Phytotoxicity of silver nanoparticles to Lemna minor L

The use of silver nanoparticles (AgNPs) in commercial products has increased significantly in recent years. Although there has been some attempt to determine the toxic effects of AgNPs, there is little information on aquatic plants which have a vital role in ecosystems. This study reports the use of Lemna minor L. clone St to investigate the phytotoxicity of AgNPs under modified OECD test conditions. AgNPs were synthesised, characterised and subsequently presented to the L. minor. Results showed that inhibition of plant growth was evident after exposure to small (∼20 nm) and larger (∼100 nm) AgNPs at low concentrations (5 μg L⁻¹) and this effect became more acute with a longer exposure time. There was a linear dose-response relationship after 14 d exposure. Using predicted environmental concentrations for wastewaters it was found that AgNPs may pose a significant potential risk to the environment.     

Influence of waste input and combustion technology on MSWI bottom ash quality

The waste input and the process technology of waste incineration plants appear to have a great influence on bottom ash quality. To better understand how these parameters can affect the characteristics of residues, bottom ash from six plants were tested and compared in this study. Bottom ash physico-chemical characteristics were investigated by chemical analyses, and leaching tests. In order to understand their long-term behavior, accelerated ageing experiments and biodegradation tests were also performed. The whole analyses gave complementary information. It was shown that the six samples do have different properties. Waste inputs have a great influence on Cl and S content in bottom ash, as well as on the Ca/Si ratio. The importance of this ratio on the carbonation process has been demonstrated. Combustion parameters have an influence on the quantity and mobility of the residual organic matter.     

Developmental dental defects in children exposed to PCBs in eastern Slovakia

The effects of long-term exposure to polychlorinated biphenyls (PCBs) on developmental dental defects of deciduous and permanent teeth in children in eastern Slovakia, where PCBs from a chemical plant manufacturing Delors contaminated the surrounding district were evaluated. Four hundred and thirtytwo children, lifelong residents, aged 8-9 years were examined. Children's caries susceptibility and gingival health was assessed by standard dental indices, and developmental enamel defects by the FDI index. Data from the PCBRISK project data set and questionnaires completed by the parents provided information on exposure and various confounding factors. The proportion of teeth with different types and extensions of developmental enamel defects correlated with serum PCB concentration. The proportion of deciduous teeth affected with enamel defects was significantly higher in higher exposed children (chi(2)=8.35; p=0.03) according to their serum PCB concentration (group 0: <200; group 1: 200-600; group 2: >600 ng PCBs g(-1) serum lipids). The proportion of permanent teeth affected with any enamel defect was significantly higher in higher exposed children (chi2=7.237; p=0.027). Furthermore, the extent of the enamel defects was also greater (chi2=10.714; p=0.005). In multivariate linear regression analysis PCB exposure was significantly related to developmental enamel defects of permanent teeth only. No associations between PCB exposure and caries susceptibility, gingival health or number of teeth were observed. This study demonstrated a dose-response relationship between PCB exposure and developmental enamel defects of permanent teeth in children, the evidence for deciduous teeth was not conclusive.     

Matrix effects on the de novo synthesis of polychlorinated dibenzo-p-dioxins, dibenzofurans, biphenyls and benzenes

The formation of polychlorinated dibenzo-p-dioxins, dibenzofurans, biphenyls and benzenes in de novo synthesis experiments have been studied on model fly ashes with a wide range of matrices. The model fly ash consisted of 18 selected matrices with the addition of CuCl(2) x 2H(2)O, activated charcoal and NaCl. The studied matrices were not restricted to the commonly investigated matrices with defined chemical composition (silica gel, alumina, florisil) and industrially produced adsorbents with silicate structures (diatomaceous earths), but also included natural occurring matrices (clays, kaolin, bentonite and feldspars). In addition fly ashes from a hazardous waste incinerator were included in the study for comparison. Differences in the isomer composition (homologue profiles and isomer patterns) of the substances formed by de novo synthesis experiments are discussed in dependence on the chemical composition of the studied matrices. The de novo synthesis experiments on matrices with silicate structures resulted in high concentration of mainly perchlorinated aromatic compounds while for other matrices in particular alkaline matrices a homologue shift to lower chlorinated homologues and lower formation rates were found. The paper discusses the resulting PCDD/PCDF pattern and compares them to the PCDD/PCDF profile found in naturally occurring kaolin and ball clay (illite).     

