Characterization of individual aerosol particles in workroom air of aluminium smelter potrooms

Aerosol particles with aerodynamic diameters between 0.18 and 10 microm were collected in the workroom air of two aluminium smelter potrooms with different production processes (Soderberg and Prebake processes). Size, morphology and chemical composition of more than 2000 individual particles were determined by high resolution scanning electron microscopy and energy-dispersive X-ray microanalysis. Based on chemical composition and morphology, particles were classified into different groups. Particle groups with a relative abundance above 1%(by number) include aluminium oxides, cryolite, aluminium oxides-cryolite mixtures, soot, silicates and sea salt. In both production halls, mixtures of aluminium oxides and cryolite are the dominant particle group. Many particles have fluoride-containing surface coatings or show agglomerations of nanometer-sized fluoride-containing particles on their surface. The phase composition of approximately 100 particles was studied by transmission electron microscopy. According to selected area electron diffraction, sodium beta-alumina (NaAl(11)O(17)) is the dominant aluminium oxide and cryolite (Na(3)AlF(6)) the only sodium aluminium fluoride present. Implications of our findings for assessment of adverse health effects are discussed.     

Peak exposures in aluminium potrooms: instrument development and field calibration

Aluminium smelter potrooms are unique in that workplace exposures to hydrogen fluoride (HF), sulfur dioxide (SO2), and particulate matter occur simultaneously for some tasks. The peak exposures to these contaminants are of increasing interest in discovering the etiology of respiratory health effects. While a variety of direct-reading instruments are available for sulfur dioxide and particulate matter, only a few exist for hydrogen fluoride. The sensors in these HF instruments have a cross-sensitivity to sulfur dioxide making it difficult to monitor HF in an environment that also contains SO2. To overcome this problem, we assessed the simultaneous use of two electrochemical instruments: one with a SO2 sensor that does not respond to HF and the second with a hydrogen fluoride sensor that responds to both HF and SO2 in a 1 : 1 ratio, termed 'total acid gas'. The difference in the response between the two instruments should indicate the HF concentration: [HF + SO2] minus SO2 equals HF. The performance characteristics of this sampling train were evaluated in the laboratory through the generation of both HF and SO2 with permeation tubes. The response and recovery times for the SO2 only instrument were acceptable (6 and 15 s, respectively), but the "total acid gas" instrument exhibited both slow response and slow recovery approaching three and six min. The association between the traditional integrated filter sampling method and the direct-reading instrument for SO2 is 0.80 (Spearman's rho). The use of the digital filter strengthens the association between the HF direct-reading instrument and the integrated samples from 0.41 to 0.68.     

Ultrafine particles at workplaces of a primary aluminium smelter

The number concentration and size distribution of ultrafine particles in a S?derberg and a prebake potroom of an aluminium primary smelter have been measured using a scanning mobility particle spectrometer. The particle morphology was studied by transmission electron microscopy (TEM). The study shows the existence of elevated number concentrations of ultrafine particles in both potrooms. The main source of these particles is likely to be the process of anode changing. The ultrafine particles were measured directly at the source but could also be identified as episodes of high number concentrations in the general background air. Unlike the larger particles belonging to the 50-100 nm mode, the nanoparticle mode could not be detected in the TEM indicating that they may not be stable under the applied sampling conditions and/or the high vacuum in the instrument.     

Methodology for designing air quality monitoring networks: I. Theoretical aspects

