Studies of toxaphene in technical standard and extracts of background air samples (Point Petre, Ontario) using multidimensional gas chromatography-electron capture detection (MDGC-ECD)

MDGC-ECD procedures have been used to provide insight into the compositional complexity of some of the specific peaks or clusters observed in the gas chromatographic analysis of a technical toxaphene standard, with reference to individual toxaphene congeners (Parlar # components) that are flow commercially available. These investigations have focussed initially upon those peaks and clusters recently identified (Shoeib. M., Brice, K.A., Hoff, R., 1999. Chemosphere 39, 849-871) as dominant constituents of background ambient air. Multiple electron-capturing components have been found to be present in all the species studied: the available individual toxaphene congeners have been matched against these components where possible. In similar fashion, the responses obtained in equivalent gas chromatographic elution windows from the analysis of typical processed air sample extracts have been investigated, with the results showing clear differences relative to the patterns found in the technical toxaphene standard. In most cases, the air sample shows reduced complexity with fewer components present in the cluster. Also, the presence of interfering responses (due to PCBs and other organochlorines) is quite apparent and significant, showing that major problems and errors could arise when using single-column GC-ECD procedures for quantitation of toxaphene in environmental samples. The presence of certain of the Parlar species in the air samples has been confirmed and in most cases these represent the dominant toxaphene component found in the targeted cluster. Furthermore, the persistence of certain congeners in the atmospheric samples appears to be strongly dependent upon chemical structure, since the congeners in question possess an alternating exo-endo chlorine substitution pattern around the six-membered ring in the bornane skeleton. Such persistence is probably the result of lower metabolization of toxaphene residues in soils, water and sediments leading to a similar pattern in the atmosphere following volatilization.     

Rapid anaerobic degradation of toxaphene in sewage sludge

We studied the degradation of technical toxaphene in anaerobic sewage sludge from a municipal waste water treatment plant. Chlorobornanes, chlorocamphenes and related compounds were rapidly degraded, with degradation rates in the order of decachloro>nonachloro>octochloro>heptachloro approximately = hexachloro compounds. The half-lives of individual congeners ranged from <1 day to several days. We also studied the degradation of technical toxaphene in previously sterilized sludge (control), and found it was slower than in the anaerobic sludge. The chlorobornanes that degraded most rapidly in the non-sterilized anaerobic sludge were those with gem chloro substitution on the 6-member carbon-ring, including the toxic congeners, Toxicant A and B. Non-gem chloro substituted congeners, like the biologically persistent P26 and P50, also degraded, but less rapidly. Toxaphene degradation in sewage sludge proceeded primarily via reductive dechlorination, leading to HxSed, HpSed, TC2 and other persistent metabolites. Enantioselective determinations indicated little, if any, enantioselectivity in the formation and/or degradation of these compounds. The isomer and enantiomer profiles of the hexa-, hepta-, and octachlorobornanes are similar to those observed in sediment from the Baltic Sea, suggesting that technical toxaphene is the source of these compounds and that its composition was changed via similar anaerobic degradation pathways.     

Impact of the Saharan dust outbreaks on the ambient levels of total suspended particles (TSP) in the marine boundary layer (MBL) of the Subtropical Eastern North Atlantic Ocean

Six years (1998–2003) of measurements of ambient air concentrations of total suspended particulate (TSP) measured at a rural background monitoring station in Tenerife (Canary Islands), the El Río station (ER, 28°08′35″N, 16°39′20″W, 500 m a.s.l.) were studied. African dust outbreaks were objectively identified using a new quantitative tool, called the African Index. This index indicates the percentage of time that an air mass remained over an African region at one of three possible height intervals of the lower troposphere. After identifying these episodes, a study of the background TSP levels at the ER station and of direct and indirect (those which cause vertical deposition of dust) African air mass intrusion impacts was performed. Taking into account both direct and indirect episodes, a total of 322 days of African dust intrusion were objectively identified (a mean of 54 episodes per year) in the period 1998–2003, some of them caused by “transition episodes” or “return African air masses”. A subjective method confirmed that 256 of these days were caused by direct impacts of African dust on the ER station. A mean TSP value of 21.6 μg m⁻³ was found at the station during this period. All the episodes occurred when the TSP concentration was >28.5 μg m⁻³. The TSP background (14 μg m⁻³) can be assumed to be representative of the MBL of the Eastern North Atlantic subtropical region. The highest number of dust gravitational settlement (or indirect) episodes occurs in summer, but the highest contribution of these episodes to the TSP levels is in March with a monthly mean TSP contribution of up to 30.5 μg m⁻³.     

