Effects of bicarbonate and cathode potential on hydrogen production in a biocathode electrolysis cell

A biocathode with microbial catalyst in place of a noble metal was successfully developed for hydrogen evolution in a microbial electrolysis cell （MEC）. The strategy for fast biocathode cultivation was demonstrated. An exoelectrogenic reaction was initially extended with an H2-full atmosphere to enrich Ha-utilizing bacteria in a MEC bioanode. This bioanode was then inversely polarized with an applied voltage in a half-cell to enrich the hydrogen-evolving biocathode. The electrocatalytic hydrogen evolution reaction （HER） kinetics of the biocathode MEC could be enhanced by increasing the bicarbonate buffer concentration from 0.05 mol·L-1 to 0.5 mol· L-1 and/or by decreasing the cathode potential from -0.9 V to - 1.3 V vs. a saturated calomel electrode （SCE）. Within the tested potential region in this study, the HER rate of the biocathode MEC was primarily influenced by the microbial catalytic capability. In addition, increasing bicarbonate concentration enhances the electric migration rate of proton carriers. As a consequence, more mass H＋ can be released to accelerate the biocathode-catalyzed HER rate. A hydrogen production rate of 8.44 m3. m 3. d1 with a current density of 951.6 A. m-3 was obtained using the biocathode MEC under a cathode potential of - 1.3 V vs. SCE and 0.4 mol· L-1 bicarbonate. This study provided information on the optimization of hydrogen production in biocathode MEC and expanded the practical applications thereof.     

Using crosslinked polyvinyl alcohol polymer membrane as a separator in the microbial fuel cell

Separator between anode and cathode is an essential part of the microbial fuel cell （MFC） and its property could significantly influence the system perfor- mance. In this study we used polyvinyl alcohol （PVA） polymer membrane crosslinked with sulfosuccinic acid （SSA） as a new separator for the MFC. The highest power density of 7594-4 mW-m-2 was obtained when MFC using the PVA membrane crosslinked with 15% of SSA due to its desirable proton conductivity （5.16 x 10-2 S.cml）. The power density significantly increased to 11064- 30 mW.m-2 with a separator-electrode-assembly config- uration, which was comparable with glass fiber （11704- 46 mW.m-2）. The coulombic efficiencies of the MFCs with crosslinked PVA membranes ranged from 36.3% to 45.7% at a fix external resistance of lO00f2. The crosslinked PVA membrane could be a promising alter- native to separator materials for constructing practical MFC system.     

Application of probabilistic risk assessment at a coking plant site contaminated by polycyclic aromatic hydrocarbons

Application of Probabilistic Risk Assessment （PRA） and Deterministic Risk Assessment （DRA） at a coking plant site was compared. By DRA, Hazard Quotient （HQ） following exposure to Naphthalene （Nap） and Incremental Life Cancer Risk （ILCR） following exposure to Benzo（a）pyrene （Bap） were 1.87 and 2.12 × 104. PRA revealed valuable information regarding the possible distribution of risk, and risk estimates of DRA located at the 99.59th and 99.76th percentiles in the risk outputs of PRA, which indicated that DRA overestimated the risk. Cleanup levels corresponding acceptable HQ level of 1 and ILCR level of 104 were also calculated for both DRA and PRA. Nap and Bap cleanup levels were 192.85 and 0.14mg.kg-1 by DRA, which would result in only 0.25% and 0.06% of the exposed population to have a risk higher than the acceptable risk, according to the outputs of PRA. The application of PRA on cleanup levels derivation would lift the cleanup levels 1.9 times for Nap and 2.4 times for Bap than which derived by DRA. For this coking plant site, the remediation scale and cost will be reduced in a large portion once the method of PRA is used. Sensitivity analysis was done by calculating the contribution to variance for each exposure parameter and it was found that contaminant concentration in the soil （Cs）, exposure duration （ED）, total hours spent outdoor per day （ETout）, soil ingestion rate （IRs）, the air breathing rate （IRa） and bodyweight （BW） were the most important parameters for risk and cleanup levels calculations.     

间作栽培对连作马铃薯根际土壤微生物区系的影响

为探究不同间作栽培模式缓解马铃薯（Solanum tuberosum）连作障碍的可行性及作用机制,以马铃薯单作为对照,研究马铃薯间作玉米（Zea mays）、蚕豆（Vicia faba）和荞麦（Fagopyrum esculentum）3种模式对连作马铃薯根际土壤养分含量及微生物区系的影响.结果表明,间作种植模式下马铃薯根际土壤全氮、全磷、速效磷和速效钾含量显著低于马铃薯单作,根际土壤速效磷降幅最大,达45％以上,土壤pH值明显下降.间作栽培模式改变了马铃薯根际土壤微生物群落结构,降低了根际土壤真菌的数量;间作栽培模式对马铃薯根际土壤微生物群落的碳源利用能力也有明显影响,其中马铃薯间作蚕豆和间作玉米处理马铃薯根际土壤微生物培养120 h的平均颜色变化率分别比对照高13.39％和4.30％.马铃薯根际土壤微生物群落总体上对碳水化合物利用率较高,对芳香化合物的利用率较低.间作蚕豆明显促进了马铃薯根际土壤微生物群落的碳源代谢强度,而且能维持较稳定的产量,因而可能是一种有利于改善马铃薯连作栽培根际微生态环境、缓解连作障碍的栽培模式.     

