Dechlorination of PCBs by electrochemical reduction with aromatic radical anion as mediator

Mediated electrochemical reduction was applied to the dechlorination of polychlorinated biphenyls (PCBs) in tetra-n-butylammonium perchlorate/dimethylformamide solution. Rapid and complete dechlorination was possible with biphenyl or naphthalene as the mediator, whereas the reaction was much slower with anthracene or 9,10-diphenylanthracene. The reaction rate was so high with naphthalene or biphenyl radical anion that differences in reactivity could not be observed between congeners. Side reactions, other than biphenyl formation, could occur depending upon the mediators and the substrates, but contributed less than 10% of the total products in the case of naphthalene-mediated dechlorination. Almost all chloride ion formed in the dechlorination remained in the cathode solution. The order of the reaction was determined to be 0.5 for the substrate and 1 for the mediator (naphthalene) in the dechlorination of 2-chlorobiphenyl; identical to results for the mediated dechlorination of 1-chloronaphthalene. The reaction rate in practical PCB dechlorination could be estimated with the use of the initial concentration of the mediator and chlorine content of the solution provided that the problem of the deactivation of the electrode surface could be solved.     

Coral skeletal tin and copper concentrations at Pohnpei, Micronesia: possible index for marine pollution by toxic anti-biofouling paints

We present 40 year-long skeletal chronologies of tin (Sn) and copper (Cu) from an annually-banded coral (Porites sp.) collected from Pohnpei Island, Micronesia (western equatorial Pacific). Both the elements are present in antifouling marine paints and are released inadvertently into ambient seawater. Especially, Sn has often been used in the form of tributyltin (TBT). Based on a stepwise pretreatment examination, Sn and Cu both inside and outside the aragonite lattice of the coral skeleton show a potential for providing marine pollution indicators. High values of extra-skeletal Cu/Ca and Sn/Ca atomic ratios were found between late 1960s and late 1980s during a period of active use of TBT-based antifouling paints worldwide. However, a significant decrease in both the ratios in the beginning of 1990s can be attributed to regulation of the use of TBT on cargo ships by countries such as the USA, Japan and Australia.     

Study of Asian Dust Phenomena in 2001–2003 Using A Network of Continuously Operated Polarization Lidars

We have conducted dust observations at a number of locations including Beijing, Hefei, Suwon, Fukue, Nagasaki, Tsukuba, and Sapporo using automated two-wavelength polarization lidars o study Asian dust phenomena, including generation, transport, and change during transport. We developed a method using the depolarization ratio for estimating the contributions of Asian dust and spherical air-pollution aerosols in observed aerosol mixtures. We analyzed the dust profiles statistically to derive climatological characteristics and year-on-year variations. We also studied dust source and transport path for each dust event using the regional chemical transport model CFORS. The statistical analysis clearly demonstrated the year-on-year variation of dust phenomena and the characteristics depending on the locations of the observational sites. Most major dust events in 2001 and 2002 originated in Inner Mongolia and/or Mongolia at the southern edge of a low-pressure area located in Siberia and were transported by strong westerlies. In 2003, the typical meteorological pattern for heavy dust cases accompanying a strong low in Siberia was not seen, except for one case in April. Furthermore, the lidar observation in Beijing suggests that less dust was generated in the source regions in Inner Mongolia and/or Mongolia, probably due to higher precipitation in 2003.     

Factors affecting the interval between clutches in the hermit crab <Emphasis Type="Italic">Pagurus nigrivittatus</Emphasis>

Interval between reproductive events is an important factor for iteroparous animals because it determines the number of clutches throughout life. This study examined whether female size, clutch size, shell size and prenuptial molting affected the clutch interval in the hermit crab Pagurus nigrivittatus. Precopulatory guarding pairs of P. nigrivittatus were sampled in the field and kept in the laboratory until the female extruded eggs. The clutch interval of each female was assessed as one of two types of relatively “short” and “long” intervals by checking whether the guarded female had eggs and/or egg cases from the preceding brood or not when the guarding pair was collected. The clutch interval was longer in females with prenuptial molting than those without molting and these females usually grew larger at the prenuptial molt. This suggests that female P. nigrivittatus with a long interval might allocate energy into growth at the expense of the number of clutches during the current reproductive season. The allocation to growth is theoretically predicted to decrease with female size. Gastropod shell size is also known to affect the reproductive activity in hermit crabs. However, female size did not significantly affect the clutch interval in P. nigrivittatus, and the effect of gastropod shell size on clutch interval was not consistent with previous empirical studies. These results may be caused by differences in the gastropod species of shell occupied by the females of P. nigrivittatus.     

