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231.
Ilias G. Kavouras Joy Lawrence Petros Koutrakis Euripides G. Stephanou Pedro Oyola 《Atmospheric environment (Oxford, England : 1994)》1999,33(30):1588
Using a novel sampler, particulate organic compounds were collected in Santiago de Chile from June 9 to August 10, 1997. This sampler consists of a diffusion denuder to remove gas-phase organics prior to particle collection, a Teflon filter, and a PUF cartridge downstream of the filter. PAHs and n-alkanes were measured using gas chromatography/mass spectrometry analysis. Volatilization of particles collected on the Teflon filter varied from 15 to 85% for both n-alkanes and PAHs, with strong dependence on molecular weight. The relative distribution of n-alkanes and the values of molecular diagnostic ratios, such as Carbon preference index, indicated a mixed origin with strong anthropogenic input. Indeed, CPI values ranged from 0.66 to 1.96 (for the whole range of n-alkanes). The percent contribution of leaf “wax” n-alkanes (4.55–20.83%) indicated the low contribution of biogenic sources. In addition, the distribution pattern of PAHs was characteristic of anthropogenic emissions. The dominant contribution of combustion-related PAHs (CPAHs), 74–84%, indicated that vehicular emissions was the major source of PAHs. 相似文献
232.
Apostolos Kapranas P. Pacheco L. D. Forster J. G. Morse R. F. Luck 《Behavioral ecology and sociobiology》2008,62(6):901-912
We examined whether several facultatively gregarious encyrtid (Hymenoptera: Encyrtidae) endoparasitoids of brown soft scale,
Coccus hesperidum L., manifest precise sex allocation under field conditions. Metaphycus luteolus (Timberlake), Metaphycus angustifrons (Compere), Metaphycus stanleyi (Compere), and Microterys nietneri (Motshulsky) evince brood sex ratios that are female-biased and extremely precise (low variance in the number of sons per
host). Typically, this sex allocation pattern is attributed to extreme local mate competition (LMC) in which only one foundress
exploits a patch of hosts and mating occurs mostly between her offspring. However, such a pattern of sex allocation was not
detected for Metaphycus helvolus (Compere). Also, a large proportion of the broods in all five species contained only daughters; thus, an excess of male-only
broods was expected if unmated females (i.e., females that can produce only sons) contribute offspring before mating. All-male
broods were rare in our samples. This finding coupled with the life history characteristics of these wasps, such as the exploitation
of aggregated hosts and the long life span and mobility of males, suggest that nonlocal mating is frequent. Our empirical
work suggests that it is advantageous to allocate precise sex ratios in cases in which mating opportunities for males are
not restricted to their natal host and/or when multiple foundresses exploit large patches of hosts. Limited theoretical work
also supports this prediction but more detailed studies of this taxon’s mating structure and other life history characteristics
are necessary to understand their sex allocation decisions. 相似文献
233.
针对一台轻型柴油机,采用国Ⅳ柴油,在不使用和使用后处理装置的条件下,进行ESC循环工况(分别记为ESC-0、ESC-DP)和ETC循环工况(分别记为ETC-0、ETC-DP)下的发动机台架测试.每次测试用一对滤膜采集颗粒物,采样前后分别称重以确定颗粒物质量,进而计算排放因子.用气相色谱-质谱联机(GC-MS)分别分析每张滤膜上颗粒物的多环芳烃(PAHs)组分.ESC-0、ESC-DP、ETC-0、ETC-DP的颗粒物排放因子分别为0.12,0.05,0.48,0.16 g/(kW·h);相应的PAHs排放因子分别为69,35,174,76 μg/(kW·h).后处理分别使颗粒物和PAHs减排56%~68%和49%~56%.总PAHs中,三环PAHs占比重最大(64%±9%).PHE在总PAHs中占比重最大(54%±9%).PAHs的分布与其物理化学特性、柴油中的芳烃含量有关.PAHs特征比值FA/(FA+PY)为0.37~0.51. 相似文献
234.
