Fabric-filter-supported catalyst for removal of harmful solid and gaseous compounds in municipal waste incinerator exhaust gas: characteristics of NO x reduction

We have investigated a fabric-filter-supported catalyst for removing harmful solid and gaseous compounds simultaneously from municipal incinerator exhaust gas. We studied the ways in which the efficiency of NO _x removal is influenced by filter temperature, gas flow rate, and catalyst content. The reduction of the catalyst content by mechanical reverse washing was investigated, and the state of the catalyst supported in the fabric filter was also observed using a scanning electron microscope. The catalyst supported by the fabric filter showed a removal efficiency above 75% when the filter temperature was 200°C, the gas flow rate was 1 m/min, and the catalyst content of the fabric filter was above 300 g/m². The catalyst was supported uniformly on the fibers of the fabric filter, and fine catalyst particles remained on the fibers after mechanical reverse washing. Received: October 15, 1997 / Accepted: March 19, 1999     

Growth and Nitrogen Availability of Red Pine Seedlings under High Nitrogen Load and Elevated Ozone

To evaluate the effect of increasing nitrogen (N) deposition and tropospheric ozone (O₃) concentrations on N-saturated forest ecosystems, we investigated the response of Japanese red pine (Pinus densiflora), an N-saturation sensitive tree species, to increasing N load under elevated O₃ concentrations. One-year-old seedlings of red pine were treated with three levels of N supply (0, 50 and 100 mg N L^-1 fresh soil volume) under two levels of atmospheric O₃ concentration (< 5 and 60 ppb) for two growing seasons. Nitrogen treatment did not stimulate dry matter production of the seedlings. Growth inhibition was observed in the highest N treatment under low O₃ and in the two higher N treatments under elevated O₃. Irrespective of the O₃ concentration, increasing N supply negatively affected root growth and mycorrhizal development in fine roots, resulting in a reduction in P and Mg uptake from the soil. Net photosynthetic rate was significantly reduced by both the highest N treatment under low O₃ and the two higher N treatments under elevated O₃, together with decreased N-availability to Rubisco. Nitrogen assimilated from NO₃ ^- to amino acid in the needles was not affected by the treatments. However, needle protein concentration was reduced by the highest N-treatment under low O₃ and by the two higher N-treatments under elevated O₃. These results suggest that elevated O₃ potentially disturbs the N-availability in the form of protein including Rubisco, and may advance the negative effects of excessive N-deposition on N-sensitive plant species in N-saturated forests.     

Extraction and cleanup methods of dioxins in house dust from two cities in Japan using accelerated solvent extraction and a disposable multi-layer silica-gel cartridge

A simple and rapid method for the extraction and cleanup of dioxins from house dust was developed using an accelerated solvent extraction (ASE) method and a multi-layer silica-gel cartridge. It was found that the WHO-TEQ levels of dioxins extracted from the house dust obtained by both a conventional soxhlet extraction and the ASE were almost equal, when the data obtained by both methods were compared. As for the cleanup method, a multi-layer silica-gel cartridge yielded higher dioxin recoveries than the alkaline digestion method. The average values of the dioxins in house dust from Kumagaya city and Sendai city in Japan (Sendai city is bigger than Kumagaya city with respect to the population and industry), were 15.6 pg TEQ/g (8.6-26.0 pg TEQ/g, n=5, Kumagaya city) and 16.0 pg TEQ/g (5.9-30.5 pg TEQ/g, n=5, Sendai city), respectively.     

Model analysis of interactive effects of ozone and water stress on the yield of soybean

The interactive effects of ozone and water stress on the yield of soybean (Glycine max (L.) Merr. 'Davis') were addressed with a growth model of soybean. Two simulations were conducted, using the data from the exposures of soybean to ozone in open-top chambers under two soil moisture regimes, and the results of the simulations were compared. In the original simulation, soil moisture content was calculated based on a water budget using the actual precipitation and irrigation data. In the modified simulation, the soil water content was given as input data. In this case, soil moisture content was maintained at the same level across the ozone treatments regardless of different water use by the plants. Both simulations included the effect of reduced ozone flux to the leaves due to water stress, whereas only the original simulation included the effect of mitigated water stress due to reduced water use by the plants under higher ozone concentration. The water stress reduced ozone impact on soybean yield in the original simulation on the basis of the ozone dosecrop yield response relationship, but not in the modified simulation. The ozone uptake rate was reduced by water stress in the original simulation, but the relationship between seasonal mean ozone uptake rate and relative yield still showed reduced impact of ozone due to water stress. These results indicated that the alleviation of water stress by ozone due to reduced plant water use in ozone-treated plots can be a contributing factor in the reduction of ozone impact by water stress. The above conclusion was partly confirmed by the actual data for soil water content, which was significantly lower in the lowest ozone treatment than in the higher ozone treatments. Further experimental and modelling studies are needed to elucidate the mechanism of the ozone X water stress interaction.     

