日本的碳储量

为估计所谓的非能源用途矿物燃料排放的CO2,建立了NEAT(Nonenergy use Emission Accounting Tables,非能源排放统计表)模型.物质流动的统计是该模型的基础.NEAT模型已在许多国家应用,以便验证该模型并促进其应用.本文讨论日本的研究案例.NEAT分析表明:1996年的CO2排放量比以前政府间气候变化委员会(IPCC)指导原则基础上的估计高出23t,相当于日本温室气体总排放量的1.9%.因此,在未来几年,调整日本的排放计算方法,提供更为详细的排放估计方法是可取的.鉴于其它国家的相似结果,建议改进IPCC的指导原则.     

Mobilization of arsenic from subsurface sediments by effect of bicarbonate ions in groundwater

Arsenic leaching by bicarbonate ions has been investigated in this study. Subsurface sediment samples from Bangladesh were treated with different carbonate and bicarbonate ions and the results demonstrate that the arsenic leaching efficiency of the carbonate solutions decreased in the order of Na2CO3>NaHCO3>BaCO3>MnCO3. Sodium carbonate and bicarbonate ions extracted arsenic most efficiently; Na2CO3 leached maximum 118.12 microg/l of arsenic, and NaHCO3, 94.56 microg/l of arsenic from the Ganges delta sediments after six days of incubation. The arsenic concentrations extracted in the batch experiments correlated very well with the bicarbonate concentrations. The kinetics study of arsenic release indicates that arsenic-leaching rate increased with reaction time in bicarbonate solutions. Bicarbonate ions can extract arsenic from sediment samples in both oxic and anoxic conditions. A linear relationship found between arsenic contents in core samples and those in leachates suggests that dissolved arsenic concentration in groundwater is related to the amount of arsenic in aquifer sediments. In batch experiment, bicarbonate solutions effectively extracted arsenic from arsenic adsorbed iron oxyhydroxide, reflecting that bicarbonate solutions may mobilize arsenic from iron and manganese oxyhydroxide in sediments that are ubiquitous in subsurface core samples. Carbonate ion may form complexes on the surface sites of iron hydroxide and substitute arsenic from the surface of minerals and sediments resulting in release of arsenic to groundwater. Like in the batch experiment, arsenic and bicarbonate concentrations in groundwater of Bangladesh correlated very well. Therefore, bicarbonate leaching is presumed to be one important mechanism to mobilize arsenic in bicarbonate dominated reducing aquifer of Bangladesh and other parts of the world as well.     

Environmental conditions for the formation of insoluble Tc in water ponds located above paddy fields

Optimum conditions for the formation of insoluble Tc (Tc in >0.2 microm size fraction) were studied using a microcosm including water ponds above a paddy field to understand Tc behavior in such fields. In the microcosm, soluble TcO(4)(-) was converted to insoluble forms, but no changes in the form of Tc were observed in filtered microcosm samples which were microorganisms-free. The formation of insoluble Tc was inhibited by the addition of the antibiotic chloramphenicol. In addition, the reduction of soluble Tc(VII)O(4)(-) to low-valence oxide was not observed in the filtered microcosm samples, although reducing conditions were present. These results indicated that bacteria were involved in the formation of insoluble Tc. Since oxidizing conditions influence bacterial metabolism, the formation of insoluble Tc by bacteria was studied under aerobic and anaerobic conditions. The results showed that anaerobic conditions were favorable for the formation of insoluble Tc. In addition, the addition of formate as an electron donor to a microcosm sample facilitated the formation of insoluble Tc. The results suggested that insoluble Tc in the water ponds above paddy fields was caused by bacteria, which were shown to couple the oxidation of formate to the reduction of Tc(VII) during anaerobic respiration.     

