Nb2O5 nanoparticles decorated with magnetic ferrites for wastewater photocatalytic remediation

Environmental Science and Pollution Research - Nanotechnology has been studied on environmental remediation processes to foster greater photocatalysts efficiency and reuse in wastewater. This study...     

Variability of dissolved organic matter in northern adriatic coastal waters

The results obtained in the four seasonal cruises planned in the PRISMA II project are reported. These concern dissolved and colloidal organic carbon, free amino acids and total dissolved carbohydrates and heterotrophic activity. Main factors controlling organic matter degradation, resulting from laboratory tests not planned in the above project, are also discussed. Dissolved organic matter shows seasonal accumulation, which may be markedly different from year to year, and large contributions by colloidal and saccharide components. Heterotrophic activities play an important role in the carbon cycle, although laboratory runs highlight limitations caused by aging of organic matter and phosphorus deficiency.     

The effect of initial concentration, co-application and repeated applications on pesticide degradation in a biobed mixture

A 180 d laboratory experiment was conducted to investigate the degradation rates of chlorpyrifos (10 and 50 mg kg(-1)) and metalaxyl (100 mg kg(-1)) separately and co-applied in a biomix constituted by topsoil, vine-branches and urban-waste-garden compost. The effect of repeated application of metalaxyl was also investigated. Microbial biomass-C (MBC) content and metabolic quotient (qCO(2)) were measured to evaluate changes in microbial biomass size and activity induced by the presence of the two pesticides. Degradation rate decreased with increasing concentration of chlorpyrifos in all treatments. Metalaxyl half-life was significantly reduced in co-application with chlorpyrifos indicating a synergic interaction between the two pesticides in favour of enhanced degradation rate for metalaxyl but not for chlorpyrifos. Furthermore, repeated application resulted in a sharp reduction of metalaxyl half-life from 37 d after first application to 4 d after third application. MBC content was negatively influenced by the addition of pesticides but it started to recover immediately, in both separate and co-applied treatments, reaching the control value when pesticide residues were about 50% of the initial concentration. The qCO(2) reached a steady-state after about 20 d in separately applied and 40 d in co-applied treatments, indicating a tendency to arrive at a new metabolic equilibrium. In conclusion, the biomix tested has been shown to degrade pesticides relatively fast and to have a microbial community that is varied enough to allow selection of those microorganisms able to degrade metalaxyl and chlorpyrifos.     

The effects of accelerated carbonation on CO2 uptake and metal release from incineration APC residues

This work presents the results of a study on accelerated carbonation of incinerator air pollution control residues, with a particular focus on the modifications in the leaching behaviour of the ash. Aqueous carbonation experiments were carried out using 100% CO₂ at different temperatures, pressures and liquid-to-solid ratios, in order to assess their influence on process kinetics, CO₂ uptake and the leaching behaviour of major and trace elements. The ash showed a particularly high reactivity towards CO₂, owing to the abundance of calcium hydroxides phases, with a maximum CO₂ uptake of ～250 g/kg. The main effects of carbonation on trace metal leaching involved a significant decrease in mobility for Pb, Zn and Cu at high pH values, a slight change or mobilization for Cr and Sb, and no major effects on the release of As and soluble salts. Geochemical modelling of leachates indicated solubility control by different minerals after carbonation. In particular, in the stability pH range of carbonates, solubility control by a number of metal carbonates was clearly suggested by modelling results. These findings indicate that accelerated carbonation of incinerator ashes has the potential to convert trace contaminants into sparingly soluble carbonate forms, with an overall positive effect on their leaching behaviour.     

Gas-particle concentration and distribution of n-alkanes and polycyclic aromatic hydrocarbons in the atmosphere of Prato (Italy)

Air samples were collected in an urban and industrialised area of Prato (Italy) during 2002, as part of a study to identify and measure aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs). Total concentrations of aliphatic hydrocarbons ranged between 170 and 282ngm(-3) in the gas phase and from 48.9 to 276ngm(-3) in the particulate phase. The average total PAH concentrations (gas+particulate) were 59.4+/-26.5ngm(-3), and both gas and particulate phase PAH concentrations decreased with increasing temperature. Source identification using diagnostic ratios and principal component analysis identified automobile traffic, in particular, the strong influence of diesel fuel burning, as the major PAH source. Gas-particle partition coefficients (K(p)'s) of n-alkane and PAHs were well correlated with the sub-cooled liquid vapour pressure (P(L)(0)) and indicate stronger sorption of PAHs to aerosol particles compared with n-alkanes.     

