Application of the rescue number to the evaluation of remediation technologies for contaminated ground

An improved rescue number, RN_SOIL, which is an indicator for evaluating remediation technologies for contaminated ground that is based on both the risk and the remediation cost, is proposed as a tool of risk communication. The risk posed by contaminated ground is indicated by the figure of treatment priority at time t, FTP(t), which represents the human health risk as the number of people affected by the contaminated ground at time t during the remediation process. The calculation of the value of FTP(t) is based on exposure to contaminants that have migrated through environmental media from the contaminated ground, and is estimated by using a CalTOX model and the Monte Carlo method. The integration of FTP(t) with time, which represents the cumulative number of people affected by the contaminated ground, is used to estimate the performance of individual remediation technologies in risk reduction. The figure of unprocessibility for waste (FUW), which represents difficulties in remediation, is expressed as the remediation cost. FUW is estimated by using actual costs per unit volume of remediated soil. As an overall performance value, the rescue number for each remediation technology for contaminated ground (RN_SOIL) is calculated by multiplication of the integral FTP(t) by FUW. Smaller values of RN_SOIL are judged to indicate a better technology. The rescue index (RI), calculated as the ratio of the reduction of the integral FTP(t) to FUW, indicates the cost-effectiveness of the remediation technologies. Successful estimation of the indices (FTP(t), integral FTP(t), FUW, RN_SOIL and RI) demonstrate the usefulness of these indices in risk communication.Part of this paper was presented at 13th meeting of Japan Society of Waste Management Experts (2002)     

Quantitative determination of Escherichia coli based on the electrochemical measurement of bacterial catalase activity using H2O2-selective organic/inorganic-hybrid sol-gel film-modified Pt electrode

Quantitative determination of Escherichia coli (E. coli) concentration was achieved by measuring the intrinsic catalase activity of E. coli using novel H₂O₂-selective organic/inorganic-hybrid sol-gel film-modified platinum (Pt) wire electrode. This hybrid sol-gel film is composed of three kinds of organosilanes and two biopolymers (i.e., chitosan and bovine serum albumin), and exhibited an excellent permselectivity toward H₂O₂ based on a size-exclusive mechanism. The steady-state anodic current for 100 [xmol/L H₂O₂ at +0.6 V (vs. Ag/AgCl) in 0.1 mol/L phosphate buffer (pH 6.5) solution was apparently diminished by the addition of E. coli samples, due to the decomposition of H₂O₂ by intrinsic catalase activity of E. coli. The time-dependent decrease in current (–AI/At) was significantly dependent on the E. coli concentration. The –AI/At was enhanced by the permeabilization pretreatment of E. coli samples with the mixed solution of polymyxin B and lysozyme. This H₂O₂-selective organic/inorganic-hybrid sol-gel film-modified platinum (Pt) wire electrode allowed quantitative determination of E. coli concentration ranging from 10⁶ to 10⁹ CFU/mL within 30 min. This method required no label and complicated procedure, and allowed rapid, simple and cost-effective quantitative electrochemical determination of catalase-positive bacteria.     

Highly sensitive flow-biosensor for toxic phenolic compounds using tyrosinase and acridine orange-adsorbed carbon felt

Tyrosinase (TYR, EC 1.14.18.1) was physically adsorbed onto a carbon felt (CF) together with acridine orange (AO). Coadsorption of AO was essential to prevent the denaturation of the TYR at the CF surface. The resulting TYR and AO-coadsorbed CF (TYR/AO-CF) was successfully utilized as a detection unit of novel and highly sensitive amperometric flow-biosensor for toxic chlorophenol compounds. Standard solutions of phenolic compounds (200 μL) were injected, and the cathodic peak currents due to the reduction current of o-quinones produced by the TYR-catalyzed oxidation (phenolase activity) were detected at the applied potential of ?50 mV vs. Ag/AgCl. In this reaction, the electrochemically generated catechol compounds from o-quinones are re-oxidized repeatedly by catecholase activity of the TYR, leading to a sufficient amplified signal. The TYR/AO-CF exhibited much higher selectivity toward p-chlorophenol as compared with other chlorophenol compounds. When 0.1 mol/L phosphate buffer (pH 7.0) was used as a carrier at flow rate of 3.0 mL/min, cathodic peaks for p-chlorophenol was linear in the concentration range between 0.1 and 10 [xmol/L (sensitivity: 1.41(mA-L)/mmol) with sampling rate (30 samples/h), and the detection limit ofp-chlorophenol was found to be 2.13 ? 10⁸ mol/L (S/N = 3. The ratio of signal and noise is 3). The TYR/AO-CF kept more than 80% of original activity after the storage in 0.1 mol/L phosphate buffer (pH 7.0) containing 0.2 mmol/L AO at 4°C.     

