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1.
Research on interactions among wave, current, and vegetation has received increasing attention. An explicit depth-averaged hydrodynamic model coupled with a wave spectral model (CMS-wave) was proposed in this study in order to simulate the wave and wave-induced current in coastal waters. The hydrodynamic model was based on the finite volume method while the intercell flux was computed by employing the Harten–Lax–van Leer approximate Riemann solver to investigate the dry-to-wet interface, and the drag force of vegetation was modeled as the sink terms in the momentum equations. The CMS-wave model was used to investigate the non-breaking and the breaking random waves propagation in vegetation fields. Afterwards, an empirical wave energy dissipation term with plant effect was derived to represent the resistance induced by aquatic vegetation in the wave-action balance equation. The established model was calibrated and validated with both the experimental and field data. The results showed that the wave height decreased significantly along the wave propagation direction in the presence of vegetations. The sensitivity analysis for the plant density, the wave height, and the water depth were performed by comparing the numerical results for the wave height attenuation. In addition, wave and wave-induced current through a finite patch of vegetation in the surf zone were investigated as well. The strong radiation stress gradient could be produced due to the variation of the energy dissipation by vegetation effect in the nearshore zone, which impacted the direction and amplitude of the longshore current. The calculated results showed that the coupling model had good performance in predicting wave propagation and the current over vegetated water regions. 相似文献
2.
δ13C was used to identify seasonal variations in the importance of autochthonous and allochthonous sources of productivity for
fish communities in intermittently connected estuarine areas of Australia’s dry tropics. A total of 224 fish from 38 species
were collected from six intermittently connected estuarine pools, three in central Queensland (two dominated by C3 forest and one by C4 pasture) and three in north Queensland (one dominated by C3 and two by C4 vegetation). Samples were collected before and after the wet season. Fish collected in the two forested areas in central
Queensland had the lowest δ13C, suggesting a greater incorporation of C3 terrestrial material. A seasonal variation in δ13C was also detected for these areas, with mean δ13C varying from −20 to −23‰ from the pre- to the post-wet season, indicating a greater incorporation of terrestrial carbon
after the wet season. Negative seasonal shifts in fish δ13C were also present at the pasture site, suggesting a greater dependence on carbon of riparian vegetation (C3
Juncus sp.) in the post-wet season. In north Queensland, terrestrial carbon seemed to be incorporated by fish in the two C4 areas, as δ13C of most species shifted towards slightly heavier values in the post-wet season. A two-source, one-isotope mixing model also
indicated a greater incorporation of carbon of terrestrial origin in the post-wet season. However, no seasonal differences
in δ13C were detected for fish from the forested area of north Queensland. Overall, hydrologic connectivity seemed to be a key factor
in regulating the ultimate sources of carbon in these areas. It is therefore important to preserve the surrounding habitats
and to maintain the hydrologic regimes as close to natural conditions as possible, for the conservation of the ecological
functioning of these areas. 相似文献
3.
Historically, small invertebrate grazers in marine plant communities have been considered to be a relatively homogeneous group
in their impact on ecosystem processes. However, recent studies propose that species composition is an important agent in
determining grazer effects. We used four mesocosm experiments to test the biomass-specific and density-dependent effects of
common mesograzers in temperate regions (Littorina littorea, Rissoa membranacea, Idotea baltica and Gammarus oceanicus) on epiphyte and eelgrass biomass and productivity. Mesograzer species identity strongly influenced epiphyte accumulation
and eelgrass growth, where Rissoa was the most efficient mesograzer (per biomass) and Gammarus had the weakest impact. Density-dependent effects varied considerably among species. Both gastropod species reduced epiphyte
accumulation in direct proportion to their density, and Littorina had the strongest negative effect on epiphyte biomass. The impact of Idotea seemed to level off to a threshold value and Gammarus had no density-dependent effect on epiphyte accumulation at all. Rissoa and Idotea increased eelgrass productivity in accordance with their effect on epiphyte accumulation, whereas Littorina showed a less positive effect than could be expected by its strong impact on epiphyte biomass. Gammarus had no significant impact on eelgrass growth. Our results show that the different functional traits of superficially similar
mesograzers can have important consequences for ecosystem processes in macrophyte systems. 相似文献
4.
