Methanogenic toxicity and continuous anaerobic treatment of wood processing effluents

Wood processing effluents contain different types of phenolic compounds, from simple monomers to high molecular weight (MW) polyphenolic polymers, that can inhibit wastewater treatment. This work presents a comparative study of the methanogenic toxicity produced by three wood processing effluents (hardboard, fiberboard and BKME (kraft mill effluent)) using Pinus radiata, Eucalyptus and Tepa as feedstock (the last one being a native Chilean tree species). This study evaluates the influence of non-adapted granular and adapted flocculent sludge on forest industrial wastewater treatment as well as continuous anaerobic biodegradation of hardboard processing effluent using the upflow anaerobic sludge blanket (UASB). The adapted biomass (flocculent sludge) did not show any lag-phase signs. The 50% IC (the concentration causing 50% inhibition of methanogenic activity) was 4.3 g COD-effluent (chemical oxygen demand (COD)-of the effluent)/l and 2.8 g COD-effluent/l for the flocculent sludge and the granular sludge, respectively. The UASB system worked at low organic load rates (0.1-0.4 g COD/l d) with the COD removal ranging between 10 and 30%, and color removal did not occur under anaerobic conditions due to high MW. Indeed, the MW analysis indicates the presence of phenolic compounds over 25,000 Da in the anaerobic effluent.     

木粉尘职业接触极限值的研究

木头作为原材料得到广泛应用 ,但硬木粉尘 (如橡木和山毛榉粉尘 )可导致人患鼻癌。不同国家的木粉尘的职业接触极限值 (或极限值 )却不尽相同。虽然关于木粉尘的极限值的国际讨论持续已久 ,但仍缺乏更好支持其极限值推导的健康相关数据。为保护木材加工工人的身体健康以及给木粉尘的职业接触极限值的制定机构提供可靠数据和科学决策方面的建议 ,笔者针对怎样为木粉尘 ,特别是致癌木粉尘制定一个合理极限值的问题 ,在“比较”和“设定”两方面对国际范围内的木粉尘的极限值进行了研究 ,其结果表明 ,大部分国家给予软木粉尘和硬木粉尘的极限值分别为 5mg/m3 和 1mg/m3 ;提出利用剂量 -影响 -关系和“线性多阶段”方法也可以给致癌硬木粉尘建立一个健康基础极限值或者一个可接受极限值 ,其极限值应该不仅根据木材类型而且还需根据工作岗位而分别综合设定。     

Improving agricultural sustainability: the case of Swedish greenhouse tomatoes

Of major concern to agriculturists and society are issues of sustainability and land and resource requirements for food and fiber. Sustainability of Swedish domestic agriculture is explored using the production of tomatoes in greenhouses as a case study. Issues of sustainability are related to net yields, environmental loading, greenhouse gases, employment and land use. A model for evaluation of sustainability is developed and illustrated using the concepts and theories of analysis. The intensive tomato production system investigated was shown to be highly dependent on non-renewable resources and human service fed back from society. Substituting wood powder from logging residues for the oil used for heating reduced the environmental load and improved the sustainability of the system significantly.     

The effect of perceived intruder proximity and resident body size on the aggressive responses of male green frogs, Rana clamitans (Anura: Ranidae)

We examined variation in aggressive responses within and among individuals in the green frog, Rana clamitans. We tested the hypothesis that resident males respond in a graded fashion to changes in perceived intruder proximity (stimulus intensity). We also investigated how response level varied with responder body size. We found that green frogs differentially alter aggressive responses (increasing movement and calling rates while decreasing the duration and dominant frequency of their calls) with an increase in stimulus intensity. Body size did not appear to be a significant influence on most response levels. We suggest that aggressive responses are graded, and advertisement and aggressive calls represent opposite ends of a continuum. Green frogs do not exhibit clearly defined thresholds for responses like those reported for some other frogs. By using graded responses rather than discrete all-or-nothing responses, males may reduce the potential costs of aggressive encounters.     

Habituation in the green frog, Rana clamitans

Habituation and its role in the dear enemy effect was investigated in a population of green frogs, Rana clamitans. Green frogs have a prolonged breeding season, and males defend territories centered around suitable oviposition sites. We tested the prediction that male green frogs will habituate to broadcasts of synthetic conspecific stimuli. Our results indicate that male green frogs can discriminate familiar from unfamiliar stimuli. We suggest that habituation helps to mediate the territorial interactions between male green frogs. Strangers present a greater threat than familiar neighbors. By habituating to the advertisement vocalizations of their near neighbors, males avoid costly interactions with individuals that are not a major threat to their territories. Received: 20 July 1998 / Accepted after revision: 6 September 1998     