Fate of metals contained in waste electrical and electronic equipment in a municipal waste treatment process

In Japan, waste electrical and electronic equipment (WEEE) that is not covered by the recycling laws are treated as municipal solid waste. A part of common metals are recovered during the treatment; however, other metals are rarely recovered and their destinations are not clear. This study investigated the distribution ratios and substance flows of 55 metals contained in WEEE during municipal waste treatment using shredding and separation techniques at a Japanese municipal waste treatment plant. The results revealed that more than half of Cu and most of Al contained in WEEE end up in landfills or dissipate under the current municipal waste treatment system. Among the other metals contained in WEEE, at least 70% of the mass was distributed to the small-grain fraction through the shredding and separation and is to be landfilled. Most kinds of metals were concentrated several fold in the small-grain fraction through the process and therefore the small-grain fraction may be a next target for recovery of metals in terms of both metal content and amount. Separate collection and pre-sorting of small digital products can work as effective way for reducing precious metals and less common metals to be landfilled to some extent; however, much of the total masses of those metals would still end up in landfills and it is also important to consider how to recover and utilize metals contained in other WEEE such as audio/video equipment.     

Modeling the Production and Uses of Biological Resources from the Viewpoint of Energy Flow in a Rural Village in Sichuan,China

This study aimed at clarifying the impact of deforestation and afforestation on the quality of life in a village in Sichuan Province, China. We devised a conceptual model of bioresource production and use based on quantified energy flow. The basic structure of the model has three sectors: production, use, and externals. We developed comprehensive methodology to quantify the model. Bioresource use per person in 1997 was 3.7 GJ for food, 10.2 GJ for fodder, 0.2–0.4 GJ for building material, 12.8 GJ for fuel, and 1.8 GJ for fertilizer, totaling 28.6–28.8 GJ.We used four environmental indicators to evaluate bioresource production and use: a biological productivity indicator, a use-efficiency indicator, a supply–demand balance indicator, and a self-sufficiency indicator. Use of these indicators showed that supply-demand balance of fuel was dramatically improved from 30% to 85% by afforestation, but 99% of bioresource use still depends on domestic products. Thus, it is necessary to improve biological productivity and promote the efficient use of bioresources to achieve sustainable living in the area. Massive deforestation in the 1950s caused a direct shortage of building material and fuel wood. The shortage of wood led to a stagnation in the rebuilding of houses, and fuel wood was substituted with crop residues. Because crop residues had been used for fertilizer and fodder, their use as fuel caused a shortage of fertilizer and fodder. This was an indirect impact of deforestation on peoples quality of life.     

Degradation of dibromophenols by UV irradiation

We examined the degradation of dibromophenols （DBPs）, i.e. 2,4-DBP, 2,6-DBP and 3,5-DBP by ultraviolet （UV） irradiation and estimated the relationship between degradability and molecular orbital properties of each dibromopbenol. The removal of DBPs under a UV lamp system was successfully performed in an aqueous solution. After 5 min of irradiation, the initial DBPs concentration of 20 mg/L was decreased to below 1 mg/L, and about 60% of bromide ion was released. A decrease in the concentration of dissolved organic carbon （DOC） suggested the mineralization of DBPs, The mineralization may occur after release of bromide ions because the decrease of DOC was slower than the release of bromide ions. The degradability of 3,5-DBP was slightly lower than 2,6-DBP and 2,4-DBE Molecular orbital calculation suggested that the electrophilic frontier density and the highest occupied molecular orbital （HOMO） energy may be related to the degradability of DBPs.     

The cost of stratospheric climate engineering revisited

Stratospheric aerosol injection (SAI) has been receiving increasing attention as a possible option for climate engineering. Its direct cost is perceived to be low, which has implications for international governance of this emerging technology. Here, we critically synthesize previous estimates of the underlying parameters and examine the total costs of SAI. It is evident that there have been inconsistencies in some assumptions and the application of overly optimistic parameter values in previous studies, which have led to an overall underestimation of the cost of aircraft-based SAI with sulfate aerosols. The annual cost of SAI to achieve cooling of 2 W/m² could reach US$10 billion with newly designed aircraft, which contrasts with the oft-quoted estimate of “a few billion dollars.” If existing aircraft were used, the cost would be expected to increase further. An SAI operation would be a large-scale engineering undertaking, possibly requiring a fleet of approximately 1,000 aircraft, because of the required high altitude of the injection. Therefore, because of its significance, a more thorough investigation of the engineering aspects of SAI and the associated uncertainties is warranted.