不同溶剂提取芦竹化感物质对铜绿微囊藻生长的影响

研究并比较了3种极性不同的有机溶剂(甲醇、乙酸乙酯、正己烷)提取的芦竹(Arundo donax Linn.)化感物质对铜绿微囊藻生长的影响.通过跟踪观察藻细胞形态,测定藻细胞密度和细胞大小,发现3种溶剂提取物对铜绿微囊藻均有抑制作用.抑藻作用出现早晚次序:甲醇提取物<乙酸乙酯提取物<正己烷提取物.随作用时间的延长,投加低浓度甲醇提取物藻细胞生长恢复明显,高浓度抑藻效果较乙酸乙酯提取物及正己烷提取物弱.高浓度乙酸乙酯提取物、正己烷提取物在分别作用2　d、 4 d　后,抑藻效果均接近100%.各溶剂提取物的半效应质量浓度(EC_50,6　d)分别为甲醇提取物0.17　 g·L^-1,乙酸乙酯提取物0.05 g·L^-1,正己烷提取物0.08 g·L^-1.研究同时发现,投加甲醇提取物藻细胞空洞化,投加乙酸乙酯提取物藻细胞空洞化、破碎以及部分抱团,投加正己烷提取物藻细胞出现褶皱及聚团现象.各溶剂提取物均引起铜绿微囊藻细胞体积减小,其中乙酸乙酯提取物的效果最强.     

Production of biologically safe digested manure for land application by a full-scale biogas plant with heat-inactivation

Inactivation of indigenous indicator micro-organisms such as faecal coliforms, coliphages, and faecal streptococci was investigated in a full-scale biogas plant that mainly digested cow manure. The biogas plant consisted principally of a feed reservoir, fermentation tank (37 degrees C), heat-inactivation process (70 degrees C), and five reservoirs for the heat-inactivated, digested manure that was used by a local livestock farmer as liquid fertilizer. Although all the indicators tended to exhibit stepwise decreases with each stage of treatment, coliphages were found to be more capable of surviving than faecal coliforms and faecal streptococci under mesophilic anaerobic conditions as well as high temperature conditions (heat-inactivation at 70 degrees C). Liquid fertilizer produced at the biogas plant had faecal coliform densities less than the stipulations of the US EPA 40 CFR 503 Class A limits. Heat-inactivation tests indicated that although coliphages exhibited more tolerance than other bacterial indicators between 37 and 70 degrees C, they were more sensitive to continuous temperature increase than faecal coliforms and faecal streptococci.     

Economic evaluation of sewage treatment processes in India

This paper evaluates the total annual cost including capital and operation and maintenance (O&M) costs for the up-flow anaerobic sludge blanket (UASB) and waste stabilization pond (WSP) systems operated in India. It also compares UASB and WSP systems with the activated sludge process (ASP) and biological aerated filter (BAF) systems in terms of total annual cost and chemical oxygen demand (COD) removal cost by assuming various annual interest rates and land prices. It was found that the relationship between capital and O&M costs per unit size of a UASB or WSP system and its treatment capacity can be established by a first-order equation. The relation between the cost of organic removal and capital or O&M cost for various sewage treatment systems at various annual interest rates revealed that, for the Indian context, UASB could be the most suitable option in terms of expenses and treatment efficiency.     

Cultured human-cell-based bioassay for environmental risk management

Among bioassays for evaluating various impacts of chemicalson humans and ecosystems, those based on culturedmammalian-cells can best predict acute lethal toxicity to humans. Weexpect them to be employed in the future in environmentalrisk management alongside mutagenicity tests and endocrine-disrupting activity tests. We recently developed adisposable bioassay device that immobilizes humanhepatocarcinoma cells in a small micropipette tip. Thisenables very quick (within 2 h) evaluation of acute lethaltoxicity to humans. For bioassay-based environmentalmanagement, 2 promising approaches have been demonstrated bythe US-EPA: toxicity identification evaluation (TIE) andtoxicity reduction evaluation (TRE). The Japanese Ministryof Environment has been supporting a multi-center validationproject, aimed at assembling a bioassay database. To makefull use of these resources, we present a numerical modelthat describes contribution of individual chemical toobserved toxicity. This will allow the selection of the mosteffective countermeasure to reduce the toxicity. Bioassay-based environmental risk management works retrospectively,whereas impact assessment using substance flow models andtoxicity databases works prospective. We expect that these 2approaches will exchange information, act complementarily,and work effectively in keeping our environment healthy inthe 21st century.     

Biological methane production coupled with sulfur oxidation in a microbial electrosynthesis system without organic substrates

Methane is produced in a microbial electrosynthesis system (MES) without organic substrates. However, a relatively high applied voltage is required for the bioelectrical reactions. In this study, we demonstrated that electrotrophic methane production at the biocathode was achieved even at a very low voltage of 0.1 V in an MES, in which abiotic HS⁻ oxidized to SO₄²⁻ at the anodic carbon-cloth surface coated with platinum powder. In addition, microbial community analysis revealed the most probable pathway for methane production from electrons. First, electrotrophic H₂ was produced by syntrophic bacteria, such as Syntrophorhabdus, Syntrophobacter, Syntrophus, Leptolinea, and Aminicenantales, with the direct acceptance of electrons at the biocathode. Subsequently, most of the produced H₂ was converted to acetate by homoacetogens, such as Clostridium and Spirochaeta 2. In conclusion, the majority of the methane was indirectly produced by a large population of acetoclastic methanogens, namely Methanosaeta, via acetate. Further, hydrogenotrophic methanogens, including Methanobacterium and Methanolinea, produced methane via H₂.     