Gas-phase organics in environmental tobacco smoke: 2. Exposure-relevant emission factors and indirect exposures from habitual smoking

Sorption of emitted gas-phase organic compounds onto material surfaces affects environmental tobacco smoke (ETS) composition and exposures indoors. We have introduced a new metric, the exposure relevant emission factor (EREF) that accounts for sorptive uptake and reemission to give the mass of individual ETS constituents available for exposure over a day in which smoking occurs. This paper describes month-long experiments to investigate sorption effects on EREFs and potential ETS exposures under habitual smoking conditions. Cigarettes were smoked in a 50-m³ furnished room over a 3-h period 6–7 days per week, with continuous ventilation at 0.3, 0.6, or 2.1 h⁻¹. Organic gas concentrations were measured every few days over 4-h “smoking”, 10-h “post-smoking” and 10-h “background” periods. Concentration patterns of volatile ETS components including 1,3-butadiene, benzene and acrolein were similar to those calculated for a theoretical non-sorbing tracer, indicating limited sorption. Concentrations of ETS tracers, e.g. 3-ethenylpyridine (3-EP) and nicotine, and lower volatility toxic air contaminants including phenol, cresols, and naphthalene increased as experiments progressed, indicating mass accumulation on surfaces and higher desorption rates. Daily patterns stabilized after week 2, yielding a steady daily cycle of ETS concentrations associated with habitual smoking. EREFs for sorbing compounds were higher under steady cycle versus single-day smoking conditions by 50% for 3-EP, and by 2–3 times for nicotine, phenol, cresols, naphthalene, and methylnaphthalenes. Our results provide relevant information about potential indirect exposures from residual ETS (non-smoker enters room shortly after smoker finishes) and from reemission, and their importance relative to direct exposures (non-smoker present during smoking). Under the conditions examined, indirect exposures accounted for a larger fraction of total potential exposures for sorbing versus non-sorbing compounds, and at lower versus higher ventilation rates. Increasing ventilation can reduce indirect exposures to very low levels for non-sorbing ETS components, but indirect routes accounted for 50% of potential nicotine exposures during non-smoking periods at all ventilation rates.     

Teil II: Analytik von Toxaphenrückst?nden (UWSF 2/1998)

Zusammenfassung  Die Rückstandsanalytik des Insektizides Toxaphen galt früher als problematisch wegen der gro?en Anzahl an Komponenten mit ?hnlicher Struktur und unterschiedlichem Chlorgehalt. Erschwerend kam hinzu, da? die Zusamensetzung von Toxaphenrückst?nden in Umweltproben sich von der des technischen Standards signifikant unterscheidet. Deshalb war die Quantifizierung einzelner Komponenten früher nicht m?glich. Seit jedoch eine ganze Reihe von Toxaphenkomponenten in ausreichenden Mengen isoliert wurden, von denen einige für Umweltproben repr?sentativ sind, besteht die M?glichkeit, Toxaphenrückst?nde in Umweltkompartimenten zuverl?ssig zu bestimmen. In der letzten Zeit konzentriert sich die Entwicklung vor allem auf die Trennung der chiralen Bestandteile des Gemisches, um anhand der Zusammensetzung der Rückst?nde Verteilungswege und Abbaumechanismen besser identifizieren zu k?nnen.

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Residue analysis of toxaphene has been difficult because of the complexicity of the technical mixture consisting of a high number of compounds with very similar structure and differing chloro content. Furthermore, the composition of toxaphene in environmental samples varies widely and is normally not like that of the technical mixture. Therefore, quantification of single components in environmental samples was impossible. After the isolation and identification of a great number of components during the last decade, enough standards are available for reliable quantification of toxaphene in all environmental compartments. Recently, most research has been done on the separation of chiral components of toxaphene with a view to identify degradation mechanisms and distribution pathways.

