De novo formation characteristics of dioxins in the dry zone of an iron ore sintering bed

The objectives of this work are to understand the details of the mechanism of dioxin formation in the part of a sintering bed termed the dry zone, and to obtain ideas on how to prevent their formation. Sinter mixtures of various composition types were heated in a packed bed reactor, and dioxins in the outlet gas and in the sinter mixture residue were measured. The dioxin formation potential of a simple sinter mixture composed of iron ore, coke and limestone was markedly lower than that of fly ash from a municipal solid waste incinerator (MSWI). In consideration of this result, a series of experiments were conducted using a sinter mixture impregnated with CuCl2. Experimental results showed that dioxin formation was temperature-dependent in the range of 300-550 degrees C, with the maximum observed at around 300 degrees C, which was quite similar to that of fly ash from the MSWI. The homologue distribution of PCDD/Fs in gas and solid reflected the possible difference in carbonaceous materials in coke and activated coke. Gaseous hydrogen chloride acted as a chlorinating reagent for dioxin formation.     

CDNA microarray assessment for ozone-stressed Arabidopsis thaliana

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.     

Polychlorinated dibenzo-p-dioxins and dibenzofurans in sediment, soil, fish, shellfish and crab samples from Tokyo Bay area, Japan

Concentrations of tetra- to octa-chlorinated dibenzo-p-dioxins and dibenzofurans in samples collected in or near Tokyo Bay, Japan, with a densely inhabited catchment area, were congener-specifically determined and discussed. Analyzed in this study were samples of surface sediment covering the whole bay area, reference soil representing atmospheric impact, and fish, shellfish and crab commonly consumed as food. The range of concentrations were comparable to or higher than those in other parts of Japan. The origins of these compounds in the catchment area of the bay were investigated in terms of homolog and isomeric compositions in the sediment samples. Biota-sediment accumulation factors for benthic species declined as the degree of chlorination increased.     

Evaluation of fecal pollution of river sediment by detection of urobilin

In this study, we attempted to establish a new indicator for fecal pollution of river sediment using a sensitive detection method for urobilin. Urobilin contained in sediment was extracted with an alkaline buffer solution. The suitable buffer solution for extraction of urobilin consisted of 0.1 M Tris-HCl buffer (pH 10.0) containing 0.1 m sodium chloride. The ratio of sediment to buffer was 1:10. The distribution of urobilin in river sediment was studied by this method. The amount of urobilin in the river sediment of Tokyo (urban) and the Miura peninsula (rural) area was surveyed. Large quantities of urobilin were detected in the sediments of the urban rivers, but it was scarce in the rural rivers. Urobilin showed a higher content in sediment than in water. Urobilin in river sediment is distributed in large amounts in the lower reaches, where the water is polluted with domestic sewage and industrial waste, but is scarce in the upper streams. The amount of urobilin decreases to the lower layers.     

Formation of mutagens by photolysis of amino acids in neutral aqueous solution containing nitrite or nitrate ion

Nine amino acids, i.e., alanine, threonine, cysteine, glutamic acid, arginine, proline, tryptophan, phenylalanine and tyrosine, were irradiated with UV light in water containing nitrite or nitrate ion under neutral conditions. The mutagenicities of the ether extracts and the residual water layers of the reaction mixtures were assayed with and without S-9 mix using $\text{Salmonella typhimurium}$ TA98 and TA100. Three aromatic amino acids, tryptophan, phenylalanine and tyrosine, were found to give direct-acting and frameshift mutagens by irradiation in aqueous nitrite solution. Among them, the ether extract of tryptophan exhibited the strongest mutagenicity toward TA98. In the case of irradiation in aqueous nitrate solution, only the ether extract of tryptophan exhibited weak mutagenicity toward TA98 without S-9 mix. The effects of nitrite concentration, irradiation time and pH on mutagen formation from tryptophan and some characteristics of the produced mutagens were examined.     

Examination of dioxin fluxes recorded in dated aquatic-sediment cores in the Kanto region of Japan using multivariate data analysis