Elementary budget of stag beetle larvae associated with selective utilization of nitrogen in decaying wood

Wood degradation by insects plays important roles for the forest matter cycling. Since wood is deficient in nitrogen compared to the insect body, wood-feeding insects need to assimilate the nitrogen selectively and discard an excess carbon. Such a stoichiometric imbalance between food and body will cause high metabolic cost; therefore, wood-feeding insects may somehow alleviate the stoichiometric imbalance. Here, we investigated the carbon and nitrogen budgets of the larvae of stag beetle, Dorcus rectus, which feed on decaying wood. Assimilation efficiency of ingested wood was 22%, and those values based on the carbon and nitrogen were 27 and 45%, respectively, suggesting the selective digestion of nitrogen in wood. Element-based gross growth efficiency was much higher for nitrogen (45%) than for carbon (3%). As a result, the larvae released 24% of the ingested carbon as volatile, whereas almost no gaseous exchange was observed for nitrogen. Moreover, solubility-based elementary analysis revealed that the larvae mainly utilized alkaline-soluble-water-insoluble fraction of wood, which is rich in nitrogen. Actually, the midgut of the larvae was highly alkaline (pH 10.3). Stag beetle larvae are known to exhibit coprophagy, and here we also confirmed that alkaline-soluble-water-insoluble nitrogen increased again from fresh feces to old feces in the field. Stable isotope analysis suggested the utilization of aerial nitrogen by larvae; however, its actual contribution is still disputable. Those results suggest that D. rectus larvae selectively utilize alkaline-soluble nitrogenous substrates by using their highly alkaline midgut, and perhaps associate with microbes that enhance the nitrogen recycling in feces.     

Concentrations of dioxins and related compounds in the blood of Fukuoka residents

Blood samples of 152 residents (male 75 and female 77) aged 20-60 years in Fukuoka, Japan, were analyzed for dioxin toxic compounds of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), non-ortho polychlorinated biphenyls (non-ortho PCBs) and mono-ortho polychlorinated biphenyls (mono-ortho PCBs) as well as 35 PCB congeners and 12 chlorinated pesticides by high-resolution gas chromatography/high-resolution mass spectrometry. Average concentrations of dioxin toxic equivalents (TEQ) from PCDDs, PCDFs, non-ortho PCBs, mono-ortho PCBs and their total in the blood of 152 residents were 10.28, 5.56, 7.75, 4.57 and 28.15 ppt in lipid, respectively. These total TEQ levels were comparable to the blood TEQ levels of normal Japanese (n=735). Lipid basis total TEQ levels progressively increased in the males from 17.1 ppt at age 20s to 47.5 ppt at age 50s and in the females from 19.5 ppt at age 20s to 54.5 ppt at age 50s. Dioxin toxic contribution of PCBs to total TEQ was increased from 31% at age 20s to 55% at age 50s. Average concentrations of total 35 PCBs and total 12 pesticides in the blood of 151 residents were 386 and 1079 ppb in lipid, respectively. Average concentrations (ppb in lipid) of total PCBs and total pesticides also progressively increased in the males from 213 and 444 at age 20s to 868 and 2140 at age 50s, respectively, and in the females from 199 and 588 at age 20s to 550 and 1977 at age 50s, respectively. The levels of TEQ, PCBs, hexachlorobenzene, beta-hexachlorocyclohexane, dieldrin, p,p'-dichlorodiphenyldichloroethylene, p,p'-dichlorodiphenyltrichloroethane, trans-nonachlor and cis-nonachlor were positively correlated with each other in most of the combinations, and the highest correlations (r>0.8) were observed between total TEQ and PCBs in both sexes.     

Analysis of bumblebee visitation sequences within single bouts: implication of the overstrike effect on short-term memory

Pollinators whose foraging habitats consist of several plant types (species or morph) may continue to choose the plant type last visited because information about the type of plant last visited dominates over all other memory contents, in particular of short-term memory. In this study, I extracted this overstrike effect on the plant choices of pollinators by analyzing patterns of visitation sequences within a single round-trip between the hive and foraging patch (bout). First, I simulated the visitation sequences within single bouts with a model to show how factors, including the bees plant-type preferences, the arrangement of plants and the effect of overstrike on short-term memory, affect visitation sequences. Here, bees are assumed to forage in a patch consisting of two plant types (H and L). The model predicts that only the effect of overstrike on short-term memory causes assorted visitation sequences according to plant type (within-bout flower constancy). That is, if the overstrike-effect on short-term memory is the primary determinant of plant choice, then bees will fly to a type-L plant after visiting a type-L plant even if they predominantly visit type-H plants and vice versa. Next, I investigated individual bumblebees visitation sequences at a patch of artificial inflorescences with a set-up similar to that assumed in the model. Two types of inflorescences were arranged on a Cartesian grid. Assorted visitation sequences according to inflorescence type were observed, depending on the distances among inflorescences. This result supports the hypotheses that bees fly to the same plant type as that last visited because short-term memory is displaced (overstruck) with information about the most recently visited plant type.Communicated by M. Giurfa     