     

Discrimination and thermal degradation of toxaphene compounds in capillary gas chromatography when using split/splitless and on-column injection

Technical toxaphene and a 22-component Reference Mixture were analyzed using capillary gas chromatography with split/splitless injection (SSL) and on-column injection (OC). In both techniques, electron-capture, negative ionization mass spectrometry (ECNI-MS) was used for detection of chlorobornanes, chlorocamphenes and related compounds. Significant discrimination of highly chlorinated congeners was observed as a result of incomplete transfer of these compounds from the vaporizer to the analytical column when using SSL. This resulted in a much lower response for nona- and decachloro congeners than when using OC. In addition, several toxaphene components, especially the chlorobornanes with gem dichloro substitution on the six-member carbon ring, undergo thermal degradation when using SSL. Some of these congeners are major components of technical toxaphene, but generally are not present, except at low concentrations, in environmental and biological samples. Therefore, technical toxaphene may be discriminated and/or degraded differently than toxaphene compounds in environmental samples when using SSL. This results in significant bias of the quantitative data when using the technical material as a reference. OC suffers much less from these deficiencies and, therefore, is a preferable technique for toxaphene analysis.     

Atmospheric deposition of toxaphene to eastern north America derived from peat accumulation

Dated peat cores from Minnesota east to Nova Scotia analyzed for toxaphene provided spatial variation in historical and recent atmospheric fluxes and an atmospheric input function for toxaphene extending over the past 40 years. This input function is consistent with toxaphene production data and the input of a well documented insecticide, DDT. Total core burdens of toxaphene across a west to east transect were highest in the upper midwest and Nova Scotia, with recent peat accumulation rates ranging from 0.5 to 9 μg m⁻²a⁻¹. Atmospheric concentrations of toxaphene, back-calculated from accumulation rates in peat, range from 8 to 150 pg m⁻³, in agreement with recently-measured concentrations in remote atmospheres. Recent atmospheric inputs of toxaphene are two to four times those of PCBs and DDT, respectively.     

Airborne concentrations of toxaphene congeners at Point Petre (Ontario) using gas-chromatography-electron capture negative ion mass spectrometry (GC-ECNIMS).

A reliable analytical method has been developed using GC-ECNIMS for the determination of individual toxaphene congeners in ambient air. To allow a reasonable comparison with previous data for toxaphene reported by Muir and co-workers using GC-ECD, this method has adopted their approach of focussing upon the identification and quantification of specific peaks or clusters ("T" species) typically observed in environmental samples, with the sum of these "T" species then being reported as "total toxaphene". Technical toxaphene has been used as the analytical standard, but independent response factors have been assigned to the target peaks and clusters. Because of the appreciable variability in ECNIMS response shown by individual toxaphene congeners, this is considered to be a reasonable and potentially more accurate procedure than the application of a "single response factor" used by many other workers. The methodology has been used for the determination of toxaphene in air samples collected over the annual cycle in 1992 and then from October 1995 to September 1997 at Point Petre, Ontario. Of the forty-four calibrated components, only 10 were detected in all of the air samples collected over the latter 2-year period. Airborne concentrations of toxaphene (defined as the sum of the calibrated components) range from 0.9 pg/m3 to 10.1 pg/m3. A clear seasonality has been observed, with a summer-to-winter concentration ratio of about 6.     

Odor compounds released from different zones of two adjacent waste treatment facilities: Interactive influence and source identification

An integrated approach was applied to identify the key odorants comprising emissions from different zones in two adjacent waste treatment facilities (an aerobic biological treatment plant and an anaerobic landfill site), identify their precise sources, and distinguish the interactive influences between them. Seven odor families were investigated, including alcohols, terpenes, carbonyls, aromatics, volatile fatty acids (VFAs), sulfur compounds, and ammonia. Principal components analysis, characteristic molecular ratios, and ternary diagrams were used to differentiate the interactive influence of the odor sources. Among typical biotic compounds, terpenes were found to be more suitable as odor markers for their better fingerprinting character than sulfur compounds and VFAs. Ratios of p-cymene at sampling locations related to the biological treatment plant (aerobic status) were between 0.00 and 0.25, whereas those at landfill-related sampling points (anaerobic status) were between 0.25 and 1.0. The molecular ratio of terpenes was also found to be an appropriate means to differentiate between homologous and similar odor sources such as an aerobic biological treatment plant and anaerobic landfill.

Implications:?The aim of this work is to identify the key odorants comprising emissions from different zones in two adjacent waste treatment facilities, identify their precise sources, and distinguish the interactive influences between them. The emission of gaseous pollutants greatly affects the living quality of nearby residents, and odor complaints are becoming a major problem. In this study we utilized various pretreatment and analytical methods to obtain integrated emission information of gaseous pollutants. The results showed terpenes were found to be more suitable as odor markers for their better fingerprinting character than sulfur compounds and VFAs.     

