Retention of arsenic on hydrous ferric oxides generated by electrochemical peroxidation

Electrochemical peroxidation (ECP), an emerging remediation technology, with direct electric current applied to steel electrode and small addition of H2O2, was used to remove As(III) from contaminated aqueous solutions. Bench scale experiments were conducted to evaluate the sorption and distribution of arsenic between the soluble and solid state hydrous ferric oxides (HFO) formed as part of the ECP process. ECP was effective in removing arsenic from the aqueous solution, with >98% of the applied As(III) adsorbed on HFO. Removal was complete within 3 min of ECP treatment and apparently independent of the initial pH of the water (3.5-9.5). In the absence of H2O2 more As(III) was adsorbed by solid state iron at pH 9.5 than at 3.5 (2600 vs. 1750 microg l(-1)). Thus H2O2 was crucial to oxidize As(III) to As(V) which is more strongly retained by HFO. Removal of As was not significantly affected by the concentration of H2O2 or by current processing time. The optimal operating conditions were pH < 6.5, H2O2 concentration of 10 mg l(-1) and current process time not exceeding 3 min. X-ray diffraction (XRD), diffuse-reflectance infrared Fourier transform (DRIFT) spectroscopy and transmission electron microscopy (TEM) were applied to study the HFO deposits. The XRD data indicated the prevalence of poorly ordered Fe minerals in the suspended ECP solids with a dominance of 5 line ferrihydrite in the absence of H2O2. At pH 3.5 and with 100 mg H2O2 l(-1), akaganeite was formed, whereas an incipient hematitic phase, reflection at 0.39 nm, occurred at pH 6.5. DRIFT data indicate that both As(III) and As(V) were specifically adsorbed onto HFO at acid and neutral pH. TEM observations indicated the presence of spherical shape ferrihydrite and provided evidence for possible formation of subrounded hematite and acicular shape goethite.     

Distribution of endocrine disruptors in the Llobregat River basin (Catalonia, NE Spain)

The Llobregat basin is a Mediterranean fluvial system with major agricultural, urban and industrial impacts. We combined chemical quantification by liquid chromatography–mass spectrometry with electrospray interface (LC-ESI-MS) and the recombinant yeast assay (RYA) assays to estimate the loads of endocrine disrupting compounds (EDCs) along the basin. Chemical analysis revealed maximum concentrations (at μg l⁻¹ level) of alkylphenols at the lower course of the Llobregat River, which correlated with high levels of estrogenic activity detected by RYA. Analysis by RYA and LC-ESI-MS of influent and effluent waters from four sewage treatment plants (STP) discharging into the basin showed the removal of 80–95% of EDCs by STP treatment. Chemical analysis data and RYA data showed a quasi-linear correlation, demonstrating the complementariness of both methods. Our data suggest that the concentrations of the analysed compounds were enough to explain the total estrogenicity of water and STP samples from the Llobregat basin.     

Soil moisture determines the effectiveness of two urease inhibitors to decrease N<Subscript>2</Subscript>O emission

Among the mitigation strategies to prevent nitrogen (N) losses from ureic fertilizers, urease inhibitors (UIs) have been demonstrated to promote high N use efficiency by reducing ammonia (NH₃) volatilization. In the last few years, some field experiments have also shown its effectiveness in reducing nitrous oxide (N₂O) losses from fertilized soils under conditions of low soil moisture. An incubation experiment was carried out with the aim of assessing the main biotic mechanisms behind N₂O emissions once that the UIs N-(n-butyl) thiophosphoric triamid (NBPT) and phenil phosphorodiamidate (PPDA) were applied with Urea (U) under different soil moisture conditions (40, 60 and 80 % water-filled pore space, WFPS). In the same study we tried to analyze to what extent soil WFPS regulates the effect of these inhibitors on N₂O emissions. The use of PPDA in our study allowed us to compare the effect of NBPT with that of another commercially available urease inhibitor, aiming to see if the results were inhibitor-specific or not. Based on the results from this experiment, a WFPS (i.e. 60 %) was chosen for a second study (i.e. mesocosm experiment) aiming to assess the efficiency of the UIs to indirectly affect N₂O emissions through influencing the pool of soil mineral N. The N₂O emissions at 40 % WFPS were almost negligible, being significantly lower from all fertilized treatments than that produced at 60 and 80 % WFPS. When compared to U alone, NBPT+U reduced the N₂O emissions at 60 % WFPS but had no effect at 80 % WFPS. The application of PPDA significantly increased the emissions with respect to U at 80 % WFPS whereas no significant effect was found at 60 %. At 80 % WFPS, denitrification was the main source of N₂O emissions for all treatments. In the mesocosm study, the application of NBPT+U was an effective strategy to reduce N₂O emissions (75 % reduction compared to U alone), due to a lower soil ammonium (NH₄ ⁺) content induced by the inhibitor. These results suggest that adequate management of the UI NBPT could provide, under certain soil conditions, an opportunity for mitigation of N₂O emissions from fertilized soils.     

