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排序方式: 共有297条查询结果,搜索用时 31 毫秒
31.
Effect of experimental nitrogen load on methane and nitrous oxide fluxes on ombrotrophic boreal peatland 总被引:8,自引:0,他引:8
Nykänen Hannu Vasander Harri Huttunen Jari T. Martikainen Pertti J. 《Plant and Soil》2002,242(1):147-155
Methane (CH4) and nitrous oxide (N2O) dynamics were studied in a boreal Sphagnum fuscum pine bog receiving annually (from 1991 to 1996) 30 or 100 kg NH4NO3-N ha–1. The gas emissions were measured during the last three growing seasons of the experiment. Nitrogen treatment did not affect the CH4 fluxes in the microsites where S. fuscum and S. angustifolium dominated. However, addition of 100 kg NH4NO3-N ha–1 yr–1 increased the CH4 emission from those microsites dominated by S. fuscum. This increase was associated with the increase in coverage of cotton grass (Eriophorum vaginatum) induced by the nitrogen treatment. The differences in the CH4 emissions were not related to the CH4 oxidation and production potentials in the peat profiles. The N2O fluxes were negligible from all microsites. Only minor short-term increases occurred after the nitrogen addition. 相似文献
32.
Pertti J. Pelto 《American anthropologist》1966,68(1):198-202
33.
Tuija Lauteala Pertti Sistonen Marja-Liisa Savontaus Juha Mykkänen Jaakko Simell Mari Lukkarinen Olli Simell Pertti Aula 《American journal of human genetics》1997,60(6):1479-1486
Lysinuric protein intolerance (LPI) is an autosomal recessive disease characterized by defective transport of cationic amino acids and by hyperammonemia. Linkage analysis in 20 Finnish LPI families assigned the LPI gene locus to the proximal long arm of chromosome 14. Recombinations placed the locus between framework markers D14S72 and MYH7, a 10-cM interval in which the markers D14S742, D14S50, D14S283, and TCRA showed no recombinations with the phenotype. The phenotype was in highly significant linkage disequilibrium with markers D14S50, D14S283, and TCRA. The strongest allelic association obtained with marker TCRA, resulting in a P(excess) value of .98, suggests that the LPI gene locus lies in close proximity to this marker, probably within a distance of < 100 kb. 相似文献
34.
35.
Siljanen HM Saari A Krause S Lensu A Abell GC Bodrossy L Bodelier PL Martikainen PJ 《FEMS microbiology ecology》2011,75(3):430-445
In lake ecosystems a major proportion of methane (CH(4) ) emissions originate from the littoral zone, which can have a great spatial variability in hydrology, soil quality and vegetation. Hitherto, spatial heterogeneity and the effects it has on functioning and diversity of methanotrophs in littoral wetlands have been poorly understood. A diagnostic microarray based on the particulate methane monooxygenase gene coupled with geostatistics was used to analyse spatial patterns of methanotrophs in the littoral wetland of a eutrophic boreal lake (Lake Kev?t?n, Eastern Finland). The wetland had a hydrology gradient with a mean water table varying from -8 to -25 cm. The wettest area, comprising the highest CH(4) oxidation, had the highest abundance and species richness of methanotrophs. A high water table favoured the occurrence of type Ib methanotrophs, whereas types Ia and II were found under all moisture conditions. Thus the spatial heterogeneity in functioning and diversity of methanotrophs in littoral wetlands is highly dependent on the water table, which in turn varies spatially in relation to the geomorphology of the wetland. We suggest that changes in water levels resulting from regulation of lakes and/or global change will affect the abundance, activity and diversity of methanotrophs, and consequently CH(4) emissions from such systems. 相似文献
36.