An objective methodology is presented for determining the number and disposition of ambient air quality stations in a monitoring network for the primary purpose of compliance with air quality standards. The methodolgy utilizes a data base with real or simulated data from an air quality dispersion model for application with a two-step process for ascertaining the optimal monitoring network. In the first step, the air quality patterns in the data base are collapsed into a single composite pattern through a figure-of-merit (FOM) concept. The most desirable locations are ranked and identified using the resultant FOM fields. In the second step the network configuration is determined on the basis of the concept of spheres of influence (SOI) developed from cutoff values of spatial correlation coefficients between potential monitoring sites and adjacent locations. The minimum number of required stations is then determined by deletion of lower-ranked stations whose SOIs overlap. The criteria can be set to provide coverage of less than some fixed, user-provided percentage of the coverage of tha SOIs of the higher ranked stations and for some desired level of minimum detection capability of concentration fluctuations.The methodology is applied in a companion paper (McElroy et al., 1986) to the Las Vegas, Nevada, metropolitan area for the pollutant carbon monoxide.Although the research described in this article has been funded wholly or in part by the United States Environmental Protection Agency through Contract No. 68-03-2446 to Systems Applications, Inc., it has not been subjected to Agency review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred.     

Long-term fate of polycyclic aromatic hydrocarbons (PAH) in sediments from Loch Leven after closure of an aluminium smelter

An aluminium smelter discharged polycyclic aromatic hydrocarbons (PAHs) into Loch Leven on the west of Scotland from 1907 until it closed in 2000, resulting in elevated PAH concentrations in the sediment. A temporal monitoring programme to investigate any recovery in sediment concentrations began in 2004, with sampling each year until 2008 and again in 2010. Cores were also collected to investigate temporal trends over a longer time scale and to estimate the sedimentation rate in the loch. The loch is divided into two basins, and PAH concentrations were significantly higher in the upper basin, closer to the smelter, than in the lower basin. The PAH distribution and concentration ratios were consistent with a pyrolytic source of PAHs, with a high proportion of heavier parent PAHs. There was no evidence of any recovery in PAH concentrations, perhaps due to the mixing and disturbances of the sediment, and the persistence of PAHs. Concentrations of all PAHs were above the Background Assessment Concentrations (BACs) in both basins. In the lower basin only the 5- and 6-ring PAHs were above the Effects Range Low (ERL) values, but in the upper basin all but naphthalene were above the ERLs. There is therefore still an unacceptable risk of chronic effects in marine species. Concentrations decreased down the cores, falling below BACs in the deepest sections. However, ERLs were exceeded as far down the core as 30 cm for some PAHs.     

Rapid quantitative assessment of visible injury to vegetation and visual amenity effects of fluoride air pollution

Quantitative measures of visible injury are proposed for the protection of the aesthetic acceptability and health of ecosystems. Visible indications of air pollutant injury symptoms can be assessed rapidly and economically over large areas of mixed species such as native ecosystems. Reliable indication requires close attention to the criteria for assessment, species selection, and the influence of other environmental conditions on plant response to a pollutant. The estimation of fluoride-induced visible injury in dicotyledonous species may require techniques that are more varied than the measurement of necrosis in linear-leaved monocotyledons and conifers. A scheme is described for quantitative estimates of necrosis, chlorosis and deformation of leaves using an approximately geometric series of injury categories that permits rapid and sufficiently consistent determination and recognises degrees of aesthetic offence associated with foliar injury to plants.     

Polycyclic aromatic hydrocarbon (PAH) concentration and composition determined in farmed blue mussels (Mytilus edulis) in a sea loch pre- and post-closure of an aluminium smelter

Concentrations of polycyclic aromatic hydrocarbons (2- to 6-ring parent and branched PAH) from an actively producing commercial shellfish farm in Loch Leven, Scotland, were found in excess of 4000 ng g(-1) wet weight tissue. These concentrations were considerably greater than had been recorded from mussels sampled elsewhere around the Scottish mainland. The PAH composition of the mussels from Loch Leven was dominated by the 5-ring, parent compounds; benzo[b]fluoranthene was the dominant compound. This data was consistent with the source being a discharge from an aluminium smelter. The individual compounds benz[a]anthracene, benzo[a]pyrene and dibenz[a,h]anthracene returned values of 304 ng g(-1), 446 ng g(-1) and 39 ng g(-1) respectively; these were well above the 15 ng g(-1) pragmatic guideline limit. Over the two year monitoring period, the concentrations of these compounds in mussels from Loch Etive, a reference location, ranged between 'not detected' and 4 ng g(-1)(for benz[a]anthracene). Mussels were transferred from a clean location to Loch Leven which demonstrated that the rate of uptake of PAH was rapid. Following closure of the aluminium smelter, the PAH concentrations in mussels decreased. Differences between the two sites within Loch Leven were noted with the longer-term impact remaining greater for the mussels closer to the original point discharge.     

