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1.
Kikuo Oikawa Hiroko Saito Ikuei Kifune Tatsuo Ohshina Masami Fujii Yukio Takizawa 《Chemosphere》1982,11(9):943-951
To study atmospheric mercury absorption in human respiratory passage-ways, mercury in expired air was measured in three different states of breathing: steady breathing, deep breathing and breath held after inspiration.In this study, air containing mercury was inhaled through the nose and expired through the mouth. The concentration of mercury in the exhaled air was determined by the technique of gold-amalgam trapping, heat vaporization, and flameless atomic absorption measurement.The subjects were 13 male adults, aged 25–62 years, and 38 cases were observed. Four different concentrations of mercury, 1–3, 4–6, 10–11, and 20–30 μg/m3 were used, and absorption for each was determined. When the concentration was 1–3 μg/m3, the absorption was 74–92%, the average being 82.5%. At concentrations of 4–6, 10–11, and 20–30 μg/m3, the absorption was 76.6–100%, 75.5–99.2%, and 79.9–95.9% respectively, and the average was 88.8%, 85.2%, and 87.7% respectively.A slightly higher rate of mercury absorption was observed in deep breathing than in steady breathing, and when expiration was suppressed for some time after inspiration, the rate increased remarkably to 97.4–99.7%. Prolonged retention of inhaled air containing mercury in the respiratory tract is believed to have caused the increased absorption. 相似文献
2.
Matsuyama T Tamaoki M Nakajima N Aono M Kubo A Moriya S Ichihara T Suzuki O Saji H 《Environmental pollution (Barking, Essex : 1987)》2002,117(2):191-194
Various detrimental factors in the environment damage plants, resulting in growth inhibition or withering. However, it is not easy to identify causal factors by visually inspecting the damaged plants. Therefore, we have developed a sensitive and reliable method for plant diagnosis, based on measuring changes in expression of a set of genes in a DNA microarray. With this method, we have been able to detect and discriminate between plants stressed by ozone, drought, or wounding. 相似文献
3.
Dechlorination of polychlorinated dibenzo-p-dioxins catalyzed by noble metal catalysts under mild conditions 总被引:3,自引:0,他引:3
Dechlorination of polychlorinated dibenzo-p-dioxins such as 2,7-dichlorodibenzo-p-dioxin (2,7-DCDD) and 1,2,6,7-tetrachlorodibenzo-p-dioxin (1,2,6,7-TCDD) was carried out in a solution of NaOH in 2-propanol in the presence of carbon-supported noble metal catalyst (Pd/C or Rh-Pt/C) at temperatures between 23 and 35 degrees C. At initial concentrations of 140-240 micrograms/ml, 2,7-DCDD and 1,2,6,7-TCDD were efficiently converted to a chlorine-free product, dibenzo-p-dioxin (DD), in high yield (60-80%). The conversion of 2,7-DCDD and 1,2,6,7-TCDD and the yield of DD were hardly affected by the atmosphere (N2 or air). We postulate that the displacement of aromatic chlorines by hydrogen selectively occurs on the catalyst, involving hydrogen-transfer from 2-propanol to the substrates. 相似文献
4.
Vagile animals usually have bilaterally symmetrical bodies and proceed with their mouth-end first. Regular sea urchins have,
however, radially symmetrical bodies with their mouth facing the substratum and show no preference in which side of the body
should be anterior in their locomotion. The elliptical sea urchins in the subfamily Echinometrinae are exceptional among regular
sea urchins in having elongated bilateral bodies. We studied whether they showed the preference in the direction of locomotion
using Echinometra sp. type A. Directional preference was not observed in the proceedings in an open space. However, they proceeded preferentially
with their long axis coinciding with the direction of locomotion when they moved along the water surface or along the wall
of the aquarium. The speed of locomotion was the same irrespective of the direction of proceedings and of whether sea urchins
moved freely or moved along the water surface or along the walls. We suggest that the bilateral body form and the habit of
long-axis lead of this sea urchin have adaptive significance to increase the protected body surfaces, not to facilitate the
efficiency in locomotion. 相似文献
5.
Regular sea urchins, which have pentaradial symmetry, have been believed to show no preference in which part of the body forward
they proceed with. Through use of circular statistics, we show that the regular sea urchin Hemicentrotus pulcherrimus had no preference with respect to what body part, as determined by Lovén’s system, should be anterior in locomotion. The
sea urchins, however, preferably proceeded with the body part, which had contacted with the aquarium walls at rest, forward.
