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E Speranza

Publications and source records attributed to E Speranza.

4 recordsLinked to original sources
PubMed2006

Sources, vertical fluxes, and equivalent toxicity of aromatic hydrocarbons in coastal sediments of the Río de la Plata Estuary, Argentina.

Settling particles and bottom sediments collected at 1, 2.5, and 4 km off the metropolitan Buenos Aires coast in the Río de la Plata were analyzed to evaluate the sources and toxicity of resolved (PAHs) and unresolved (AROUCM) aromatic hydrocarbons. PAHs (0003-2.1 microg g(-1)) and AROUCM (0.01-78 microg g(-1)) presented the highest concentrations nearthe Buenos Aires port and sewer and decreasing values up- and downstream and along on- and offshore gradients. Sediment traps deployed in the Central area revealed large aromatic fluxes (1.3 +/- 1.5 and 31 +/- 47 mg m(-2) day(-1) for PAHs and AROUCM). The composition of sedimentary PAHs was dominated by uniformly distributed high molecular weight pyrogenic PAHs (53 +/- 11% fluoranthene, pyrene, and heavier PAHs), followed by diagenetically derived perylene more abundant in less polluted sites (29 +/- 15%) and lower molecular weight petrogenic PAHs (18 +/- 7.1% phenanthrene, anthracene, and methylated compounds), which covaried inversely with perylene. PAH diagnostic ratios indicated a stronger influence of petrogenic discharges close to the shore and the prevalence of combustion of fossil fuels and vehicle emissions over wood in offshore sediments. Sediment cores showed sustained hydrocarbon levels with decreasing proportion of petrogenic PAHs and relative enrichment of pyrogenic components and perylene down to 20-cm depth. PAH toxicity assessment by sediment quality guidelines (SQG) and dioxin-equivalent factors (PAH TEQ: 0.08-395 pg g(-1) dw) identified 1-2.5 km sediments close to the port and sewer as the most affected area. According to SQG, dibenz[a,h]anthracene and pyrene were the most critical PAHs, followed by benzo[a]pyrene, benz[a]anthracene, and chrysene. In contrast, PAH TEQs were dominated by indeno[1,2,3-cd]pyrene, benzo[k]fluoranthene, benzo[a]pyrene, perylene, and benz[a]anthracene which accounted for an average 86 +/- 5.7% of total TEQs.

Argentina↗
PubMed2005

Sources, vertical fluxes, and accumulation of aliphatic hydrocarbons in coastal sediments of the Río de la Plata Estuary, Argentina.

Settling particles and underlying sediments collected at 1, 2.5 and 4 km off the metropolitan Buenos Aires coast were analyzed to evaluate the sources and accumulation of resolved (RES), unresolved (UCM), and biomarker aliphatic hydrocarbons. Sedimentary aliphatic concentrations (RES 0.11-14 microg x g(-1); UCM 0.1-800 microg x g(-1)) included variability associated with north-south gradients and an exponential offshore reduction. Highest concentrations were registered close to Buenos Aires port and sewer, compared to cleaner northern stations and southward sites affected by a seaward residue transport. Sediment traps deployed in the sewer area revealed large hydrocarbon (38 and 319 mg x m(-2) x day(-1), RES and UCM) and total organic carbon fluxes (29 +/- 26 g x m(-2) x day(-1). The composition of RES and hopanes evaluated by principal component analysis indicated a consistent offshore gradient defined bythe relative contribution of lower vs higher molecular weight components. Distant sites showed decreasing proportions of petrogenic n-C(17-26) alkanes, isoprenoids, and C(20-27) terpanes and relative enrichment of n-C(27,29,31,33) terrestrial plant alkanes and C(31-33) homohopanes. Sediment hydrocarbon profiles showed an average 2-fold reduction down to 20 cm depth with preferential removal of lower molecular weight components and enrichment of n-C(23-35) alkanes and hopanes. Sediment inventories and trap depositional fluxes indicate the accumulation of 5800-9700 tons of aliphatic hydrocarbons in the top 0-5 cm sediments with a strong interfacial alteration and selective preservation of refractory components: n-C(13-22) (1.0%) < isoprenoids (3.2%) < n-C(23-35) (6.1%) < hopanes (47%) approximately UCM (50%), compared to intermediate stability of organic carbon (12%) and quantitative preservation of polychlorinated biphenyls (PCBs) (91%).

Argentina↗
PubMed2005

Leading-edge vortex stability in insect wings.

An analytical study is presented to determine if the persistency of the leading-edge vortex in an insect wing can be explained as the balance between vorticity generation at the leading edge and advection plus effects of vorticity stretching and tilting by the flow along the wing span. It is found that a spanwise flow of the required magnitude is produced by the simple rotation of the wing about its root at a constant angle of attack (no supination or pronation), and that the regions where this equilibrium exists in stable form are well localized, independent of the rotation velocity, almost independent of the position along the wing, and weakly dependent on the angle of attack, for angles below approximately equal to 70 degrees. In contrast, extended regions of vorticity are expected for angles of attack above approximately equal to 75 degrees.

Animals↗