artificial reef and in its proximity, have been identified and studied. Hard bottom fauna has been sampled by professional scuba divers, while mobile bottom fauna has been sampled using a dredge. Taxonomic identification has been carried out to the species level, only in few taxa to genus or family level. Polychaetes was the most frequent taxon, followed by Bivalve Molluscs, both on hard and mobile bottom. The Salerno anti-trawling reef allowed the reappearance of taxa that had not been recorded in this area for a very long time
Predicting the effects of capping contaminated sediments via numerical simulations
Full text linkContaminated sediments are one of the key risks to human health and the environment, due to high
concentrations of many types of substances contained in them and their direct contact with the aquatic
fauna. This contributes to fish consumption advisories and limits the uses of many water bodies. In
this study, an in situ capping (ISC) is considered as a potential remedy to minimise the exposure of
aquatic ecosystems to sediment contaminants and a valid alternative to ex situ remediation options,
by reducing contaminant fluxes to the upper water. Numerical design simulations, taking into
account a biosorptive sediment cap and comparing different adsorptive characteristics of sediments,
are proposed. As a case study, polychlorinated biphenyls contaminated sediments of Lake Hartwell,
an artificial lake located in South Carolina, USA, were considered. A numerical predictive model of
concentrations in a multilayered bed sediment and overlying water was developed in order to evaluate
the long-term effectiveness of ISC of different thicknesses. Results showed that, for the case study, a
minimum 20 cm cap allows to reduce the contaminant flux to the overlying water through reaction of
the contaminants with the capping matrix, by highlighting how sediment biosorptive characteristics
can influence the cap design
Macromolecular structure of a commercial humic acid sample
No full textThe molecular structure of a commercial sample of humic acids (HA) was investigated by membrane dialysis experiments (MD) and low-pressure size-exclusion chromatography (LP-SEC). MD showed that HA molecules were retained by dialysis membrane with a cut-off of 6–8 kDa, independently from HA concentration (15 or 150 mg L−1), NaHCO3 concentration (0.005–2.0 mol L−1), and from propan 2-ol (0–5 v/v %). SEC experiments at low pressure gave chromatograms with a broad peak, with an elution volume between those of the globular proteins bovine serum albumin (molecular weight = 66.5 kDa) and lysozyme from egg (molecular weight = 14.4 kDa). The pattern of the chromatogram did not vary with HA concentration, and second-run chromatograms of single eluted fractions showed relatively sharp peaks. From these data, we reveal that the commercial HA sample analysed has a macromolecular structure rather than being a supramolecular aggregate of relatively small molecules, as recently proposed for some samples of HA obtained from different sources
Economic Evaluation of a Large-Scale PHBV Production Facility: Impact of Polymer Content on the Final Selling Price
No full textPoly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a biodegradable polymer with excellent thermal and mechanical properties comparable to fossil-based plastics. Scaling up the production of this polymer could provide a viable solution for reducing the use of fossil-based materials. However, its current production capacities are limited, with only a few facilities implementing the process at pilot or semi-industrial scales. The primary challenge lies in the high production costs, with 40% of the expenses attributed to the feedstock used for fermentation. Additionally, the energy required for sterilization in processes using pure methanotrophic cultures further reduces its economic viability. In this study, the economic aspects of the PHBV production process were assessed at an industrial level (100,000 t/y PHBV), using cheap and renewable substrates such as valeric acid and methane. A mixed methanotrophic consortium was used to reduce the need for sterility. The techno-economic analysis was based on estimating both fixed investment and operating costs. Then, a sensitivity analysis was performed to analyse the effect that the polymer content has on the final selling price: the initial biomass concentration was set to 30 g L-1 and the PHBV content was considered to be 20, 30, 40, 50 and 70% wt on a dry weight basis. The results revealed that increasing the polymer content beyond 40% wt led to a more competitive PHBV selling price, thus opening significant market opportunities
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