Respiratory uptake kinetics of neutral hydrophobic organic chemicals in a marine benthic fish, Pseudopleuronectes yokohamae

We investigated the respiratory uptake kinetics of polychlorinated biphenyls (PCBs), organohalogen pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), and 2,2′,4,4′-tetrabrominated diphenyl ether (BDE #47) in a marine benthic fish, Pseudopleuronectes yokohamae. The respiratory uptake efficiencies (E_W) of the chemicals, of which there have been no reports for the majority of persistent organic pollutants (POPs), were obtained by measuring the respiratory uptake rate constants (k₁) and the oxygen consumption rates of fish. Fish were exposed to water in which these chemicals were dissolved at environmentally relevant concentrations for 28 d, followed by 168 d of depuration in clean seawater. The k₁ and E_W values for 99 compounds were obtained, and they ranged from 2000 to 42 000 L kg-lipid⁻¹ d⁻¹ and from 0.060 to 1.3, respectively. The E_W values of the chemicals, except for PAHs, tended to increase with increasing values of the log octanol–water partition coefficients (K_OW) of the chemicals up to a log K_OW of 5. For log K_OW in the range 3–5, the E_W values in this study were much lower than those in a published study (about one-third). As a result of analysis by a two-phase resistance model, the resistance of transport rates to the lipid phase in this study was lower than was the case in the published study. These findings indicate that the E_W predicted by the published study for log K_OW in the range 3–5 may differ among fish species and water temperature, and further study is needed.     

Sedimentation and remobilization of radiocesium in the coastal area of Ibaraki, 70 km south of the Fukushima Dai-ichi Nuclear Power Plant

Sedimentation and remobilization processes of radiocesium were investigated from time-series observations at nine stations in the coastal area of Ibaraki, 70–110 km south of the Fukushima Dai-ichi Nuclear Power Plant (1FNPP). Sediment samples were collected four times between June 2011 and January 2012, and concentrations of radiocesium as well as sediment properties such as grain size and elemental compositions were analyzed. Cumulative inventory of ¹³⁷Cs in sediment (0–10 cm) ranged between 4?×?10³ and 3?×?10⁴ Bq/m² as of January 2012. This amount was generally higher at stations nearer 1FNPP and has remained at the same level since August 2011. From these results, it can be inferred that dissolved radiocesium advected southward from the region adjacent to the 1FNPP and was deposited to the sediment of the study area in the early stage after the accident. The incorporation of radiocesium into sediments was almost irreversible, and higher concentrations of ¹³⁷Cs were obtained from the finer-grained fraction of sediments. In the northern offshore stations, resuspension of the fine-grained sediments formed a high-turbidity layer 10–20 m above the seabed. These results indicate that radiocesium-enriched fine particles were transported from the coast to offshore regions through the bottom high-turbidity layer.     

Comparison of arsenic uptake ability of barnyard grass and rice species for arsenic phytoremediation

In this research, the relative performance in arsenic (As) remediation was evaluated among some barnyard grass and rice species under hydroponic conditions. To this end, four barnyard grass varieties and two rice species were selected and tested for their remediation potential of arsenic. The plants were grown for 2 weeks in As-rich solutions up to 10 mg As L^?1 to measure their tolerance to As and their uptake capabilities. Among the varieties of plants tested in all treatment types, BR-29 rice absorbed the highest amount of As in the root, while Nipponbare translocated the maximum amount of As in the shoot. Himetainubie barnyard grass produced the highest biomass, irrespective of the quantity of As in the solution. In all As-treated solutions, the maximum uptake of As was found in BR-29 followed by Choto shama and Himetainubie. In contrast, while the bioaccumulation factor was found to be the highest in Nipponbare followed by BR-29 and Himetainubie. The results suggest that both Choto shama and Himetainubie barnyard grass varieties should exhibit a great potential for As removal, while BR-29 and Nipponbare rice species are the best option for arsenic phytoremediation.     

