Saburo Matsui

Biodegradation of high molecular weight lignin under sulfate reducing conditions: Lignin degradability and degradation by-products

This study is designed to investigate the biodegradation of high molecular weight (HMW) lignin under sulfate reducing conditions. With a continuously mesophilic operated reactor in the presence of co-substrates of cellulose, the changes in HMW lignin concentration and chemical structure were analyzed. The acid precipitable polymeric lignin (APPL) and lignin monomers, which are known as degradation by-products, were isolated and detected. The results showed that HMW lignin decreased and showed a maximum degradation capacity of 3.49 mg/l/day. APPL was confirmed as a polymeric degradation by-product and was accumulated in accordance with HMW lignin reduction. We also observed non-linear accumulation of aromatic lignin monomers such as hydrocinnamic acid. Through our experimental results, it was determined that HMW lignin, when provided with a co-substrate of cellulose, is biodegraded through production of APPL and aromatic monomers under anaerobic sulfate reducing conditions with a co-substrate of cellulose.

Adsorption of mercury vapor on particles.

The adsorption of mercury vapor on particles was studied by using soot particles generated by incineration of sewage sludge (EP-ash) and activated carbon particles. Through the experiments, it was found that, at 298 K, the EP-ash has a fairly high adsorption capacity for mercury vapor in the order of 10/sup -6/g/g, which is between that of the ordinary soils and that of activated carbon particles. Furthermore, it was found that physical adsorption of mercury vapor on the studied particles at high temperature is described by Dubinins equation. On the basis of the equation, it was shown that EP-ash physically adsorbs very little mercury at high temperature, and therefore, most mercury in the EP-ash is chemically adsorbed or contained in a form of mercury compounds. Nevertheless, the total amount of mercury contained in the particles is very little compared to the total mercury in the exhaust gases so that most mercury behaves as a vapor in the presence of particulate matter. 8 references, 4 figures, 3 tables.

Aryl hydrocarbon receptor ligand activity of polycyclic aromatic ketones and polycyclic aromatic quinones

Polycyclic aromatic ketones (PAKs) and polycyclic aromatic quinones (PAQs) are oxygenated polycyclic aromatic hydrocarbons (PAHs), and reports about the aryl hydrocarbon receptor (AhR) ligand activities of these compounds are few. In this study, activation of AhR by 41 polycyclic aromatic compounds (PACs), focusing especially on PAKs and PAQs, was determined by measuring beta-galactosidase activity from a reporter plasmid in yeast engineered to express human AhR and the AhR nuclear translocator proteins and by measuring luciferase activity from mouse hepatoma (H1L1) cells (chemical-activated luciferase expression [CALUX] assay). The PACs used in these experiments included 11 PAKs, seven PAQs, and 21 PAHs. In this study, the PAKs 11H-benzo[a]fluoren-11-one (B[a]FO), 11H-benzo[b]fluoren-11-one (B[b]FO) and 7H-benzo[c]fluoren-7-one and the PAQs 5,12-naphthacenequinone, 1,4-chrysenequinone, and 7,12-benz[a]anthracenequinone showed high AhR activities in H1L1 cells, although these values were not as high as that for benzo[a]pyrene (B[a]P). These PAKs and PAQs showed significantly stronger activities in yeast cells relative to B[a]P. It was predicted that PAKs such as B[a]FO and B[b]FO occupied 0.06% to 1.3% of the total induction equivalents, and each contribution matched the contribution of PAHs such as B[a]P, chrysene, and benz[a]anthracene in gasoline exhaust particulates and airborne particulates using data of CALUX assay.

