Research on leachate recirculation from different types of landfills

Landfills can produce a great amount of leachate containing highly concentrated organic matter. This is especially true for the initial leachate from landfilled municipal solid wastes (MSW) that generally has concentrations of COD(Cr) and BOD(5) up to 80,000 and 50,000mg/L, respectively. The leachate could be disposed by means of recirculating technique, which decomposes the organics through the action of proliferating microorganisms and thereby purifies the leachate, and simultaneously accelerates organic decomposition through water saturation control. Data from experimental results indicated that leachate recirculating could reduce the organic concentration considerably, with a maximum reduction rate of COD(Cr) over 95%; and, using a semi-aerobic process, NH(3)-N concentration of treated leachate could be under 10mg/L. In addition, the organic concentration in MSW decreased greatly.     

Assays of dioxins and dioxin-like compounds in actually contaminated soils using transgenic tobacco plants carrying a recombinant mouse aryl hydrocarbon receptor-mediated β-glucuronidase reporter gene expression system

The transgenic tobacco plant XD4V-26 carrying the recombinant mouse aryl hydrocarbon receptor XD4V-mediated β-glucuronidase (GUS) reporter gene expression system was used for assay of dioxins and dioxin-like compounds consisting of polychlorodibenzo-p-dioxins, polychlorinated dibenzofurans, and coplanar polychlorinated biphenyls (Co-PCBs) in actually contaminated soils. The transgenic tobacco plant XD4V-26 showed a significant dose-dependent induced GUS activity when cultured on MS medium containing PCB126 [toxic equivalency factor (TEF) = 0.1]. In contrast, PCB169 and PCB180, which have 0.03 of TEF and unassigned TEF values, respectively, did not significantly induce GUS activity under the same conditions as with PCB126. When the tobacco plants were cultivated for up to 5 weeks on actually contaminated soils with dioxins and dioxin-like compounds collected from the periphery of an incinerator used for disposal of life and industrial wastes, GUS activity in the leaves was dose-dependently increased. The plants clearly detected 360 pg-TEQ g(-1) of dioxins and dioxin-like compounds in this assay. There was a positive correlation between GUS activity and TEQ value of dioxins and dioxin-like compounds in the plants. This assay does not require any extraction and purification processes for the actually contaminated soil samples.     

Aryl hydrocarbon receptor activities of hydroxylated polycyclic aromatic hydrocarbons in recombinant yeast cells

Hydroxylated polycyclic aromatic hydrocarbons (OH-PAH) with less than four rings are frequently found in the environment, whereas the toxicities associated with these compounds remain unclear. In this study, aryl hydrocarbon receptor (AhR)–ligand binding activities of OH-PAH were investigated by using a recombinant yeast assay system. The majority of the OH-PAH tested showed AhR–ligand binding activities, especially, when the hydroxylated derivatives of naphthalene were incubated with recombinant yeast. The structure–activity relationship between AhR activity and molecular weight or the octanol–water partition coefficient value of OH-PAH displayed significant correlations. These findings indicate that the site and number of hydroxy-groups substituted on PAH skeleton apparently influenced the AhR – ligand binding activity in the recombinant yeast assay.     

Tyrosinase-modified carbon felt-based flow-biosensors: The role of ultra-sonication in shortening the enzyme immobilization time and improving the sensitivity for p-chlorophenol

Tyrosinase (TYR) was covalently immobilized onto amino-functionalized carbon felt surface via glutaraldehyde-coupling under ultrasonic treatment for 10 min. The resulting TYR-immobilized carbon felt was used as a working electrode unit of bioelectrocatalytic flow-through detector for TYR substrates (catechol, p-chlorophenol (p-CP), p-cresol, phenol etc.). Cathodic peak currents based on the electroreduction of enzymatically produced o-quinones were detected at –50 mV vs. Ag/AgCl. Compared with previous work in which TYR was immobilized onto amino-functionalized carbon felt for 16 hr without the ultrasonic treatment, we succeeded in (1) shortening the enzyme immobilization time from 16 hr to 10 min, (2) enhancing the sensitivity of p-CP, and (3) improving the operational stability of p-CP. The ultrasonic treatment during the TYR immobilization step would lead to certain changes in the structure of the immobilized TYR and the morphology of the immobilized TYR-layer on the carbon felt surface.     

Factors affecting the burrowing behaviour of Helice tridens (Grapsidae) and Macrophthalmus japonicus (Ocypodidae) in an estuary of northeast Japan

Helice tridens (De Haan) (Grapsidae) and Macrophthalmus japonicus (De Haan) (Ocypodidae) build separate burrows in reed marshes and muddy tidal flats, respectively, in the brackish-water estuaries of northeast Japan (38°11N, 141°48E). Habitat segregation between burrows of these two species was analysed by comparing the density of burrows of both species in their natural habitats, and on tidal flats subjected to various types of artificial treatment, in the summer of 1981 and 1982. Baskets, containing many stones, were placed on the ground in the reed marsh, tidal flat and creek and attracted many individuals of H. tridens, but not M. japonicus. When stones were placed on an area of tidal flat, H. tridens frequently formed burrows at the border between the stones and mud, suggesting that burrowing of H. tridens was related to the presence of solid substances lying on the ground, such as stones and shoots of the reed Phragmites australis (Cav.) Trin. In closed systems on the tidal flat and reed marsh, H. tridens and M. japonicus were able to construct burrows in both substrata regardless of high or low frequency. Moreover, it was recognized that H. tridens prevented the burrowing of M. japonicus in these closed systems. These results suggested that habitat segregation between H. tridens and M. japonicus burrows was caused primarily by an exclusive interaction between individuals of these two species.     