Photooxidant-forming monoterpenes in air plumes from kraft pulp industries

Monoterpenes emitted to air from two Swedish kraft (sulphate) pulp-mills were determined by sampling on the Tenax adsorbent followed by laboratory analysis using thermal desorption combined with high-resolution gas chromatography. The composition of the terpenes was found to be similar in the emissions from various parts of the process as well as in the mill plume. The bicyclic terpenes alpha-pinene and 3-carene, originating principally from wood of Scots pine (Pinus sylvestris), predominated among the thirteen assessed hydrocarbon monoterpenes. Terpinolene was the most prominent among the particularly reactive terpenes with a lifetime in ozone-rich air of only a few minutes. The rapid formation of photooxidants by chemical reactions of the terpenes with other components of the mill plume is discussed. It is concluded that a variety of phytotoxic photooxidants are formed which may contribute significantly to forest decline within 50 km of mills located along coasts.     

Organochlorine pesticides in the ambient air of Chiapas, Mexico

Organochlorine (OC) pesticides were measured in the ambient air of Chiapas, Mexico during 2000-2001. Concentrations of some OC pesticides (DDTs, chlordanes, toxaphene) were elevated compared with levels in the Great Lakes region, while those of other pesticides were not (hexachlorocyclohexanes, dieldrin). While this suggests southern Mexico as a source region for the former group of chemicals, comparably high levels have also been reported in parts of the southern United States, where their suspected sources are soil emissions (DDTs, toxaphene) and termiticide usage (chlordane). Ratios of p,p'-DDT/p,p'-DDE and trans-chlordane/cis-chlordane/trans-nonachlor (TC/CC/TN) in Chiapas suggest a mixture of fresh and weathered sources, while congener profiles of toxaphene suggest emission of old residues from soils. This is supported by air parcel back trajectory analysis, which indicated that air masses over Chiapas at the time of sampling had previously passed over areas of continuing or recent use of some OC pesticides as well as areas of past use.     

PCDD, PCDF, AND PCB concentrations in human milk from two areas in Finland

Concentrations of 17 toxic 2,3,7,8-chlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and of 36 polychlorinated biphenyl congeners (PCBs) were analyzed from 167 randomly sampled human milk samples from Southern (77 samples) and Eastern (90) Finland. The level of PCDD/Fs and PCBs in human milk in Southern Finland was about 25% higher than those from Eastern Finland. The level of PCDD/Fs in human milk in Finland was the same as in Sweden, 30–50 % lower than in milk from Central Europe but about 45% higher than values from Norway or Russia. The PCB concentrations in Southern Finland were at the same level as in the Netherlands, and in Eastern Finland at the same level as in Norway. The levels of PCDD/Fs and PCBs decreased with increasing number of children: the third child was exposed to about 70% of the amount of PCDD/Fs and PCBs as compared with the first child, and the eighth to tenth child to about 20%. The congener patterns of PCDD/Fs and PCBs in Finnish human milk were similar to the countries of Central Europe, however, the levels of penta- and heptachlorinated furans were slightly higher than in milk from other countries.     

Experiments probing the influence of air exchange rates on secondary organic aerosols derived from indoor chemistry

Reactions between ozone and terpenes have been shown to increase the concentrations of submicron particles in indoor settings. The present study was designed to examine the influence of air exchange rates on the concentrations of these secondary organic aerosols as well as on the evolution of their particle size distributions. The experiments were performed in a manipulated office setting containing a constant source of d-limonene and an ozone generator that was remotely turned “on” or “off” at 6 h intervals. The particle number concentrations were monitored using an optical particle counter with eight-channels ranging from 0.1–0.2 to>2.0 μm diameter. The air exchange rates during the experiments were either high (working hours) or low (non-working hours) and ranged from 1.6 to>12 h⁻¹, with intermediate exchange rates. Given the emission rates of ozone and d-limonene used in these studies, at an air exchange rate of 1.6 h⁻¹ particle number concentration in the 0.1–0.2 μm size-range peaked 1.2 h after the ozone generator was switched on. In the ensuing 4.8 h particle counts increased in successive size-ranges up to the 0.5–0.7 μm diameter range. At higher air exchange rates, the resulting concentrations of total particles and particle mass (calculated from particle counts) were smaller, and at exchange rates exceeding 12 h⁻¹, no excess particle formation was detectable with the instrument used in this study. Particle size evolved through accretion and, in some cases, coagulation. There was evidence for coagulation among particles in the smallest size-range at low air exchange rates (high particle concentrations) but no evidence of coagulation was apparent at higher air exchange rates (lower particle concentrations). At higher air exchange rates the particle count or size distributions were shifted towards smaller particle diameters and less time was required to achieve the maximum concentration in each of the size-ranges where discernable particle growth occurred. These results illustrate still another way in which ventilation affects human exposures in indoor settings. However, the ultimate effects of these exposures on health and well being remain to be determined.     