Evaluation of the treatment performance of a multistage ozone/hydrogen peroxide process by decomposition by-products

The performance of a multistage ozone/hydrogen peroxide (O3/H2O2) process was evaluated with respect to total organic carbon (TOC) removal of waste waters. An aqueous humic acid solution (5.2 mgC l(-1) as TOC) and a sand filtered secondary sewerage effluent (5.6mgC l(-1) as TOC) were used as model waste waters. Appropriate range of hydrogen peroxide (H2O2) dose at each stage depended upon the components of the tested solutions that changed as the process proceeded. Higher hydrogen peroxide dose was required at later stages in which low reactivity compounds with hydroxyl radical (HO*), low molecular fatty acids, were predominant. And, oxalic acid concentration related to H2O2 demand at later stages. This was assumed that the slow decomposition of oxalic acid was rate-determining step for TOC removal after its accumulation. Also, it is important to maintain dissolved ozone at low concentration for efficient TOC removal because rapid ozone consumption is required for the rapid formation of hydroxyl radical (HO*).

The Bacillus subtilis rec-assay: a powerful tool for the detection of genotoxic substances in the water environment. Prospect for assessing potential impact of pollutants from stabilized wastes

The Bacillus subtilis rec-assay has been specially developed to detect genotoxicity in environmental water samples. The rationale of the B. subtilis rec-assay is based on the relative difference of survival of a DNA repair-recombination proficient strain and its deficient strain, which is interpreted as genotoxicity. This assay method can be very powerful in that it has higher sensitivity for the detection of mutagens in highly polluted waters than other bacterial mutation assays. Hydrophobic fractions from various environmental waters were fractionated by using XAD-2 resins and assayed, targeting the detection of organic genotoxic substances. Genotoxic response was detected in most of them, which revealed that many unknown micropollutants with genotoxicity occur in public water bodies. Positive response was also detected from a treated municipal solid waste (MSW) landfill leachate. Genotoxicity remaining in the treated effluent suggests that genotoxic micropollutants may pass through conventional water treatment processes such as activated sludge treatment process. Without proper control of waste quality and landfill facilities, waste landfill could be a heavy pollution source.

Erratum: 4-Oxo-2-hexenal, A Mutagen Formed by Omega-3 Fat Peroxidation, Causes DNA Adduct Formation in Mouse Organs

To identify mutagens formed in a model reaction of lipid peroxidation, linolenic acid methyl ester and hemin were reacted with dG. As a result, a 4-oxo-2-hexenal-dG adduct (dG*) was identified in the model reaction mixture. The 4-oxo-2-hexenal (4-OHE) showed mutagenic activity in the Salmonella typhimurium strains TA100 and TA104. After 4-OHE was orally administered to mice, dG, 4-OHE-dC- and 4-OHE-5-methyl-dC adducts were detected in esophageal, stomach and intestinal DNA. In the vapor phase released from the methyl linolenate-hemin model system, and in the smoke released during the broiling of fish, 4-OHE was detected by GCMS. The 4-OHE seems to be produced by the auto-oxidation of omega-3 polyunsaturated fatty acids. These results provide a warning to workers dealing with omega-3 fats, who may be exposed to this volatile mutagen.

Aryl Hydrocarbon Receptor and Estrogen Receptor Ligand Activity of Organic Extracts from Road Dust and Diesel Exhaust Particulates

A wide variety of contaminants derived from diesel and gasoline engines, tire, asphalt, and natural organic compounds is found in road dust. Polycyclic aromatic compounds (PACs) are the important toxic targets among various contents in road dust and diesel exhaust particulates (DEPs), and endocrine-disrupting activity of PACs was suggested. In the present study, aryl hydrocarbon receptor (AhR) ligand activity was confirmed in the extract of both road dust and DEPs. In the separation of the extracts for both road dust and DEPs with reversed-phase HPLC, it was found that polar fractions contributed to significant AhR ligand activity in both a mouse hepatoma (H1L1) cell system and a yeast system. Furthermore, the contribution of these polar fractions was higher in DEPs than in road dust, probably because of the greater concentration of oxy-PAHs in DEPs than in road dust. The contribution of contaminants associated with the polar region to AhR ligand activity was also evident following the separation of road dust with normal-phase HPLC. Additionally, remarkable estrogen receptor (ER) ligand activity was detected in the highly polar region separated with normal-phase HPLC. It is suggested that many unknown AhR or ER ligand active compounds are contained in the polar region.

