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541.
Direct and indirect effects of ammonia, ammonium and nitrate on phosphatase activity and carbon fluxes from decomposing litter in peatland 总被引:1,自引:0,他引:1
David Johnson Lucy Moore Ian D. Leith 《Environmental pollution (Barking, Essex : 1987)》2010,158(10):3157-3163
Here we investigate the response of soils and litter to 5 years of experimental additions of ammonium (NH4), nitrate (NO3), and ammonia (NH3) to an ombrotrophic peatland. We test the importance of direct (via soil) and indirect (via litter) effects on phosphatase activity and efflux of CO2. We also determined how species representing different functional types responded to the nitrogen treatments. Our results demonstrate that additions of NO3, NH4 and NH3 all stimulated phosphatase activity but the effects were dependent on species of litter and mechanism (direct or indirect). Deposition of NH3 had no effect on efflux of CO2 from Calluna vulgaris litter, despite it showing signs of stress in the field, whereas both NO3 and NH4 reduced CO2 fluxes. Our results show that the collective impacts on peatlands of the three principal forms of nitrogen in atmospheric deposition are a result of differential effects and mechanisms on individual components. 相似文献
542.
Nicole Schütze Xiaoyin Zhong Stefan Kirschbaum Iustinian Bejan Ian Barnes Thorsten Benter 《Atmospheric environment (Oxford, England : 1994)》2010,44(40):5407-5414
Relative kinetic studies have been performed on the reactions of Cl atoms with a series of methyl alkyl esters in a 405-liter borosilicate glass chamber at (298 ± 3) K and one atmosphere of synthetic air using in situ FTIR spectroscopy to monitor the reactants. Rate coefficients (in units of cm3 molecule?1 s?1) were determined for the following compounds: methyl acetate (2.48 ± 0.58) × 10?12; methyl propanoate (1.68 ± 0.36) × 10?11; methyl butanoate (4.77 ± 0.87) × 10?11; methyl pentanoate (7.84 ± 1.15) × 10?11; methyl hexanoate (1.09 ± 0.31) × 10?10; methyl heptanoate (1.56 ± 0.37) × 10?10; methyl cyclohexane carboxylate (3.32 ± 0.76) × 10?10; methyl-2-methyl butanoate (9.41 ± 1.39) × 10?11.In addition rate coefficients (in units of 10?11 cm3 molecule?1 s?1) have been obtained for the reactions of OH radicals with the following compounds: methyl butanoate (3.55 ± 0.71), methyl pentanoate (5.41 ± 1.08), and methyl-2-methyl butanoate (4.08 ± 0.82).Using the kinetic rate data tropospheric lifetimes for the methyl alkyl esters with respect to their reactions with OH, and Cl have been estimated for typical ambient air concentrations of these oxidants. 相似文献
543.
Male pine engravers, Ips pini (Coleoptera: Scolytidae), assist their mates during reproduction by removing the debris that accumulates while females excavate
oviposition tunnels in the phloem tissue of host tree bark. Although duration of paternal care and male reproductive success
are positively correlated, large males leave their mates and brood sooner than small males. We address two hypotheses to
explain the earlier departure of larger males from their breeding galleries: (1) females oviposit most rapidly when paired
with large males, thereby reducing the length of time that paternal care increases male reproductive success, (2) larger males
have better prospects for future reproduction, and thus leave their galleries in search of new breeding opportunities sooner
than smaller males. Contrary to the first hypothesis, when females were paired either with large or small males, there was
no effect of male size on their rate of oviposition. Consistent with the second hypothesis, males that initiated breeding
galleries were larger than males from the general population. In addition, large males flew farther and faster on flight mills
than small males, which may indicate that large males have an advantage in locating suitable breeding sites. Thus, we suggest
that large male pine engravers leave their galleries earlier than small males because large individuals have better prospects
for future reproduction.
Received: 30 November 1997 / Accepted after revision: 23 May 1998 相似文献
544.
Biomonitoring with Gammarus pulex at the Meuse (NL), Aller (GER) and Rhine (F) rivers with the online Multispecies Freshwater Biomonitor 总被引:1,自引:0,他引:1
Gerhardt A Kienle C Allan IJ Greenwood R Guigues N Fouillac AM Mills GA Gonzalez C 《Journal of environmental monitoring : JEM》2007,9(9):979-985
Biological early warning systems represent a set of tools that may be able to respond to certain chemical monitoring requirements of recent European legislation, the Water Framework Directive (WFD2000/60/EC), that aims to improve and protect water quality across Europe. In situ biomonitoring was performed along the rivers Meuse (NL), Aller (GER) and Rhine (F) within the frame of the European Union-funded Project SWIFT-WFD. Gammarus pulex was used as a test organism during the evaluation of the Multispecies Freshwater Biomonitor(R) (MFB), an online biomonitor to quantitatively record different behaviour patterns of animals. At the river Meuse G. pulex reacted to pulse exposure of either a mixture of trace metals or of several organic xenobiotics, by showing up to 20% decreased locomotory activity (already at the 1st pulse) and increased mortality (at 2nd or 3rd pulse only). G. pulex deployed within the MFB system were observed to survive well at the monitoring station on the Aller (100%) and monitoring did not result in the measurement of chemical irregularities. In contrast, deployment at the monitoring station on the Rhine river demonstrated that the test organism was able to detect chemical irregularities by up to 20% decreased locomotory activity in the animals. The MFB proved to be an alert system for water quality monitoring at sensitive sites and sites with accidental pollution. 相似文献
545.