木材点燃温度的测定

本文叙述了在15-32KW/㎡辐射条件下对四种木材点燃性的研究，测定了木材（64×64×18mm）水平方向着火点（点燃状态形成）时的木材表面温度及点燃时间。结果表明：辐射强度等于或高于24KW/㎡时，可以较准确地测量木材的点燃温度，且此温度基本保持一致（±20℃）。辐射强度较低时，木材表观点燃温度大大高于辐射强度较高时的点燃温度，本文对这一现象进行了讨论。     

Effects of Forest Fragmentation and Habitat Degradation on West African Leaf-Litter Frogs

Abstract:  Habitat degradation alters the dynamics and composition of anuran assemblages in tropical forests. The effects of forest fragmentation on the composition of anuran assemblages are so far poorly known. We studied the joint influence of forest fragmentation and degradation on leaf-litter frogs. We specifically asked whether the processes structuring leaf-litter anuran assemblages in fragmented forests are the same as those in continuous forests. We analyzed anuran assemblages with respect to habitat characteristics, including fragmentation and degradation parameters. In comparison with continuous forests, species richness and diversity were lower and assemblage composition was altered in forest fragments. These changes seemed to be mainly caused by habitat degradation rather than forest fragmentation. Availability of aquatic sites for breeding, vegetation structure (including those variables indicating degradation), and leaf-litter cover had the most influence on the presence of single species. The comparatively small impact of fragmentation on anurans might be due to the location of the study area; it still possessed large tracts of continuous forest. These forest blocks may stabilize the regional rainforest climate and thus weaken the effects of fragmentation .     

Selective phonotaxis by male wood frogs (<Emphasis Type="Italic">Rana sylvatica</Emphasis>) to the sound of a chorus

Frogs and toads commonly form large choruses around suitable breeding habitat during the mating season. Although often regarded as a constraint on the acoustic behavior of signalers and receivers, the sounds of a chorus could also serve as an acoustic beacon that allows some frogs to locate the breeding aggregation. Attraction to chorus sounds might be particularly important for explosively breeding frogs. In these species, which often mate just one or a few days during the year, the timing and location of breeding aggregations can be unpredictable because their formation often depends on local climatic factors, such as rainfall or a change in temperature. I used laboratory playback experiments to test the hypothesis that male wood frogs (Rana sylvatica), an explosively breeding frog, exhibit positive phonotaxis toward the sound of a conspecific chorus. Males were released at the center of a rectangular arena with a speaker positioned in each corner facing toward the release point. In a single-stimulus experiment, more males approached a speaker broadcasting a conspecific chorus than the three silent speakers in the arena. In a two-stimulus experiment, more males approached a speaker broadcasting a conspecific chorus compared to the two silent speakers or a fourth speaker simultaneously broadcasting the spectrally overlapping sound of a heterospecific (R. septentrionalis) chorus. These results are consistent with the hypothesis that male wood frogs could use the sound of a chorus as a beacon to locate a short-lived breeding aggregation.     

Explosion parameters of wood chip-derived syngas in air

The wood gasification process poses serious concerns about the risk of explosion. The design of prevention and mitigation measures requires the knowledge of safety parameters, such as the maximum explosion pressure, the maximum rate of pressure rise and the gas deflagration index, K_G, at standard ambient temperature (25 °C) and pressure (1 bar) conditions. However, the analysis at specific process conditions is strongly recommended, as the explosion behavior of gas mixtures may be completely different.In the work presented in this paper, the explosion behavior of mixtures with composition representative of wood chip-derived syngas (CO/H₂/CH₄/CO₂/N₂ mixtures with and without H₂O) was experimentally studied in a closed combustion chamber. Experiments were run at two temperatures, 300 °C and 10 °C, and at atmospheric pressure. Test conditions were requested by the safety engineering designer of an existing industrial-scale wood gasification plant. In order to identify the specific fuel–air ratios to be analyzed, thus reducing the number of experimental tests, a preliminary thermo-kinetic study was performed.Results have shown that the mixtures investigated can be classified as low-reactivity mixtures, the higher value of K_G found (∼36 bar m/s) being much lower than the K_G value of methane (55 bar m/s @ 25 °C).     

Gonadal histology and reproductive steroidogenesis in Lithobates pipiens exposed to atrazine

Abstract

Atrazine, an endocrine-disrupting compound and environmental pollutant, can have adverse effects on amphibian reproductive development and function. To determine the effects of atrazine on anuran gonadal development, Lithobates pipiens larvae were exposed from Gosner stage 25 through 1-month post metamorphosis to 0, 2, 20, or 200?μg/L atrazine or estradiol. Exposure to atrazine did not markedly alter tadpole growth, development, gonadal histology, or reproductive steroidogenesis. Testicular ovarian follicles appeared in L. pipiens metamorphs following all treatments, including controls, whereas ovotestes occurred only in positive controls. Testicular ovarian follicles may be a natural ontogenetic occurrence in this species while ovotestes indicate disruption in development. Establishing the normal pattern of reproductive development for anuran species and conducting comparisons in fully sexually differentiated animals is necessary to clarify the influence of endocrine disrupting compounds.