COD/N与pH值对短程硝化反硝化过程中N2O产生的影响 总被引:1,自引:0,他引:1
利用SBR反应器,通过投加乙醇控制COD/N为0、1.5、3、4.5,调节pH值分别在6、7、8,反硝化初始投加NO2--N为30mg/L,考察了缺氧条件下COD/N与pH值对短程硝化反硝化过程中N2O产量的影响.结果表明:低COD/N可以造成N2O持续较高的逸出,N2O最大产生量为2.35mg/L;低pH值条件下增加了N2O的积累,pH值在6时的N2O积累量是pH在7、8时的800倍;高COD/N和高pH值下的N2O产生速率最小,而当pH=6,COD/N=0时,N2O产生速率最大,为2.35×10-3mgN/(mgMLSS?L?h).其原因是:N2O还原酶争夺电子的能力较弱,充足的电子供体有利于N2O的还原;低pH值可影响微生物的代谢,且在H+存在时产生的游离亚硝酸(HNO2)对N2O还原酶具有抑制作用.充足的碳源和碱性条件,是降低短程硝化反硝化过程中N2O产量的关键因素. 相似文献
235.
236.
王 《防灾减灾工程学报》2006,26(4):395-403
应用法国地震学家G.Poup inet等关于双子地震的有关理论,对云南地震台网数字地震资料开展应用研究,通过基线校正、数字滤波、波形对比等方法获得8对3级双子地震和武定地震易门台7对双子地震。对以上双子地震取起始3秒P波作富氏谱分析后进行谱比对数的斜率拟合。结果显示,由发生在6.5级姚安地震前7个月之内与之外时段的地震构成的双子地震,其P波谱比对数斜率绝对值都达到0.030以上,明显高于均由震前7个月之外发生的地震构成的双子地震谱比对数斜率;在距主震2°范围以内的台站可观测到双子波发生的变化。常熟台双子地震P波谱比对数斜率时间进程在南黄海地震发生之前也存在这一现象,但出现异常的时间扩大到9个月之内。 相似文献
237.
Atmospheric phenanthrene pollution modulates carbon allocation in red clover (Trifolium pratense L.)
Desalme D Binet P Epron D Bernard N Gilbert D Toussaint ML Plain C Chiapusio G 《Environmental pollution (Barking, Essex : 1987)》2011,159(10):2759-2765
The influence of atmospheric phenanthrene (PHE) exposure (160 μg m−3) during one month on carbon allocation in clover was investigated by integrative (plant growth analysis) and instantaneous 13CO2 pulse-labelling approaches. PHE exposure diminished plant growth parameters (relative growth rate and net assimilation rate) and disturbed photosynthesis (carbon assimilation rate and chlorophyll content), leading to a 25% decrease in clover biomass. The root-shoot ratio was significantly enhanced (from 0.32 to 0.44). Photosynthates were identically allocated to leaves while less allocated to stems and roots. PHE exposure had a significant overall effect on the 13C partitioning among clover organs as more carbon was retained in leaves at the expense of roots and stems. The findings indicate that PHE decreases root exudation or transfer to symbionts and in leaves, retains carbon in a non-structural form diverting photosynthates away from growth and respiration (emergence of an additional C loss process). 相似文献
238.
Erika Andersson Anna Rotander Thomas von Kronhelm Anna Berggren Per Ivarsson Henner Hollert Magnus Engwall 《Environmental science and pollution research international》2009,16(5):521-530
Background, aim, and scope Degradation of the 16 US EPA priority PAHs in soil subjected to bioremediation is often achieved. However, the PAH loss is
not always followed by a reduction in soil toxicity. For instance, bioanalytical testing of such soil using the chemical-activated
luciferase gene expression (CALUX) assay, measuring the combined effect of all Ah receptor (AhR) activating compounds, occasionally
indicates that the loss of PAHs does not correlate with the loss of Ah receptor-active compounds in the soil. In addition,
standard PAH analysis does not address the issue of total toxicant bioavailability in bioremediated soil.
Materials and methods To address these questions, we have used the CALUX AhR agonist bioassay and the Comet genotoxicity bioassay with RTL-W1 cells
to evaluate the toxic potential of different extracts from a PAH-contaminated soil undergoing large-scale bioremediation.
The extracts were also chemically analyzed for PAH16 and PCDD/PCDF. Soil sampled on five occasions between day 0 and day 274
of biological treatment was shaken with n-butanol with vortex mixing at room temperature to determine the bioavailable fraction
of contaminants. To establish total concentrations, parts of the same samples were extracted using an accelerated solvent
extractor (ASE) with toluene at 100°C. The extracts were tested as inducers of AhR-dependent luciferase activity in the CALUX
assay and for DNA breakage potential in the Comet bioassay.
