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991.
梯级河滩湿地模型对受污染河水氮磷和CODCr的净化效果 总被引:2,自引:0,他引:2
在贾鲁河畔构建3组并联的梯级河滩湿地模型,引种9种不同类型的湿地植物进行筛选试验,将湿地模型串联运行比较研究3种不同植物配置的梯级湿地对受污染河水的净化效果,在此基础上设定12h和24h等两组不同水力滞留时间,研究延长滞留时间对水质净化效果的影响。试验结果表明:对氮磷和有机物的去除效果挺水植物明显好于沉水植物,其中茭草(Zizania caduciflora)、荆三棱(Scirpus fluviatilis)和狭叶香蒲(Typha angustifolia)去除效果最好;沉水植物和挺水植物对氨氮的去除表现好于浮叶植物;延长水力滞留时间对改善水质净化效果明显,滞留时间由12h延长到24h后,TN、TP、氨氮和CODCr去除率分别提高10.2%、21.7%、30.2%和12.9%,对氨氮的净化效果改善最为明显;挺水植物+沉水植物+浮叶植物组合较单纯挺水植物组合在对氨氮和TN去除效果方面表现出较明显的优势,主要是由于不同类型湿地植物所营造的好氧、厌氧环境提高了对氨氮和TN去除效果。研究结果证明在湿地植被组建中,根据进水水质,应灵活选择植物种类,进行合理的植物配置,可提高湿地的净化效果。 相似文献
992.
We studied a guild of desert winter annual plants that differ in long-term variation in per capita reproductive success (lb, the product of per capita survival from germination to reproduction, l, times per capita reproduction of survivors, b) to relate individual function to population and community dynamics. We hypothesized that variation in lb should be related to species' positions along a trade-off between relative growth rate (RGR) and photosynthetic water-use efficiency (WUE) because lb is a species-specific function of growing-season precipitation. We found that demographically variable species have greater RGR and greater leaf carbon isotope discrimination (Delta, a proxy inversely related to WUE). We examined leaf nitrogen and photosynthetic characteristics and found that, in this system, variation in Delta is a function of photosynthetic demand rather than stomatal regulation of water loss. The physiological characteristics that result in low Delta in some species may confer greater photosynthetic performance during the reliably moist but low temperature periods that immediately follow winter rainfall in the Sonoran Desert or alternatively during cool periods of the day or early growing season. Conversely, while species with high Delta and high RGR exhibit low leaf N, they have high biomass allocation to canopy leaf area display. Such trait associations may allow for greater performance during the infrequent conditions where high soil moisture persists into warmer conditions, resulting in high demographic variance. Alternatively, high variance could arise from specialization to warm periods of the day or season. Population dynamic buffering via stress tolerance (low RGR and Delta) correlates negatively with buffering via seed banks, as predicted by bet-hedging theory. By merging analyses of population dynamics with functional trait relationships, we develop a deeper understanding of the physiological, ecological, and evolutionary mechanisms involved in population and community dynamics. 相似文献
993.
The gastropods Lepetodrilus fucensis and Depressigyra globulus are abundant faunal components of animal communities at deep-sea hydrothermal vents along the Juan de Fuca Ridge in the NE
Pacific. The population structure and recruitment pattern of both species were studied using modal decomposition of length–frequency
distributions. Gastropod populations were collected from Axial Volcano and Endeavour Segment in 2002 and 2003. Polymodal size–frequency
distributions, particularly at Axial Volcano vent sites, suggest a discontinuous recruitment pattern for D. globulus. In contrast, there were no distinct peaks visible in the distributions of L. fucensis, suggesting a continuous recruitment pattern for this species. For both species, distributions were positively skewed towards
the smaller length–classes, implying post-settlement mortality is high. However, variations in growth, due to short- and long-term
variability in environmental conditions in the hydrothermal vent habitat, as well as biological interactions, may also be
influencing the distribution and abundance of subsequent life-history stages. Using maximum shell lengths from populations
of known ages, the growth rate of L. fucensis was estimated as 9.6 μm day−1, indicating adulthood would be reached in ∼1 year. Our results suggest that, despite occupying the same habitat, abundance
and population structure are regulated by different biotic and abiotic processes in L. fucensis and D. globulus. 相似文献
994.
Maria Valeria Migliori Antonella Pettinari Anna Maria Ciaschini Paola Piermattei Francesco Pigliapoco Giancarlo Discepoli 《黑龙江环境通报》2004,24(4):290-292
We report the prenatal diagnosis of an extra der(4) resulting from 4:2 malsegregation of a maternal balanced complex translocation involving chromosomes 4, 10, and 11. The woman was referred for amniocentesis because of recurrent miscarriages. Fluorescence in situ hybridization was performed in order to characterize the complex chromosome rearrangement. Following genetic counselling, the couple decided to terminate the pregnancy. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
995.
996.
There is a paucity of theory pertaining to social surveys of annoyance and community noise. A new psychophysical model addresses data concerning resident annoyance in sites exposed to various maximum noise levels and different numbers of noise events. The best fits of this model point to the relevance of response variance for understanding the results obtained with category response scales. The argument identifies a number of psychological and physical variables that may influence annoyance reactions to community noise. Most importantly, the model suggests that the truncation inherent in category scales biases the responses, and that response variability may be critical in determining the detailed shape of the dose–response function. Regulatory decisions concerning annoyance and community noise should be more valid when based on a deeper understanding of the theoretical basis of the empirical data. 相似文献
997.
998.
Kivimäenpää M Jönsson AM Stjernquist I Selldén G Sutinen S 《Environmental pollution (Barking, Essex : 1987)》2004,127(3):441-453
Light (LM) and transmission electron (TEM) microscopy were used to study previously specified ozone symptoms in the foliage of Norway spruce. The three youngest green needle generations from twenty mature trees in two stands on sites of different soil fertility at Asa, southern Sweden, were sampled in 1999. The critical dose of ozone, expressed as AOT40, was 6,362 ppb.h. LM showed ozone-specific symptoms: decreased chloroplast size with electron dense stroma advancing gradually from the outer to the inner cell layers, being most severe in the needle side facing the sky. The symptoms were expressed as ozone syndrome indices at the needle generation, tree and stand levels. The index had higher values at the low fertility site. TEM was used to confirm the LM results. The study shows that LM can be used for diagnosis of the impact of ozone on conifers in the field. 相似文献
999.
Extractable organic halogens (EOX) in sediments from selected Polish rivers and lakes--a measure of the quality of the inland water environment 总被引:1,自引:0,他引:1
EOX in sediments from the two main Polish rivers (the Vistula and the Oder/Odra) as well as five lakes was assayed coulometrically and its values examined with respect to the location of the sample collection points. EOX values were found to increase near industrial areas and large urban agglomerations, although mean values--comparable for rivers and lakes--were similar to those recorded elsewhere. EOX tends to rise as TOC does so. On the other hand, the EOX:TOC ratio decreases sharply in the case of lakes, since TOC values there are roughly one order of magnitude higher than in rivers. Furthermore, the contents of selected polychlorinated biphenyls and organochlorine pesticides are directly related to EOX values. These relationships constitute a basis for the application of EOX as a parameter reflecting the level of organochlorine compounds in environmental quality evaluation. 相似文献
1000.
The herbicide glyphosate was used as a selection agent for isolation of fungal strains capable to degrade phosphorus-to-carbon bond from standard sandy-clay soil. The studies have shown that the herbicide used in Martin medium as a sole source of phosphorus br carbon caused the decrease of the fungal population and substantially changed strain composition, thus selecting those which are able to degrade glyphosate. 相似文献