A steady state model is developed to describe the bioaccumulation of organic contaminants by 14 species in a Baltic food web including pelagic and benthic aquatic organisms. The model is used to study the bioaccumulation of five PCB congeners of different chlorination levels. The model predictions are evaluated against monitoring data for five of the species in the food web. Predicted concentrations are on average within a factor of two of measured concentrations. The model shows that all PCB congeners were biomagnified in the food web, which is consistent with observations. Sensitivity analysis reveals that the single most sensitive parameter is log K(OW). The most sensitive environmental parameter is the annual average temperature. Although not identified amongst the most sensitive input parameters, the dissolved concentration in water is believed to be important because of the uncertainty in its determination. The most sensitive organism-specific input parameters are the fractional respiration of species from the water column and sediment pore water, which are also difficult to determine. Parameters such as feeding rate, growth rate and lipid content of organism are only important at higher trophic levels. 相似文献
546.
547.
548.
Allan IJ Knutsson J Guigues N Mills GA Fouillac AM Greenwood R 《Journal of environmental monitoring : JEM》2008,10(7):821-829
This work aimed to evaluate whether the performance of passive sampling devices in measuring time-weighted average (TWA) concentrations supports their application in regulatory monitoring of trace metals in surface waters, such as for the European Union's Water Framework Directive (WFD). The ability of the Chemcatcher and the diffusive gradient in thin film (DGT) device sampler to provide comparable TWA concentrations of Cd, Cu, Ni, Pb and Zn was tested through consecutive and overlapping deployments (7-28 days) in the River Meuse (The Netherlands). In order to evaluate the consistency of these TWA labile metal concentrations, these were assessed against total and filtered concentrations measured at relatively high frequencies by two teams using standard monitoring procedures, and metal species predicted by equilibrium speciation modeling using Visual MINTEQ. For Cd and Zn, the concentrations obtained with filtered water samples and the passive sampling devices were generally similar. The samplers consistently underestimated filtered concentrations of Cu and Ni, in agreement with their respective predicted speciation. For Pb, a small labile fraction was mainly responsible for low sampler accumulation and hence high measurement uncertainty. While only the high frequency of spot sampling procedures enabled the observation of higher Cd concentrations during the first 14 days, consecutive DGT deployments were able to detect it and provide a reasonable estimate of ambient concentrations. The range of concentrations measured by spot and passive sampling, for exposures up to 28 days, demonstrated that both modes of monitoring were equally reliable. Passive sampling provides information that cannot be obtained by a realistic spot sampling frequency and this may impact on the ability to detect trends and assess monitoring data against environmental quality standards when concentrations fluctuate. 相似文献
549.
Tsuji LJ Martin ID Martin ES LeBlanc A Dumas P 《Environmental monitoring and assessment》2008,146(1-3):91-104
We examined matched-tissue samples (the right pectoral muscle plus the associated skin and fat was considered a breast portion) of 81 spring-harvested waterfowl and 19 summer-harvested godwits (Limosa spp.) to assess the potential of these water birds contributing to the body burden of PCBs and DDT noted in First Nation people of the western James Bay region, northern Ontario, Canada. In general, the dabbling ducks (mallard duck, Anas platyrhynchos; and northern pintail, A. acuta) had significantly lower percent lipid (gravimetrically determined) values in skin tissue, fat tissue, and breast muscle compared to the goose species (Canada goose, Branta canadensis; lesser snow goose, Chen caerulescens); godwits had percent lipid values not significantly different than ducks and geese. Also, the percent lipid values in skin for all species of birds examined approached those found in fat tissue. Organochlorine data were expressed as the amount (microg) of each contaminant per breast portion to show contaminant consumption in terms of typical and easily recognizable dietary portions; direct comparisons were made to acceptable daily intake (ADI) or tolerable daily intake (TDI) values as recommended by Health Canada. Significant differences in the amount of organochlorines between bird species for skin, fat tissue, and breast muscle samples were found. In general, breast portions from snow geese contained the least amount of organochlorines, followed by godwits (except for mirex) and then Canada geese; the dabbling ducks had the greatest amount of organochlorines on a breast portion basis. However, on average, no 60 kg person would exceed the calculated organochlorine ADI/TDI values consuming one breast portion (i.e., breast + associated skin and fat), but the maximum value of SigmaPCBs for skin tissue alone in male mallards (47 microg) was more than twice the ADI/TDI (18 microg/day); while, that in fat tissue alone (17 microg) approached the ADI/TDI. Thus, the consumption of dabbling ducks by children is an issue that should be explored further, if tissue other than breast muscle is eaten. Lastly, the consumption of waterfowl was a source of PCBs for people of Fort Albany and Kashechewan, but not DDT, as this organochlorine was infrequently detected. 相似文献
550.
Janice P. Susaya Ki-Hyun Kim Victor B. Asio Zueng-Sang Chen Ian Navarrete 《Environmental monitoring and assessment》2010,167(1-4):505-514
In this study, concentrations of nickel (Ni) were quantified in the soils and plants in the agricultural areas of Salcedo watershed in Eastern Samar Island, Philippines. The quantity of total Ni in soils (TS-Ni) was significantly high with a mean of 1,409 mg kg?1, while the soil available Ni (SA-Ni) was low with a mean of 8.66 mg kg?1. As the levels of TS-Ni in the Salcedo watershed greatly exceeded the maximum allowable concentrations for agricultural soils, the site is not suitable for agricultural purposes. Despite significant TS-Ni levels, SA-Ni levels were very low due to tight binding between Ni and soil components. Consequently, all plants investigated did not meet the criterion for a Ni hyperaccumulator plant with low Ni contents (mean TP-Ni of 14.7 mg kg?1). Comparison of Ni levels between food plants and its recommended daily intake (RDI) suggests that consumption of food-plants grown in the study area is unlikely to pose health risks. However, caution must be taken against combined consumption of food plants with high Ni levels or their prolonged consumption, as it can induce accumulation of Ni above RDI. 相似文献