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Study on chromium cluster formation by laser desorption: Application to industrial hygiene
1364
Abstracts
ON THE AGROCHEMICAL AEROSOLS K. R. S p u r n y Aerosol Chemist, Eichenweg St. 6, D-57392 Schmallenberg, Germany Abstract--The presentation is an overview dealing with the secondary air pollution produced by applications of agrochemical aerosols. Agrochemical aerosols have been used for different applications as pesticides, herbicides, fungicides, etc. since the beginning of our century. Nevertheless, the main expansion of their applications, started in the seventies. During the first application period, i.e. till the middle of this century, only a small amount of basic investigation was done. It has been recognized much later that applications of agricultural sprays can have a very negative impact on the total environment and produce additional health risks for the general population. During spray application, secondary aerosols and gaseous toxic air pollutants are produced. The fine particle fraction of the sprayed liquids or solids escapes into atmosphere and is transported toward residential areas. Besides, volatile particles and droplets evaporate and/or produce fine secondary aerosols and vapours, which are toxic or carcinogenic, and can be inhaled by the general population, children, etc. The losses of agrochemical aerosols into the air depend on vapour pressure of the active ingredient, application technique, climate, etc. Their degradation and transformation in the atmosphere are driven primarily by solar irradiation. Before 1960, the development of agroaerosols was almost entirely in the hands of entomologists, microbiologists, chemists, and agronomists. Toxicological and epidemiological studies have been developed much later. Both, epidemiological studies done on collectives of farmers as well as animal exposure studies have shown that the majority of used agrochemicals are toxic, teratogenic or carcinogenic.
NANOMETRIC Si/C/N COMPOSITE POWDERS ELABORATION BY LASER-AEROSOL INTERACTION E. M u s s e t , N . H e r l i n , M . C a u c h e t i e r a n d M . L u c e CEA-DSM-DRECAM-Service des Photons, Atomes et Mol6cules, CE Saclay, 91191 Gif-sur-Yvette Cedex, France Abstract--Recently it has been shown that ultrafine Si/C/N ceramic powders (in the nanometric range, below 100 nm) have been obtained by combining the ultrasonic injection of a liquid precursor with CO 2 laser irradiation. At the CEA the first experiments with aerosol-laser interaction were conducted with hexamethyldisilazane as the precursor which strongly absorbs the CO 2 laser radiation at 10.6 p.m. The aerosol droplets formed by the Pyrosol process are carried out with a flow of argon (or nitrogen) or argon-ammonia mixture into the beam of a high powered continuous wave industrial CO 2 laser. The as-formed powders are nanosized (30-60 nm), monodispersed and amorphous. Yield and particle composition were controlled by varying the synthesis conditions. Production up to 80 g h - 1 with a conversion rate > 55% has been attained when the liquid precursor was heated at about ll0°C. The powders crystallize by heating treatment under nitrogen. The coupling between an aerosol of a liquid precursor and the CO2 laser irradiation is a new route for the laser process of ultrafine powder synthesis which deals mainly with gaseous reactants and now the process can be extended to a wide range of compounds.