Lognormality of trace contaminant concentrations in sewage effluents

It is important to understand the statistical distribution of monitoring data for them to be of value in determining the parameters of environmental models. No such distributional information has been available for many trace contaminants in sewage effluents. This paper applies the data of a major UK sewage works’ effluent monitoring programme to determine the validity of the common assumption that data are lognormally distributed. Effluent quality was monitored at 162 wastewater treatment works over 1 year, generating over 3,000 results for each of over 40 substances, including metals, trace organic substances and pharmaceuticals. It is demonstrated that the lognormal assumption is clearly justified for the great majority of substances in the spatial case—for annual average effluent concentrations across different treatment works. In the site-specific, temporal case—for individual determinations of concentration at a single site over an annual period—lognormality is generally supported but not demonstrated so unequivocally for all site/substance combinations. The principal source of uncertainty was lack of sufficient numbers of observations reported to adequately low reporting limits.     

A comparison of X-ray fluorescence and wet chemical analysis for lead on air filters from different personal samplers used in a secondary lead smelter/solder manufacturer

Portable X-ray fluorescence (XRF) technology may provide faster turn-around without compromising accuracy when assessing personal exposures to metals such as lead, but it has only been tested in limited field environments. This study is part of a series, where various types of sampler are used to collect airborne lead in different environments for presentation to a portable XRF analyzer. In this case personal samples were taken at a manufacturer of solder alloys consisting mainly of lead and tin, using the closed-face 37 mm cassette (CFC), the 37 mm GSP or "cone" sampler, the 25 mm Institute of Occupational Medicine (IOM) inhalable sampler, the 25 mm button sampler, and the open-face 25 mm cassette. Mixed cellulose-ester filters were used in all samplers. Following XRF analysis the samples were extracted with acid and analyzed by inductively coupled plasma optical emission spectroscopy (ICP). The internal surfaces of CFC's and 25 mm open-face cassettes were also wiped, and the wipes analyzed for lead to assess wall-losses in these two samplers. Analysis of all elements present is useful to ascertain contributions to matrix interference effects. In addition to lead, other metals such as tin, copper, iron, silver, cadmium and antimony were also detected in some or all of the samples by ICP analysis, but only copper and iron could be determined using the XRF analyzer under test. After the removal of a few outliers, all five samplers gave good correlations (r(2) > 0.9) between the two analytical methods over the entire range of found lead mass, which encompassed both the action level and the permissible exposure limit enforced in the USA by the Occupational Safety and Health Administration (OSHA). Linear regression on the results from most samplers gave almost 1 ratio 1 correlations without additional correction, indicating an absence of matrix effects, particularly from tin, which was the most common element after lead. The average of three XRF readings across filters from the GSP samplers gave the best results with 96.7% of results within +/-25% and 100% within +/-30% of the associated ICP values. Using the center reading only was almost as good with 90.0% of results within +/-25% and 96.7% within +/-30% of the associated ICP values, and results can be obtained faster with a single reading. The use of an algorithm developed by OSHA for three readings from the CFC filter samples gave the next best results with 93.3% of XRF results within +/-25% of the corresponding ICP values. However, analysis of wipes from the interior of the cassettes indicated a substantial loss of sample to the walls, and even larger wall-losses were encountered in the 25 mm open-face cassette. Neither this latter sampler nor the IOM or button sampler met the 95% criterion, even for +/-30% accuracy.     