Woody biomass and RPF gasification using reforming catalyst and calcium oxide

This study focused on steam gasification and reforming of waste biomass using a reforming catalyst. The purpose of the study was to evaluate the durability of a commercial Ni reforming catalyst and the effect of CaO on the reforming behavior, and to clarify detailed factors of catalytic performance, as well as the effect of operating parameters on the characteristics of produced gas composition. Moreover, catalyst regeneration was carried out and the behavior of catalytic activity based on gas composition was investigated. Using a fluidized bed gasifier and a fixed bed reformer, gasification and reforming of waste biomass were carried out. Commercial Ni-based catalyst and calcined limestone (CaO) were applied to the reforming reaction. Temperature of the gasifier and reformer was almost 1023 K. Ratio of steam to carbon in the feedstock [mol mol⁻¹] and equivalence ratio (i.e., ratio of actual to theoretical amount of oxygen) [-] were set at about 2 and 0.3, respectively. The feed rate of the feedstock into the bench-scale gasifier was almost 15 kg h⁻¹. The results of waste biomass gasification confirmed the improvement in H₂ composition by the CO₂ absorption reaction using the reforming catalyst and CaO. In addition, CaO proved to be especially effective in decreasing the tar concentration in the case of woody biomass gasification. Catalytic activity was maintained by means of catalyst regeneration processing by hydrogen reduction after air oxidation when woody biomass was used as feedstock.     

Determination of dioxin concentrations in fish and seafood samples using a highly sensitive reporter cell line, DR-EcoScreen cells

There is a strong need for the development of relatively rapid and low-cost bioassays for the determination of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and dioxin-like polychlorinated biphenyls (dl-PCBs) in environmental and food samples. In this study, we applied a reporter gene assay using DR-EcoScreen cells (DR-cell assay), which is highly sensitive to dioxins, to the determination of PCDD/Fs and dl-PCBs in fish and seafood samples. The PCDD/Fs and dl-PCBs were extracted from homogenated samples (10 g) of 30 fish and shellfish, purified by clean-up procedure using a multilayered silica gel column and an alumina column, and applied to DR-cell assay. Interestingly, the bioanalytical equivalent (BEQ) values obtained from the DR-cell assay [<0.1 ∼ 5.4 pg BEQ g⁻¹ wet weight (ww)] were closely correlated with the toxicity equivalent (TEQ) values from conventional high-resolution gas chromatography/high-resolution mass spectrometry (HRGC-HRMS) analysis (r² = 0.912), and the slope of regression line was 0.913. Therefore, we multiplied the BEQ values from the DR-cell assay by a conversion coefficient (1.095, the reciprocal of 0.913) to approximate the TEQ values from the HRGC-HRMS analysis. Furthermore, we used this DR-cell assay to perform a prescreening test of PCDD/Fs and dl-PCBs in 16 fish and seafood samples purchased from a supermarket, revealing that a sample from the fatty flesh of a bluefin tuna exceeded 8 pg TEQ g⁻¹ ww (the European Union-tolerance limit). Taken together, these results suggest that the DR-cell assay might be applicable as a rapid and low-cost prescreening method to determine dioxin levels in fish and seafood samples.     

Removal of carotene-like colored compounds by liquid-liquid extraction during polycyclic aromatic hydrocarbons analysis of plant tissue

Plants contain a wide variety of chemicals, some of which may have similar chromatographic behavior to polycyclic aromatic hydrocarbons (PAHs). During solid phase extraction (SPE) with Si-gel for instance, the co-elution of carotene-like colored compounds with PAHs has been observed. In this paper, liquid–liquid extraction was applied for the separation and subsequent analysis of PAHs from plant extracts. PAHs containing 2–6 rings, which include naphthalene, phenanthrene, pyrene, benzo[a]pyrene and benzo[ghi]perylene, were used as representative target chemicals. Carotene-like compounds extracted from Komatsuna (Brassica campestris) shoot by acetone followed by Si-gel treatment were incorporated as undesired components in the model matrix. Results showed the feasibility of employing either acetonitrile or 2% (w/v) KOH–methanol as solvents for high PAHs recovery and low extraction of colored fraction. For acetonitrile, 86.9–93.5% of each PAH could be recovered after three extraction cycles (relative standard deviation, RSD < 1.6%) with only about 10% co-extraction of colored fraction. For 2% KOH–methanol, PAHs recoveries ranging from 79.3% to 83.1% after five cycles (RSD < 1.5%) were achieved while the percent extraction of colored fraction was also low at 10%. The relatively higher selectivity of the solvents for PAHs over the colored fraction as well as the solubility of the matrix solution in the solvent may have contributed to these results. On this basis, liquid–liquid extraction is very useful for the pre-treatment of plant extracts for PAHs analysis.