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991.
Paul?WoodcockEmail author David?P.?Edwards Rob?J.?Newton Felicity?A.?Edwards Chey?Vun?Khen Simon?H.?Bottrell Keith?C.?Hamer 《Die Naturwissenschaften》2012,99(4):275-283
Nitrogen isotope signatures (δ15N) provide powerful measures of the trophic positions of individuals, populations and communities. Obtaining reliable consumer
δ15N values depends upon controlling for spatial variation in plant δ15N values, which form the trophic ‘baseline’. However, recent studies make differing assumptions about the scale over which
plant δ15N values vary, and approaches to baseline control differ markedly. We examined spatial variation in the δ15N values of plants and ants sampled from eight 150-m transects in both unlogged and logged rainforests. We then investigated
whether ant δ15N values were related to variation in plant δ15N values following baseline correction of ant values at two spatial scales: (1) using ‘local’ means of plants collected from
the same transect and (2) using ‘global’ means of plants collected from all transects within each forest type. Plant δ15N baselines varied by the equivalent of one trophic level within each forest type. Correcting ant δ15N values using global plant means resulted in consumer values that were strongly positively related to the transect baseline,
whereas local corrections yielded reliable estimates of consumer trophic positions that were largely independent of transect
baselines. These results were consistent at the community level and when three trophically distinct ant subfamilies and eight
abundant ant species were considered separately. Our results suggest that assuming baselines do not vary can produce misleading
estimates of consumer trophic positions. We therefore emphasise the importance of clearly defining and applying baseline corrections
at a scale that accounts for spatial variation in plant δ15N values. 相似文献
992.
Bacterial diversity and distribution in the southeast edge of the Tengger Desert and their correlation with soil enzyme activities 总被引:2,自引:0,他引:2
Wei Zhang Gaosen Zhang Guangxiu Liu Zhibao Dong Tuo Chen Manxiao Zhang Paul J. Dyson Lizhe An 《环境科学学报(英文版)》2012,24(11):2004-2011
The nature of microbial communities and their relation to enzyme activities in desert soils is a neglected area of investigation. To address this, the bacterial diversity and distribution and soil physico-chemical factors were investigated in the soil crust, the soil beneath the crust and rhizosphere soil at the southeast edge of the Tengger Desert, using the denaturing gradient gel electrophoresis of 16S rRNA genes amplified by the polymerase chain reaction. Phylogenetic analysis of the sequenced DGGE bands revealed a great diversity of bacteria. The Proteobacteria, consisting of the α, β, and γ subdivisions, were clearly the dominant group at all depths and in rhizosphere soil. Analysis of the enzyme activities indicated that the rhizosphere soil of Caragana korshinskii exhibited the highest protease and polyphenol oxidase activities, and in the soil crust there were increased activities of catalase, urease, dehydrogenase and sucrase. The bacterial community abundance closely correlated with soil enzyme activities in different soils. The presence of Cyanobacteria correlated with significant increases in protease, catalase and sucrase in the soil crust, and increased urease in the rhizosphere soil of Artemisia ordosica. The occurrence of Acidobacteria was associated with significant increases in urease, dehydrogenase, and sucrase in the rhizosphere soil of C. korshinski. The presence of γ-Proteobacteria correlated with a significant increase in polyphenol oxidase in the rhizosphere soil of A. ordosica. The study indicated a close relationship between the soil bacterial community and soil enzymes, suggesting the necessity of further investigations into bacterial function in this desert ecosystem. 相似文献
993.
A significant barrier to the diffusion bonding of microchannel arrays is the large capital investment required to setup production. This large capital investment extends from long heating and cooling cycles leading to poor production capacities. Empirical studies in industry have shown that cooling rate is limited by the warpage of microchannel laminae, which is believed to be caused by thermal buckling. In this paper, the limits of cooling rates based on thermal buckling during the diffusion bonding of microchannel laminae are investigated. Finite element analyses of the transient thermal and stress behaviors of these microchannel laminae were conducted to identify the maximum cooling rates for different lamina thicknesses. Findings confirm that cooling rates are limited by the thermal buckling of unconstrained microchannel laminae during cooling of the device. Finite element analysis results are used to extrapolate implications for microchannel production. 相似文献
994.
Dyer Andrew C. Nahil Mohamad A. Williams Paul T. 《Journal of Material Cycles and Waste Management》2022,24(2):477-490
Journal of Material Cycles and Waste Management - Biomass and waste polystyrene plastic (ratio 1:1) were co-pyrolysed followed by catalysis in a two-stage fixed bed reactor system to produce... 相似文献
995.
