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101.
Bonton A Bouchard C Rouleau A Rodriguez MJ Therrien R 《Journal of contaminant hydrology》2012,128(1-4):1-18
Groundwater contamination by nitrate was investigated in an agricultural area in southern Quebec, Canada, where a municipal well is the local source of drinking water. A network of 38 piezometers was installed within the capture zone of the municipal well to monitor water table levels and nitrate concentrations in the aquifer. Nitrate concentrations were also measured in the municipal well. A Water flow and Nitrate transport Global Model (WNGM) was developed to simulate the impact of agricultural activities on nitrate concentrations in both the aquifer and municipal well. The WNGM first uses the Agriflux model to simulate vertical water and nitrate fluxes below the root zone for each of the seventy agricultural fields located within the capture zone of the municipal well. The WNGM then uses the HydroGeoSphere model to simulate three-dimensional variably-saturated groundwater flow and nitrate transport in the aquifer using water and nitrate fluxes computed with the Agriflux model as the top boundary conditions. The WNGM model was calibrated by reproducing water levels measured from 2005 to 2007 in the network of piezometers and nitrate concentrations measured in the municipal well from 1997 to 2007. The nitrate concentrations measured in the network of piezometers, however, showed greater variability than in the municipal well and could not be reproduced by the calibrated model. After calibration, the model was validated by successfully reproducing the decrease of nitrate concentrations observed in the municipal well in 2006 and 2007. Although it cannot predict nitrate concentrations in individual piezometers, the calibrated and validated WNGM can be used to assess the impact of changes in agricultural practices on global nitrate concentrations in the aquifer and in the municipal well. 相似文献
102.
Delatolla R Tufenkji N Comeau Y Gadbois A Lamarre D Berk D 《Water environment research》2012,84(4):328-338
Attached growth biological treatment systems are a promising solution to ammonia removal in cold-temperature climates. Environmental scanning electron microscopy (ESEM) and confocal laser scanning microscopy in combination with fluorescent in situ hybridization (FISH) was used to investigate the effects of 4 months of exposure to 4 degrees C on nitrifying biofilm and biomass. These molecular and microscopic methods were modified to minimize loss of mass and distortion of in situ perspectives. Environmental scanning electron microscopy revealed that nitrifying biofilm did not exhibit significant changes in volume with exposure to 4 degrees C. Confocal laser scanning microscopy in combination with FISH showed that the number of ammonia-oxidizing bacteria (AOB) cells present in the biofilm was statistically consistent during exposure to 4 degrees C. The RNA content of AOB cells remained sufficient for FISH enumeration. The number of nitrite-oxidizing bacteria cells remained steady during exposure to 4 degrees C; however, the RNA content of the cells appeared to decrease with exposure to 4 degrees C, thereby preventing their enumeration using FISH. 相似文献
103.
Barillet S Adam-Guillermin C Palluel O Porcher JM Devaux A 《Environmental pollution (Barking, Essex : 1987)》2011,159(2):495-502
Because of its toxicity and its ubiquity within aquatic compartments, uranium (U) represents a significant hazard to aquatic species such as fish. In a previous study, we investigated some biological responses in zebrafish either exposed to depleted or to enriched U (i.e., to different radiological activities). However, results required further experiments to better understand biological responses. Moreover, we failed to clearly demonstrate a significant relationship between biological effects and U radiological activity. We therefore chose to herein examine U bioaccumulation and induced effects in zebrafish according to a chemical dose-response approach. Results showed that U is highly bioconcentrated in fish, according to a time- and concentration-dependent model. Additionally, hepatic antioxidant defenses, red blood cells DNA integrity and brain acetylcholinesterase activity were found to be significantly altered. Generally, the higher the U concentration, the sooner and/or the greater the effect, suggesting a close relationship between accumulation and effect. 相似文献
104.
Alain Copinet Estelle Copinet-Legin Florence Fricoteaux Damien Erre 《Journal of Polymers and the Environment》2011,19(1):172-176
The aim of this work was to estimate the biodegradation of a poly(lactic acid) polymeric material by the actinomycetes Kibdelosporangium aridum using a vermiculite based inert solid medium which could simulate compost medium and enable us to achieve complete carbon
balances. The mineralisation rate at the end of the test was compared to those obtained for two basal media. It was shown
that cumulative mineralisation after 45 days of degradation was greater (70%) in vermiculite with a basal medium containing
gelatin than in vermiculite with a basal medium containing glucose (20%). 相似文献
105.
Vigiak O Ribolzi O Pierret A Sengtaheuanghoung O Valentin C 《Journal of environmental quality》2008,37(3):889-897
In northern Laos, intensification of cultivation on sloping land leads to accelerated erosion processes. Management of riparian land may counteract the negative impacts of higher sediment delivery rates on water quality. This study assessed water and sediment concentration trapping efficiencies of riparian vegetation in northern Laos and the effect of cultivation of riparian land on water quality. Runoff flowing in and out of selected riparian sites was monitored by means of open troughs. In 2005, two native grass, two bamboo, and two banana sites were monitored. In 2006, adjacent to steep banana, bamboo, and native grass sites, three upland rice sites were established and monitored. Water trapping efficiency (WTE) and sediment concentration trapping efficiency (SCTE) were calculated on an event basis; means and 95% confidence intervals (CIs) were estimated with a bootstrapping approach. Confidence intervals were large and overlapping among sites. Seepage conditions severely limited trapping efficiency. Native grass resulted in the highest WTE (95% CI, -0.10 to 0.23), which was not significantly different from zero. Banana resulted in the highest SCTE (95% CI, 0.06-0.40). Bamboo had negative WTE and SCTE. Median outflow runoff from rice sites was nine times the inflow. Median outflow sediment concentration from rice sites was two to five times that of their adjacent sites and two to five times the inflow sediment concentration. Although low-tillage banana plantation may reduce sediment concentration of runoff, cultivation of annual crops in riparian land leads to delivery of turbid runoff into the stream, thus severely affecting stream water quality. 相似文献
106.
