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91.
Amador JA Potts DA Savin MC Tomlinson P Görres JH Nicosia EL 《Journal of environmental quality》2006,35(4):1160-1169
Aeration improves the capacity of leachfields to decontaminate and reduce the nutrient load of wastewater. To gain a better understanding of the effects of aeration, we examined the faunal and microbial communities of septic system leachfield soil (0-4 and 4-13 cm) using replicated (n = 3) mesocosms that were actively aerated (AIR) or unaerated (LEACH). Protozoa were 40 to 140 times more abundant in AIR than in LEACH soil. No nematodes were found in LEACH soil, whereas AIR soil contained 5 to 14 x 10(3) nematodes (all bacteriovores) kg(-1). Active microbial biomass was four to five times higher in AIR than LEACH soil. Proteobacteria and actinomycetes/sulfate-reducing bacteria constituted a higher proportion of the community in AIR soil, whereas anaerobic Gram-negative bacteria/firmicutes were more prominent in LEACH soil. Ratios of prokaryotic to eukaryotic phospholipid fatty acids (PLFAs) were higher in LEACH soil, as were membrane stress index values, whereas the starvation index was higher in AIR soil. Community-level physiological profiles showed that 29 and 30 different substrates were used for growth by LEACH and AIR soil microorganisms, respectively. The AIR soil had more microorganisms capable of growing on 10 substrates, whereas growth on two substrates was higher in LEACH soil. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis of 16S rRNA gene fragments revealed greater diversity of dominant phylotypes in AIR than LEACH soil, with communities separated by treatment. Aerated leachfield soil had a larger and more diverse faunal and microbial community than unaerated soil, possibly due to differences in the type and availability of electron acceptors. 相似文献
92.
Unlike synthetic metal chelators, microbe-assisted phytoremediation provides plants with natural metal-solubilizing chelators which do not constitute a potential source of environmental pollution. Concurrently with microbial chelators, plant growth promotion can be enhanced through bacterially-produced phytohormones. In this work, the simultaneous production of siderophores and auxins by Streptomyces was studied to gain insight for future application in plant growth and phytoremediation in a metal-contaminated soil. Standard auxin and siderophore detection assays indicated that all of the investigated Streptomyces strains can produce these metabolites simultaneously. However, Al(3+), Cd(2+), Cu(2+), Fe(3+) and Ni(2+), or a combination of Fe(3+) and Cd(2+), and Fe(3+) and Ni(2+) affected auxin production negatively, as revealed by spectrophotometry and gas chromatography-mass spectrometry. This effect was more dramatic in a siderophore-deficient mutant. In contrast, except for Fe, all the metals stimulated siderophore production. Mass spectrometry showed that siderophore and auxin-containing supernatants from a representative Streptomyces species contain three different hydroxamate siderophores, revealing the individual binding responses of these siderophores to Cd(2+) and Ni(2+), and thus, showing their auxin-stimulating effects. We conclude that siderophores promote auxin synthesis in the presence of Al(3+), Cd(2+), Cu(2+) and Ni(2+) by chelating these metals. Chelation makes the metals less able to inhibit the synthesis of auxins, and potentially increases the plant growth-promoting effects of auxins, which in turn enhances the phytoremediation potential of plants. 相似文献
93.
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
94.
Lyudmila Lyubenova Erika Nehnevajova Rolf Herzig Peter Schröder 《Environmental science and pollution research international》2009,16(5):573-581
Background, aim, and scope Tobacco, Nicotiana tabacum, is a widely used model plant for growth on heavy-metal-contaminated sites. Its high biomass and deep rooting system make
it interesting for phytoextraction. In the present study, we investigated the antioxidative activities and glutathione-dependent
enzymes of different tobacco clones optimized for better Cd and Zn accumulation in order to characterize their performance
in the field.
Main features The improved heavy metal resistance also makes the investigated tobacco clones interesting for understanding the plant defense
enzyme system in general. Freshly harvested plant material (N. tabacum leaves) was used to investigate the antioxidative cascade in plants grown on heavy metal contaminated sites with and without
amendments of different ammonium nitrate and ammonium sulfate fertilizers.