Rejection of pharmaceuticals and personal care products (PPCPs) and endocrine disrupting chemicals (EDCs) by low pressure reverse osmosis membranes

This paper aims to elucidate retention characteristics of some pharmaceuticals and personal care products (PPCPs), and endocrine disrupting chemicals (EDCs), by two polyamide low pressure reverse osmosis (LPRO) membranes. Feed solution pH did not have an influence on rejections of undissociated solutes, which was most likely governed by adsorption, size exclusion and diffusion simultaneously. Size exclusion was presumably dominant, especially with tight membranes (UTC-70U). Rejections of the solutes with low dipole moment (<1.0 debye) decreased with increasing octanol-water partition coefficient (K(ow)). The solutes with large K(ow) values were most likely adsorbed on membrane and subsequently passed through it resulting in larger diffusion coefficient (D(p)). The rejections decreased with increasing D(p) values irrespective of their dipole moments. Rejections of solutes with comparatively larger dipole moments might be dominated by diffusion and/or convection rather than their hydrophobicity. However, rejections of solutes with hydroxyl and carboxyl functional groups by UTC-60 increased with solution pH. More than 80% rejections were obtained for degree of dissociation (alpha)>0.5. Electrostatic repulsion played a key role for rejection of dissociated solutes, especially by loose LPRO membranes. Therefore, assessing the dissociation degree at desired pH values can be a key step to obtain an insight of rejection mechanisms by polyamide membranes.

Characterizations of the first flush in storm water runoff from an urban roadway

Storm water runoff from urban roadways contains anthropogenic pollutants, which are mainly generated from traffic-related activities. The purpose of this study was to evaluate the characteristics of pollutants from the roadway runoff as well as first flush effects. Storm water runoff was sampled during five storm events from the experimental site in Otsu, Shiga, Japan. From the hydrographs and pollutographs for the roadway runoff, the concentration of pollutants increased with increasing runoff flow in the low flow rate event, but did not significantly increase in the high flow rate event. Moreover, according to the analysis of cumulative pollutant mass versus runoff volume curves from five storm events, the first 50% of the runoff volume transported 62% of TOC and Mo, 60% of SS, 59% of Fe, Mn and Cu, 58% of Ni, 57% of Cd and Pb, 56% of Al, 55% of Zn, and 54% of Cr, as the mean values. The first 30% and 80% of the runoff volume also transported 34-43% mass of the pollutants and 82-88% mass of the pollutants, respectively. This study for storm water runoff may also provide useful information to correctly design treatment facilities, such as detention tanks and ponds, filtration and adsorption systems.

Use of chlorophyll fluorescence of Closterium ehrenbergii and Lemna gibba for toxic effect evaluation of sewage treatment plant effluent and its hydrophobic components

In this study fluorometric methods using an alga, Closterium ehrenbergii, and a higher plant, Lemna gibba, were employed to evaluate the toxicity of sewage treatment plant (STP) effluent and its hydrophobic components. Fluorescence parameters such as the operational photosystem II quantum yield at steady state of electron transport, the nonphotochemical quenching, and the complementary area were modified in the presence of hydrophobic components, particularly with C. ehrenbergii. It was found that C. ehrenbergii was a suitable species to be used in a hydrophobic components bioassay, since this alga was 400 times more sensitive than L. gibba to hydrophobic components. Results indicate that hydrophobic STP effluent components are less toxic as a constituent of the STP effluent than when they are extracted from the effluent. We also demonstrated here that in addition to the growth inhibition test, fluorometric methods can be usefully employed in bioassays for the toxic effect evaluation of pollutants present in municipal wastewater treatment plant effluents.