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191.
《Chemical Speciation and Bioavailability》2013,25(1):41-42
AbstractMetal fractionation is a powerful tool for studying the mobility, bioavailability and toxicity of metals in sediments and soils. A seven-step sequential extraction technique was used to determine the potential mobility of selected heavy metals (Fe, Mn, Zn, Cu, Pb, Cd and Ni) in the sediments of Lake Naivasha. Results indicate that residual fraction was the most important phase for the elements Fe, Mn, Cu and Zn. However, Pb and Cd are highly enriched in the non-residual phases. Nickel on the other hand was distributed evenly between the non-residual and the residual fractions.The total concentrations of the heavy metals suggested a decreasing order of iron ?> manganese ? zinc > nickel > copper ? lead > cadmium. However, the detailed sequential extraction data indicated an order of release or mobility of cadmium > lead ? nickel ? zinc > manganese > copper > iron. The high percentage of Cd and Pb in the mobile fractions suggests high bioavailability of these two elements in the study area and maybe a pointer to anthropogenic input of the two elements in the study area. 相似文献
192.
Authigenic mineralization and detrital clay binding by freshwater biofilms: The Brahmani river,India
Alexander Likhoshvay Tatiana Khanaeva Alexander Gorshkov Tamara Zemskaya Mikhail Grachev 《Geomicrobiology journal》2013,30(3):209-213
This study sought to understand the origin and fate of one of the bitumen mounds found on the bottom of Lake Baikal. These mounds are located at a depth of 900 m beneath oil spots detected on the surface of Lake Baikal (53° 18′24″, 108° 23′20″). The two mounds were sampled with a manipulator from a “MIR” deep-water manned submersible. Mature mound No. 8 was subjected to chemical and microbiological studies. Mound No. 3 was subjected only to chemical studies; we failed to perform microbiological analyses of this mound for logistic reasons. Oil spots collected from the water surface, samples of mound No. 3 and No. 8, were subjected to GC/MS analysis. The water contained aliphatic hydrocarbons with chains between C8 and C23, with the most abundant chain length being C18. Mound No. 3 with the most abundant chain length being C18 actively released oil droplets into the water. It contained 770 mg/g of C13-C32 n-alkanes, with a maximum at C23 (160 mg/g). Mound No. 8 was inactive and contained 148 mg/g of aliphatic C22-C34 n-alkanes, with a maximum at C25. Mound No. 8 also consisted of 3% inorganic matter, 48% unresolved complex mixture (UCM) and less than 1% other compounds (polyaromatic hydrocarbons, isoprenoids, carotenoids, and hopanes). The core of this sample used as inoculate, yielded Rhodococci when cultivated on oil as the only source of carbon. Cultivation of the sample on agar-containing Raymond inorganic medium with crude West Siberian oil as the only source of carbon revealed colonies of these bacteria, which all appeared identical. PCR was performed with DNA isolated from 5 colonies, using primers for 16S rRNA genes. Comparison of the sequences of the 5 PCR products over a length of 714 bp revealed that they were almost identical. Phylogenetic analysis of these homologous sequences showed that they were similar to the corresponding sequences of the genus Rhodococcus. Substrate demands, the morphology of the colonies, and SEM and TEM data confirmed that the isolates obtained could indeed be Rhodococci. All of the isolates could grow in bulk cultures with inorganic medium supplemented with crude oil. Moreover, all of the isolates degraded aliphatic hydrocarbons with lengths between C11 and C29. C23-C29 hydrocarbons were degraded completely. The isolates could grow at 4–37°C. The most unexpected finding was that of the many microorganisms capable of consuming oil, only Rhodococci exhibited this ability in the inactive bitumen mound. The possible mechanisms of how crude oil is transformed into bitumen mounds and mature bitumen are discussed. 相似文献
193.
