Shino Mohri

RESPONSE OF ANTIOXIDATIVE ENZYMES AND APOPLASTIC BYPASS TRANSPORT IN THLASPI CAERULESCENS AND RAPHANUS SATIVUS TO CADMIUM STRESS

A hydroponics experiment using hyperaccumulator Thlaspi caerulescens (alpine pennycress) and non-specific accumulator Raphanus sativus (common radish) was conducted to investigate the short-term effect of increasing Cd concentrations (0, 25, 50, 75, 100 μM) on metal uptake, chlorophyll content, antioxidative enzymes, and apoplastic bypass flow. As expected, T. caerulescens generally showed better resistance to metal stress, which was reflected by higher Cd accumulation within plant tissues with no signs of chlorosis, or wilt. Glutathione reductase (GR) and superoxide dismutase (SOD) activities in fresh leaves were monitored as the plant metal-detoxifying response. In general, both plant species exhibited an increase trend of GR activity before declining at 100 μM likely due to excessive levels of phytotoxic Cd. SOD activity exhibited almost a similar variation pattern to GR and decreased also at 100 μM Cd. For both plant species, fluorescent PTS uptake (8-hydroxy-l,3,6-pyrenetrisulphonic acid) increased significantly with metal level in exposure solutions indicating that Cd has a comparable effect to drought or salinity in terms of the gain of relative importance in apoplastic bypass transport under such stress conditions.

A rapid and simple evaluation system for gas toxicity using luminous bacteria entrapped by a polyion complex membrane

We have developed a rapid and simple gas toxicity evaluation system based on bioluminescence inhibition of a marine-derived wild luminous bacterium, Vibrio fischeri. The luminous bacteria were trapped using a thin polyion complex membrane in order to allow semi direct contact between the bacteria and toxic gases. Bioluminescence inhibition ratios of the present system to six reference gases, including benzene, trichloroethylene, acetone, NO(2), SO(2), and CO, were evaluated, and dose-response relationships were successfully obtained after 15 min of gas exposure, except for CO gas. The sensitivity to the five gases except for CO gas of the present system was 1-3 orders of magnitude higher than that in acute animal tests. The present system also allowed for the evaluation of overall toxicity of some environmental gases containing various chemicals. These results clearly demonstrated that the present system would be a valuable prototype for rapid and on-site acute toxicity detection of a gas mixture, such as environmental gases.

Ecotoxicity assessment of sludge and leaching test eluates of sludge.

Sludge mainly collected from wastewater treatment plants were subjected to chemical and ecotoxicological characterization to provide a preliminary assessment of their suitability for land application. We examined the leachability and toxicity of organic compounds in several industrial wastes and recovered materials such as dewatered sludge through standard leaching tests. Several toxicity tests were performed under standard laboratory conditions using a freshwater alga, a crustacean, and some terrestrial plants. Some eluates showed high toxicity. No correlation was found between the ecotoxicological and chemical characteristics or the sum parameters (TOC, total organic carbon concentration). Further, bioassays are extended to exhibit the toxicity, which can be explained by the presence of organic compounds. In general, the eluates differed in their toxicity profiles and their organic chemical composition. Therefore, chemical analyses are unreliable for quantifying biological effects. The samples can be classified as ecotoxic/hazardous based on the LC/EC50 (lethal concentration/effective concentration reducing 50% of survival or biological activity) values. It is necessary to know the relative ecotoxicity of the potential leachate from organic sludge waste before landfill in order to predict the environmental impact in the event of leakage from the landfill.

Evaluation of the ecotoxicity of solid wastes using rapid leaching test and bioassays

A rapid leaching test (RLT) involving the use of ultrasonic irradiation was developed. The applicability and suitability of different leaching procedures for solid wastes were evaluated in terms of the leached concentration of heavy metals and total organic carbon and the ecotoxicity potential of the solid wastes. Solid wastes, including incineration ash and sludge, were used. We performed the RLT and the Japanese standard leaching test (JLT-13) to evaluate the ecotoxicity of the solid wastes. The leaching test samples were analyzed using 3 different bioassays. A higher concentration of heavy metals was obtained by the RLT than by JLT-13. The concentrations of organic compounds leached by the RLT correlated well with those of the organic compounds leached by JLT-13. These results indicate that the RLT developed in this study is a useful method to estimate the leachability of heavy metals and organic compounds in solid waste samples. Although the 50% effective concentration (EC50) values of the RLT and JLT-13 solid waste eluates derived by a human cell-based bioassay were slightly different, the EC50 values of these eluates derived by 2 other ecotoxicity tests correlated well.

Application of Biotests for Toxicity of Leachate and Evaluation Monitoring

廃棄物最終処分場が周辺水環境に与える影響の評価を行うため, 本研究では3種のバイオアッセイ (遺伝子毒性試験, ヒト乳癌由来細胞 (MCF-7) 増殖活性試験, 培養細胞毒性試験) を用い, 6ヶ月間にわたって廃棄物処分場試料, 周辺環境水の毒性監視を行った。また, 遺伝子毒性試験umu試験について環境監視に適した試料前処理法と新たな毒性単位を検討, 提唱した。その結果, 各試料の遺伝子毒性に季節特異的な変動は見られず, 浸出水に検出された毒性は生物処理によって周辺環境水程度に低減していた。浸出水のMCF-7増殖活性の平均値は低く, 放流先河川への影響はほとんどないと考えられた。細胞毒性試験において濃縮試料も細胞の生存率を50％以上低下させる毒性を示さず, 濃縮試料で検出された細胞毒性も, その由来は浸透圧であると推測された。この処理後放流水の細胞毒性の最大値は放流先上流の約9倍であり, 放流先河川に全く影響を与えないためには, 10倍の希釈が必要であった。