Materials and methods Plants were grown on heavily polluted soils in north-east Switzerland. Leaves were harvested at the field site and directly
deep frozen in liquid N2. Studies were concentrated on the antioxidative enzymes of the Halliwell–Asada cycle, and spectrophotometric measurements
of catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), superoxide dismutase (SOD, EC 1.15.1.1), glutathione
peroxidase (GPX, EC 1.11.1.9), glutathione reductase (GR, EC 1.6.4.2), glutathione S-transferase (GST, EC 2.5.1.18) were performed.
Results and discussion We tried to explain the relationship between fertilizer amendments and the activity of the enzymatic defense systems. When
tobacco (N. tabacum) plants originating from different mutants were grown under field conditions with varying fertilizer application, the uptake
of cadmium and zinc from soil increased with increasing biomass. Depending on Cd and Zn uptake, several antioxidant enzymes
showed significantly different activities. Whereas SOD and CAT were usually elevated, several other enzymes, and isoforms
of GST were strongly inhibited.
Conclusions Heavy metal uptake represents severe stress to plants, and specific antioxidative enzymes are induced at the cost of more
general reactions of the Halliwell–Asada cycle. In well-supplied plants, the glutathione level remains more or less unchanged.
The lack of certain glutathione S-transferases upon exposure to heavy metals might be problematic in cases when organic pollutants coincide with heavy metal
pollution. When planning phytoremediation of sites, mixed pollution scenarios have to be foreseen and plants should be selected
according to both, their stress resistance and hyperaccumulative capacity. 相似文献
95.
We assessed human impacts on ecosystems by calculating the proportion of aboveground net primary production appropriated by
humans (aHANPP) in the territory of the Czech Republic. The human appropriation of aboveground net primary production reached
21.5 Tg C per year in 2006 or 56% of the annual potential natural productivity. Harvested productivity equivalent aNPPH is contributing to the overall appropriation of photosynthetic production by 80%. Considerable productivity losses have been
induced by agricultural land conversion and urbanization. While artificial surfaces are responsible for the appropriation
of whole ecosystem production, productivity of urban green areas and managed forests can even exceed natural productivity
levels. In the period 1990–2000, the aHANPP dropped by 7%, but the indicator shows an increase by over 2% in the period 2000–2006.
The indicator of human appropriation of net primary production enables translation of land cover changes into measures of
ecosystem services affected by human activities. We found aHANPP to be a suitable indicator of human impacts on ecosystems,
as it detects trends and enables spatial mapping of human impacts. 相似文献
96.
In the present research mortar pastes obtained by replacing a commercial cement with the equivalent mass of 5, 10, 20 and 30 wt.% of fly ash or bottom ash from fir chips combustion, were prepared and rheologically characterized. It was observed that the presence of ash modifies their rheological behaviour with respect to the reference blend due to the presence, in the ashes, of KCl and K2SO4 which cause precipitation of gypsum and portlandite during the first hydration stages of the pastes. Hydrated materials containing 5 wt.% of ash display compression strength and absorption at 28 d of same magnitude as the reference composition; conversely, progressive increase of ash cause a continuous decline of materials performances. Conversely, samples tested after 180 d display a marked decline of compression strength, as a consequence of potassium elution and consequent alkali-silica reaction against materials under curing. 相似文献
97.
Erika de Visser Chris Hendriks Maria Barrio Mona J. Mlnvik Gelein de Koeijer Stefan Liljemark Yann Le Gallo 《International Journal of Greenhouse Gas Control》2008,2(4):478
In the carbon capture and storage (CCS) chain, transport and storage set different requirements for the composition of the gas stream mainly containing carbon dioxide (CO2). Currently, there is a lack of standards to define the required quality for CO2 pipelines. This study investigates and recommends likely maximum allowable concentrations of impurities in the CO2 for safe transportation in pipelines. The focus is on CO2 streams from pre-combustion processes. Among the issues addressed are safety and toxicity limits, compression work, hydrate formation, corrosion and free water formation, including the cross-effect of H2S and H2O and of H2O and CH4. 相似文献
98.