Effects of compliance boundary location on contaminant detection networks in aquifers

Groundwater monitoring networks were derived for 15 alternative compliance boundaries, located from 10 to 150 meters downgradient of a landfill. For each compliance boundary, a mass transport model was used to define the linear monitoring transect, perpendicular to groundwater flow, requiring the fewest detection wells. The distance (d_t) to the optimal monitoring transect was consistently 0.40 to 0.75 times the distance to the compliance boundary (d_c). Compliance boundaries located near a landfill provide capability for early detection, but also require a substantial number of closely spaced wells. As d_c increases, the minimum number of wells (N_o) required along the optimal transect decreases. However, the rate of decrease (N_o/d_c) is progressively smaller in the downgradient direction. And there is a value for d_c, in this example 70 meters, beyond which the decrease in N_o is negligible.     

Influence of aerosol spectrum and air pollutants on fog formation in urban environment of megacity Delhi, India

Urban areas are facing increasing fog frequencies that may result due to increased air pollution emanating from variety of sources. The increased pollution levels may lead to the atmospheric reactions resulting into the formation of secondary pollutants that may also lead to increased aerosol number concentrations (ANC) in the atmosphere. This could cause enhanced water aerosols in the presence of favourable meteorological conditions and high relative humidity. This study deals with the atmospheric pollution and visibility during winter season of megacity Delhi in order to assess the relationship between the two specifically during fog episodes. Thus, this study analyses the levels of air pollutants, aerosol spectrum and meteorological conditions during one week each in the winter season of the years 2004 and 2006 in order to have an improved understanding of their role in fog formation in mega-city Delhi. More than 300 h of measurements which included episodes of dense, thick and moderate fogs of about 25 h, were studied. The measurements cover most of the accumulation mode and greater size spectrum of aerosols. Thus, the analysis is performed for the entire period, specifically, before the fog sets up, during and afterwards. In general, the relatively small variations in number concentration show larger variations in visibility prior and post dense fog formation than during dense fog episodes. Preliminary analysis of monthly averaged RSPM (Respirable Suspended particulate Matter or PM(10)) concentration values for four winter months for a period of 6 years (1996-2001) and visibility did not show a good correlation with total occurrences of fog. However, daily averaged RSPM concentration showed a good correlation with the occurrences of thick fog. Diurnal variation of Sulfur-dioxide and Nitrogen dioxide were found to have inverse relationship with visibility during fog which may be due to formation of secondary pollutants such as sulfate and to a lesser extent nitrates. Amongst, the daily averaged concentrations of all the criteria pollutants, RSPM was found to be best correlated with the fog in comparison to other pollutants.     

Determination of aluminium in groundwater samples by GF-AAS, ICP-AES, ICP-MS and modelling of inorganic aluminium complexes

The paper presents the results of aluminium determinations in ground water samples of the Miocene aquifer from the area of the city of Poznań (Poland). The determined aluminium content amounted from <0.0001 to 752.7 μg L(-1). The aluminium determinations were performed using three analytical techniques: graphite furnace atomic absorption spectrometry (GF-AAS), inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The results of aluminium determinations in groundwater samples for particular analytical techniques were compared. The results were used to identify the ascent of ground water from the Mesozoic aquifer to the Miocene aquifer in the area of the fault graben. Using the Mineql+ program, the modelling of the occurrence of aluminium and the following aluminium complexes: hydroxy, with fluorides and sulphates was performed. The paper presents the results of aluminium determinations in ground water using different analytical techniques as well as the chemical modelling in the Mineql+ program, which was performed for the first time and which enabled the identification of aluminium complexes in the investigated samples. The study confirms the occurrence of aluminium hydroxy complexes and aluminium fluoride complexes in the analysed groundwater samples. Despite the dominance of sulphates and organic matter in the sample, major participation of the complexes with these ligands was not stated based on the modelling.     

