Characterization of Activated Carbon Fiber Filters for Pressure Drop,Submicrometer Particulate Collection,and Mercury Capture

ABSTRACT

The use of activated carbon fiber (ACF) filters for the capture of particulate matter and elemental Hg is demonstrated. The pressure drop and particle collection efficiency characteristics of the ACF filters were established at two different face velocities and for two different aerosols: spherical NaCl and combustion-generated silica particles. The clean ACF filter specific resistance was 153 kg m^-2 sec^-1. The experimental specific resistance for cake filtration was 1.6 × 10⁶ sec^-1 and 2.4 × 10⁵ sec^-1 for 0.5- and 1.5-μm mass median diameter particles, respectively. The resistance factor R was approximately 2, similar to that for the high-efficiency particulate air filters. There was a discrepancy in the measured particle collection efficiencies and those predicted by theory. The use of the ACF filter for elemental Hg capture was illustrated, and the breakthrough characteristic was established. The capacity of the ACF filter for Hg capture was similar to other powdered activated carbons.     

Removal of hydrogen chloride from gaseous streams using magnesium-aluminum oxide

Magnesium-aluminum oxide (Mg-Al oxide) obtained by thermal decomposition of Mg-Al layered double hydroxide (Mg-Al LDH) effectively removed HCl from gaseous streams. HCl removal was greater in the presence of added water vapor at all temperatures examined and increased with decreasing temperature in both the presence and absence of added water vapor. Wet and dry removal of gaseous HCl were attributed to the production of MgCl2 . 6H2O and MgCl2 . 4H2O, respectively. For the wet scrubbing process, the reconstruction reaction of Mg-Al LDH from Mg-Al oxide was the primary mechanism for increased HCl removal.     

Levels and regional trends of persistent organochlorines and polybrominated diphenyl ethers in Asian breast milk demonstrate POPs signatures unique to individual countries

Human breast milk samples collected in 2007–2008 from four countries, Vietnam (Hanoi), China (Beijing), Korea (Seoul) and Japan (Sendai, Kyoto and Takayama), were analyzed for persistent organic pollutants (POPs) such as dichlorodiphenyltrichloroethane and its metabolites (DDTs), chlordane-related compounds (CHLs), hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). Comparing with previous surveys, the present study indicates that the DDTs in breast milk from China and Vietnam had gradually decreased during the last decade, but were still 5–10 times higher than those in other nations. The ratios of p,p′-DDE/p,p′-DDT and o,p′-DDT/p,p′-DDT were higher in Beijing than in the other countries, suggesting that there is less fresh intake of commercial DDT products and a possible exposure to dicofol in China. CHL and PCB levels were relatively higher in mothers from Japan, whereas β-HCH and HCB were more common in Chinese women. In Japan, it is suspected that mothers in the urban/coastal area (Sendai) were more continuously exposed to organochlorine pesticides (OCPs) than mothers in the rural/inland area (Takayama). In addition, OCP levels in primiparae were significantly higher than those in multiparae from Japan and Korea. These indicate that both parity and regional factors are major determinants of the levels of OCPs and PCBs in human milk. On the other hand, higher concentrations of PBDEs were observed in mothers' milk from Korea. The congener was dominated by BDE-47 (43–54%), followed by BDE-153 (23–33%) in all regions except for Beijing where BDE-28 (23%) was relatively abundant. In Japanese breast milk, regional and parity-dependent distributions were not observed for PBDEs. Among PBDE congeners, age-dependency was observed for BDE-153, which was negatively correlated (p < 0.05) to the age of mothers in Kyoto (17 participants were housewives), while it increased with age in Sendai (10 participants were clerks). No such correlation was seen for BDE-47, indicating that BDE-47 was ingested and assimilated via different kinetics or routes from BDE-153 in Japan.     