Spatial distribution and source identification of wet deposition at remote EANET sites in Japan

Wet deposition of major ions was discussed from the viewpoint of its potential sources for six remote EANET sites in Japan (Rishiri, Happo, Oki, Ogasawara, Yusuhara, and Hedo) having sufficiently high data completeness during 2000–2004. The annual deposition for each site ranged from 12.1 to 46.6 meq m⁻² yr⁻¹ for nss-SO₄²⁻, from 5.0 to 21.9 meq m⁻² yr⁻¹ for NO₃⁻. The ranges of annual deposition of the two ions for the sites were lower than those for urban and rural sites in Japanese Acid Deposition Survey by Ministry of the Environment, Japan, and higher than those for global remote marine sites. Factor analysis was performed on log-transformed daily wet deposition of major ions for each site. The obtained two factors were interpreted as (1) acid and soil source (or acid source for some sites), and (2) sea-salt source for all the sites. This indicates that wet deposition of ions over the remote areas in Japan has a similar structure in terms of types of sources. Factor scores of acid and soil source were relatively high during Kosa (Asian dust) events in spring in western Japan. Back-trajectories for high-deposition episodes of acid and soil source (or acid source) for the remote sites showed that episodic air masses frequently came from the northeastern area of Asian Continent in spring and winter, and from central China in summer and autumn. This indicates a large contribution of continental emissions to wet deposition of ions over the remote areas in Japan.     

The influence of lower extremity postures on kinematics and injuries of cyclists in vehicle side collisions

Objective: A cyclist assumes various cyclic postures of the lower extremities while pushing the pedals in a rotary motion while pedaling. In order to protect cyclists in collisions, it is necessary to understand what influence these postures have on the global kinematics and injuries of the cyclist.

Method: Finite element (FE) analyses using models of a cyclist, bicycle, and car were conducted. In the simulations, the Total Human Model of Safety (THUMS) occupant model was employed as a cyclist, and the simulation was set up such that the cyclist was hit from its side by a car. Three representative postures of the lower extremities of the cyclist were examined, and the kinematics and injury risk of the cyclist were compared to those obtained by a pedestrian FE model. The risk of a lower extremity injury was assessed based on the knee shear displacement and the tibia bending moment.

Results: When the knee position of the cyclist was higher than the hood leading edge, the hood leading edge contacted the leg of the cyclist, and the pelvis slid over the hood top and the wrap-around distance (WAD) of the cyclist's head was large. The knee was shear loaded by the hood leading edge, and the anterior cruciate ligament (ACL) ruptured. The tibia bending moment was less than the injury threshold. When the cyclist's knee position was lower than the hood leading edge, the hood leading edge contacted the thigh of the cyclist, and the cyclist rotated with the femur as the pivot point about the hood leading edge. In this case, the head impact location of the cyclist against the car was comparable to that of the pedestrian collision. The knee shear displacement and the tibia bending moment were less than the injury thresholds.

Conclusion: The knee height of the cyclist relative to the hood leading edge affected the global kinematics and the head impact location against the car. The loading mode of the lower extremities was also dependent on the initial positions of the lower extremities relative to the car structures. In the foot up and front posture, the knee was loaded in a lateral shear direction by the hood leading edge and as a result the ACL ruptured. The bicycle frame and the struck-side lower extremity interacted and could influence the loadings on lower extremities.     

Effect of carbon particles on heavy metal emissions under ash-melting conditions

In Japan, incineration ash is subjected to a melting process to reduce waste volume and to stabilize hazardous heavy metals. In previous articles, we reported that large quantities of volatile metals are emitted under ash-melting conditions at temperatures higher than 1200°C and that such emissions are considerably increased under reducing conditions. However, the emission behavior in the presence of large amounts of char particles was unclear, and we suspected that emissions under these conditions might differ from emissions under the previous conditions. Therefore, we investigated heavy metal emissions and the melting characteristics of ash in the presence of carbon particles. In this experiment, a small crucible with ash and carbon was rapidly heated using a high-frequency induction-heating furnace to simulate the melting ash gasification with carbon. As a result, it was found that additive carbon can promote emissions of heavy metals such as zinc and lead and control the melt of the ash.