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11.
Thermodynamic analysis of the role of chlorine and sulfur environments during combustion and incineration processes 总被引:1,自引:0,他引:1
Iddi S.N. Mkilaha Hong Yao Ichiro Naruse 《Journal of Material Cycles and Waste Management》2002,4(2):143-149
In order to control the emission of trace metals from combustion and incineration systems, sorbents and filters are sometimes
used. However, the effectiveness of these methods is greatly affected by the volatility of the metals and the way in which
they speciate during combustion, and afterwards during condensation, and physical or chemical sorption. Although there has
been a lot of research into the mechanisms by which trace metals speciate and subsequently appear in submicron particles,
the details of these mechanisms are not yet thoroughly understood. In this study, a chemical equilibrium approach was used
to qualitatively determine the speciation of lead, cadmium, and chromium in Cl and S environments. The reaction conditions
of sorbents were also tested numerically in order to understand the reaction behavior of metals with sorbents. This article
reports the influence of different concentrations of Cl and SO2 on Pb, Cd, and Cr speciation, as representatives of other trace elements. The partitioning behavior of metals during combustion
was also examined for Cl and S. The results obtained indicate that most metals exist in the vapor phase, even at low temperatures,
when chlorine is present. However, the addition of SO2 enhances the formation of the condensed phase, except at extremely high temperatures. This observation was not significant
for Cd or Cr. The higher the concentration of Cl the higher the retention of trace metals in the vapor phase, even at low
temperatures. Results from comparisons of the reactivities of mixed metals with Cl indicate that the presence of Fe limits
the reactivity of most trace metals with Cl except at higher concentrations. In the presence of Fe, alkali metals are the
first to react with Cl. If Fe is not present, most trace metals react with Cl, and the activity increases with higher concentrations.
On the other hand, the partitioning characteristics of S show that its presence generally means that metals remain in the
condensed phase. Sulfur is more reactive with alkali metals than with other trace metals.
Received: June 6, 2001 / Accepted: April 30, 2002 相似文献
12.
Evaluation of surface runoff and road dust as sources of nitrogen using nitrate isotopic composition 总被引:1,自引:0,他引:1
Stable nitrogen and oxygen isotope ratios of nitrate (δ15N-NO3 and δ18O-NO3) have recently been used to identify nitrogen sources in water environments. However, there have been no investigations designed to determine nitrate isotopes in non-point sources in urban areas for evaluating the impact of surface deposits on nitrogen in surface runoff. In this study, we collected rainwater, surface runoff and surface deposits (road dust, roof dust and soil) to evaluate the nitrogen sources in surface runoff using nitrate isotopes. There were no large differences in δ15N-NO3 among rainwater (−0.3‰ to 1.5‰), surface runoff (−2.7‰ to 0.4‰), leachates from road dust (−5.8‰ to 6.2‰) and soil (−11.5‰ to 0.6‰). In contrast, the δ18O-NO3 in surface runoff (28.5-47.9‰) was lower than that in rainwater (62.7-78.6‰), and higher than that in leachates from road dust (6.1-27.6‰) and soil (−1.1‰ to 6.6‰). δ18O-NO3 is a useful indicator for evaluating the NO3-N sources in surface runoff. Using this indicator, NO3-N from road dust was estimated to account for more than half of the NO3-N in surface runoff. This is consistent with a result based on a comparison of their loads per unit surface between rainwater and surface runoff, which also showed that most of the nitrogen in surface runoff was derived from surface deposits. 相似文献
13.
Ichiro Naruse Ryo Yoshiie Tsutomu Kameshima Tsuyoshi Takuwa 《Journal of Material Cycles and Waste Management》2010,12(2):154-160
Homogeneous oxidation reactions of gaseous elemental mercury were experimentally tested to study the behavior of mercury compounds
that contribute to toxic emissions in combustion flue gas. Chemical equilibrium calculations and reaction kinetics analysis
were also carried out to help explain the experimental results. In particular, the chemical forms of oxidized mercury and
their reaction paths were verified in detail. Among the experimental results, molecular chlorine was confirmed to have a higher
oxidizing ability toward elemental mercury than hydrogen chloride does. From the chemical equilibrium calculation, the final
product of mercury compounds oxidized by chlorine was confirmed to be mercury chloride (HgCl2). Numerical analyses of reaction kinetics were mostly consistent with the experimental results and the chemical equilibrium
calculations. The ratio of mercury oxidization by chlorine increases with temperature from 473 K to 873 K, although it decreases
at temperatures higher than 1000 K. Sensitivity analysis revealed the dominant reaction path of the mercury oxidation by chlorine.
First, elemental mercury reacts with Cl radicals to form HgCl. Then, the HgCl reacts with Cl2 to produce HgCl2. 相似文献
14.