Book Reviews

The study focused on the so-called dark coniferous forest belt on the northern slope of Changbai Mountain, at an altitude of 1100 to 1700 m. Forty tree species, 50 shrub species and 165 herb species were recorded in a series of transects. The main impact factors on forest diversity and proposals for sustainable management of this diversity were studied using an altitude and area gradient pattern method. The results showed that the diversity of dark coniferous forest gradually decreased from lower to upper altitude; while the importance value of key species increased. The methodology used to assess attributes for conservation of dark coniferous forest diversity involved measurement of individual trees, number of species, age structure, stand structure, diameter at breast height (DBH), and cumulative wood storage. Different conservation strategies have been developed and are discussed for different parts of the forest.     

Traditional Ecological Knowledge and Practice for Edible Wild Plants: Biodiversity Use by the Rarámuri,in the Sirerra Tarahumara,Mexico

The Rarámuri who live in the Sierra Tarahumara of Chihuahua State, Mexico have developed local knowledge and harvesting strategies for edible wild plants that have the effect of conserving the biodiversity of their forest ecosystem. This paper presents the results of ethnobotanical research undertaken in the community of Basìhuare in the Sierra Tarahumara, to provide details on some practical aspects of the Raráamuri worldview regarding interconnections between people and their environment. This traditional philosophy forms the basis for the use of edible wild plants and the harvesting strategies practiced in Basìhuare, such as selective harvesting, environmental modification and domestication. These activities provide the opportunity for harvesters to monitor the landscape and the plant resources that occur on the land, as well as present a setting for the communication and exchange of traditional ecological knowledge. However, Rarámuri harvesting practices are under stress because of increased external pressures from commercial timber extraction and other development. We discuss the state of traditional ecological knowledge and its transmission in the context of development activities in the region. The key to sustainability in the Sierra Tarahumara may be the maintenance of traditional management practices for edible wild plants, and other nontimber forest products, that lead to the conservation of biodiversity by creating patchiness and renewing the plant cover on the land.     

白云岩单轴压缩试验声发射特性研究

在单轴压缩条件下,进行白云岩破坏全过程的声发射试验研究,得到应力、声发射特性与时间的关系,并研究了岩体的Kaiser效应。结果表明:（1）岩石单轴压缩破坏过程中并不是所有试验岩样有具有典型的声发射特征阶段,部分岩样AE曲线中可以找到Kaiser效应特征点,但是多数岩样的Kaiser效应特征点不明显;（2）岩样的AE现象在应力达到峰值前会经过一个平静期,而在岩石发生破坏直至彻底破坏阶段,AE现象明显增加,这个先平静后剧增的过程可以作为预报岩爆发生的一种警示信号;（3）大多数岩样都在AE能量达到最大时发生彻底破坏。     

杉木人工林碳收获预估技术研究

从收获预估的角度确定森林碳收获大小与林分之间的关系,定义了碳收获和碳收获表的概念.采用二次正交旋转设计设置杉木(Cunninghamia lanceolata)人工林典型标准地,调查测定获取典型样地杉木人工林样木各器官碳含量及碳贮量基本数据,基于相对生长方程以单株胸径、树高、材积为自变量建立杉木人工林单木碳收获量模型,以林分平均胸径、平均树高、密度指数和蓄积量为自变量建立杉木人工林林分碳收获量模型并编制其可变密度碳收获量表.经检验,所建立杉木人工林单木各器官碳收获量模型和林分碳收获量模型预估精度均达95%以上,且模型充分考虑了单株材积和林分蓄积量对碳收获量的影响,具有较强的兼容性和可操作性,在森林碳汇估测中具有应用价值.将所建立杉木人工林碳收获量模型应用于杉木人工林单木碳收获量及林分碳收获量预估,实例计算表明其预估精度较高,单木碳收获模型的相对误差仅为4.70 %,说明所建立杉木人工林碳收获量模型可应用于福建省杉木人工林单木和林分碳储量估计,从而丰富了森林资源动态预测内容,并可为森林资源监测及其相关研究提供基础数据.     

基于模糊综合判别的森林火险等级预报研究

森林火险气象因子的预报具有很大的不确定和模糊性,而依赖于气象预报因子的森林火险预报同样具有等级判别的模糊性.以海南岛森林火险气象等级预报为例建立森林火险预报模糊数学模型,研究建立森林火险预报模糊综合判别数学模型的关键技术,并分析对比模糊数学模型与其它常用森林火险预报方法模型的优劣.结果表明模糊数学模型在海南岛森林火险等级预报中显现出明显优势,它能够更好地分辨出高森林火险与低森林火险,较好反映森林火险等级与气象因子之间存在的复杂关系.     

Report of A Survey of the State of the Environment in the Estonia,Latvia and Lithuania

In connection with the change in economic principles and disintegration of big industrial enterprises, the environmental pollution in Baltic States decreased considerably in 1991-1996. Although there are still many things waiting to be done, the improvement of the Baltic environmental situation during the years of independence gives us a cause to be optimistic.