Modelling of spatial contaminant probabilities of occurrence of chlorinated hydrocarbons in an urban aquifer

In this study, a 3D urban groundwater model is presented which serves for calculation of multispecies contaminant transport in the subsurface on the regional scale. The total model consists of two submodels, the groundwater flow and reactive transport model, and is validated against field data. The model equations are solved applying finite element method. A sensitivity analysis is carried out to perform parameter identification of flow, transport and reaction processes. Coming from the latter, stochastic variation of flow, transport, and reaction input parameters and Monte Carlo simulation are used in calculating probabilities of pollutant occurrence in the domain. These probabilities could be part of determining future spots of contamination and their measure of damages. Application and validation is exemplarily shown for a contaminated site in Braunschweig (Germany), where a vast plume of chlorinated ethenes pollutes the groundwater. With respect to field application, the methods used for modelling reveal feasible and helpful tools to assess natural attenuation (MNA) and the risk that might be reduced by remediation actions.     

Some considerations on the use of simple box models of contaminant fate in soils

A simple box model computing time-averaged concentrations in soil and water of contaminants such as pesticides, following a pulse emission under the assumption of constant removal rates, is presented and evaluated against a benchmark model and some lysimeter experiments representative of different soil and climate settings in Europe. The simple box model allows capturing to some extent the trends of contaminant releases observed from lysimeters or predicted by the benchmark model. This suggests that the correct order of magnitude of environmental concentrations and loads of contaminants can be described as a first approximation by a very simple back-of-the-envelope calculation. In the calculation, the time lag between contaminant application and the start of runoff or leaching should be considered. In the absence of more detailed information, repeating the calculation for the extreme cases of zero and one month lag yields a reasonably realistic range, and the geometric mean of the two is suggested as a first guess estimate. This configures a practical approach for the screening of contaminant losses especially suited for the mapping of predicted environmental concentrations (PECs) for assessment at broad scale (such as continental Europe, a country or a large catchment), where contingent determinants of contaminant fate tend to be averaged out and use of more detailed models usually promises to yield little improvement of PECs.     

Monitoring contaminant exposure: Relative concentrations of organochlorines in three tissues of American black ducks

Comparison of organochlorine residues in wildlife must often be made to regulatory standards or to values of known biological significance; this is difficult when dissimilar tissues are analyzed and results are expressed on different bases. To relate levels in the different tissues used for regulatory and monitoring purposes and for biological assessments, we exposed American black ducks to mixtures of three organochlorines. Differences in residue burdens among tissues were not statistically significant when levels were expressed on a lipid weight basis. Levels of heptachlor and Aroclor 1254 in one tissue can be accurately predicted from those in another; such predictions for endrin are less reliable. Lipid weight based residue concentrations in wings may be used to predict whether levels in fat exceed residue standards set for human health or approach those associated with effects on populations of species sampled.     

Influence of cabin conditions on placement and response of contaminant detection sensors in a commercial aircraft

Potential causalities due to airborne disease transmission and risk of chem-bio terrorism in commercial airliner cabins can be reduced by fast responses. Fast responses are only possible by using sensors at appropriate locations in the cabins. Cost, size and weight factors restrict the number of sensors that could be installed inside a cabin. Since release locations and seating patterns of passengers can impact airborne contaminant transports, this study first addressed this impact by using a validated computational fluid dynamics (CFD) program in a four-row mockup of twin-aisle airliner cabin. It was observed that occupancy patterns and release locations have little influence on longitudinal contaminant transports though localized variations of contaminant concentrations may exist. The results show that response time of the sensors is considerably reduced with the increase in number of sensors. If only a single sensor is available across a cabin cross-section then it should be placed at the middle of the ceiling. A cabin model of a fully occupied twin-aisle airliner with 210 seats was also build to study the diverse contaminant distribution trends along cabin length. The results reveal that seating arrangements can make cross-sectional airflow pattern considerably asymmetrical. Similar airflow patterns make the longitudinal contaminant transport in the business and economy classes alike. The presence of galleys greatly affected the longitudinal transport of contaminants in a particular cabin section. The effects due to galleys were less significant if a multipoint sampling system was used. The multipoint sampling system can also reduce the number of sensors required in a cabin.     