Masashi Kato Shoko Onuma Yoko Kato Nguyen D. Thang Ichiro Yajima Mohammad Zahirul Hoque 《毒物与环境化学》2013,95(9):1609-1612
Toxic elements present in well water that is used for drinking pose a threat to the human health in many countries. However, there are few reports on the toxic elements in well water in Malaysia. Since a native doctor informed us about the increasing number of patients with depigmented skin (vitiligo) in Rosob Village, Sabah State, Malaysia, the origin of diseases associated with well water was suspected. Thus, the concentrations of 15 toxic elements in 52 well water samples from Rosob (n = 21), and the control areas of Pitas (n = 8) and Telaga (n = 23) within the same state were measured. No toxic elements with levels exceeding that of the WHO health-based guidelines were detected in the well water samples from Pitas and Telaga. On the other hand, the concentration levels of arsenic (As), uranium (U), and manganese (Mn), independently found in 19% (4/21), 4.8% (1/21), and 19% (4/21), respectively, of the well water samples from Rosob, exceeded the levels given in the WHO health-based guidelines. In the well water samples from Rosob, the average concentration of Mn was found to be higher and its maximum value with levels up to 10-fold higher, respectively, than the value in the WHO health-based guidelines. Significant correlations between Mn and As and between Mn and U were noted. Thus, for the first time, the results of this pilot study showed that the levels of the toxic elements in 42.9% (9/21) of well water samples from Rosob in Malaysia were higher than the values in WHO health-based guidelines indicating the need for further studies. 相似文献
15.
Shinji Kumagai Ichiro Matsunaga Yukinori Kusaka Koichi Takagi 《Environmental Modeling and Assessment》1996,1(4):277-280
Short-term exposure datasets of 10 workers exposed to organic solvents and daily average exposure datasets of seven workers exposed to cobalt and organic solvents were analyzed in order to clarify whether these exposure data fit an inverse Gaussian distribution. The goodness-of-fit test showed that time-weighted average (TWA) values with averaging times of 30 min, 60 min and 8 hours can be described by an inverse Gaussian distribution, but not those with averaging times of 7.5 min and 15 min. 相似文献
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19.
Ryo Yamada Keita Kodama Takashi Yamakawa Toshihiro Horiguchi Ichiro Aoki 《Marine Biology》2007,151(3):961-971
We investigated the growth and reproductive biology of the penaeid shrimp Trachysalambria curvirostris in Tokyo Bay, Japan, by monthly bottom-trawl surveys from May 2002 to December 2004. We also examined oogenesis in T. curvirostris by histological observation of the ovary. Females grew faster and attained a larger body size for age than males. The growth
rate was high in summer and low in winter and was likely to be associated with seasonal changes in water temperature. The
carapace length (CL) at which 50% of females contained vitellogenic oocytes was estimated to be 17.0 mm. The reproductive
season extended from May to October. Young-of-the-year appeared in October and could be traced across the months on CL histograms
to the following September or October, indicating a 1-year life cycle. This extended reproductive season, together with our
observation of asynchronous development of oocytes in the ovary, suggests that multiple spawning by individual females may
occur during the reproductive season. Postovulated oocytes were not found among the samples we collected during the daytime,
suggesting that final oocyte maturation and spawning occur at night. Cortical crypts in the cytoplasm of the oocyte, considered
to be a general feature of oogenesis in penaeid shrimps, were not found in T. curvirostris, even in oocytes undergoing germinal vesicle breakdown. This result implies that the cortical reaction after spawning of
T. curvirostris may be different from that of other penaeid shrimps. 相似文献
20.
White rot fungi can degrade a wide spectrum of recalcitrant organic pollutants, including polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated biphenyls (PCBs). In this experiment, 20 white rot fungi, belonging to genus Phlebia, were investigated for their ability to degrade dieldrin. Based on the screening results, we further investigated Phlebia acanthocystis, Phlebia brevispora, and Phlebia aurea to determine their degradation capacity and metabolic products towards dieldrin and aldrin. The three fungi were able to remove over 50% of dieldrin in a low nitrogen medium, after 42 d of incubation. Three hydroxylated products were detected as metabolites of dieldrin, suggesting that in Phlebia strains, hydroxylation reactions might play an important role in the metabolism of dieldrin. In contrast to dieldrin, aldrin exhibited higher levels of degradation activity. Over 90% of aldrin was removed after 28 d of incubation, and several new metabolites of aldrin in microorganisms, including 9-hydroxyaldrin and two carboxylic acid products, were detected in fungal cultures. These results indicate that the methylene moiety of aldrin and dieldrin molecules might be prone to enzymatic attack by white rot fungi. In this study, we describe for the first time a new metabolic pathway of both compounds by fungi of genus Phlebia. 相似文献