Herbivorous amphipods inhabit protective microhabitats within thalli of giant kelp <Emphasis Type="Italic">Macrocystis pyrifera</Emphasis>

Many small marine herbivores utilize specific algal hosts, but the ultimate factors that shape host selection are not well understood. For example, the use of particular microhabitats within algal hosts and the functional role of these microhabitats have received little attention, especially in large algae such as kelps. We studied microhabitat use of the herbivorous amphipod Peramphithoe femorata that inhabits nest-like domiciles on the blades of giant kelp Macrocystis pyrifera. The vertical position of nest-bearing blades along the stipe of the algal thallus and the position of the nests within the lateral blades of M. pyrifera were surveyed in two kelp forests in northern-central Chile. Additionally, we conducted laboratory and field experiments to unravel the mechanisms driving the observed distributions. Peramphithoe femorata nests were predominantly built on the distal blade tips in apical sections of the stipes. Within-blade and within-stipe feeding preferences of P. femorata did not explain the amphipod distribution. Amphipods did not consistently select distal over proximal blade sections in habitat choice experiments. Mortality of tethered amphipods without nests was higher at the seafloor than at the sea surface in the field. Nests mitigated mortality of tethered amphipods, especially at the seafloor. Thus, protective microhabitats within thalli of large kelp species can substantially enhance survival of small marine herbivores. Our results suggest that differential survival from predation might be more important than food preferences in determining the microhabitat distribution of these herbivores.     

Foliar uptake and metal(loid) bioaccessibility in vegetables exposed to particulate matter

At the global scale, high concentrations of particulate matter (PM) enriched with metal(loid)s are currently observed in the atmosphere of urban areas. Foliar lead uptake was demonstrated for vegetables exposed to airborne PM. Our main objective here was to highlight the health risk associated with the consumption of vegetables exposed to foliar deposits of PM enriched with the various metal(loid)s frequently observed in the atmosphere of urban areas (Cd, Sb, Zn and Pb). Leaves of mature cabbage and spinach were exposed to manufactured mono-metallic oxide particles (CdO, Sb₂O₃ and ZnO) or to complex process PM mainly enriched with lead. Total and bioaccessible metal(loid) concentrations were then measured for polluted vegetables and the various PM used as sources. Finally, scanning electronic microscopy coupled with energy dispersive X-ray microanalysis was used to study PM–phyllosphere interactions. High quantities of Cd, Sb, Zn and Pb were taken up by the plant leaves. These levels depended on both the plant species and nature of the PM, highlighting the interest of acquiring data for different plants and sources of exposure in order to better identify and manage health risks. A maximum of 2 % of the leaf surfaces were covered with the PM. However, particles appeared to be enriched in stomatal openings, with up to 12 % of their area occupied. Metal(loid) bioaccessibility was significantly higher for vegetables compared to PM sources, certainly due to chemical speciation changes. Taken together, these results confirm the importance of taking atmospheric PM into account when assessing the health risks associated with ingestion of vegetables grown in urban vegetable crops or kitchen gardens.     

Establishing conversation spaces in hastily formed networks: the worst fire in modern Swedish history

In presenting examples from the most extensive and demanding fire in modern Swedish history, this paper describes challenges facing hastily formed networks in exceptional situations. Two concepts that have been used in the analysis of the socio‐technical systems that make up a response are conversation space and sensemaking. This paper argues that a framework designed to promote understanding of the sensemaking process must take into consideration the time and the location at which an individual is engaged in an event. In hastily formed networks, location is partly mediated through physical systems that form conversation spaces of players and their interaction practices. This paper identifies and discusses four challenges to the formation of shared conversation spaces. It is based on the case study of the 2006 Bodträskfors forest fire in Sweden and draws on the experiences of organised volunteers and firefighters who participated in a hastily formed network created to combat the fire.