Biomineralization dependent on bacterial activity has been described for struvite which is formed in soils, guano, putrescent matter and sediments. A new biomineral containing nickel instead of magnesium, Ni(NH4)(PO4) . 6H2O, has been identified. It was formed by nickel resistant Streptomyces acidiscabies E13, and putatively named nickel struvite. The mineral formation is dependent on biological activity since non-viable bacterial cells are not capable to induce formation of Ni-struvite under identical conditions. Formation of Ni-struvite was observed on colony surfaces upon prolonged incubation of solid minimal or complex media containing elevated concentrations of 8-15mM NiCl2. The formation of magnesium containing crystals was not observed although Mg2+ is present in the medium. However, the process was not depending on desiccation since small crystals attached to the mycelial biomass of the bacteria were observed microscopically also in liquid cultures of nickel supplemented minimal and complex media after two weeks of incubation. The capacity to induce biomineralization of a nickel containing mineral is postulated to constitute a resistance factor, allowing the soil bacterium to withstand high nickel concentrations. The strain shows nickel resistance as an adaption to its habitat, since this bacterium was isolated from a former uranium mining site in Eastern Thuringia, Germany, where nickel concentrations of up to 2000ppm (translating to appr. 30mM) occur as a result of former mining activities. 相似文献
99.
Alexandra G. Ponette-González Kate A. Brauman Erika Marín-Spiotta Kathleen A. Farley Kathleen C. Weathers Kenneth R. Young Lisa M. Curran 《Ambio》2015,44(5):367-375
Watershed investment programs frequently use land cover as a proxy for water-based ecosystem services, an approach based on assumed relationships between land cover and hydrologic outcomes. Water flows are rarely quantified, and unanticipated results are common, suggesting land cover alone is not a reliable proxy for water services. We argue that managing key hydrologic fluxes at the site of intervention is more effective than promoting particular land-cover types. Moving beyond land cover proxies to a focus on hydrologic fluxes requires that programs (1) identify the specific water service of interest and associated hydrologic flux; (2) account for structural and ecological characteristics of the relevant land cover; and, (3) determine key mediators of the target hydrologic flux. Using examples from the tropics, we illustrate how this conceptual framework can clarify interventions with a higher probability of delivering desired water services than with land cover as a proxy.
Electronic supplementary material
The online version of this article (doi:10.1007/s13280-014-0578-8) contains supplementary material, which is available to authorized users. 相似文献100.
Nathalie Pérez Rodríguez Francesca Langella Ilia Rodushkin Emma Engström Erika Kothe Lena Alakangas Björn Öhlander 《Environmental science and pollution research international》2014,21(11):6836-6844
Copper and iron isotope fractionation by plant uptake and translocation is a matter of current research. As a way to apply the use of Cu and Fe stable isotopes in the phytoremediation of contaminated sites, the effects of organic amendment and microbial addition in a mine-spoiled soil seeded with Helianthus annuus in pot experiments and field trials were studied. Results show that the addition of a microbial consortium of ten bacterial strains has an influence on Cu and Fe isotope fractionation by the uptake and translocation in pot experiments, with an increase in average of 0.99?‰ for the δ65Cu values from soil to roots. In the field trial, the amendment with the addition of bacteria and mycorrhiza as single and double inoculation enriches the leaves in 65Cu compared to the soil. As a result of the same trial, the δ56Fe values in the leaves are lower than those from the bulk soil, although some differences are seen according to the amendment used. Siderophores, possibly released by the bacterial consortium, can be responsible for this change in the Cu and Fe fractionation. The overall isotopic fractionation trend for Cu and Fe does not vary for pot and field experiments with or without bacteria. However, variations in specific metabolic pathways related to metal–organic complexation and weathering can modify particular isotopic signatures. 相似文献