Partitioning of dioxins and dibenzofurans: Whole blood, blood plasma and adipose tissue

It has become relatively common to estimate human dioxin body burden and to document dioxin exposures by measuring dioxin and dibenzofuran congeners in adipose tissue, whole blood or blood plasma, and reporting these values on a lipid basis. It has not been determined whether these three types of specimens contain identical dioxin and dibenzofuran levels. This paper compares paired plasma and adipose tissue and paired whole blood and adipose tissue in analyses from two groups of patients. The first group consists of twenty U.S. veterans with paired plasma and adipose specimens. The second group consists of four German adults with whole blood compared to adipose tissue. Forty-eight analyses were performed. The results suggest that for some higher chlorinated compounds, such as OCDD, plasma lipid values may be higher than adipose lipid values, but whole blood lipid values for the higher as well as lower chlorinated PCDD/Fs may be relatively similar. On the other hand, the values for the lower chlorinated PCDD/Fs, such as TCDD, are similar in blood plasma, adipose tissue and whole blood. Total PCDD/F dioxin “toxic equivalents” are similar within each of the two series reported here, using the current “International Dioxin Toxic Equivalent” system.     

Residues of organochlorine pesticides in Alabama soils

A survey was made of 36 Alabama agricultural soils to assess residues of formerly used organochlorine pesticides. Compounds determined comprised alpha- and gamma-hexachlorocyclohexane, heptachlor, heptachlor-exo-epoxide, trans- and cis-chlordane, trans-nonachlor, dieldrin, toxaphene, DDT and DDE. Concentrations varied by several orders of magnitude among farms and appeared to be log-normally distributed. Highest concentrations (ng g(-1) dry soil, arithmetic means) were found for toxaphene (285+/-390) and DDTs (p,p'-DDE, 22.7+/-21.4; p,p'-DDT, 24.6+/-30.5; o,p'-DDT, 4.00+/-5.86; p,p'-DDD, 2.40+/-2.41) which were once heavily used in the southern USA. Pesticide residues were not proportional to soil organic carbon content indicating that residue concentrations were a reflection of pesticide application history and dissipation rates rather than air-soil equilibrium. Mean ratios of DDT/DDE in six regions of the state ranged from 0.39 to 1.5, and compound ratios for chlordanes and toxaphene were different from those in the technical mixtures.     

Coupled infrared extinction spectra and size distribution measurements for several non-clay components of mineral dust aerosol (quartz, calcite, and dolomite)

Simultaneous size distributions and Fourier transform infrared (FTIR) extinction spectra have been measured for several representative components of mineral dust aerosol (quartz, calcite, and dolomite) in the fine particle size mode (D=0.1–1 μm). Optical constants drawn from the published literature have been used in combination with the experimentally determined size distributions to simulate the extinction spectra. In general, Mie theory does not accurately reproduce the peak position or band shape for the prominent IR resonance features in the 800–1600 cm⁻¹ spectral range. The resonance peaks in the Mie simulation are consistently blue shifted relative to the experimental spectra by 20–50 cm⁻¹. Spectral simulations, derived from a simple Rayleigh-based analytic theory for a “continuous distribution of ellipsoids” particle shape model, better reproduce the experimental spectra, despite the fact that the Rayleigh approximation is not strictly satisfied in these experiments. These results differ from our previous studies of particle shape effects in silicate clay mineral dust aerosols where a disk-shaped model for the particles was found to be more appropriate.     

Geographical variation of persistent organochlorine concentrations in blubber of ringed seal (Phoca hispida) from the Canadian Arctic: univariate and multivariate approaches

