Bioremediation of petroleum hydrocarbons in anoxic marine sediments: Consequences on the speciation of heavy metals

We investigated the effects of biostimulation and bioagumentation strategies applied to harbor sediments displaying reducing conditions and high concentrations of petroleum hydrocarbons and heavy metals. We compared the microbial efficiency of hydrocarbon removal from sediments maintained for 60 days in anoxic conditions and inoculated with acetate, sulfate-reducing bacterial strains and acetate and sulfate-reducing bacteria. All treatments determined a significant increase in the microbial growth and significant decreases of hydrocarbon contents and of redox potential values. The addition of sulfate-reducing bacterial strains to the sediment was the most efficient treatment for the hydrocarbon removal. In all experiments, significant changes of the heavy metals’ phase repartition were observed. The results reported here suggest that the biodegradation of petroleum hydrocarbons in anoxic marine sediments may be enhanced by stimulating microbial anaerobic metabolism, but care should be applied to monitor the potential changes in the mobility and bioavailability of heavy metals induced by bio-treatments.     

Discriminating the long distance dispersal of fine ash from sustained columns or near ground ash clouds: The example of the Pomici di Avellino eruption (Somma-Vesuvius,Italy)

Ash samples from tephra layers correlated with the Pomici di Avellino (Avellino Pumice) eruption of Somma-Vesuvius were collected in distal archives and their composition and particle morphology investigated in order to infer their behaviour of transportation and deposition. Differences in composition and particle morphologies were recognised for ash particles belonging to the magmatic Plinian and final phreatomagmatic phases of the eruption. The ash particles were dispersed in opposite directions during the two different phases of the eruption, and these directions are also different from that of coarse-grained fallout deposits. In particular, ash generated during magmatic phase and injected in the atmosphere to form a sustained column shows a prevailing SE dispersion, while ash particles generated during the final phreatomagmatic phase and carried by pyroclastic density currents show a general NW dispersion. These opposite dispersions indicate an ash dispersal influenced by both high and low atmosphere dynamics. In particular, the magmatic ash dispersal was first driven by stratospheric wind towards NE and then the falling particles encountered a variable wind field during their settling, which produced the observed preferential SE dispersal. The wind field encountered by the rising ash clouds that accompanied the pyroclastic density currents of the final phreatomagmatic phase was different with respect to that encountered by the magmatic ash, and produced a NW dispersal. These data demonstrate how ash transportation and deposition are greatly influenced by both high and low atmosphere dynamics. In particular, fine-grained particles transported in ash clouds of small-scale pyroclastic density currents may be dispersed over distances and cover areas comparable with those injected into the stratosphere by Plinian, sustained columns. This is a point not completely addressed by present day mitigation plans in case of renewal of activity at Somma-Vesuvius, and can yield important information also for other volcanoes potentially characterised by explosive activity.     

From paleo to policy: partitioning the historical point and nonpoint phosphorus loads to the St. Croix River,Minnesota-Wisconsin,USA

Paleolimnological studies show that phosphorus (P) loads to the federally protected St. Croix River, a tributary of the Upper Mississippi River, have increased about threefold over the last century. Ongoing management efforts to protect and restore the river hinge on the question of whether the increased nutrient load results from point-source discharges or nonpoint runoff from agricultural intensification and urban expansion. Here we determine the historical contribution of point source phosphorus (P) loads to the St. Croix watershed from 1900–2000 A.D. Historical point source loads were estimated based on discharge volumes, demographics, industrial sources, wastewater technologies, and facility discharge records, where available. Sewering in the basin began in 1905, and since that time, there have been as many as 169 permitted point source dischargers basinwide, including municipal, industrial, and agricultural facilities. Early wastewater management typically discharged untreated sewage; technological advances had secondary treatment in place at most facilities by the 1960s–1970s and much of the municipal population was served by tertiary treatment by the 1990s. Peak nutrient discharges from point sources occurred in the 1960s–1970s. Detergent phosphorus bans instituted in the late 1970s for Minnesota and Wisconsin, greater use of land and groundwater effluent disposal, and improvements in treatment technology brought about decreases in P loads in the 1980s and 1990s. Point-source discharges were compared to historical total phosphorus loads estimated in a whole-basin phosphorus mass balance to calculate the historical contribution of point sources, anthropogenic nonpoint sources, and natural or background sources. We estimated 1990s point source loads at 48 t P yr⁻¹, which represents about 10% of the total phosphorus load (459 t P yr⁻¹, flow-corrected to 412 t P yr⁻¹) to the basin. Without further controls on nutrient inputs to the St. Croix River, annual flow-corrected P loads are projected to increase to 498 t P yr⁻¹ by the 2020s with point source phosphorus loading contributions at 65 t P yr⁻¹ or 13% of the total load. However, if we exclude background P loads to the St. Croix (166 t P yr⁻¹), recent nutrient loads are primarily from anthropogenic nonpoint sources. Point sources also contribute over 19% of the current and future phosphorus load that can be attributed to human activities in the watershed. Interstate and federal efforts to decrease P loading to the St. Croix River by 20% will need to target both point and nonpoint sources. This is one of eight papers dedicated to the “Recent Environmental History of the Upper Mississippi River” published in this special issue of the Journal of Paleolimnology. D.R. Engstrom served as guest editor of the special issue.     

