Determination of zinc speciation in basic oxygen furnace flying dust by chemical extractions and X-ray spectroscopy

There is a growing concern regarding the environmental and public health risks associated with airborne particulate matter (PM). The basic oxygen furnace is one of the most important atmospheric dust sources of the steel manufacturing process. It emits dust enriched in heavy metal such as Zn, which is assumed to contribute to the toxic potential of atmospheric PM. Dust collected before and after the filtration system was analyzed to determine Zn speciation. To this end, a variety of analytical tools were used and a sequential extraction protocol has been specifically developed for iron and steel dust. The Zn speciation results obtained by EXAFS and sequential extraction were in excellent agreement. Before filtration, the speciation of Zn in BOF was 43% ZnFe₂O₄, 23% ZnCO₃ and 16% ZnO. The same species were detected after filtration with different proportions. BOF dust after filtration contains more soluble Zn phases which may play a role in the toxic effects of the emissions.     

The Pb pollution fingerprint at Lochnagar: the historical record and current status of Pb isotopes

Ratios of 206Pb/207Pb in a Lochnagar sediment core slowly decline from c. 1.32 at 140 cm to c. 1.23 at 9 cm, and then rapidly decline to c. 1.15 at the surface. Ninety percent of the Pb in the surface sediments can be attributed to anthropogenic sources. The 206Pb/207Pb ratio data imply that catchment peat surface contains a higher fraction of anthropogenic Pb than the sediment surface. The 206Pb/207Pb ratios in the surface of the sediment core are consistent with ratios in trapped sediments collected annually between 1998 and 2003. However, there is no significant decline in these recent samples suggesting that the reduction in atmospheric Pb emissions has not yet been recorded by the sediments due to Pb inputs from the catchment. As catchment peats store about 840 kg previously deposited anthropogenic Pb since 1860, it is likely that catchment inputs will continue to affect future 206Pb/207Pb ratios.     

The role of humic non-exchangeable binding in the promotion of metal ion transport in groundwaters in the environment

Metal ions form strong complexes with humic substances. When the metal ion is first complexed by humic material, it is bound in an 'exchangeable' mode. The metal ion in this fraction is strongly bound, however, if the metal-humic complex encounters a stronger binding site on a surface, then the metal ion may dissociate from the humic substance and be immobilised. However, over time, exchangeably-bound metal may transfer to a 'non-exchangeable' mode. Transfer into this mode and dissociation from it are slow, regardless of the strength of the competing sink, and so immobilisation may be hindered. A series of coupled chemical transport calculations has been performed to investigate the likely effects of non-exchangeable binding upon the transport of metal ions in the environment. The calculations show that metal in the non-exchangeable mode will have a significantly higher mobility than that in the exchangeable mode. The critical factor is the ratio of the non-exchangeable first-order dissociation rate constant and the residence time in the groundwater column, metal ion mobility increasing with decreasing rate constant. A second series of calculations has investigated the effect of the sorption to surfaces of humic/metal complexes on the transport of the non-exchangeably bound metal. It was found that such sorption may reduce mobility, depending upon the humic fraction to which the metal ion is bound. For the more weakly sorbing humic fractions, under ambient conditions (humic concentration etc.) the non-exchangeable fraction may still transport significantly. However, for the more strongly sorbed fractions, the non-exchangeable fraction has little effect upon mobility. In addition to direct retardation, sorption also increases the residence time of the non-exchangeable fraction, giving more time for dissociation and immobilisation. The non-exchangeable dissociation reaction, and the sorption reaction have been classified in terms of two Damkohler numbers, which can be used to determine the importance of chemical kinetics during transport calculations. These numbers have been used to develop a set of rules that determine when full chemical kinetic calculations are required for a reliable prediction, and when equilibrium may be assumed, or when the reactions are sufficiently slow that they may be ignored completely.     

Economic resilience to natural and man-made disasters: Multidisciplinary origins and contextual dimensions

Economic resilience is a major way to reduce losses from disasters. Its effectiveness would be further enhanced if it could be precisely defined and measured. This paper distinguishes static economic resilience—efficient allocation of existing resources—from dynamic economic resilience—speeding recovery through repair and reconstruction of the capital stock. Operational definitions are put forth that incorporate this important distinction. The consistency of the definitions is examined in relation to antecedents from several disciplines. The effectiveness of economic resilience is evaluated on the basis of recent empirical studies. In addition, its potential to be enhanced and eroded is analyzed in various contexts.     