Geographical variation of organochlorine (OC) concentrations in ringed seal (Phoca hispida) in the Canadian Arctic was studied using univariate and multivariate statistical techniques. The dataset consisted of 80 individual OC components (58 PCB congeners plus DDT- and chlordane (CHL)-related compounds, toxaphene, hexachlorocyclohexanes (HCH), chlorobenzenes (CBz), and dieldrin) determined in 221 ringed seal blubber samples from 13 locations throughout the Canadian Arctic from the period 1983 to 1989. Mean concentrations of the major OC groups in ringed seal blubber (SigmaPCBs, SigmaDDT, SigmaCHL and toxaphene), adjusted for the age and sex of the seals, showed few significant geographical differences. Principal components analysis was used to examine geographical trends. Significant differences in mean factor scores for three of four principal components were found between sampling locations. Locations in the western and high Arctic could be distinguished from those in Hudson Bay by highest scores along principal component two which was associated principally with CBz. PCB congeners with six or more chlorine substitutions declined with increasing north latitude, whereas more volatile OCs (CBz, HCH, less chlorinated PCBs) increased in the proportion of total OCs with latitude. Proportions of less chlorinated PCBs also decreased with increasing longitude, whereas slopes of regressions for more highly chlorinated PCBs increased significantly. The results were generally consistent with the 'cold condensation' hypothesis of increasing proportions of more volatile OCs with increasing latitude and distance from sources.     

Induction of rat hepatic microsomal enzymes by toxaphene pretreatment

Abstract

The effects of pretreatment of rats with toxaphene on hepatic drug metabolizing enzymes and several other parameters of the mixed function oxidase system were investigated. Adult male Sprague‐Dawley rats were fed diets containing 0, 50, 100, 150 and 200 ppm of toxaphene for 14 days. The body weight gain was unaltered as well as the food consumption in all the toxaphene fed groups. There was no change in the weights of brain, kidney, heart, and testes but the liver weight was significantly increased. The thymus weight in all the toxaphene fed groups was decreased. Hydroxylation of pentobarbital and aniline was significantly enhanced in rats exposed to toxaphene. Ethylmorphine‐N‐demethy‐lase activity in the toxaphene treated rats was also elevated. Enhanced hydroxylation of pentobarbital was also evident from the decreased sleeping time following pentobarbital administration. Exposure to toxaphene increased cytochrome P‐450, NADPH‐cytochrome c‐reductase and dehydrogenase in hepatic microsomal fractions. The binding of aniline and hexobarbital to microsomes was also enhanced, suggesting that the intermediate steps in the electron‐transfer system were increased. In conclusion, pretreatment of rats with toxaphene for fourteen days resulted in the induction of the hepatic mixed function oxidase system.     

Norwegian Meteorological Institute’s real-time dispersion model snap (Severe Nuclear Accident Program): Runs for ETEX and ATMES II experiments with different meteorological input

The Norwegian Meteorological Institute (DNMI) has developed and implemented for operational use a real-time dispersion model Severe Nuclear Accident Program (SNAP) with capability for predicting concentrations and depositions of the radioactive debris from large accidental releases. SNAP has been closely linked to DNMI’s operational numerical weather prediction (NWP) models.How good are these predictions? Participation in ETEX has partly answered this question. DNMI used SNAP with LAM50S giving meteorological input for these real-time dispersion calculations. LAM50S Limited Area Model with 50 km grid squareswas DNMI’s operational NWP model in 1994 when ETEX took place.In this article we report on how SNAP performed in the first of the ETEX releases in near-real-time mode, using LAM50S—and in hindcast mode for ATMES II, using “ECMWF 1995: ETEX Data set (ATMES II)”as meteorological input data. These two input data sets came from NWP models with quite different characteristics but with similar resolution in time and space.The results from these dispersion simulations matched closely. Deviations early in the simulation period shrank to insignificant differences later on. Since both input data sets were based on “weather analysis” and had similar resolution in space and time, SNAP described the dispersion of the released material very similar in these two simulations.     

Estimating fugitive dust emission rates using an environmental boundary layer wind tunnel

Emissions from fugitive dust due to erosion of “natural” wind-blown surfaces are an increasingly important part of PM₁₀ (particulate matter with sizes of 10 μm aerodynamic diameter) emission inventories. These inventories are particularly important to State Implementation Plans (SIP), the plan required for each state to file with the Federal government indicating how they will comply with the Federal Clean Air Act (FCAA). However, techniques for determining the fugitive dust contribution to over all PM₁₀ emissions are still in their developmental stages. In the past, the methods have included field monitoring stations, specialized field studies and field wind-tunnel studies. The measurements made in this paper allow for systematic determination of PM₁₀ emission rates through the use of an environmental boundary layer wind tunnel in the laboratory. Near surface steady-state concentration profiles and velocity profiles are obtained in order to use a control volume approach to estimate emission rates. This methodology is applied to soils retrieved from the nation's single largest PM₁₀ source, Owens (dry) Lake in California, to estimate emission rates during active storm periods. The estimated emission rates are comparable to those obtained from field studies and lend to the validity of this method for determining fugitive dust emission rates.