我国填埋场改造及发展方向的探讨

对我国部分生活垃圾填埋场和室内填埋设施的填埋气组分进行了现场测试和分析,结果表明,厌氧填埋场的CH₄含量高,半好氧填埋场CH₄含量很低。并针对我国填埋场的现状提出了如果打算利用填埋气进行发电,填埋构造可以作成厌氧填埋,否则,填埋场应以安全性为 主,应建造成半好氧结构。      

Assays of dioxins and dioxin-like compounds in actually contaminated soils using transgenic tobacco plants carrying a recombinant mouse aryl hydrocarbon receptor-mediated β-glucuronidase reporter gene expression system

The transgenic tobacco plant XD4V-26 carrying the recombinant mouse aryl hydrocarbon receptor XD4V-mediated β-glucuronidase (GUS) reporter gene expression system was used for assay of dioxins and dioxin-like compounds consisting of polychlorinated dibenzeno-p-dioxins, polychlorinated dibenzofurans, and coplanar polychlorinated biphenyls (Co-PCBs) in actually contaminated soils. The transgenic tobacco plant XD4V-26 showed a significant dose-dependent induced GUS activity when cultured on MS medium containing PCB126 [toxic equivalency factor (TEF) = 0.1]. In contrast, PCB169 and PCB180, which have 0.03 of TEF and unassigned TEF values, respectively, did not significantly induce GUS activity under the same conditions as with PCB126. When the tobacco plants were cultivated for up to 5 weeks on actually contaminated soils with dioxins and dioxin-like compounds collected from the periphery of an incinerator used for disposal of residential and industrial wastes, GUS activity in the leaves was dose-dependently increased. The plants clearly detected 360 pg-TEQ g(-1) of dioxins and dioxin-like compounds in this assay. There was a positive correlation between GUS activity and TEQ value of dioxins and dioxin-like compounds in the plants. This assay does not require any extraction and purification processes for the actually contaminated soil samples.     

Sensitive voltammetric and amperometric responses of respiratory toxins at hemin-adsorbed carbon-felt

A hemin [iron-Fe(III) protoporphyrin IX chloride] was adsorbed onto a carbon-felt (CF), which is a microelectrode ensemble of micro carbon fiber (ca. 7 μm diameter). The resulting hemin-adsorbed-CF (hemin-CF) showed a well-defined redox wave based on the hemin-Fe(III)/Fe(II) redox process with the formal potential of -0.225 V vs. Ag/AgCl in deoxygenated phosphate/citrate buffer solution (0.1 mol/L, pH 5.0). The apparent heterogenous electron transfer rate constant was estimated to be 8.6 sec^-1. In air-saturated electrolyte solution, the hemin-CF exhibited an excellent electrocatalytic activity for the reduction of dioxygen (O₂). This activity was reversibly inhibited by respiratory toxins such as cyanide and azide, which bind sixth coordination position of iron active center of hemin. The electrocatalytic O₂ reduction current at the hemin-CF was modulated by the toxins in a concentration-depending manner. Based on the relationship between the inhibition and the toxin concentration, apparent inhibition constants of cyanide and azide were evaluated to be 4.52 and 1.98 μmol/L, respectively. When the hemin-CF was used as a working electrode unit of the CF-based electrochemical flow-through detector with air-saturated carrier, the injection of the azide induced peak-shape current responses, which allowed rapid and continuous flow-amperometric determination of azide with high sensitivity.     

Nematomorph parasites drive energy flow through a riparian ecosystem

Parasites are ubiquitous in natural systems and ecosystem-level effects should be proportional to the amount of biomass or energy flow altered by the parasites. Here we quantified the extent to which a manipulative parasite altered the flow of energy through a forest-stream ecosystem. In a Japanese headwater stream, camel crickets and grasshoppers (Orthoptera) were 20 times more likely to enter a stream if infected by a nematomorph parasite (Gordionus spp.), corroborating evidence that nematomorphs manipulate their hosts to seek water where the parasites emerge as free-living adults. Endangered Japanese trout (Salvelinus leucomaenis japonicus) readily ate these infected orthopterans, which due to their abundance, accounted for 60% of the annual energy intake of the trout population. Trout grew fastest in the fall, when nematomorphs were driving energy-rich orthopterans into the stream. When infected orthopterans were available, trout did not eat benthic invertebrates in proportion to their abundance, leading to the potential for cascading, indirect effects through the forest-stream ecosystem. These results provide the first quantitative evidence that a manipulative parasite can dramatically alter the flow of energy through and across ecosystems.