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 10,214 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The assessment of the fire-fighters' exposure to harmful chemicals during the fire attendance is presented. The assessment was based on measurements of carbon monoxide, nitrogen dioxide, sulfur dioxide, formaldehyde and aromatic hydrocarbons of five fire-fighting actions. Using passive dosimeters, personal air samples were collected. A portable Draeger-PAC III was used for measuring carbon monoxide. Above 130 chemicals were detected in the environment of the fire attendance. Among them aliphatic hydrocarbons C6-C16 were dominant. Benzene and its aliphatic homologues were also found in all air samples. The carbon monoxide concentration accounted for up to 720 mg/m3. Concentrations of nitrogen dioxide, sulfur dioxide, formaldehyde and benzene ranged from 0.0 to 49.9 mg/m3; 84.5 mg/m3; 5.3 mg/m3 and 89.4 mg/m3, respectively.
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PMID:[Chemical hazards in fire-fighting environments]. 1105 6

The design and operation of air sparging and soil vapor extraction (AS/SVE) remediation systems remains in large an art due to the absence of reliable physically based models that can utilize the limited available field data. In this paper, a numerical model developed for the design and operation of air sparging and soil vapor extractions systems was used to simulate two field case studies. The first-order mass transfer kinetics were incorporated into the model to account for contaminant mass transfer between the water and air (stripping), NAPL and water (dissolution), NAPL and air (volatilization), and water and soil (sorption/desorption), the model also accounted for soil heterogeneity. Benzene, toluene, ethyl benzene and xylenes (BTEX) were the contaminants of concern in both case studies. In the second case study, the model was used to evaluate the effect of pulsed sparging on the removal rate of BTEX compounds. The pulsed sparging operation was approximated assuming uniform contaminant redistribution at the beginning of the shut-off period. The close comparison between the observed and simulated contaminant concentration in the aqueous phase showed that the approximation of the pulsed sparging operation yielded reasonable prediction of the removal process. Field heterogeneity was simulated using Monte Carlo analysis. The model predicted about 80-85% of the contaminant mass was removed by air-water mass transfer, which was similar to the average removal obtained by Monte Carlo analysis. The analysis of the removal/rebound cycles demonstrated that removal rate was controlled by the organic-aqueous distribution coefficient K(oc). Due to the lack of site-specific data, the aerobic first-order biodegradation coefficients (k(bio)) were obtained from a literature survey, therefore, uncertainty analysis of the k(bio) was conducted to evaluate the contribution of the aerobic biodegradation to total contaminant removal. Results of both case studies showed that biodegradation played a major role in the remediation of the contaminated sites.
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PMID:Application of multiphase transport models to field remediation by air sparging and soil vapor extraction. 1714 13