Zur chemie der marsoberfläche

Analyses of 13 samples of Martian surface materials with the Viking X-ray fluorescence spectrometers show SiO₂ similar to that of terrestrial mafic rocks, whereas Fe₂O₃, Cl, and S are higher and Al₂O₃, K₂O, Rb, Sr, Y, and Zr are lower. Low totals suggest presence of CO₂, H₂O, and Na₂O. Duricrust fragments are higher in S than fines, but samples from both landing sites are surprisingly similar. We suggest that Martian surface materials are aeolian deposits of complex mixtures of weathering products of maficultramafic rocks, possibly consisting of iron-rich clays, sulfates, iron oxides, carbonates, and chlorides.     

Die räumliche Orientierung vonParamecium aurelia

The Science of Nature -     

Spatial and Temporal Comparison of Polycyclic Aromatic Hydrocarbons and Spheroidal Carbonaceous Particles in Remote European Lakes

Spheroidal carbonaceous particles (SCP) and polycyclicaromatic hydrocarbons (PAH) have been measured in the dated sediment cores of 10 remote lakes distributed across Europe. The geographic trends were evaluated by examination of the superficial sediment fluxes and total sediment inventories. The highest levels of both markers were observed in the Eastern European lakes whereas the minimal values corresponded to the lake located in the Arctic. However, this SCP-PAH correlation was not observed after exclusion of the end member lakes from the series. The temporal trends of both pollutant markers are consistent with the history of pyrolytic emissions over Europe. However, the downcore SCP distributions are shorter than the PAH profiles in nearly all lakes. The differences are probably related to the different size particle fractions involved in the measurement of each marker, >5 and >1 m for SCP and PAH, respectively. Thus, the two proxies probably reflect pollution inputs from closer (SCP) and more distant sites (PAH).     

Chloramine demand estimation using surrogate chemical and microbiological parameters

A model is developed to enable estimation of chloramine demand in full scale drinking water supplies based on chemical and microbiological factors that affect chloramine decay rate via nonlinear regression analysis method. The model is based on organic character (specific ultraviolet absorbance (SUVA)) of the water samples and a laboratory measure of the microbiological (F m ) decay of chloramine. The applicability of the model for estimation of chloramine residual (and hence chloramine demand) was tested on several waters from different water treatment plants in Australia through statistical test analysis between the experimental and predicted data. Results showed that the model was able to simulate and estimate chloramine demand at various times in real drinking water systems. To elucidate the loss of chloramine over the wide variation of water quality used in this study, the model incorporates both the fast and slow chloramine decay pathways. The significance of estimated fast and slow decay rate constants as the kinetic parameters of the model for three water sources in Australia was discussed. It was found that with the same water source, the kinetic parameters remain the same. This modelling approach has the potential to be used by water treatment operators as a decision support tool in order to manage chloramine disinfection.     

Occurrence and Trend of Hepatitis A Virus in Bivalve Molluscs Production Areas Following a Contamination Event

The aim of this study was to assess the trend of hepatitis A virus (HAV) in a coastal zone impacted by a contamination event, providing data for the development of management strategies. A total of 352 samples, including four bivalve mollusc species (Mytilus galloprovincialis, Solen vagina, Venus gallina and Donax trunculus), were taken over a period of 6 months from 27 production areas of the coast and analysis were performed according to ISO/TS 15216-1:2013. HAV presence was detected in 77 samples from 11 production areas and all positive results were related to samples collected in the first 3 months of the surveillance, during which HAV prevalence was 39.9% and values as high as 5096 genome copies/g were detected. A progressive reduction of viral contamination was evident during the first trimester of the monitoring, with prevalence decreasing from 78.8% in the first month, to 37.8% in the second and 3.9% in the third and quantitative levels reduced from an average value of 672 genome copies/g to 255 genome copies/g over a period of 4 weeks (virus half-life: 21.5 days). A regression analysis showed that, during the decreasing phase of the contamination, the data fitted a reciprocal quadratic model (Ra² = 0.921) and, based on the model, a residual presence of HAV could be estimated after negativization of the production areas. The statistical analysis of the results per shellfish species and per production area showed that there were limited differences in contamination prevalence and levels among diverse bivalve species, while a statistically significant difference was present in quantitative levels of one production area. These data could be useful for the development of both risk assessment models and code of practice for the management of viral contamination in primary production.