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981.
The fate and effect of nanomaterials in the environment is of paramount importance towards the technological application of the materials. This work shows the ecotoxicological potential of polyaniline (PANI) nanofibers in the larvae Rhinella arenarum by means of AMPHITOX test. Acute toxicity of PANI nanofibers towards embryos of the common South American toad R. arenarum (Anura: bufonidae) was evaluated in the premetamorphosis (stage 25) larvae. The exposure of R. arenarum larvae to at dose of 150, 250 and 400 mg L−1 resulted in 100% viability within 96 h exposure. The embryos at 2-4 blastomers stage (early life stage teratogenic test) revealed that embryos were not killed and no teratogenic effects were observed when embryos were incubated with PANI nanofibers (150 and 250 mg L−1), while only a growth retardation of embryos was induced at levels of 250 mg PANI nanofibers L−1. On the other hand, at 400 mg L−1 concentration, a reduction in the body length of larvae and tail malformation was observed. This results suggest that a concentration-dependent toxicity is operative, typified by phenotypes that had abnormal body axes. The presence of PANI nanofibers in gut contents and its excretion by larval stages of R. arenarum was confirmed by UV-visible spectroscopy. 相似文献
982.
In this study we assessed the degree of copper (Cu) tolerance in two common lichen species (Cladonia furcata and Cladina arbuscula subsp. mitis) that grow on both uncontaminated substrata and the surface of waste heaps from abandoned old Cu-mines. Regardless of their locality, populations of these lichens contain identical strains of photobionts (Asterochloris clade A in C. arbuscula subsp. mitis and clade D in C. furcata). Therefore, it was expected that if there were differences in Cu toxicity or tolerance between populations, that the photobiont could not be a key element of Cu tolerance in these two lichen species. In laboratory experiments samples of both lichen species (from contaminated and control sites) were incubated in Cu solutions (500 μM) for 24 h. We attempted to determine whether Cu tolerance in these lichens was constitutive, or inducible form. Based on measurements of Cu accumulation, chlorophyll a integrity, chlorophyll a fluorescence, photosynthesis, respiration, measurements of the content of thiobarbituric acid reactive substances (TBARS), the content of soluble proteins, reactive oxygen species (ROS) and the amount of extracellular secondary metabolites of both lichens we found that there were no significant differences in the response of all selected populations of both lichen species to short-term exposure to these high levels of Cu. As a result, we conclude that Cu tolerance in these two lichen species is the constitutive rather than the inducible. 相似文献
983.
Regional dynamics of persistent organic pollutants (POPs) in the Pearl River Delta, China: implications and perspectives 总被引:1,自引:0,他引:1
Zhang K Zhang BZ Li SM Zeng EY 《Environmental pollution (Barking, Essex : 1987)》2011,159(10):2301-2309
The mass transport budgets of 1,1,1-trichloro-2,2-bis(chlorophenyl)ethane (p,p′-DDT) and decabromodiphenyl ether (BDE-209) in the Pearl River Delta, South China were calculated based on previously collected data. Residual p,p′-DDT, mostly related to historical use, has largely settled into soil (780,000 kg), while the soil BDE-209 inventory (44,000 kg) is considerably smaller. Conversely, large amounts of BDE-209 currently used in numerous commercial products have resulted in a much higher atmospheric depositional flux of BDE-209 (28,100 kg/yr) relative to p,p′-DDT (310 kg/yr). The soil inventory of p,p′-DDT is predicted to decrease to half of its current value after 22 years, and the percent area containing soil p,p′-DDT at levels exceeding the effects range-medium (27 ng/g) will decrease from 40% to 20%. Finally, soil BDE-209 inventory will reach an equilibrium value of 940 tons in ∼60 years, when BDE-209 levels in 50% of soil will be above an equivalent risk guideline value (125 ng/g). 相似文献
984.
985.
986.
用透射电镜研究聚硅酸硫酸铁混凝剂的形态 总被引:9,自引:0,他引:9
由水玻璃、硫酸和硫酸铁制备聚硅酸硫酸铁(PFSS)混凝剂,用透射电镜观察PFSS的形态,研究了PFSS的形态随硅酸聚合时间,SiO2/Fe摩尔比和熟化时间的变化。结果表明,硅酸聚合时间,SiO2/Fe摩尔比及熟化时间对PFSS的形态有较大的影响。 相似文献
987.
北京低山区森林土壤中CH4排放通量的研究 总被引:5,自引:0,他引:5
CH4是大气中一种重要的温室气体,与土壤圈有着频繁的交换过程。用静态箱式技术原位测定了北京西山低山区油松人工林地土壤中CH4的排放通量,结果显示北京西山森林土壤为大气CH4重要的汇。年平均吸收值为20.47 g(m-2(h-1,变动范围0~44.8 g(m-2(h-1。 吸收值有一定的季节变化规律, 冬季的吸收值最小,几乎为0,春秋季较高,夏季最高。影响吸收的外界环境因素主要有地表下5 cm处的土壤温度。原状土壤氧化CH4的模拟实验表明吸收过程为纯生物化学过程,吸收作用主要发生在0~5 cm的矿质土层,而枯落物层和20 cm以下的层次基本无吸收反应。CH4的氧化速率在开始的12 h内可用一级反应动力学方程 C =C 0e-kt很好地模拟 。 相似文献
988.
利用软锰矿与微生物联合催化氧化烟气SO2.分别选取氧化亚铁硫杆菌(T. ferrooxidans菌)和锰氧化细菌,研究微生物对SO2-3的氧化性能和恢复体系中Mn(Ⅱ)和Fe(Ⅲ)的活性性能.采用紫外线诱变法,选育出了对SO2-3和Fe2+转化效率高T. ferrooxidans菌的优势菌株,对Fe2+的完全氧化时间缩短为约24 h.通过分析细菌与软锰矿联合催化氧化脱除SO2的脱硫效率变化、液相中SO2-3离子的变化,以及二者的关系,探讨了细菌在软锰矿脱硫体系中所起的作用,并用透射电子显微镜观察了反应前后锰氧化细菌的形态变化.结果表明Fe2+与T. ferrooxidans菌共同存在时,T. ferrooxidans菌对SO32-的转化速率可达到0.015?3 g/(L·min),优于化学氧化.T. ferrooxidans菌和锰氧化菌联合软锰矿脱硫实验结果表明,细菌对软锰矿脱硫存在强化作用;锰氧化细菌促进脱硫存在适应期,T. ferrooxidans菌和锰氧化菌存在协同效应,微生物可以完成铁锰催化剂的再生循环. 相似文献
989.
990.
The purpose of this study is to understand the effect and mechanism of preventing membrane fouling, by coagulation pretreatment, in terms of fractional component and molecular weight of natural organic matter (NOM). A relatively higher molecular weight (MW) of hydrophobic compounds was responsible for a rapid decline in the ultrafiltration flux. Coagulation could effectively remove the hydrophobic organics, resulting in the increase of flux. It was found that a lower MW of neutral hydrophilic compounds, which could remove inadequately by coagulation, was responsible for the slow declining flux. The fluxes in the filtration of coagulated water and supernatant water were compared and the results showed that a lower MW of neutral hydrophilic compounds remained in the supernatant water after coagulation could be rejected by a membrane, resulting in fouling. It was also found that the coagulated flocs could absorb neutral hydrophilic compounds effectively. Therefore, with the coagulated flocs formed on the membrane surface, the flux decline could be improved. 相似文献