Paul Upham Katinka Johansen Paula Maria Bögel Stephen Axon Jennifer Garard Sebastian Carney 《Local Environment》2018,23(9):912-919
Public engagement in local environmental planning and decision-making is often advocated on various grounds, both instrumental and normative. Yet in developed countries in the context of renewable energy infrastructure deployment, place attachment, place identity and place-protective action continue to be implicated in public objection. We set out an interdisciplinary change readiness hypothesis of specifically how local participatory scenario or visioning processes that include climate mitigation measures may support the mobilisation of place attachment for climate mitigation, including renewable energy deployment. We hypothesise that local visioning may support movement towards change readiness by helping to anchor unfamiliar social representations of low carbon energy infrastructure and new patterns of urban form in existing, more positive representations of localities and associated attachments. To this end, seeking ways to modify threat perceptions relating to climate change and renewable energy infrastructure is advocated as a key direction for study. 相似文献
996.
Paul M. Bradley Celeste A. Journey 《Journal of the American Water Resources Association》2014,50(2):388-400
The U.S. Geological Survey is conducting a combined pre/post‐closure assessment at a long‐term wastewater treatment plant (WWTP) site at Fort Gordon near Augusta, Georgia. Here, we assess select endocrine‐active chemicals and benthic macroinvertebrate community structure prior to closure of the WWTP. Substantial downstream transport and limited instream attenuation of endocrine‐disrupting chemicals (EDCs) was observed in Spirit Creek over a 2.2‐km stream segment downstream of the WWTP outfall. A modest decline (less than 20% in all cases) in surface water detections was observed with increasing distance downstream of the WWTP and attributed to partitioning to the sediment. Estrogens detected in surface water in this study included estrone (E1), 17β‐estradiol (E2), and estriol (E3). The 5 ng/l and higher mean estrogen concentrations observed in downstream locations indicated that the potential for endocrine disruption was substantial. Concentrations of alkylphenol ethoxylate (APE) metabolite EDCs also remained statistically elevated above levels observed at the upstream control site. Wastewater‐derived pharmaceutical and APE metabolites were detected in the outflow of Spirit Lake, indicating the potential for EDC transport to aquatic ecosystems downstream of Fort Gordon. The results indicate substantial EDC occurrence, downstream transport, and persistence under continuous supply conditions and provide a baseline for a rare evaluation of ecosystem response to WWTP closure. 相似文献
997.
Alan D. Tappin J. Paul Loughnane Alan J. McCarthy Mark F. Fitzsimons 《Environmental Chemistry Letters》2016,14(4):455-465
Contamination of surface waters by pharmaceuticals is now widespread. There are few data on their environmental behaviour, particularly for those which are cationic at typical surface water pH. As the external surfaces of bacterio-plankton cells are hydrophilic with a net negative charge, it was anticipated that bacterio-plankton in surface-waters would preferentially remove the most extensively-ionised cation at a given pH. To test this hypothesis, the persistence of four, widely-used, cationic pharmaceuticals, chloroquine, quinine, fluphenazine and levamisole, was assessed in batch microcosms, comprising water and bacterio-plankton, to which pharmaceuticals were added and incubated for 21 days. Results show that levamisole concentrations decreased by 19 % in microcosms containing bacterio-plankton, and by 13 % in a parallel microcosm containing tripeptide as a priming agent. In contrast to levamisole, concentrations of quinine, chloroquine and fluphenazine were unchanged over 21 days in microcosms containing bacterio-plankton. At the river-water pH, levamisole is 28 % cationic, while quinine is 91–98 % cationic, chloroquine 99 % cationic and fluphenazine 72–86 % cationic. Thus, the most neutral compound, levamisole, showed greatest removal, contradicting the expected bacterio-plankton preference for ionised molecules. However, levamisole was the most hydrophilic molecule, based on its octanol–water solubility coefficient (K ow). Overall, the pattern of pharmaceutical behaviour within the incubations did not reflect the relative hydrophilicity of the pharmaceuticals predicted by the octanol–water distribution coefficient, D ow, suggesting that improved predictive power, with respect to modelling bioaccumulation, may be needed to develop robust environmental risk assessments for cationic pharmaceuticals. 相似文献
998.
Ehimai?OhiozebauEmail author Brett?Tendler Allison?Hill Garry?Codling Erin?Kelly John?P.?Giesy Paul?D.?Jones 《Environmental geochemistry and health》2016,38(2):577-591
Concentrations of products of biotransformation of polycyclic aromatic hydrocarbons (PBPAH) were measured in bile of five fishes of nutritional, cultural and ecological relevance from the Athabasca/Slave river system. Samples were collected in Alberta and the Northwest Territories, Canada, during three seasons. As a measure of concentrations of PBPAHs to which fishes are exposed and to gain information on the nature and extent of potential exposures of people or piscivorous wildlife, concentrations of biotransformation products of two- and three-ringed, four-ringed and five-ringed PAHs were measured using synchronous fluorescence spectroscopy. Spatial and seasonal differences were observed with greater concentrations of PBPAHs in samples of bile of fish collected from Fort McKay as well as greater concentrations of PBPAHs in bile of fish collected during summer compared to those collected in other seasons. Overall, PBPAHs were greater in fishes of lower trophic levels and fishes more closely associated with sediments. In particular, goldeye (Hiodon alosoides), consistently contained greater concentrations of all the PBPAHs studied. 相似文献
999.
1000.