Assessment of the PCDD/F fate from MSWI residue used in road construction in France

MSWI fly ash is susceptible to contain high amount of polychlorinated dibenzo-dioxins and polychlorinated dibenzo-furans. However, the use of MSWI residue for road construction started in France at a period when MSWI Bottom Ash and MSWI fly ash were not separated. From four old road sites, MSWI residue, road soils, reference soils and geo-textiles were sampled and their PCDD/F contents were analyzed. MSWI residue show a great heterogeneity but also high amounts of PCDD/F (14-2960 ng I-TEQ kg(-1)dm). Soils underlying the road show less heterogeneity and PCDD/F contents between 0.57 and 7.23 ng I-TEQ kg(-1)dm, lower than ordinary soils. Moreover, the specific analysis of the 17 toxic PCDD/F congeners (notably the 2,3,7,8-TetraCDD) indicates the very low harmfulness of road soils. The study also allows to assert the relation between the MSWI residue particle size and the PCDD/F content.     

MSWI bottom ash used as basement at two pilot-scale roads: Comparison of leachate chemistry and reactive transport modeling

The recycling of municipal solid waste incineration bottom ash as aggregates for road basement requires assessing the long-term evolution of leachate chemistry. The Dåva (Sweden) and Hérouville (France) pilot-scale roads were monitored during 6 and 10 years, respectively. Calculated saturation indices were combined to batch test modeling to set a simplified geochemical model of the bottom ash materials. A common reactive transport model was then applied to both sites. At Hérouville, pH and the concentration of most elements quickly drop during the first two years to reach a set of minimum values over 10 years. The decrease is less pronounced at Dåva. The evolutions of pH and major element concentrations are fairly well related to the following pH-buffering sequence: portlandite, C-S-H phases or pseudo-wollastonite and, finally, calcite in equilibrium with atmospheric CO₂. Al(OH)₃, barite, ettringite and monohydrocalcite may also control leachate chemistry. Cu release is correctly modeled by DOM complexation and tenorite equilibrium. Temperature has no significant effect on the modeling of leachate chemistry in the range 5-30 °C, except at high pH. Effects at road edges and roadside slopes are important for the release of the less reactive elements and, possibly, for carbonation processes.     

Tolerance to agricultural pesticides of strains belonging to four genera of Rhizobiaceae

In order to determine their tolerance to pesticides, 122 strains of rhizobia isolated from different geographical regions, and belonging to the genera Rhizobium, Mesorhizobium, Sinorhizobium and Bradyrhizobium were tested against eight herbicides, four fungicides and five insecticides. Sensitivity to the pesticides was measured by using the filter paper disk method at four concentrations, 0.45, 4.5, 45 and 450 μg per disk. When the pesticides were used at 0.45 μg per disk, a concentration similar to that found when pesticides are applied under field conditions, no inhibition was observed. Strains growth was affected at concentrations of 45 and 450 μg pesticide per disk. These higher concentrations can be encountered when seeds are treated with pesticides. Pesticides tolerance level was correlated to pesticide function, i.e rhizobial strains were more tolerant to insecticides, followed by herbicides and then fungicides. Two fungicides, captan and mancozeb, inhibited the highest number of strains. Only one insecticide, carbaryl, affected the growth of some rhizobial strains. Strains isolated from the arctic (Mesorhizobium spp. and R. leguminosarum bv. viciae), a putative pesticides-free environment, were either less or equally affected by pesticides compared to strains isolated from agricultural regions.     

Modelling of long-term dynamic leaching tests applied to solidified/stabilised waste

The paper aims at simulating the closed-system dynamic leaching of a cement-based monolith containing lead with the numerical reactive transport code HYTEC in a 3D-cylindrical geometry. The model considers, simultaneously, the chemical evolution of pore water, the progression of mineralogical alteration fronts, and the concomitant release of elements from the S/S waste. In good agreement with the experiment, element releases were found to be mainly controlled by either diffusion (Na, K, and, to a lesser extent, Cl), by surface dissolution (Ca, Si) or by a mixed evolution (Pb, SO4). All of the calculated mineralogical transformations take place in a thin layer beyond the monolith surface. Consequently, modelling of Ca, Si and SO4 releases was quite sensitive to the node size of the simulation grid and was improved by taking into account the increase of porosity and effective diffusion coefficient due to mineral dissolution in the leached layer. In agreement with experimental results, the deepest front corresponds under closed-system conditions to portlandite dissolution and calcium silicate hydrates CSH 1.8 transformation into CSH of lower Ca/Si ratio. A second, distinct and intermediate, front is made by ettringite dissolution. The network of CSH is globally preserved in the leached layer, complete dissolution occurring over a very small thickness only. Finally, hydrotalcite precipitation in the leached layer is expected by modelling due to pH drop.     

Neurotoxicity and oxidative stress induced by permethrin in gills of the freshwater mussel Unio ravoisieri

Pyrethroids are contaminants found in the aquatic environment, and their toxicological effects on aquatic organisms have received extensive attention. However, the impact on freshwater bivalve of exposure to these chemicals is still largely unknown. Freshwater mussels Unio ravoisieri were exposed to two nominal permethrin (PM) concentrations C1?=?50?µg/L and C2?=?100?µg/L during 7 days. The measured concentrations of PM using gas chromatography (GC/ECD) in the treated aquariums were, respectively, 28.7–62.3?µg/L. Catalase (CAT), Glutathione-S-transferase (GST), and Acetylcholinesterase (AChE) activities, Glutatione (GSH) and Malondialdehyde (MDA) levels were determined in gills of U. ravoisieri. Significant increase in CAT activity by the lowest concentration and decrease by highest concentration were observed. Additionally, GST activity was increased in a concentration-dependent manner. However, statistically significant decrease in GSH levels (about 39%) was observed only at high concentration of this compound (100?µg/L). PM generated an increase in MDA levels reaching the highest value at the high concentration. AChE activity of mussel ranging from 51% inhibition at lowest concentration 50?µg/L to 89% inhibition at highest concentration 100?µg/L. The results indicated that oxidative stress and cell damage might be one of the main mechanisms of PM toxicity to freshwater mussels.