Investigation of physicochemical form of uranium in sediment of brackish Lake Obuchi using sequential extraction procedure 总被引:1,自引:0,他引:1
The physicochemical form of uranium (238U) in the sediment of brackish Lake Obuchi was investigated using the standard procedures of sequential extraction. Approximately
60% to 70% of 238U was composed of the form bound to carbonates and iron (Fe)-manganese (Mn) oxides in silty sediments, whereas more than 50%
of 238U existed in the minerals of sandy sediments. The proportions of 238U bound to carbonates in the sediments of brackish Lake Obuchi were larger than those in fresh-water lake sediments. Most
of the uranium in the brackish lake sediment was considered to be mainly influenced by UO2(CO3)3
4− in seawater, judging from the fact that the 234U/ 238U activity ratios (1.13 to 1.16) of silty sediments were very close to that of seawater (1.14). The high correlation found
between the 238U concentration in the sediment and the amount of organic matter demonstrated that organic matter acts as a scavenger for
238U accumulation on the lake bottom.
Received: July 2, 1999 / Accepted: May 25, 2000 相似文献
194.
The influence of brackish phytoplankton cell classes upon the response of urea decomposition was investigated in Lake Nakaumi.
The urea decomposition rate was 5 to 350 μmol urea m−3 h−1 in the light and 3 to 137 μmol urea m−3 h−1 in the dark. The urea decomposition rates in the light were obviously higher than in the dark. An extremely high rate (350
μmol urea m−3 h−1) was observed in Yonago Bay. The rate in the smaller fraction (<5 μm) exceeded that in the middle (5–25 μm) and larger fractions
(>25 μm). The chlorophyll- and photosynthesis-specific rates for urea decomposition in the light were 0.5 to 3.9 μmol urea
mg chl.a
−1 h−1 and 0.3 to 1.3 μmol urea mg photo.C−1. The specific urea decomposing activities were higher in the smaller fraction than in the other two fractions. The present
results suggest that in brackish waters urea decomposition occurred with coupling to the standing crop and photosynthetic
activity of phytoplankton.
Received: May 22, 1999 / Accepted: August 15, 1999 相似文献
195.
196.
Fluctuations in the salinity and physicochemical characteristics of water quality were surveyed in brackish Lake Obuchi on
the Shimokita Peninsula in Aomori, Japan. The mean salinity in the surface layer in all regions of Lake Obuchi was about 10
psu, whereas in the basin region at depths of greater than 3 m it was 20 psu. Furthermore, all the year round the halocline
was formed at depths of 1–4 m. The maximum density gradient along a vertical axis in the center of the lake was observed at
depths of 1–2 m in summer and 2–4 m in spring and fall. The depth of the maximum density gradient fluctuated with the seasons.
In summer the water in the bottom layer was anoxic, and Fe, Mn, PO4
3−-P, and NH4
+-N supplied from the bottom sediment accumulated at high concentrations below the halocline. Thus, it was observed that the
transfer of substances between the layers above and below the barrier formed by the halocline is suppressed. Although Lake
Obuchi is small and shallow, the inflowing seawater easily resides, and a stable halocline readily forms because of the shape
of its basin, which suddenly deepens on the Pacific Ocean side.
Received: May 24, 1999 / Accepted: September 25, 1999 相似文献
197.
Sébastien Personnic Isabelle Domaizon Ursula Dorigo Lyria Berdjeb Stéphan Jacquet 《Hydrobiologia》2009,627(1):99-116
Flow cytometry (FCM) was used to assess microbial community abundances and patterns in three natural, large and deep peri-alpine
hydrosystems, i.e., lakes Annecy (oligotrophic), Bourget, and Geneva (mesotrophic). Picocyanobacteria, small eukaryotic autotrophs,
heterotrophic prokaryotes, and viruses were studied in the 0–50 m surface layers to highlight the impact of both physical
and chemical parameters as well as possible biotic interactions on the functioning of microbial communities. Some specificities
were recorded according to the trophic status of each ecosystem such as the higher number of viruses and heterotrophic bacteria
in mesotrophic environments (i.e., Lakes Geneva and Bourget) or the higher abundance of picocyanobacteria in the oligotrophic
Lake Annecy. However, both seasonal (temperature) and spatial (depth) variations were comparatively more important than the
trophic status in driving the microbial communities’ abundances in these three lakes, as revealed by principal component analysis
(PCA). A strong viral termination of the heterotrophic bacterial blooms could be observed in autumn for each lake, in parallel
to the mixing of the upper lit layers. As virus to bacteria ratio (VBR) was indeed very high at this period with values varying
between 87 and 114, such important relationships between viruses and bacteria were likely. The magnitudes of seasonal variations
in VBR, with the highest values ever reported so far, were largely greater than the magnitude of theoretical variations due
to the trophic status, suggesting also a strong seasonality in virioplankton production associated to prokaryotic dynamics.
