Traffic-generated fugitive dust is a source of urban atmospheric particulate pollution in Beijing. This paper introduces the resuspension method, recommended by the US EPA in AP-42 documents, for collecting Beijing ro...Traffic-generated fugitive dust is a source of urban atmospheric particulate pollution in Beijing. This paper introduces the resuspension method, recommended by the US EPA in AP-42 documents, for collecting Beijing road-surface dust. Analysis shows a single-peak distribution in the number size distribution and a double-peak mode for mass size distribution of the road surface dust. The median diameter of the mass concentration distribution of the road dust on a high-grade road was higher than that on a low-grade road. The ratio of PM2.5 to PM10 was consistent with that obtained in a similar study for Hong Kong. For the two selected road samples, the average relative deviation of the size distribution was 10.9% and 11.9%. All results indicate that the method introduced in this paper can effectively determine the size distribution of fugitive dust from traffic.展开更多
In this paper we investigate the dust surface potential at the sheath edge of electronegative dusty plasmas theoretically, using the standard fluid model for the sheath and treating electrons and negative ions as Bolt...In this paper we investigate the dust surface potential at the sheath edge of electronegative dusty plasmas theoretically, using the standard fluid model for the sheath and treating electrons and negative ions as Boltzmann particles but positive ions and dust grains as cold fluids. The dust charging model is self-consistently coupled with the sheath formation criterion by the dust surface potential and the ion Mach number, moreover the dust density variation is taken into account. The numerical results reveal that the dust number density and negative ion number density as well as its temperature can significantly affect the dust surface potential at the sheath edge.展开更多
Concentrations of polybrominated diphenyl ethers(PBDEs)and selected novel brominated flame retardants(NBFRs)were measured in indoor dust from the living areas of 18 homes in Basrah,Iraq.This is the first report of con...Concentrations of polybrominated diphenyl ethers(PBDEs)and selected novel brominated flame retardants(NBFRs)were measured in indoor dust from the living areas of 18 homes in Basrah,Iraq.This is the first report of contamination of the Iraqi environment with these chemicals.To evaluate the implications for human exposure,samples were collected from both the floor and from elevated surfaces like tables,shelves and chairs.When normalised for the organic carbon content of the dust sample,concentrations in elevated surface dust of BDE-99,BDE-209,pentabromoethylbenzene(PBEB),bis(2-ethylhexyl)3,4,5,6-tetrabromophthalate(BEH-TEBP),and decabromodiphenylethane(DBDPE)exceeded significantly(p<0.05)those in floor dust from the same rooms.This suggests that previous studies that base estimates of adult exposure via dust ingestion on floor dust,may underestimate exposure.Such underestimation is less likely for toddlers who are far more likely to ingest floor dust.Concentrations of PBDEs and NBFRs in indoor dust from Basrah,Iraq are at the lower end of levels reported elsewhere.The PBDE contamination pattern in our samples suggests that use in Iraq of the Deca-BDE formulation,exceeds substantially that of Penta-BDE,but that use of the Octa-BDE formulation has been higher in Iraq than in some other regions.Reassuringly,our estimates of exposure to our target BFRs via dust ingestion for the Iraqi population fall well below the relevant health-based limit values.展开更多
文摘Traffic-generated fugitive dust is a source of urban atmospheric particulate pollution in Beijing. This paper introduces the resuspension method, recommended by the US EPA in AP-42 documents, for collecting Beijing road-surface dust. Analysis shows a single-peak distribution in the number size distribution and a double-peak mode for mass size distribution of the road surface dust. The median diameter of the mass concentration distribution of the road dust on a high-grade road was higher than that on a low-grade road. The ratio of PM2.5 to PM10 was consistent with that obtained in a similar study for Hong Kong. For the two selected road samples, the average relative deviation of the size distribution was 10.9% and 11.9%. All results indicate that the method introduced in this paper can effectively determine the size distribution of fugitive dust from traffic.
文摘In this paper we investigate the dust surface potential at the sheath edge of electronegative dusty plasmas theoretically, using the standard fluid model for the sheath and treating electrons and negative ions as Boltzmann particles but positive ions and dust grains as cold fluids. The dust charging model is self-consistently coupled with the sheath formation criterion by the dust surface potential and the ion Mach number, moreover the dust density variation is taken into account. The numerical results reveal that the dust number density and negative ion number density as well as its temperature can significantly affect the dust surface potential at the sheath edge.
基金financial support and the Ministry of Higher Education and Scientific Research(MOHESR)for administrative support.
文摘Concentrations of polybrominated diphenyl ethers(PBDEs)and selected novel brominated flame retardants(NBFRs)were measured in indoor dust from the living areas of 18 homes in Basrah,Iraq.This is the first report of contamination of the Iraqi environment with these chemicals.To evaluate the implications for human exposure,samples were collected from both the floor and from elevated surfaces like tables,shelves and chairs.When normalised for the organic carbon content of the dust sample,concentrations in elevated surface dust of BDE-99,BDE-209,pentabromoethylbenzene(PBEB),bis(2-ethylhexyl)3,4,5,6-tetrabromophthalate(BEH-TEBP),and decabromodiphenylethane(DBDPE)exceeded significantly(p<0.05)those in floor dust from the same rooms.This suggests that previous studies that base estimates of adult exposure via dust ingestion on floor dust,may underestimate exposure.Such underestimation is less likely for toddlers who are far more likely to ingest floor dust.Concentrations of PBDEs and NBFRs in indoor dust from Basrah,Iraq are at the lower end of levels reported elsewhere.The PBDE contamination pattern in our samples suggests that use in Iraq of the Deca-BDE formulation,exceeds substantially that of Penta-BDE,but that use of the Octa-BDE formulation has been higher in Iraq than in some other regions.Reassuringly,our estimates of exposure to our target BFRs via dust ingestion for the Iraqi population fall well below the relevant health-based limit values.