When the contact part was artificially altered, the body part facing forward in the following proceeding changed accordingly:
the animals walked with the part that had contacted last forward. The biological significance of this behavior was discussed
in relation to the aggregation formation and homing behavior. 相似文献
6.
In order to determine competency of sexual reproduction and survival rate after fragmentation, the branching coral Acropora formosa was fragmented and fragments in three different sizes (ca. 5, 10 and 20 cm long) and three different stages of gametogenesis
were transplanted on coral pavement. Their oocyte development and fecundity, as well as spawning were monitored for a 3-year
period. The oocyte development was affected by both fragment size and by the developmental stage of oocytes when fragmented.
In small fragments, the oocytes were resorbed while in large fragments they continued development. Oocytes in the early vitellogenic
stage at the time of fragmentation were resorbed, whereas those in the late stage continued developing. Smaller fragments
showed a lower survival rate and histological observations of their gonads revealed resorption of oocytes, suggesting that
there was a trade-off of energy between reproduction and survival. Transplanted fragments often spawned one month earlier
than the donor colonies in the first year, but spawning occurred in the same month as the donors or did not occur at all in
the second year and none spawned in the third year. The risk of colony death may cause the fragments to re-allocate energy
for sexual reproduction. 相似文献
7.
Measuring sorption of hydrophilic organic compounds in soils by an unsaturated transient flow method
Determination of sorption of hydrophilic, weakly sorbing organic compounds in soil by conventional batch methods using a slurried suspension is often prone to considerable errors because small changes in the solution concentration on equilibration must be accurately determined. This difficulty is exacerbated for compounds susceptible to degradation, which also decreases the solution concentration. The objective of this study was to determine sorption of hydrophilic pesticides by applying an unsaturated transient flow method, which enables determination of sorption at sufficiently small solution to soil ratios. The method makes use of piston-like displacement of the antecedent solution in equilibrium with sorbed phase when pesticide-free water is infiltrated into a soil column spiked with a pesticide. Pesticide sorption and the solution concentration are inferred from a plot of total pesticide content per unit mass of soil vs. water content in a region where the antecedent solution is accumulated. Thus, extraction of solution from relative dry soil is unnecessary. We tested this method for two hydrophilic pesticides, monocrotophos [dimethyl (E)-1-methyl-2-(methyl-carbamoyl) vinyl phosphate] and dichlorvos (2,2-dichlorovinyl dimethyl phosphate). The sorption coefficient, K(d), obtained for monocrotophos was slightly lower than that by batch method (K(d) = 0.10 vs. 0.19 L kg(-1)), whereas for dichlorvos, a compound highly susceptible to degradation, the unsaturated flow method yielded a much smaller K(d) (0.19 vs. 3.22 L kg(-1)). The K(d) values for both compounds were consistent with the observed retardation in the pesticide displacement in the columns. The proposed method is more representative of field conditions and particularly suitable for weakly sorbing organic compounds in soils. 相似文献
8.
In this study, the TiO2 photocatalytic decomposition process of aqueous phenol was investigated. The intermediate products generated in the elementary reaction steps in the mineralization process were experimentally identified as hydroquinone, catechol and hydroxyhydroquinone. The concentration variations of these intermediate products with time passage were traced by high performance liquid chromatograph. The pathways of the decomposition process were given. Based on Langmuir isothermal theory and Langmuir-Hinshelwood mechanism, the multi-compounds competition kinetic model was established. In this model, the observed time-dependent concentrations of phenol and the intermediate products were simulated. 相似文献
9.
10.
A review of rapid transport of pesticides from sloping farmland to surface waters:Processes and mitigation strategies 总被引:3,自引:0,他引:3
Pesticides applied to sloping farmland may lead to surface water contamination through rapid transport processes as influenced by the complex topography and high spatial variability of soil properties and land use in hilly or mountainous regions. However, the fate of pesticides applied to sloping farmland has not been sufficiently elucidated. This article reviews the current understanding of pesticide transport from sloping farmland to surface water. It examines overland flow and subsurface lateral flow in areas where surface soil is underlain by impervious subsoil or rocks and tile drains. It stresses the importance of quantifying and modeling the contributions of various pathways to rapid pesticide loss at catchment and regional scales. Such models could be used in scenario studies for evaluating the effectiveness of possible mitigation strategies such as constructing vegetated strips, depressions, wetlands and drainage ditches, and implementing good agricultural practices. Field monitoring studies should also be conducted to calibrate and validate the transport models as well as biophysical-economic models, to optimize mitigation measures in areas dominated by sloping farmland. 相似文献