The hygroscopic behaviour of individual aerosol particles in nickel refineries as investigated by environmental scanning electron microscopy

The hygroscopic properties of individual aerosol particles (1-35 microm equivalent projected area diameter) from the Roasting, Anode Casting and Electrorefining Departments of two Ni refineries were studied by environmental scanning electron microscopy (ESEM) and energy-dispersive X-ray microanalysis (EDX) at a relative humidity of 96-98% (at a temperature of 5 degrees C). In the Roasting and Anode Casting Departments, most particles (60-85% by number) showed no visible change in size or surface morphology when exposed to high relative humidity. Approximately 15-30% of the particles developed a thin water film (growth factors between 1.006 and 1.06) indicating the presence of thin surface coatings of sulfates. About 10% of the particles in the Roasting Department formed droplets (growth factors between 1.1 and 2.6) which always contained a large portion of insoluble material. In the Electrorefining Department, most particles (approximately 60%) were residues from the electrolysis bath solution. At a relative humidity of 96-98% these particles formed a solution which contained only small insoluble inclusions. About 30% of the particles in the Electrorefining Department developed thin water films. As only a small fraction of the particles increased substantially in size when exposed to high relative humidity, the deposition pattern of the total aerosol mass fraction will not be changed substantially by hygroscopic growth. The frequent occurrence of thin surface coatings of soluble material on insoluble Ni compounds has to be considered for health assessment purposes.     

Evaluation of confocal laser scanning microscopy for enumeration of virus-like particles in aquatic systems

Abundances of virus-like particles (VLPs, mostly bacteriophages) are high in aquatic environments; therefore, techniques for precise enumeration are essential in ecological monitoring. VLPs were determined after staining with SYBR Gold by conventional epifluorescence microscopy and compared to enumerations performed by confocal laser scanning microscopy (CLSM). In order to assess the potential of CLSM for viral direct counts (VDCs), we processed samples from different freshwater and marine systems. Optical sectioning by CLSM and production of an overlay picture of multiple scans enables the often uneven whole investigated filter area to be brought to the plane of focus. This allows for subsequent image analysis of digitally created high-quality images. Another advantage using the CLSM was that the short spot excitation of the stain via laser beam minimized fading of the stain. The VDC results show that there is no significant difference between the two methods. Regarding the known difficulties of viral abundance estimates on particulate material, CLSM was further applied to enumerate VLPs on a small set of marine transparent exopolymeric particles sampled from the Atlantic Ocean. Our data suggest that CLSM is a useful tool to count viruses in water samples as well as attached to certain types of aquatic aggregates.     

Classification of particles from the farm environment by automated sizing, counting and chemical characterisation with scanning electron microscopy-energy dispersive spectroscopy

About 60,000 particles in 288 aerosol samples collected during farm work have been characterised with automated particle analysis using scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). Based on EDS-analysis of materials with known composition (potato flour, alpha-quartz, K-feldspar and beta-wollastonite), criteria were developed for classification of particles as: (1) organic, (2) silicon-rich (silica), and (3) other inorganic particles. The reproducibility of the relative mass proportions in dust samples collected during farm work was 0.078 when approximately 200 particles were characterised per sample. Field samples from the farm environment showed clear differences in composition. Generally, inorganic particles dominated the particle mass. The proportion of the organic particle mass was highest for tending of swine and poultry, 55 and 38% respectively. Silica particles amounted to 10 to 20% of the total mass during handling crops, e.g. grain, straw, hay, potatoes, and onions. It seems likely that the results can be used in etiologic studies, but further validation would be needed for quantitative purposes.     

The heterogeneous composition of working place aerosols in a nickel refinery: a transmission and scanning electron microscope study

Size, morphology and chemical composition of individual aerosol particles collected in a nickel refinery were analyzed by scanning electron microscopy and energy-dispersive X-ray microanalysis (EDX). The phase composition was determined by selected area electron diffraction and EDX in a transmission electron microscope. Most particles are heterogeneous on a nanometer scale and consist of various phases. Nickel phases observed in the roasting and anode casting departments include metallic nickel, bunsenite (NiO), trevorite (Ni,Cu)Fe2O4, heazlewoodite Ni3S2, godlevskite (Ni,Cu)9S8, orthorhombic NiSO4 and an amorphous Ni,Cu.Al,Pb sulfate of variable composition. Additional phases encountered include corundum (Al2O3), murdochite (PbCu6O8), hexagonal Na2SO4, anhydrite (CaSO4), graphite (C) and amorphous carbon. The implications of the occurrence of the different Ni phases and their nanometer size for the study of adverse health effects are explored.     

Beryllium natural background concentration and mobility: a reappraisal examining the case of high Be-bearing pyroclastic rocks

Beryllium is widely distributed in soils at low levels, but it can also occur naturally in higher concentrations in a variety of materials exploited for many industrial applications. Beryllium is also one of the most toxic natural elements and is known to be a human carcinogen. A concise account of the literature data on baseline concentrations of Be in soils illustrates the possibility of worldwide presence of areas with a high natural background concentration of Be (up to 300 mg/kg), the crustal abundance of which is generally estimated to be in the range 2–6 mg/kg. Nevertheless, the number of available data is rather limited in comparison with those about other toxic elements such as Pb, Cd and Cr. This has probably caused the choice of low values of concentration level as the reference for the definition of soil contamination: these values are not always realistic and are not applicable to large areas. As a case study, we report and analyse a diffuse, unusually high (up to 80 mg/kg, average approximately 20 mg/kg), natural occurrence of beryllium in loose and poorly consolidated pyroclastic layers related to the Pleistocene activity of the Vico volcano. Additionally, the analysis of Be leachability has been carried out, providing evidence of a not negligible mobility in contrast with the scarce data presented in the literature that usually indicate beryllium as an element with low mobility in oxidising surface environmental conditions. This research marks the beginning of a possible reappraisal of beryllium geochemical behaviour and background levels, providing more realistic reference values for risk assessment and land management.     

Organophosphate and phthalate esters in indoor air: a comparison between multi-storey buildings with high and low prevalence of sick building symptoms

An extensive study has been conducted on the prevalence of organophosphorous flame retardants/plasticizers and phthalate ester plasticizers in indoor air. The targeted substances were measured in 45 multi-storey apartment buildings in Stockholm, Sweden. The apartment buildings were classified as high or low risk with regard to the reporting of sick building symptoms (SBS) within the project Healthy Sustainable Houses in Stockholm (3H). Air samples were taken from two to four apartments per building (in total 169 apartments) to facilitate comparison within and between buildings. Association with building characteristics has been examined as well as association with specific sources by combining chemical analysis and exploratory uni- and multivariate data analysis. The study contributes to the overall perspective of levels of organophosphate and phthalate ester in indoor air enabling comparison with other studies. The results indicated little or no difference in the concentrations of the target substances between the two risk classifications of the buildings. The differences between the apartments sampled within (intra) buildings were greater than the differences between (inter) buildings. The concentrations measured in air ranged up to 1200 ng m(-3) for organophosphate esters and up to 11?000 ng m(-3) for phthalate esters. Results in terms of sources were discerned e.g. PVC flooring is a major source of benzylbutyl phthalate in indoor air.