Electropolymerized poly（Toluidine Blue）-modified carbon felt for highly sensitive amperometric determination of NADH in flow injection analysis

Poly(pheniothiazine) films were prepared on a porous carbon felt (CF) electrode surface by an electrooxidative polymerization of three phenothiazine derivatives (i.e.,Tthionine (TN), Toluidine Blue (TB) and Methylene Blue (MB)) from 0.1 mol/L phosphate buffer solution (pH 7.0). Among the three phenothiazies, the poly(TB) film-modified CF exhibited an excellent electrocatalytic activity for the oxidation of nicotinamide adenine dinucleotide reduced form (NADH) at +0.2 V vs. Ag/AgCl. The poly(TB) film-modified CF was successfully used as working electrode unit of highly sensitive amperometric flow-through detector for NADH. The peak currents (peak heights) were almost unchanged, irrespective of a carrier flow rate ranging from 2.0 to 4.1 mL/min, resulting in the measurement of NADH (ca. 30 samples/hr) at 4.1 mL/min. The peak current responses of NADH showed linear relationship over the concentration range from 1 to 30 mol/L (sensitivity: 0.318 A/( mol/L); correlation coefficient: 0.997). The lower detection limit was found to be 0.3 mol/L (S/N = 3).     

Direct electrochemistry of glucose oxidase and biosensing for glucose based on DNA/chitosan film

Glucose oxidase (GOD) is widely used in the glucose biosensor industry. The amperometric biosensors based on directly electron transfer (DET) between an electrode and immobilized GOD are especially promising. In this article, GOD was immobilized with a DNA/chitosan bio-material film on GC electrode, and the DET of GOD on DNA/chitosan was studied. The cyclic voltammetric results indicated that the GOD immobilized in the DNA/chitosan film underwent DET reaction, and the cyclic voltammogram displayed a pair of well-defined redox peaks with a formal potential of ?0.45 V (vs. Ag/AgCl) at pH 5.5. The response showed a surface-controlled electrode process with an electron transfer rate constant of 0.91 sec^?1 determined in the scan rate range from 10 to 100 mV/sec. The GOD immobilized in DNA/chitosan membrane retained its biocatalytic activity and stability. The immobilized GOD could electrocatalyze the reduction of dissolved oxygen and resulted in a great increase of the reduction peak current. Upon the addition of glucose, the reduction peak current decreased, which could be used for glucose detection with a sensitivity of 0.48 μA/(mmol/L), a linear range from 0.04 to 2.28 mmol/L and a detection limit of 0.04 mmol/L at a signal-to-noise ratio of 3. The sensor could exclude the interference of commonly coexisted uricacid and ascorbic acid.     

A spatially explicit empirical model of structural development processes in natural forests based on climate and topography

Stand structure develops with stand age. Old-growth forests with well-developed stand structure support many species. However, development rates of stand structure likely vary with climate and topography. We modeled structural development of 4 key stand variables and a composite old-growth index as functions of climatic and topographic covariates. We used a hierarchical Bayesian method for analysis of extensive snap-shot National Forest Inventory (NFI) data in Japan (n = 9244) to account for differences in stand age. Development rates of structural variables and the old-growth index exhibited curvilinear responses to environmental covariates. Flat sites were characterized by high rates of structural development. Approximately 150 years were generally required to attain high values (approximately 0.8) of the old-growth index. However, the predicted age to achieve specific values varied depending on environmental conditions. Spatial predictions highlighted regional variation in potential structural development rates. For example, sometimes there were differences of >100 years among sites, even in the same catchment, in attainment of a medium index value (0.5) after timber harvesting. The NFI data suggested that natural forests, especially old natural forests (>150 years), remain generally on unproductive ridges, steep slopes, or areas with low temperature and deep snow, where many structural variables show slow development rates. We suggest that maintenance and restoration of old natural forests on flat sites should be prioritized for conservation due to the likely rapid development of stand structure, although remaining natural forests on low-productivity sites are still important and should be protected.     