This study was designed to determine the protective effects of zinc (Zn) using liver marker enzymes in the serum and liver along with hepatic elemental profile in lead (Pb)-treated protein-deficient (PD) Sprague–Dawley male rats. Zn in the form of zinc sulfate at a dose of 227?mg?L?1 in drinking water was administrated to control, PD as well as Pb-treated PD rats for 8 weeks. Pb treatment was given orally as lead acetate at a dose level of 100?mg?kg?1 body weight to control and PD rats. The effects of different treatments were studied on the activities of enzymes that included alkaline phosphatase (ALP), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in serum. The status of different elements (Cl, K, Mn, Fe, Cu, Zn, Se, Rb, Pb) in liver was also studied. Rats given PD diet and Pb showed significant inhibition in serum ALP activity associated with significant elevation in both AST and ALT activities. Serum ALP activity showed a significant inhibition week 1 until week 8 in Pb-treated PD rats. In contrast, serum AST activity was elevated both at 3 and 8 weeks while serum ALT activity was elevated at 8 weeks in Pb-treated PD rats. Pb treatment to PD rats elevated hepatic ALP, AST and ALT activities but depressed hepatic AST. Zn supplementation to Pb-treated PD rats restored the altered enzyme activities. The levels of K, Fe, Cu, Zn, Se and Rb were altered in protein deficiency. Furthermore, treatment with Pb to these animals depressed the Cu levels. Zn treatment to Pb-treated PD animals tended to restore the levels of altered elements. Hence, the present study clearly suggests that Zn plays an important role in regulating the liver marker enzymes and essential elements under conditions of Pb toxicity and protein deficiency. 相似文献
5.
Kim Seong Hee Choi Byoung-Young Lee Gyemin Yun Seong-Taek Kim Soon-Oh 《Environmental geochemistry and health》2019,41(1):357-380
Environmental Geochemistry and Health - The CO2-rich spring water (CSW) occurring naturally in three provinces, Kangwon (KW), Chungbuk (CB), and Gyeongbuk (GB) of South Korea was classified based... 相似文献
6.
Large rivers often present a river–lake–delta system, with a wide range of temporal and spatial scales of the flow due to the combined effects of human activities and various natural factors, e.g., river discharge, tides, climatic variability, droughts, floods. Numerical models that allow for simulating the flow in these river–lake–delta systems are essential to study them and predict their evolution under the impact of various forcings. This is because they provide information that cannot be easily measured with sufficient temporal and spatial detail. In this study, we combine one-dimensional sectional-averaged (1D) and two-dimensional depth-averaged (2D) models, in the framework of the finite element model SLIM, to simulate the flow in the Mahakam river–lake–delta system (Indonesia). The 1D model representing the Mahakam River and four tributaries is coupled to the 2D unstructured mesh model implemented on the Mahakam Delta, the adjacent Makassar Strait, and three lakes in the central part of the river catchment. Using observations of water elevation at five stations, the bottom friction for river and tributaries, lakes, delta, and adjacent coastal zone is calibrated. Next, the model is validated using another period of observations of water elevation, flow velocity, and water discharge at various stations. Several criteria are implemented to assess the quality of the simulations, and a good agreement between simulations and observations is achieved in both calibration and validation stages. Different aspects of the flow, i.e., the division of water at two bifurcations in the delta, the effects of the lakes on the flow in the lower part of the system, the area of tidal propagation, are also quantified and discussed. 相似文献
7.