Cariou R Antignac JP Zalko D Berrebi A Cravedi JP Maume D Marchand P Monteau F Riu A Andre F Le Bizec B 《Chemosphere》2008,73(7):1036-1041
A French monitoring study was initiated to evaluate the exposure of fetus and newborn to brominated flame retardants (BFR). A previously developed multi-residue analytical method was used for measuring the main classes of BFR (tetrabromobisphenol-A, and tri- to decabomodiphenyl ethers) in various human biological matrices. Analyzed samples (maternal and cord serum, adipose tissue and breast milk) were collected from 93 volunteer women during caesarean deliveries. TBBPA was detected in 44% of the analyzed breast milk samples, at levels varying from 0.06 to 37.34 ng g(-1) lipid weight, but was not detected in adipose tissue. This compound was also detected in 30% of the analyzed serum samples, with similar average values in maternal and cord serum (154 pg g(-1) fresh weight versus 199 pg g(-1) fresh weight, respectively). The interpretation of the collected data permitted the demonstration of (1) a significant exposure to TBBPA both for mothers and fetuses and (2) a possible risk of overexposure of newborns through breastfeeding. 相似文献
107.
108.
Ana M. M. Viana Anne Frézard Christian Malosse Terezinha M. C. Della Lucia Christine Errard Alain Lenoir 《Chemoecology》2001,11(1):29-36
Summary. Leaf cutting ants live in symbiosis with a basidiomycete fungus that is exploited as a source of nutrients for the ant larvae.
Tests of fungus transport demonstrated that Acromyrmex subterraneus subterraneus workers discriminate concolonial fungus from alien fungus, and rejected the latter. Larvae and pupae of the ant were used
as controls. Chemical analysis of the fungus revealed a great similarity between its hydrocarbon profile and that found on
the ant brood. Experiments with lures showed that chemical extracts from the fungus are responsible for this discrimination
process. Moreover, the presence of brood inside the fungus seemed to be important for discrimination of the fungus by workers.
Resident workers accepted concolonial broodless fungus less than concolonial fungus inoculated with brood odor. Fungus seems
to acquire colonial odor passively, simply by contact with the brood. The impact of fungus volume present in the nest on closure
of the colony is discussed. We show here for the first time the importance of a symbiotic vegetal organism in colonial recognition
in social insects.
Received 14 April 2000; accepted 29 September 2000 相似文献
109.
The transformation of natural forest regeneration processes by human activities has created the need to develop and implement new models of forest management. Alternative silvicultural systems such as variable retention harvest, partial and patch cuts, and older forest management practices such as under-planting, are used in many forests around the world, particularly in North American oak stands, the boreal and coastal temperate rain forests of Canada and the United States, and in many degraded tropical regions of Asia and the Americas. Specific objectives are pursued in each of these biomes, but some are common to most regions, such as preservation of cover and structure and their associated benefits for natural or artificial regeneration due to moderation of the microclimate, development of optimal light and competition conditions, and reduced predation by herbivores. Shelterwoods are often presented as an alternative to clear-cutting to improve the survival of planted trees. A meta-analysis of published results with randomization tests was performed to test the relationship between overstory density and planted seedling growth and survival. Multiple comparisons were also used to reveal optimal levels of overstory density, if they exist. A majority of studies show that survival and growth improve as stand density decreases to an intermediate level, below which they either drop or stabilize. This level seems optimal in most conditions, as it is also more apt to fulfill other objectives imposed on today's forest activities, such as the conservation of forest processes and structures, and the reconstruction of degraded stands through the accelerated return of mid- to late-successional species. 相似文献
110.
Although associations between myrmecophytes and their plant ants are recognized as a particularly effective form of protective
mutualism, their functioning remains incompletely understood. This field study examined the ant-plant Hirtella physophora and its obligate ant associate Allomerus decemarticulatus. We formulated two hypotheses on the highly specific nature of this association: (1) Ant presence should be correlated with
a marked reduction in the amount of herbivory on the plant foliage; (2) ant activity should be consistent with the "optimal
defense" theory predicting that the most vulnerable and valuable parts of the plant are the best defended. We validated the
first hypothesis by demonstrating that for ant-excluded plants, expanding leaves, but also newly matured ones in the long
term, suffered significantly more herbivore damage than ant-inhabited plants. We showed that A. decemarticulatus workers represent both constitutive and inducible defenses for their host, by patrolling its foliage and rapidly recruiting
nestmates to foliar wounds. On examining how these activities change according to the leaves’ developmental stage, we found
that the number of patrolling ants dramatically decreased as the leaves matured, while leaf wounds induced ant recruitment
regardless of the leaf’s age. The resulting level of these indirect defenses was roughly proportional to leaf vulnerability
and value during its development, thus validating our second hypothesis predicting optimal protection. This led us to discuss
the factors influencing ant activity on the plant’s surface. Our study emphasizes the importance of studying both the constitutive
and inducible components of indirect defense when evaluating its efficacy and optimality. 相似文献