Determination of contaminant levels and remediation efficacy in groundwater at a former in situ recovery uranium mine

There has been increasing interest in uranium mining in the United States via in situ recovery techniques. One of the main environmental concerns with in situ uranium mining is the potential for spreading groundwater contamination. There is a dearth of detailed analysis and information regarding the outcome of in situ uranium mine remediation to ascertain the environmental impacts. Regulatory measurements performed at a Wyoming in situ uranium mine were collected and analysed to ascertain the efficacy of remediation and potential long term environmental impact. Based on the measurements, groundwater sweeping followed by reverse osmosis (RO) treatment proved to be a highly efficient method of remediation. However, injection of a reductant in the form of H(2)S after groundwater sweeping and RO did not further reduce the aqueous concentration of U, Mn, or Fe. Low concentrations of target species at monitoring wells outside the mined area appear to indicate that in the long term, natural attenuation is likely to play a major role at reductively immobilizing residual (after remediation) concentrations of U(VI) thus preventing it from moving outside the mined area. Our analysis indicates the need for additional monitoring wells and sampling in conjunction with long term monitoring to better understand the impacts of the different remediation techniques.     

Determination of isocyanic acid in air

A method is presented for the determination of isocyanic acid (ICA), HNCO, in air samples as a di-n-butylamine (DBA) derivative. The method is based on sampling in midget impinger flasks containing 10 ml of 0.01 mol l-1 DBA in toluene. Quantification was made using liquid chromatography (LC) and electrospray mass spectrometry (MS) monitoring positive ions. The instrumental detection limit for the LC-MS was 10 fmol of ICA-DBA. ICA was generated by thermal decomposition of urea. A standard solution containing the DBA derivatives of ICA was prepared by collecting the emitted ICA in an impinger flask containing DBA. ICA in the reference solution was characterised by LC and time-of-flight (TOF) MS and quantified by LC chemiluminescent nitrogen detection (LC-CLND). The instrumental detection limit for the LC-CLND was 1 ng of nitrogen. ICA was emitted during thermal degradation of PFU resins and polyurethane (PUR) lacquers, from car metal sheets. ICA was the most dominant isocyanate and in PUR coating up to 8% of the total weight was emitted as ICA and for PFU resins up to 14% was emitted as ICA. When air samples were collected in an iron foundry during casting in sand moulds with furan resins, concentrations of ICA in the range 50-700 micrograms m-3 were found in the working atmosphere.     

Calibration of two passive air sampler configurations for monitoring concentrations of hexabromocyclododecanes in indoor air

While polyurethane foam (PUF) disk passive air samplers are employed increasingly to monitor persistent organic pollutants in indoor air, they essentially sample only the vapour phase. As a previous investigation of the vapour : particle phase partitioning of hexabromocyclododecanes HBCDs in (outdoor) air reported them to be present largely in the particulate phase, we monitored three offices using active air samplers. In each, approximately 65% of HBCDs were present in the vapour phase, suggesting PUF disk passive samplers are suitable for monitoring HBCDs in indoor air. Concentrations in the three offices (239-359 pg Sigma HBCD m(-3)) exceed substantially those reported in outdoor air from the United States (2.1-11 pg Sigma HBCD m(-3)), but are in line with outdoor air from Stockholm. The relative abundance of the three principal diastereomers in office air was closer to that found in technical HBCD formulations (i.e. predominantly gamma-HBCD) than in most US outdoor air samples. Time integrated air concentrations of alpha-, beta-, and gamma-HBCD were obtained for an office using a low volume sampler operated over a 50 d period alongside PUF disk samplers. This calibration exercise yielded the following passive air sampling rates for both a fully- and part-sheltered PUF disk sampler design: for alpha-, beta-, and gamma-HBCD, 0.87, 0.89, and 0.91 m3 d(-1) respectively (fully-sheltered) and 1.38, 1.54, and 1.55 m3 d(-1) respectively (part-sheltered). Deployment of the part-sheltered configuration yielded concentrations approximately 35% lower than those obtained using a high volume sampler, consistent with PUF disk samplers measuring primarily the vapour phase.