Fire and explosion hazards during filling/emptying of tanks

Loading and unloading operations produce 8% of all accidents which occur in process plants and in the transportation of hazardous materials. A survey of 738 accidents was performed, allowing the identification of the accident type distribution and of their cause. Some considerations on flammable mixtures are also presented, and the procedures to avoid these mixtures occurring when filling or emptying a tank are briefly discussed.     

Spatial Relationships of Levees and Wetland Systems within Floodplains of the Wabash Basin,USA

Given the unique biogeochemical, physical, and hydrologic services provided by floodplain wetlands, proper management of river systems should include an understanding of how floodplain modifications influence wetland ecosystems. The construction of levees can reduce river–floodplain connectivity, yet it is unclear how levees affect wetlands within floodplains, let alone the cumulative impacts within an entire watershed. This paper explores spatial relationships between levee and floodplain wetland systems in the Wabash Basin, United States. We used a hydrogeomorphic floodplain delineation technique to map floodplain extents and identify wetlands that may be hydrologically connected to river networks. We then spatially examined the relationship between levee presence, wetland area, and other river network attributes within discrete subbasins. Our results show that cumulative wetland area is relatively constant in subbasins that contain levees, regardless of maximum stream order within the subbasin. In subbasins that do not contain levees, cumulative wetland area increases with maximum stream order. However, we found that wetland distributions around levees can be complex, and further studies on the influence of levees on wetland habitat may need to consider finer resolution spatial scales.     

Sulphurous air pollutants and exposure events of workers in thermal-mineral springs: a case study of Contursi Terme (Salerno,Italy)

Environmental Science and Pollution Research - Thermo-mineral springs are widely spread over the volcanic areas of Salerno, a city in southern Italy. Although the water of thermal structures...     

Remote sensing for mapping algal blooms in freshwater lakes: a review

Environmental Science and Pollution Research - A large number of freshwater lakes around the world show recurring harmful algal blooms, particularly cyanobacterial blooms, that affect public health...     

Spatio-temporal log-Gaussian Cox processes for modelling wildfire occurrence: the case of Catalonia, 1994–2008

Wildfires have become one of the principal environmental problems in the Mediterranean basin. While fire plays an important role in most terrestrial plant ecosystems, the potential hazard that it represents for human lives and property has led to the application of fire exclusion policies that, in the long term, have caused severe damage, mainly due to the increase of fuel loadings in forested areas, in some forest systems. The lack of an easy solution to forest fire management highlights the importance of preventive tasks. The observed spatio-temporal pattern of wildfire occurrences may be idealized as a realization of some stochastic process. In particular, we may use a space–time point pattern approach for the analysis and inference process. We studied wildfires in Catalonia, a region in the north-east of the Iberian Peninsula, and we analyzed the spatio-temporal patterns produced by those wildfire incidences by considering the influence of covariates on trends in the intensity of wildfire locations. A total of 3,166 wildfires from 1994–2008 have been recorded. We specified spatio-temporal log-Gaussian Cox process models. Models were estimated using Bayesian inference for Gaussian Markov Random Field through the integrated nested Laplace approximation algorithm. The results of our analysis have provided statistical evidence that areas closer to humans have more human induced wildfires, areas farther have more naturally occurring wildfires. We believe the methods presented in this paper may contribute to the prevention and management of those wildfires which are not random in space or time.     

Response of benthic foraminifera to heavy metal contamination in marine sediments (Sicilian coasts,Mediterranean Sea)

To examine the suitability of benthic foraminifera and their test deformations as bioindicators of pollution in coastal marine environments, we studied foraminifera and metal concentrations in 72 marine sediment samples, collected from the inner shelf along the Sicilian coast (Gulfs of Palermo and Termini) and on the south-eastern coast of Lampedusa Island. These areas are characterised by different environmental conditions. On the basis of pollution sources and foraminiferal assemblages, we recognised different zones in the Gulf of Palermo. The most polluted zones showed high metal concentrations, and low diversity of benthic foraminifera with species typical of stressed environments. By contrast, the lowest polluted zones showed a high population density and the highest percentages of epiphytes. Epiphytes were abundant where a Posidonia oceanica meadow was present and decreased in the most polluted zones. Sediments of the Gulf of Termini and Lampedusa exhibited high percentages of benthic foraminifera typical of well-oxygenated waters and low concentrations of metals, with the exception of sites located near sewage outfalls and harbour areas. Furthermore, even though deformed tests are commonly known in natural stressed environmental conditions, this study shows that in the most polluted zones, benthic foraminifera were characterised by the highest percentages of deformed individuals.