Lindberg HK Korpi A Santonen T Säkkinen K Järvelä M Tornaeus J Ahonen N Järventaus H Pasanen AL Rosenberg C Norppa H 《Mutation research》2011,723(1):1-10
Toluene diisocyanate (TDI) and 4,4'-methylenediphenyl diisocyanate (MDI), used in the production of polyurethane foam, are well known for their irritating and sensitizing properties. Contradictory results have been obtained on their genotoxicity. We investigated the genotoxicity and protein binding of inhaled TDI and MDI in mice by examining micronucleated polychromatic erythrocytes (PCEs) in bone marrow and peripheral blood and TDI- and MDI-derived adducts in hemoglobin. Male C57Bl/6J mice (8 per group) were exposed head-only to TDI vapour (mean concentrations 1.1, 1.5, and 2.4mg/m(3); the mixture of isomers contained, on the average, 63% 2,4-TDI and 37% 2,6-TDI) or MDI aerosol (mean concentrations 10.7, 20.9 and 23.3mg/m(3)), during 1h/day for 5 consecutive days. Bone marrow and peripheral blood were collected 24h after the last exposure. Inhalation of TDI caused sensory irritation (SI) in the upper respiratory tract, and cumulative effects were observed at the highest exposure level. Inhalation of MDI produced SI and airflow limitation, and influx of inflammatory cells into the lungs. Hemoglobin adducts detected in the exposed mice resulted from direct binding to globin of 2,4- and 2,6-TDI and MDI, and dose-dependent increases were observed especially for 2,4-TDI-derived adducts. Adducts originating from the diamines of TDI (toluene diamine) or MDI (methylene dianiline) were not observed. No significant increase in the frequency of micronucleated PCEs was detected in the bone marrow or peripheral blood of the mice exposed to TDI or MDI. The ratio of PCEs and normochromatic erythrocytes (NCEs) was reduced at the highest concentration of MDI, and a slight reduction of the PCE/NCE ratio, dependent on cumulative inhaled dose, was also seen with TDI. Our results indicate that inhalation of TDI or MDI (1h/day for 5 days), at levels that induce toxic effects and formation of TDI- or MDI-specific adducts in hemoglobin, does not have detectable genotoxic effects in mice, as studied with the micronucleus assay. 相似文献
37.
Shinjini Mukherjee Heli Juottonen Pauli Siivonen Cosme Lloret Quesada Pirjo Tuomi Pertti Pulkkinen Kim Yrj?l? 《The ISME journal》2014,8(10):2131-2142
Restoration of polluted sites via in situ bioremediation relies heavily on the indigenous microbes and their activities. Spatial heterogeneity of microbial populations, contaminants and soil chemical parameters on such sites is a major hurdle in optimizing and implementing an appropriate bioremediation regime. We performed a grid-based sampling of an aged creosote-contaminated site followed by geostatistical modelling to illustrate the spatial patterns of microbial diversity and activity and to relate these patterns to the distribution of pollutants. Spatial distribution of bacterial groups unveiled patterns of niche differentiation regulated by patchy distribution of pollutants and an east-to-west pH gradient at the studied site. Proteobacteria clearly dominated in the hot spots of creosote pollution, whereas the abundance of Actinobacteria, TM7 and Planctomycetes was considerably reduced from the hot spots. The pH preferences of proteobacterial groups dominating in pollution could be recognized by examining the order and family-level responses. Acidobacterial classes came across as generalists in hydrocarbon pollution whose spatial distribution seemed to be regulated solely by the pH gradient. Although the community evenness decreased in the heavily polluted zones, basal respiration and fluorescein diacetate hydrolysis rates were higher, indicating the adaptation of specific indigenous microbial populations to hydrocarbon pollution. Combining the information from the kriged maps of microbial and soil chemistry data provided a comprehensive understanding of the long-term impacts of creosote pollution on the subsurface microbial communities. This study also highlighted the prospect of interpreting taxa-specific spatial patterns and applying them as indicators or proxies for monitoring polluted sites. 相似文献
38.
1. The predominantly nocturnal constrained drift of stream invertebrates is commonly regarded as a behaviour that avoids encounters with visually foraging fish in the water column. The alternative explanation, that drift peaks are caused by bottom-feeding, nocturnal predators, has rarely been tested.