FCM analyses allowed discriminating several viral groups. Virus-Like Particles group 1 (VLP1) and group 2 (VLP2) were always
observed and significantly correlated to bacteria for the former and chlorophyll a and picocyanobacteria for the latter, suggesting that most of VLP1 and VLP2 could be bacteriophages and cyanophages, respectively.
On the basis of these results, new ways of investigation emerge concerning the study of relationships between specific picoplanktonic
groups; and overall these results provide new evidence of the necessity to consider further viruses for a better understanding
of lake plankton ecology.
Handling editor: Luigi Naselli-Flores 相似文献
198.
湿地生态旅游研究进展 总被引:13,自引:0,他引:13
湿地富有生物多样性和文化多样性,具有较高的旅游价值、环境教育功能及社区参与功能,湿地生态旅游体现了旅游经济与湿地保护的可持续协调发展,目前已引起国内外政府和学者的普遍关注. 本文对国内外相关研究理论和实践进行了总结,对湿地生态旅游的研究意义、进程、内容、方法和结果等进行了综述,并对湿地生态旅游研究进行了展望,以期推动湿地生态旅游研究的发展,为湿地及相关旅游区的资源开发、环境保护和科学管理提供参考. 相似文献
199.
This study was carried out on the transported bed soil dredged from the outlet of Lake Burullus to the Mediterranean Sea and deposited nearby, forming by this way new land that underwent a primary plant succession. The multi-methodological approach comprised floristic inventories, vegetation sampling and soil composition analyses of the study site in order to detect the crucial parameters controlling the plant resettlement on recently deposited soil as related to time, local micro-topography and substrate characteristics. Floristic composition was assessed for the first 10 years of primary succession (2001–2010) on 18 stands of the area, distributed on basement, slope stands and plateau of the landfill, respectively. Vegetation surveys were the basis of multivariate analyses of the vegetation and soil data using TWINSPAN, DCA and CCA. Relationships between the edaphic gradients, floristic composition and species diversity were assessed. 相似文献
200.
Elizabeth A. Nyboer Lauren J. Chapman 《Biological journal of the Linnean Society. Linnean Society of London》2013,110(2):449-465
Habitat‐associated trait divergence may vary across ontogeny if there are strong size‐related shifts in selection pressures. We quantified patterns of phenotypic divergence in Nile perch (Lates niloticus) from ecologically distinct wetland edge and forest edge habitats in Lake Nabugabo, Uganda, and we compared patterns of divergence across three size classes to determine whether trends are consistent through Nile perch ontogeny. We predicted that inter‐habitat variation in biotic (e.g. vegetation structure) and abiotic (e.g. dissolved oxygen concentration) variables may create divergent selective regimes. We compared body morphology using geometric morphometrics and found substantial differences between habitats, although not all trends were consistent across size classes. The most striking aspects of divergence in small Nile perch were in mouth orientation, head size, and development of the caudal region. Medium‐sized Nile perch also showed differences in mouth orientation. Differences in large individuals were related to eye size and orientation, as well as caudal length. The observed patterns of divergence are consistent with functional morphological predictions for fish across divergent trophic regimes, high and low predation environments, and complex and simple habitats. Although this suggests adaptive divergence, the source of phenotypic variation is unknown and may reflect phenotypic plasticity and/or genetic differences. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 449–465. 相似文献