STUDY ON CHROMIUM CLUSTER FORMATION BY LASER DESORPTION: APPLICATION TO INDUSTRIAL HYGIENE A. H a c h i m i , * E. P o i t e v i n , J. F. M u l l e r , * G . K r i e r , * M . R u i z - L o p e z , * F. K l e i n * a n d L. S o w a * *Laboratoire de Spectrom6trie de Masse et Chimie Laser, I.P.E.M Universit6 de Metz-technopole Metz 2000, 1 Bd Arago, 57078 Metz Cedex 3, France, *Laboratoire de Chimie Th/:orique, Universit6 de Nancy I, 54600 Vandoeuvre les Nancy, France and *Laboratoire d'Etude de Contr61e de l'Environnement Sid6rurgique vole romaine, BP 320, 57214 Maizi6res-les-Metz, France Abstract--Over the last 10 years interest in metal compounds present in industrial environmental fumes has been increasing because of their toxicicity in the human body. Hexavalent chromium
Abstracts
1365
belongs to the category of toxic metals which are associated with allergic reactions and cancer. Laser microprobe is a mass spectrometric technique coupled to laser ionization which permits the in situ analysis of elements. In 1989, a methodology of determination of valency in reference chromium compounds (oxides and salts) was established by LAMMA from spectrum fingerprintings and cluster study in both ionization modes. This empirical method is the transposition of a stoichiometric study of metallic oxides by SIMS. We have noticed a great spectral similarity between chromium(VI) oxide and hydrated chromium(III) salts leading to difficulties in differentiating these two kinds of compounds and determining the valency of chromium. The presence of CrO~ ions could be associated with product hydration and could modify the fingerprint spectra of the corresponding compound without hydration. In this paper we contribute to the understanding of cluster formation mechanisms and evaluate the effects of other neutral or ionized molecules in the plasma arising from initial compound, on intensity ratio of chromium oxide clusters and particularly on CrO~ formation for hydrated chromium(IIl) salts. Our results presented here permit us to understand the effects of cluster formation on the determination of chromium valency established in our laboratory. We demonstrate that the CrO~" ion arises from collision between molecules present in the plasma generated by laser ablation. The mechanism of cluster formation is intimately associated with the presence of neutral or ionized species (water, sulfate, nitrate...). In particular, the hydration effect is very dependent on initial chromium salt. This methodology is used for the determination of chromium valency in aerosols less than 10 Ixrn in size emitted as dust by the steel industry. The systematic LAMMA analysis of the aerosols showed that the oxidation of chromium depends on the aerosol size.
A VECTOR MODEL FOR PREDICTING PARTICLE DEPOSITION IN GRANULAR BEDS AND IN THE RESPIRATORY TRACT UNDER THE SIMULTANEOUS ACTION OF DIFFUSION AND SEDIMENTATION J. W . G e n t r y , J. G e b h a r t a n d G . S c h e u c h GSF-Forschungszentrum f/Jr Umwelt und Gesundheit GmbH, Paul Ehrlich Strasse 20, D-60596 Frankfurt/Main, Germany Abstract--A vector model has been developed for prediction of particle deposition in porous bed filters and in lungs when diffusion and sedimentation operate simultaneously. The model is used to calculate upper and lower bounds for the deposition efficiency. The model shows good agreement with experiment.
Abstracts
ON THE AGROCHEMICAL AEROSOLS K. R. S p u r n y Aerosol Chemist, Eichenweg St. 6, D-57392 Schmallenberg, Germany Abstract--The presentation is an overview dealing with the secondary air pollution produced by applications of agrochemical aerosols. Agrochemical aerosols have been used for different applications as pesticides, herbicides, fungicides, etc. since the beginning of our century. Nevertheless, the main expansion of their applications, started in the seventies. During the first application period, i.e. till the middle of this century, only a small amount of basic investigation was done. It has been recognized much later that applications of agricultural sprays can have a very negative impact on the total environment and produce additional health risks for the general population. During spray application, secondary aerosols and gaseous toxic air pollutants are produced. The fine particle fraction of the sprayed liquids or solids escapes into atmosphere and is transported toward residential areas. Besides, volatile particles and droplets evaporate and/or produce fine secondary aerosols and vapours, which are toxic or carcinogenic, and can be inhaled by the general population, children, etc. The losses of agrochemical aerosols into the air depend on vapour pressure of the active ingredient, application technique, climate, etc. Their degradation and transformation in the atmosphere are driven primarily by solar irradiation. Before 1960, the development of agroaerosols was almost entirely in the hands of entomologists, microbiologists, chemists, and agronomists. Toxicological and epidemiological studies have been developed much later. Both, epidemiological studies done on collectives of farmers as well as animal exposure studies have shown that the majority of used agrochemicals are toxic, teratogenic or carcinogenic.