2. We examined these hypotheses by collecting invertebrate drift in five streams in northern Finland: one with brown trout ( Salmo trutta , a drift-feeding fish), one with alpine bullhead ( Cottus poecilopus , a benthic fish), one with both species, and two fishless streams.
3. Drift by Baetis mayflies was aperiodic or slightly diurnal in both fishless streams on all sampling occasions. In contrast, drift was nocturnal in streams with trout and, to a lesser extent, in the stream with bullhead. Non-dipteran prey drifted mainly nocturnally in all streams with fish, whereas Diptera larvae were less responsive to the presence of fish.
4. In laboratory experiments, bullheads were night-active, causing a much higher frequency of drift by touching Baetis at night than during the day. Thus, increased nocturnal drift may serve to avoid both visual predators (a pre-contact response) and benthic fish (a post-contact response). In streams with bottom-feeding fish, nocturnal drift should be caused by increased drift by night rather than by reduced drift by day. 相似文献
2. We examined these hypotheses by collecting invertebrate drift in five streams in northern Finland: one with brown trout ( Salmo trutta , a drift-feeding fish), one with alpine bullhead ( Cottus poecilopus , a benthic fish), one with both species, and two fishless streams.
3. Drift by Baetis mayflies was aperiodic or slightly diurnal in both fishless streams on all sampling occasions. In contrast, drift was nocturnal in streams with trout and, to a lesser extent, in the stream with bullhead. Non-dipteran prey drifted mainly nocturnally in all streams with fish, whereas Diptera larvae were less responsive to the presence of fish.
4. In laboratory experiments, bullheads were night-active, causing a much higher frequency of drift by touching Baetis at night than during the day. Thus, increased nocturnal drift may serve to avoid both visual predators (a pre-contact response) and benthic fish (a post-contact response). In streams with bottom-feeding fish, nocturnal drift should be caused by increased drift by night rather than by reduced drift by day. 相似文献
39.
Charlotte E. Carlberg Lennart Moller Pauliina Paakki Marjatta Kantola Helene Stockmann Raija Purkunen Peruka Wagner Urs Lauper Mairi Kaha Eivor Elovaara Pertti Kirkinen Markku Pasanen 《Biomarkers》2000,5(3):182-191
During pregnancy, mothers are exposed to complex chemical mixtures, such as air pollution and smoke from incomplete combustion. In this study DNA adducts were measured in human placentas from 29 mothers. Environmental exposure and several possible biomarkers in relation to levels of DNA adducts were measured. Placental aromatic and bulky DNA adducts were measured with the 32 相似文献
40.
S. Saarnio Jukka Alm Jouko Silvola Annalea Lohila Hannu Nykänen Pertti J. Martikainen 《Oecologia》1997,110(3):414-422
Temporal and spatial variation in CH4 emissions was studied at hummock, Eriophorum lawn, flark and Carex lawn microsites in an oligotrophic pine fen over the growing season using a static chamber method, and CH4 production and oxidation potentials in peat profiles from hummock and flark were determined in laboratory incubation experiments.
Emissions were lowest in the hummocks, and decreased with increasing hummock height, while in the lawns and flarks they increased
with increasing sedge cover. Statistical response functions with water table and peat temperature as independent variables
were calculated in order to reconstruct seasonal CH4 emissions by reference to the time series for peat temperature and water table specific to each microsite type. Mean CH4 emissions in the whole area in the snow-free period of 1993, weighted in terms of the proportions of the microsites, were
1.7 mol CH4 m–2. Potential CH4 production and oxidation rates were very low in the hummocks rising above the groundwater table, but were relatively similar
when expressed per dry weight of peat both in the hummocks and flarks below the water table. The CH4 production potential increased in autumn at both microsites and CH4 oxidation potential seemed to decrease. The decrease in temperature in autumn certainly reduced in situ decomposition processes,
possibly leaving unused substrates in the peat, which would explain the increase in CH4 production potential.
Received: 16 August 1996 / Accepted: 30 November 1996 相似文献