Distribution of PAHs and trace metals in urban stormwater sediments: combination of density fractionation,mineralogy and microanalysis

Sediment management from stormwater infiltration basins represents a real environmental and economic issue for stakeholders due to the pollution load and important tonnages of these by-products. To reduce the sediment volumes to treat, organic and metal micropollutant-bearing phases should be identified. A combination of density fractionation procedure and microanalysis techniques was used to evaluate the distribution of polycyclic aromatic hydrocarbons (PAHs) and trace metals (Cd, Cr, Cu, Ni, Pb, and Zn) within variable density fractions for three urban stormwater basin sediments. The results confirm that PAHs are found in the lightest fractions (d?d??3) whereas trace metals are equally distributed within the light, intermediary, and highest fractions (d?d?d?d?>?2.8 g cm^?3) and are mostly in the 2.3?d??3 fraction. The characterization of the five fractions by global analyses and microanalysis techniques (XRD and MEB-EDX) allowed us to identify pollutant-bearing phases. PAHs are bound to the organic matter (OM) and trace metals to OM, clays, carbonates and dense particles. Moreover, the microanalysis study underlines that OM is the main constituent responsible for the aggregation, particularly for microaggregation. In terms of sediment management, it was shown that density fractionation is not suitable for trace metals but could be adapted to separate PAH-enriched phases.     

Social feeding in ladybird beetles: adaptive significance and mechanism

Summary. Young larvae of Adalia bipunctata search an area more intensively when exposed to the odour from other larvae feeding on aphids than when exposed only to the odour of aphids. In an olfactometer young larvae were significantly attracted either to the odour of crushed aphids or larvae feeding on aphids, but not to that of aphids, larvae, larvae plus aphids or larvae feeding on an artificial diet. That is, the change in searching behaviour appears in response to a volatile released by aphids when attacked. The odour released by crushed aphids is made up entirely of aphid alarm pheromone, β-farnesene. It is likely that the adaptive significance of this response is that it increases the ability of larvae to locate larvae that have already caught prey. By sharing the aphid kill of another larva it is likely that a first instar ladybird larva greatly increases its probability of surviving to the next instar. It is suggested that this social feeding is facilitated by egg clustering, which also may additionally account for why aphidophagous ladybirds lay their eggs in clusters. Received 28 February 2000; accepted 24 March 2000     

Packing material formulation for odorous emission biofiltration

In biological gas treatment, like biofiltration of volatile organic compounds or odorous substances, the microbial nutritional needs could be a key factor of the process. The aim of this work is to propose a new packing material able to provide the lacking nutrients. In the first part of this study, two kinds of material composed of calcium carbonate, an organic binder and two different nitrogen sources, ammonium phosphate and urea phosphate (UP), were compared. The new supports present bulk densities between 0.88 and 1.15g cm(-3), moisture retention capacities close to 50% and 70%, and water cohesion capacities greater than six months for the material with 20% binder. In the second part, oxygen consumption measurements in liquid experiments show that these packing materials could enhance bacterial growth compared to pine bark or pozzolan and have no inhibitory effect. The biodegradation of different substrates (sodium sulfide and ammonia) and the support colonization by the biomass were evaluated. Finally, UP 20 was chosen and tested in a hydrogen sulfide or ammoniac biofiltration process. This showed that, for H2S concentrations greater than 100mg m(-3), UP 20 has a real advantage over pine bark or pozzolan.     

Effect of the bacterial pyoverdine siderophore on the phytoextraction of cesium from illite

Environmental Chemistry Letters - Radioactive Cs contamination is a major concern in case of a nuclear accident such as the Fukushima accident in 2011. Remediation methods have been proposed...