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301.
Biodegradation capacity of tributyltin by two Chlorella species 总被引:2,自引:0,他引:2
Two microalgal species, Chlorella vulgaris and Chlorella sp., which showed high tributyltin (TBT) tolerant ability were investigated for their capabilities in degrading TBT at sublethal concentration. The distribution of TBT and its degraded products dibutyltin (DBT) and monobutyltin (MBT) in the incubation medium, extracellular surface and intracellular fraction were monitored during an exposure period of 14 days. Results showed that biosorption of TBT by the algal cell wall was the major mechanism in reducing 40% of the initial TBT from the medium in the first 2 days. The half-life of TBT incubated with C. vulgaris was 60 h while that of Chlorella sp. was 80 h. The occurrence of DBT at Day 1 in the culture medium provided direct evidence to the biodegradation of TBT by both Chlorella species. At the end of the experimental period, 27 and 41% of the original TBT were recovered as DBT and MBT in cultures of C. vulgaris, respectively. In contrast, DBT appeared to be the only degradation product of Chlorella sp. and only 26% of the original TBT was transformed to DBT. Despite the same genus, TBT was debutylated to a greater extent to MBT by C. vulgaris, while DBT was the end degradation product by Chlorella sp. The capability of such debutylating process therefore accounted for the higher tolerant ability of C. vulgaris than Chlorella sp. 相似文献
302.
Development and performance of an alternative biofilter system 总被引:3,自引:0,他引:3
Step tracer tests were carried out on lab-scale biofilters to determine the residence time distributions (RTDs) of gases passing through two types of biofilters: a standard biofilter with vertical gas flow and a modified biofilter with horizontal gas flow. Results were used to define the flow patterns in the reactors. "Non-ideal flow" indicates that the flow reactors did not behave like either type of ideal reactor: the perfectly stirred reactor [often called a "continuously stirred tank reactor" (CSTR)] or the plug-flow reactor. The horizontal biofilter with back-mixing was able to accommodate a shorter residence time without the usual requirement of greater biofilter surface area for increased biofiltration efficiency. Experimental results indicated that the first bed of the modified biofilter behaved like two CSTRs in series, while the second bed may be represented by two or three CSTRs in series. Because of the flow baffles used in the horizontal biofilter system, its performance was more similar to completely mixed systems, and hence, it could not be modeled as a plug-flow reactor. For the standard biofilter, the number of CSTRs was found to be between 2 and 9 depending on the airflow rate. In terms of NH3 removal efficiency and elimination capacity, the standard biofilter was not as good as the modified system; moreover, the second bed of the modified biofilter exhibited greater removal efficiency than the first bed. The elimination rate increased as biofilter load increased. An opposite trend was exhibited with respect to removal efficiency. 相似文献
303.
Karl-Heinz Schwind Jamshid Hosseinpour Heidelore Fiedler Christoph Lau Otto Hutzinger 《Umweltwissenschaften und Schadstoff-Forschung》1994,6(5):243-246
Im Rahmen eines Untersuchungsprogrammes zur Schadstoffemission von Paraffin-, Stearin- und Bienenwachskerzen ohne Farb- und
Lackbeimischungen wurden sowohl die Wachse und Dochte als auch die Brandgase dieser Kerzen auf die toxikologisch besonders
relevanten Schadstoffklassen der PCDD/PCDF, PAK und kurzkettigen Aldehyde untersucht. Die toxikologische Bewertung kommt selbst
bei einem angenommenen „worst case“-Szenario und unter Berücksichtigung von geltenden Grenz- und Richtwerten zu dem Ergebnis,
da? von den untersuchten Kerzen kein zus?tzliches Gesundheitsrisiko ausgeht.
Exhaust fumes of paraffin, beeswax and stearin candles without any further paint or decorative element were analysed for the
toxicological important substance classes of PCDD/PCDF, PAH and short chain aldehydes. The candle waxes and wicks were investigated
for chlorinated dioxins, furans and some known precursors. Toxicological risk assessment shows that emissions of the investigated
candles are much lower than all administrative limitation values — even under “worst case conditions”. Thus, they do not produce
a toxicological risk for human health. 相似文献
304.
Farming Endangered Turtles to Extinction in China 总被引:1,自引:0,他引:1
305.
306.
分析了粉末烧结材料泊松比与屈服准则的关系 ,指出了泊松比Kuhn模型的等价假设 ,比较了几种泊松比模型的特点 ,提出了一种能反映致密过程中密度较大时泊松比增长率减缓的特点的箕舌线函数型泊松比模型。 相似文献
307.
308.
利用高温变形实验 ,研究了 14 2 0铝锂合金在不同变形条件下的变形行为 ,获得合金的塑性图、变形抗力图、晶粒尺寸 变形程度关系图 ,确定出合金的锻造工艺参数 :锻造温度为 35 0~4 2 0℃ ,临界变形程度为 8%~ 10 % ,变形速率以低速为宜。结合实际情况 ,制定出合理的、经济的14 2 0铝锂合金模锻件成形工艺 ,即 6 0 0 0t水压机上多方锻开坯→车成锥体→ 80 0 0t卧式挤压机上终压模成形。生产出的 14 2 0合金模锻件尺寸精度高 ,综合性能优良。 相似文献
309.
交通噪声污染经济损失估算方法比较研究 总被引:3,自引:0,他引:3
目前闷内外对于噪声污染经济损失的研究还相当有限,且采用的方法也存在很大的差别。运用环境经济学的观点和方法,提出了估算噪声污染损失的3种常用方法;损害费用法、意愿型调查评估法和防护费用法,并对其进行了比较研究。 相似文献
310.