NANOMETRIC Si/C/N COMPOSITE POWDERS ELABORATION BY LASER-AEROSOL INTERACTION E. M u s s e t , N . H e r l i n , M . C a u c h e t i e r a n d M . L u c e CEA-DSM-DRECAM-Service des Photons, Atomes et Mol6cules, CE Saclay, 91191 Gif-sur-Yvette Cedex, France Abstract--Recently it has been shown that ultrafine Si/C/N ceramic powders (in the nanometric range, below 100 nm) have been obtained by combining the ultrasonic injection of a liquid precursor with CO 2 laser irradiation. At the CEA the first experiments with aerosol-laser interaction were conducted with hexamethyldisilazane as the precursor which strongly absorbs the CO 2 laser radiation at 10.6 p.m. The aerosol droplets formed by the Pyrosol process are carried out with a flow of argon (or nitrogen) or argon-ammonia mixture into the beam of a high powered continuous wave industrial CO 2 laser. The as-formed powders are nanosized (30-60 nm), monodispersed and amorphous. Yield and particle composition were controlled by varying the synthesis conditions. Production up to 80 g h - 1 with a conversion rate > 55% has been attained when the liquid precursor was heated at about ll0°C. The powders crystallize by heating treatment under nitrogen. The coupling between an aerosol of a liquid precursor and the CO2 laser irradiation is a new route for the laser process of ultrafine powder synthesis which deals mainly with gaseous reactants and now the process can be extended to a wide range of compounds.
STUDY ON CHROMIUM CLUSTER FORMATION BY LASER DESORPTION: APPLICATION TO INDUSTRIAL HYGIENE A. H a c h i m i , * E. P o i t e v i n , J. F. M u l l e r , * G . K r i e r , * M . R u i z - L o p e z , * F. K l e i n * a n d L. S o w a * *Laboratoire de Spectrom6trie de Masse et Chimie Laser, I.P.E.M Universit6 de Metz-technopole Metz 2000, 1 Bd Arago, 57078 Metz Cedex 3, France, *Laboratoire de Chimie Th/:orique, Universit6 de Nancy I, 54600 Vandoeuvre les Nancy, France and *Laboratoire d'Etude de Contr61e de l'Environnement Sid6rurgique vole romaine, BP 320, 57214 Maizi6res-les-Metz, France Abstract--Over the last 10 years interest in metal compounds present in industrial environmental fumes has been increasing because of their toxicicity in the human body. Hexavalent chromium
Abstracts
1365
belongs to the category of toxic metals which are associated with allergic reactions and cancer. Laser microprobe is a mass spectrometric technique coupled to laser ionization which permits the in situ analysis of elements. In 1989, a methodology of determination of valency in reference chromium compounds (oxides and salts) was established by LAMMA from spectrum fingerprintings and cluster study in both ionization modes. This empirical method is the transposition of a stoichiometric study of metallic oxides by SIMS. We have noticed a great spectral similarity between chromium(VI) oxide and hydrated chromium(III) salts leading to difficulties in differentiating these two kinds of compounds and determining the valency of chromium. The presence of CrO~ ions could be associated with product hydration and could modify the fingerprint spectra of the corresponding compound without hydration. In this paper we contribute to the understanding of cluster formation mechanisms and evaluate the effects of other neutral or ionized molecules in the plasma arising from initial compound, on intensity ratio of chromium oxide clusters and particularly on CrO~ formation for hydrated chromium(IIl) salts. Our results presented here permit us to understand the effects of cluster formation on the determination of chromium valency established in our laboratory. We demonstrate that the CrO~" ion arises from collision between molecules present in the plasma generated by laser ablation. The mechanism of cluster formation is intimately associated with the presence of neutral or ionized species (water, sulfate, nitrate...). In particular, the hydration effect is very dependent on initial chromium salt. This methodology is used for the determination of chromium valency in aerosols less than 10 Ixrn in size emitted as dust by the steel industry. The systematic LAMMA analysis of the aerosols showed that the oxidation of chromium depends on the aerosol size.
A VECTOR MODEL FOR PREDICTING PARTICLE DEPOSITION IN GRANULAR BEDS AND IN THE RESPIRATORY TRACT UNDER THE SIMULTANEOUS ACTION OF DIFFUSION AND SEDIMENTATION J. W . G e n t r y , J. G e b h a r t a n d G . S c h e u c h GSF-Forschungszentrum f/Jr Umwelt und Gesundheit GmbH, Paul Ehrlich Strasse 20, D-60596 Frankfurt/Main, Germany Abstract--A vector model has been developed for prediction of particle deposition in porous bed filters and in lungs when diffusion and sedimentation operate simultaneously. The model is used to calculate upper and lower bounds for the deposition efficiency. The model shows good agreement with experiment.