4种水生植物根际磷素耗竭效应的比较

利用短期盆栽试验和抖根法研究了喜旱莲子草(Alternanthera philoxeroides)、香蒲(Typha latifolia)、慈姑(Sagittaria sagittifolia)和芦苇(Phragmites communis)4种水牛植物的根际磷素耗竭效应,分析了植物根冠比、根系形态、磷素吸收有效性和磷素利用有妓性等差异,探讨了植物根际磷素耗竭效应的吸收利用调控机制.结果表明,与非根际土壤(有效磷含量为167.53ìg穏-1)相比,喜旱莲子草、香蒲、慈姑和芦苇根际土壤的有效磷含量分别减少至80.17、124.37、155.38和161.75ìg穏-1,水溶性磷含量分别减少了81%、42%、18%和16%.喜旱莲子草根系较小,但磷素吸收有效性高(1.32 mg·m-1),其磷素利用有效件不高(0.34 g·mg-1);香蒲的磷素吸收有效性虽然比喜旱莲子草低许多(0.52 mg·m-1),但其有强大的根系,且磷素利用有效性高(0.64 g·mg-1)、根冠比大(0.35).喜旱莲子草和香蒲耗竭根际磷素的能力高于慈姑和芦苇.     

Diphenylmethane diisocyanate self-polymerization: Thermal hazard evaluation and proof of runaway reaction in gram scale

Thermal analysis by differential scanning calorimetry and thermogravimetric/differential thermal analysis mass spectrometry, adiabatic calorimetry, a gram-scale heating test, and infrared spectroscopy were performed to evaluate the thermal hazards of diphenylmethane diisocyanate (MDI) and prove the occurrence of a runaway reaction. The self-polymerization of MDI was found to occur at about 340 °C under rapid heating conditions. Carbon dioxide was eliminated and heat was generated to allow polymerization. Under adiabatic and closed conditions, the runaway reaction of MDI can begin at least from 220 °C. Besides it is highly probable that the runaway reaction of MDI can begin from a lower temperature in an actual process scale. More heat was generated than in the previous case and the pressure rose rapidly. A closed 2-mm-thick glass vessel exploded because of the runaway reaction of MDI even if the temperature was lower than 300 °C. Therefore, MDI could cause fatal runaway reactions below 300 °C, where MDI had been assumed to self-polymerize by eliminating carbon dioxide previously.     

Integrated biological–physical process for biogas purification effluent treatment

Biogas purification via water scrubbing produces effluent containing dissolved CH₄, H₂S, and CO₂, which should be removed to reduce greenhouse gas emissions and increase its potential for water regeneration. In this study, a reactor built with air supplies at the top and bottom was utilized for the treatment of biogas purification effluent through biological oxidation and physical stripping processes. Up to 98% of CH₄ was removed through biological treatment at a hydraulic retention time of 2 hr and an upper airflow rate of 2.02?L/day. Additionally, a minimum CH₄ concentration of 0.04% with no trace of H₂S gas was detected in the off gas. Meanwhile, a white precipitate was captured on the carrier showing the formation of sulfur. According to the developed mathematical model, an upper airflow rate of greater than 2.02?L/day showed a small deterioration in CH₄ removal performance after reaching the maximum value, whereas a 50?L/day bottom airflow rate was required to strip the CO₂ efficiently and raise the effluent pH from 5.64 to 7.3. Microbiological analysis confirmed the presence of type 1 methanotroph communities dominated by Methylobacter and Methylocaldum. However, bacterial communities promoting sulfide oxidation were dominated by Hyphomicrobium.     

湿地植物香蒲体内氮、磷含量的季节变化及适宜收割期

通过实地调查,研究了南四湖湿地生态自然保护区香蒲对氮、磷元素的吸收与蓄积规律.结果表明:氮磷元素在香蒲体内的蓄积含量具有季节性规律,随生长发育时期的延长,香蒲组织内氮、磷均具有随季节而向上输送蓄积或向下进行"营养回流"的特点.结合香蒲资源化利用的途径,香蒲的收割方式应按照其分布特点,分区域交替收割,既要保证香蒲的正常繁殖,还要保证香蒲能够从湿地环境带出一定量的氮磷,收割期宜在10月下旬或11月份.从香蒲吸收氮磷元素的年际间对比,发现2008年度地上部较2007年度有明显的累积,香蒲具有年际间的累积特点,但在生长后期一部分营养可能转运至土壤环境,使得累积现象不明显.氮磷营养元素在植物体内的高度分布规律在湿地生态管理中具有重要的指导意义,调研结果显示,生长初期与生长后期香蒲体内营养元素的高度分布具有近似相反的规律性.