Bendway weirs are one of the most practical in–stream rock structures utilized to protect the outer bend of meandering streams and rivers from erosion. We present development of a simulation-based paradigm for effective design of bendway weir structures to enhance meandering stream bank stability and control lateral migration. To do so, we employ the St. Anthony Falls Laboratory Virtual StreamLab (VSL3D) code to elucidate the flow and sediment transport phenomena induced by interaction of flow, mobile bed, and in–stream structures in large rivers under prototype conditions. We carried out numerous numerical experiments to systematically simulate various arrangements of bendway weir in two river test-beds and gaining insights into the physical mechanisms via which such bendway weirs modify turbulent flow, sediment transport and scour processes. The so-gained physical insights are then taken into account to develop a set of practical physics-based design criteria for optimal placement of bendway weirs in large rivers. 相似文献
8.
9.
Alice Harang Olivier Thual Pierre Brancher Thomas Bonometti 《Environmental Fluid Mechanics》2014,14(4):743-769
The temporal stability of a parallel shear flow of miscible fluid layers of different density and viscosity is investigated through a linear stability analysis and direct numerical simulations. The geometry and rheology of this Newtonian fluid mixing can be viewed as a simplified model of the behavior of mudflow at the bottom of estuaries for suspension studies. In this study, focus is on the stability and transition to turbulence of an initially laminar configuration. A parametric analysis is performed by varying the values of three control parameters, namely the viscosity ratio, the Richardson and Reynolds numbers, in the case of initially identical thickness of the velocity, density and viscosity profiles. The range of parameters has been chosen so as to mimic a wide variety of real configurations. This study shows that the Kelvin–Helmholtz instability is controlled by the local Reynolds and Richardson numbers of the inflection point. In addition, at moderate Reynolds number, viscosity stratification has a strong influence on the onset of instability, the latter being enhanced at high viscosity ratio, while at high Reynolds number, the influence is less pronounced. In all cases, we show that the thickness of the mixing layer (and thus resuspension) is increased by high viscosity stratification, in particular during the non-linear development of the instability and especially pairing processes. This study suggests that mud viscosity has to be taken into account for resuspension parameterizations because of its impact on the inflection point Reynolds number and the viscosity ratio, which are key parameters for shear instabilities. 相似文献
10.
Weng HX Yan AL Hong CL Qin YC Pan L Xie LL 《Environmental geochemistry and health》2009,31(3):401-411
Radioactive iodide (125I) is used as a tracer to investigate the fate and transport of iodine in soil under various leaching conditions as well as
the dynamic transfer in a soil–plant (Chinese cabbage) system. Results show that both soils (the paddy soil and the sandy
soil) exhibit strong retention capability, with the paddy soil being slightly stronger. Most iodine is retained by soils,
especially in the top 10 cm, and the highest concentration occurs at the top most section of the soil columns. Leaching with
1–2 pore volume water does not change this pattern of vertical distributions. Early breakthrough and long tailing are two
features observed in the leaching experiments. Because of the relatively low peak concentration, the early breakthrough is
really not an environmental concern of contamination to groundwater. The long tailing implies that the retained iodine is
undergoing slow but steady release and the soils can provide a low but stable level of mobile iodine after a short period.
The enrichment factors of 125I in different plant tissues are ranked as: root > stem > petiole > leaf, and the 125I distribution in the young leaves is obviously higher than that in the old ones. The concentrations of 125I in soil and Chinese cabbage can be simulated with a dual-chamber model very well. The biogeochemical behaviors of iodine
in the soil-cabbage system show that cultivating iodized cabbage is an environmentally friendly and effective technique to
eliminate iodine deficiency disorders (IDD). Planting vegetables such as cabbage on the 129I-contaminated soil could be a good remediation technique worthy of consideration. 相似文献
11.