Agroforestry as a sustainable landuse option in degraded tropical forests: a study from Bangladesh

The tropical deciduous forest in Bangladesh provides a substantial part of country’s forest and where the government has introduced participatory agroforestry landuse. This study examined management issues, financial viability, and environmental as well as social sustainability of this landuse system. The forest department allocated a plot of size 1.0 ha among the selected participants where they were allowed to practice agriculture as well as to plant tree species for 10 years. The financial indicators indicated that the landuse system was profitable and attractive [net present value (NPV) = US$ 17,710 and benefit-cost ratio (BCR) = 4.12]. It was also viable and suitable from the social and environmental stand points. The study concluded that under the present environmental and socio-economic scenario, this production system could be the best management tool that would earn money, stop forest degradation, and finally be a model of sustainable land management in an overpopulated country.     

Passive air monitoring of PCBs and PCNs across East Asia: a comprehensive congener evaluation for source characterization

A comprehensive congener specific evaluation of polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) in the atmosphere was conducted across East Asia in spring 2008, applying polyurethane foam (PUF) disk passive air sampler (PAS) as monitoring device. Mean concentrations derived for Japan, China and Korea were 184 ± 24, 1100 ± 118, and 156 ± 20 pg m⁻³ for ∑₂₀₂ PCBs, and 9.5 ± 1.5, 61 ± 6, and 16 ± 2.4 pg m⁻³ for ∑₆₃ PCNs, respectively. Relative to reported data from 2004, the present results suggest that air PCBs concentrations have not changed much in Japan and Korea, while it has increased by one order of magnitude in China. From principal component analysis, combustion emerged highly culpable in contemporary emissions of both PCBs and PCNs across the East Asian sub-region. Another factor derived as important to air PCBs was re-emissions/volatilization. Signals from PCBs formulations were also picked, but their general importance was virtually consigned to the re-emissions/volatilization tendencies. On the contrary, counterpart PCNs formulations did not appear to contribute much to air PCNs.     

Environmental risk assessment and concentration trend of atmospheric volatile organic compounds in Hyogo Prefecture, Japan

Purpose  

The purpose of this study was to evaluate the influences of volatile organic compounds (VOCs) emissions on hazardousness and photochemical reactivity and to propose efficient VOCs abatement strategies.     

Assays of PCB congeners and organochlorine insecticides with the transgenic Arabidopsis and tobacco plants carrying recombinant guinea pig AhR and GUS reporter genes

Certain congeners of polychlorinated biphenyls (PCBs) and organochlorine insecticides are ligands of aryl hydrocarbon receptors (AhRs) in animals. A recombinant guinea pig (g) AhR, XgDV, was constructed by fusing the ligand-binding domain of gAhR, the DNA-binding domain of LexA, and the transactivating domain of VP16. Then, the expression unit of β-glucuronidase (GUS) reporter gene regulated by XgDV was introduced into Arabidopsis and tobacco plants. When the transgenic Arabidopsis XgDV plants were cultured on Murashige–Skoog (MS) medium containing PCB congeners, the GUS activity in the plants increased toxic equivalent (TEQ)-dependently. The GUS activity in the transgenic Arabidopsis XgDV plants cultured on MS medium containing the organochlorine insecticide dieldrin was also induced. On the other hand, in the case of DDT, the GUS activity induced by 3-methylcholanthere in the plants decreased. The transgenic Arabidopsis XgDV plants detected 1000 ng g^?1 PCB126 in 1 g of soils. Thus the XgDV plants seemed to be useful for convenient assays of PCB congeners and organochlorine insecticides, without any extraction and purification steps.