Past dioxin (coplanar polychlorinated biphenyl (Co-PCB), 2,3,7,8-substituted polychlorinated dibenzo-p-dioxin (PCDD) and 2,3,7,8-substituted polychlorinated dibenzofuran (PCDF)) fluxes recorded in dated aquatic-sediment cores were analyzed using principal component analysis (PCA). The data set consisted of samples from four cores collected from the Kanto region of Japan. Time trends and spatial differences in the dioxin flux were examined, and the potential relationship to emission sources was investigated. Twenty-five compounds and 58 core slices, corresponding to the later half of the 20th century, were subjected to the analysis. The PCA of both log-transformed and maximum-value-standardized data successfully divided the dioxin compounds into a small number of groups, and three similar clusters of Co-PCBs, PCDDs and penta- to hepta-CDFs were identified. PCB formulations used in the past are judged to have been responsible for the major part of the Co-PCB flux recorded in the sediment cores. However, the relationship to emission sources needs further investigation. It is suggested that most 2,3,7,8-substituted PCDDs and PCDFs are different from Co-PCBs in their emission sources or movements in the environment. The subcore clusters obtained from the PCA of log-transformed data show that the cores from different sampling areas exhibited distinct dioxin fluxes and compositions. Common time trends among the cores were more effectively summarized by the PCA of maximum-value-standardized data focusing on relative time trends. PC scores show that recently the flux of each dioxin compound in the four cores has been generally declining after having reached a peak.     

Variation in CO2 assimilation rate induced by simulated dew waters with different sources of hydroxyl radical (*OH) on the needle surfaces of Japanese red pine (Pinus densifora Sieb. et Zucc.)

The hydroxyl radical (*OH) is generated in polluted dew on the needle surfaces of Japanese red pine (Pinus densiflora Sieb. et Zucc.). This free radical, which is a potent oxidant, is assumed to be a cause of ecophysiological disorders of declining trees on the urban-facing side of Mt. Gokurakuji, western Japan. Mists of *OH-generating N(III) (HNO2 and NO2-) and HOOH + Fe + oxalate solutions (50 and 100 microM, pH 5.1-5.4) simulating the dew water were applied to the foliage of pine seedlings grown in open-top chambers in the early morning. Needles treated with 100 microM N(III) tended to have a greater maximum CO2 assimilation rate (Amax), a greater stomatal conductance (g(s)) and a greater needle nitrogen content (Nneedle), suggesting that N(III) mist acts as a fertilizer rather than as a phytotoxin. On the other hand, needles treated with 100 microM HOOH + Fe + oxalate solution showed the smallest Amax, g(s), and Nneedle, suggesting that the combination of HOOH + Fe + oxalate caused a decrease in needle productivity. The effects of HOOH + Fe + oxalate mist on pine needles were very similar to the symptoms of declining trees at Mt. Gokurakuji.     

Chlorobenzenes removal from municipal solid waste incineration fly ash by surfactant-assisted column flotation

The organic contaminants in municipal solid waste incineration (MSWI) fly ash, including chlorinated aromatic compounds and polycyclic aromatic hydrocarbons, have high toxicity and a potential negative impact on the environment. An effective and low energy consumption technique to remove the organic contaminants from MSWI fly ash is required urgently. Organic contaminants, such as chlorobenzenes (CBzs), in MSWI fly ash are known to become enriched in the unburnt carbon (UC) fraction. It is proposed that removal of UC from fly ash will result in the effective removal of most organic micropollutants. In this research, we use a technique of surfactant-assisted column flotation to decontaminate MSWI fly ash by removal of the CBzs-enriched UC from MSWI fly ash. We find that 39.8% of CBzs can be removed from fresh MSWI fly ash with 61.7% UC removal efficiency, whereas only 33.2% of CBzs can be removed from weathered MSWI fly ash with a low UC removal efficiency of 33.7%. By adding a mixture of two kinds of surfactants: sorbitan mono-oleate and polyoxyethylene (20) sorbitan mono-oleate to the weathered fly ash, 47.0% of CBzs were removed at the hydrophile lipophile balance value of 13.5, while the UC removal efficiency increased to 49.0%. The results show that surfactants can enhance CBzs and UC removal efficiencies during the column flotation process. Higher CBzs and UC removal efficiencies can be expected by further optimizing the conditions of surfactant-assisted column flotation.     

Removal of organic polyelectrolytes and their metal complexes by adsorption onto xonotlite

Natural organic polyelectrolytes (humic and fulvic acids) and their metal complexes were removed by adsorption onto xonotlite. The removal percentages of humic and fulvic acids by xonotlite were approximately 80% and 30%, respectively. Humic acid removal from solution by adsorption onto xonotlite took place more readily than fulvic acid removal. The molecular weight distributions of the humic substances remaining in solution after adsorption with the xonotlite were measured with size exclusion chromatography. A comparison of molecular weight distributions demonstrated conclusively that large molecular weight components were adsorbed preferentially, indicating that adsorption efficiency depends on the number of functional groups of humic substances. Furthermore, the surface topography of the adsorbent was observed before and after adsorption by scanning electron microscopy. The calculated heat of adsorption was of 330 kJ mol(-1) which was evaluated from the Clapeyron-Clausius equation. Therefore, the adsorption type can be considered chemical. Since xonotlite can be easily synthesized and obtained at low cost, the adsorption method of humic and fulvic acids is superior to their precipitation.