Porewater as a matrix in toxicity bioassays with sea urchins and bivalves: evaluation of applicability to the Venice lagoon (Italy)

Porewater plays an important role in sediment toxicity assessment using bioassays, but the most reliable extracting method and the potential contribution of confounding factors to the real toxicity need to be studied. The applicability of bioassays with the early life stages of Paracentrotus lividus, Mytilus galloprovincialis and Crassostrea gigas on porewaters extracted by centrifugation from the Venice Lagoon (Italy) is evaluated and demonstrated: toxicity tests can discriminate the toxicity of porewaters from sites with different kinds and levels of pollution and, using toxicity scores, data are classified in five toxicity classes. Sulphides do not represent a confounding factor in porewater toxicity; in contrast ammonia exhibited some concentrations above the toxicity threshold for sea urchin embryos.     

Reduction of Cr(VI) by caffeic acid

In the soil-plant system, the Cr(VI) toxicity can be moderated through redox reactions involving phenolic substances. In such a context, we report the reducing activity of caffeic acid (CAF) towards Cr(VI) in aqueous phase. The redox reaction between Cr(VI) and CAF was studied as a function of both time and pH at different initial metal concentrations. The reaction was particularly effective at pH 2.5. The kinetic data indicate that the reaction proceeds through two steps: the first is faster and involves four electrons, the latter, which is slower, five electrons. The chromatograms evidence the formation of oxidation products (OP) with a different redox activity towards Cr(VI). A yield of Cr(III) equal to that obtained at pH 2.5 and pH 3.1 in about 7 and 25 h, respectively, was reached at pH 4.2 only after a much longer reaction time (50h). At pH>4.2 the reaction occurred even more slowly, and its kinetic trend was more and more difficult to study at pH values higher than 5.0 due to the formation of precipitates. Other phenolics investigated (o-, m-, p-coumaric acids) showed a reducing activity negligible compared to that of CAF: about 30% of p-coumaric acid was oxidized at pH 2.5 only after two months of reaction.     

TEQ(S) and body burden for PCDDs, PCDFs, and dioxin-like PCBs in human adipose tissue

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), mono-ortho and non-ortho polychlorinated biphenyls (dioxin-like PCBs) were determined in samples of human fat tissue from nine Italian obese patients. The toxicity equivalent (TEQ) values ranged from 9 to 25pgTEQg(-1) lipid (WHO-TEF values, 2005 [Van den Berg, M., Birnbaum, L.S., Denison, M., De Vito, M., Farland, W., Feeley, M., Fiedler, H., Hakansson, H., Hanberg, A., Haws, L., Rose, M., Safe, S., Schrenk, D., Tohyama, C., Tritscher, A., Tuomisto, J., Tysklind, M., Walker, N., Peterson, R.E., 2006. The 2005 World Health Organization reevaluation of human and mammalian Toxic Equivalency Factors for dioxins and dioxin-like compounds. Toxicol. Sci. 93, 223-241]), the contribution of dioxin-like PCBs was more than 30% of the total TEQ values. The obese body burdens varied from 6 to 11ngTEQkg(-1) body weight (BW), exceeding the estimated steady-state body burden 5ngTEQkg(-1) BW, based on lipid adjusted serum concentrations from several populations in the mid-1990s, calculated in the risk assessment US EPA document.     

Phytoplankton photosynthetic activity and growth rates in the NW Adriatic Sea

Taxonomic composition, biomass, primary production and growth rates of the phytoplankton community were studied in two stations in the NW Adriatic Sea on a seasonal basis, in areas characterized by differing hydrological and trophic conditions. The main differences between the two stations were quantitative rather than qualitative, most phytoplankton species being common to both stations. The effects of differing nutrient concentrations and plume spreading were evident. Biomass and primary production rates were significantly higher in the coastal station (S1), and the phytoplankton distribution in the water column was markedly stratified in S1 and more even in the offshore station (S3). However, chlorophyll a specific production, potential growth rate and production efficiencies were very similar in both stations, even when phosphorus concentrations were limiting. A discrepancy between potential and actual growth rate was observed: as a feature common to both stations, comparisons between potential and actual growth rates revealed that little carbon produced by phytoplankton accumulated as algal biomass; therefore, very high loss rates were estimated.