Seasonal variation in di-nitrogen fluxes and associated processes (denitrification, anammox and nitrogen fixation) in sediment subject to shellfish farming influences

Seasonal patterns of di-nitrogen fluxes together with denitrification, anammox, and N-fixation rates were studied in sediment in an area subject to strong human pressure via waste water, tributaries and shellfish farming in the Mediterranean Sea (Carteau Cove, NW area of the Gulf of Lion). Ammonium concentration demonstrated no seasonal variation, however, a large increase in its concentration was observed over a 10 years period due to intense biodeposition of organic matter. In contrast, nitrate concentration demonstrated no seasonal or long-term (10 years) variation. The main processes affecting di-nitrogen flux magnitudes were denitrification and N-fixation. Anammox was only detected occasionally, nevertheless it represented at times up to 39% of the N₂-flux. Nitrate reducing processes were variable and denitrification showed a 20-fold increase over the past 10 years and might actually have reached its potential maximal activity. Rates of N₂ production (denitrification and anammox) were generally higher than those of N-fixation, leading to elimination of nitrogen from the ecosystem.     

Buckling of circular, solid and annular plates with an intermediate circular support

The title problem is solved in the case where uniform applied loading is present at the plate outer boundary. Two independent solutions are obtained: the optimized Rayleigh–Ritz method and the finite element algorithmic procedure. Good engineering agreement is shown to exist. The proposed analytical procedure is convenient from a designer's viewpoint. Admittedly exact analytical solutions can be found in terms of Bessel functions, the procedure being rather complex from an engineering viewpoint.     

Plane state of stress and transverse oscillations of a simply supported rectangular plate

This paper deals with a general discussion of the subject matter. Recent literature is analyzed including some incorrect treatments of particular cases. Finally, a variational solution is obtained for the case where a linear distribution of stresses is applied to the plate boundaries. The lower natural frequencies are then tabulated as a function of the governing geometric and mechanical parameters.     

Spectrophotometry of three planetary nebulae

The results of a spectroscopic investigation of three possible planetary nebulae, K4- 53, K4- 55, and K4- 57, are presented. It is shown that K4- 53 and K4- 55 are planetary nebulae while K4- 57 can be considered with high probability to be one. The temperatures of the nuclei of these nebulae are determined by Ambartsumian’s method. The optical depths for L_c photons in the region of λ ≤ 912 Å are determined. An anomalously high nitrogen abundance is observed in K4- 55.     

Adsorption of Copper, Nickel, and Cadmium on Goethite in the Presence of Organic Ligands

Adsorption of copper, cadmium and nickel at low concentrations on goethite was studied in the presence of the simple organic ligands oxalate, salicylate, and pyromellitate. The experimental metal adsorption behavior was compared to calculations with a surface complexation model to evaluate the most important interactions. Oxalate mostly decreased Cu and Ni adsorption at high pH-values by competition between solution and surface complexation but had no effect on Cd adsorption. Cu adsorption in the presence of oxalate below pH 6 could best be described by defining a ternary complex of type A (surface-metal-ligand). Salicylate had only minor effects on metal adsorption. The adsorption of Cu in the presence of salicylate above pH 5 could be explained by a ternary complex of type A. Pyromellitate increased the adsorption of Cu and Cd in the acidic pH-range, likely by formation of ternary surface complexes of type B (surface-ligand-metal).     

Eclogite relics in the Variscan orogenic belt of Bulgaria (SE Europe)

Eclogitic rocks were sampled from two zones in the basement of the Sredna Gora terrane (central western Bulgaria): (1) partially retrogressed eclogites and amphibolites embedded in sillimanite-bearing garnet-micaschists with kyanite relics and migmatites and (2) banded amphibolites associated with muscovite-bearing metagranites within two-mica paragneisses. Rutile relics and oligoclase + green hornblende + epidote ± biotite pseudomorphs after garnet suggest an eclogite facies event. A tholeiitic, transitional affinity was determined for the protoliths, suggesting a continental rift environment, consistent with several eclogite-bearing complexes in the eastern segments of the Variscan belt that arose from the Cambro-Ordovician Gondwana break-up. Decreasing pressure after the eclogite overprint was demonstrated by (a) diopside-albite symplectite, and (b) plagioclase + red–brown to green amphibole kelyphite. The early static re-equilibration, dated to 398 ± 5.2 Ma by ⁴⁰Ar–³⁹Ar technique, was followed by an amphibolite facies foliation, which was pervasive in amphibolites, gneisses and micaschists, and poorly developed in eclogites. The lithospheric PT paths corresponding to higher and lower metamorphic gradients reflect the juxtaposition of crustal and lithospheric mantle units, respectively. In the build-up of the basement of the Balkan orogen, the physical properties of the lithological complexes might have influenced the collisional pattern of involved microplates.