The relationship between seasonal variations of total-nitrogen and total-phosphorus in rainfall and air mass advection paths in Matsue,Japan

We collected rainwater samples from every rainfall in Matsue, Japan in order to study variations of nitrogen and phosphorus concentrations over time. The seasonal average concentration by magnitude order of Total Nitrogen (here after T-N) was highest in winter, then in spring, fall, and summer and that of Total Phosphorus (here after T-P) was highest in spring, then in winter, fall, and summer. These seasonal variations were examined in relation to the transportation paths of arrived air masses by using a backward trajectory and rainfall patterns from a surface synoptic weather chart. In winter, continental air masses frequently flow from China or Siberia and the resultant winter rainfall is on many occasions of a continental type. In summer, maritime air masses frequently arrive from the Pacific Ocean and this resultant rainfall therefore was often of maritime type. Looking at average concentrations of T-N and T-P for each rainfall type, continental types were high range and maritime types were low. It was therefore concluded that the monthly average concentration of T-N was affected by continental air masses from northern China in winter and by maritime ones from the Pacific Ocean in summer. The maximum deposition of T-N was caused by this concentration in winter and rainfall depth in summer. Seasonal variation of T-P showed a different fluctuation tendency from T-N, with a maximum concentration in spring, and minimum in summer and fall. T-P was susceptible to the yellow sand phenomenon which maximised T-P deposition in spring.     

Annual reproductive cycle of the chiton Acanthopleura japonica

Annual reproductive cycle of the chiton Acanthopleura japonica (Lischke) was studied by observing both gonad index and histological features from October 1980 to October 1981. No significant changes in each factor were observed from October to April. Increased values of gonad index and spermatogenesis or vitellogenesis in gondas were observed from May to September. In the same time, gonad index decreased and sperms or oocytes in gonalds disappeared in the days around spring tide, and they were recovered around neap tide. Suggested spawning around spring tide from May to September is also supported by the occurrence of released eggs in the days around the new and full moons.     

Detection of Asian dust aerosols using meteorological satellite data and suspended particulate matter concentrations

The advection and dispersion of Asian dust events from China to the Pacific Ocean around Japan during 2000–2002 were investigated using the meteorological satellite data of NOAA/AVHRR and GMS-5/VISSR. Aerosol vapour index images, taking the brightness temperature difference between 11 and 12 μm, are very effective for monitoring the Asian dust phenomenon in the East Asia region, with their capacity for detection during the day or night. We discuss the dust events, focusing on the advection patterns shown in satellite images, which are classified into three types as ‘dry slot’, ‘high-pressure wedge’ and ‘travelling high’, based on synoptic patterns. The results are compared with suspended particulate matter concentrations measured at Japanese surface stations and with ground-based observations of Sakurajima volcano by a web camera system at Kagoshima in Kyushu, Japan. We found that the passage of cold fronts caused a rapid increase of suspended particulate matter (SPM) concentrations, which exceeded 100 μg m⁻³, and that deep low-pressure complexes strengthened the dust phenomenon. The ‘high-pressure wedge’ type is seen much more clearly in satellite images than the ‘travelling high’ type, but SPM concentrations and visibility were similar in both owing to the differences in the vertical distribution of the dust and in viewing conditions.     

Investigation of the hemolytic effects of various organophosphoric acid triesters (OPEs) and their structure‐activity relationship

The hemolytic effects of various organophosphonc acid triesters (OPEs) were investigated and they showed strong hemolyic toxicity except triethyl phosphate and tris(chloroethyl)phosphate. 2‐Ethylhexyl diphenyl phosphate (EHDP) showed the strongest toxicity. By quantitative structure‐activity relationship (QSAR) study, one‐parameter regression equation to estimate hemolysis was not obtained. But, two‐parameter regression equations were obtained which were enought to estimate EC₅₀ and EC₂₀. The correlation coefficients with the two‐parameter regression equations were 0.939 for log(l/EC₅₀) and 0.946 for log(l/EC₂₀).     

The effects of KI/Se(VI) molar ratio and initial concentration of Se(VI) on the reduction of Se(VI) to Se(IV) by KI

In this study, potassium iodide (KI) was found to be capable of reducing selenium(VI) to selenium(IV). When KI was added to Se(VI) solution, the Se(VI) concentration rapidly decreased with an increase in the KI/Se(VI) molar ratio. By using the potential-pH equilibrium diagram for the selenium/water system, we confirmed that Se(VI) reduced to Se(IV) because the potential of the solution shifted to the stable Se(IV) region upon the addition of KI. This reduction accompanies the oxidation of I⁻ to I₃⁻. The reduction of Se(VI) by KI was found to be effective for concentrated Se(VI) solutions.