Results The chemical analysis of the toluene extracts indicated slow degradation rates and the CALUX assay indicated high levels of
AhR agonists in the same extracts. Compared to day 0, the bioavailable fractions showed no decrease in AhR agonist activity
during the treatment but rather an up-going trend, which was supported by increasing levels of PAHs and an increased effect
in the Comet bioassay after 274 days. The bio-TEQs calculated using the CALUX assay were higher than the TEQs calculated from
chemical analysis in both extracts, indicating that there are additional toxic PAHs in both extracts that are not included
in the chemically derived TEQ.
Discussion The response in the CALUX and the Comet bioassays as well as the chemical analysis indicate that the soil might be more toxic
to organisms living in soil after 274 days of treatment than in the untreated soil, due to the release of previously sorbed
PAHs and possibly also metabolic formation of novel toxicants.
Conclusions Our results put focus on the issue of slow degradation rates and bioavailability of PAHs during large-scale bioremediation
treatments. The release of sorbed PAHs at the investigated PAH-contaminated site seemed to be faster than the degradation
rate, which demonstrates the importance of considering the bioavailable fraction of contaminants during a bioremediation process.
Recommendations and perspectives It has to be ensured that soft remediation methods like biodegradation or the natural remediation approach do not result in
the mobilization of toxic compounds including more mobile degradation products. For PAH-contaminated sites this cannot be
assured merely by monitoring the 16 target PAHs. The combined use of a battery of biotests for different types of PAH effects
such as the CALUX and the Comet assay together with bioavailability extraction methods may be a useful screening tool of bioremediation
processes of PAH-contaminated soil and contribute to a more accurate risk assessment. If the bioremediation causes a release
of bound PAHs that are left undegraded in an easily extracted fraction, the soil may be more toxic to organisms living in
the soil as a result of the treatment. A prolonged treatment time may be one way to reduce the risk of remaining mobile PAHs.
In critical cases, the remediation concept might have to be changed to ex situ remediation methods. 相似文献
239.
Tervahauta AI Fortelius C Tuomainen M Akerman ML Rantalainen K Sipilä T Lehesranta SJ Koistinen KM Kärenlampi S Yrjälä K 《Environmental pollution (Barking, Essex : 1987)》2009,157(1):341-346
Two birch clones originating from metal-contaminated sites were exposed for 3 months to soils (sand-peat ratio 1:1 or 4:1) spiked with a mixture of polyaromatic hydrocarbons (PAHs; anthracene, fluoranthene, phenanthrene, pyrene). PAH degradation differed between the two birch clones and also by the soil type. The statistically most significant elimination (p ≤ 0.01), i.e. 88% of total PAHs, was observed in the more sandy soil planted with birch, the clearest positive effect being found with Betula pubescens clone on phenanthrene. PAHs and soil composition had rather small effects on birch protein complement. Three proteins with clonal differences were identified: ferritin-like protein, auxin-induced protein and peroxidase. Differences in planted and non-planted soils were detected in bacterial communities by 16S rRNA T-RFLP, and the overall bacterial community structures were diverse. Even though both represent complex systems, trees and rhizoidal microbes in combination can provide interesting possibilities for bioremediation of PAH-polluted soils. 相似文献
240.
Polycyclic aromatic hydrocarbons and their hydroxylated metabolites in fish bile and sediments from coastal waters of Colombia 总被引:3,自引:0,他引:3
Johnson-Restrepo B Olivero-Verbel J Lu S Guette-Fernández J Baldiris-Avila R O'Byrne-Hoyos I Aldous KM Addink R Kannan K 《Environmental pollution (Barking, Essex : 1987)》2008,151(3):452-459
Sediments and fish bile collected from the Atlantic coastal waters of Colombia were analyzed for 16 parent polycyclic aromatic hydrocarbons (PAHs), and 23 hydroxylated PAHs (OH-PAHs), respectively. Sediments contained overall mean SigmaPAH concentrations of 2090, 234 and 170 ng/g, dry wt, for Cartagena Bay, Caimanera Marsh, and Totumo Marsh, respectively. The mean concentration of the summed OH-PAHs in fish bile was 1250, 180 and 64.1 ng/g bile wt for Cartagena Bay, Caimanera Marsh, and Totumo Marsh, respectively. The results suggest that Cartagena Bay is heavily polluted by PAHs, and that exposure to high concentrations of PAHs together with other factors could contribute to the decreased health of fish living in this ecosystem. This is one of the first studies to describe the analysis of 23 individual OH-PAHs in fish bile, using authentic standards. 相似文献