Kim S. Jacobsen Amy J. Dickman David W. Macdonald Susana Mourato Paul Johnson Lovemore Sibanda Andrew Loveridge 《Conservation biology》2021,35(4):1233-1244
Conflict with humans is one of the major threats facing the world's remaining large carnivore populations, and understanding human attitudes is key to improving coexistence. We surveyed people living near Hwange National Park about their attitudes toward coexisting with lions. We used ordinal regression models with the results of the survey to investigate the importance of a range of tangible and intangible factors on attitudes. The variables investigated included the costs and benefits of wildlife presence, emotion, culture, religion, vulnerability, risk perception, notions of responsibility, and personal value orientations. This was for the purpose of effectively tailoring conservation efforts but also for ethical policy making. Intangible factors (e.g., fear and ecocentric values) were as important as, if not more important than, tangible factors (such as livestock losses) for understanding attitudes, based on the effect sizes of these variables. The degree to which participants’ fear of lions interfered with their daily activities was the most influential variable. The degree to which benefits accrue to households from the nearby protected area was also highly influential, as was number of livestock lost, number of dependents, ecocentric value orientation, and participation in conflict mitigation programs. Contrary to what is often assumed, metrics of livestock loss did not dominate attitudes to coexistence with lions. Furthermore, we found that socioeconomic variables may appear important when studied in isolation, but their effect may disappear when controlling for variables related to beliefs, perceptions, and past experiences. This raises questions about the widespread reliance on socioeconomic variables in the field of human–wildlife conflict and coexistence. To facilitate coexistence with large carnivores, we recommend measures that reduce fear (through education and through protective measures that reduce the need to be fearful), reduction of livestock losses, and ensuring local communities benefit from conservation. Ecocentric values also emerged as influential, highlighting the need to develop conservation initiatives tailored to local values. 相似文献
12.
Liang T Zhang S Wang L Kung HT Wang Y Hu A Ding S 《Environmental geochemistry and health》2005,27(4):301-311
With the continual increase in the utilization of rare earth elements (REEs) for industrial and agricultural purposes in China,
the research into the environmental biogeochemical behavior of REEs has become a pressing issue. The REEs’ content in soil
and various parts of wheat under different conditions in soil–plant systems were measured by INAA and ICP-MS. The results
showed four aspects. (1) The mean value of total REEs in soil of China was 176.8 mg kg−1. The mean ratio of ΣLREE/ΣHREE in soils was 8.0 and cerium accounts for 42% of the total REEs. The content of REEs in wheat
seed ranged between 10−11 and 10−8 g g−1, 3–4 orders of magnitude lower than that in soil. (2) The REEs contents in ryegrass, especially in roots, were significantly
related to that of soil. The bioavailability of REEs in soil mainly depended on the exchangeable fraction of REEs, which was
strongly affected by the physico–chemical properties of the soil. (3) Long-term foliage-dressing with Changle microfertilizer
of REEs did not affect the contents and distribution patterns of REEs in soil. At the maturing stage of spring wheat, the
REEs content was in the order of root > leaf >stem and crust. Compared with the control, foliage-dressing has a higher accumulation
of REEs in root and leaf. However, no significant difference was found in stem and crust between the two treatments. (4) There
was no significant accumulation with the soil-dressing method. When comparing controls in both foliage- and soil-dressing
methods, no distinct residue of REEs in grains was found. 相似文献
13.
The annual averages (1986–1997) of pH are analysed for the most important European Monitoring and Evaluation Programme stations in Europe. The first objective is to discover the different temporal patterns and trends for the pH. To do this, a cluster analysis is developed. The trends are analysed by linear regression for the annual averages. In general, the pH shows an increasing trend significant at 0.05 level and the annual change ranging from +0.01 to +0.05 pH‐units per year for the different clusters obtained. The second objective is to examine the spatial variability of pH in precipitation through the use of principal component analysis. Six statistically significant modes of variability are obtained for the pH which represent the 84.5% of the total variance. 相似文献
14.
To better understand the dynamics of Kelvin–Helmholtz instabilities in environmental flows, their evolution is investigated using direct numerical simulations (DNS). Two-dimensional DNS is used to examine the large-scale and small-scale structures of the instability at high Reynolds and Prandtl numbers that represent real environmental flows. The semi-analytical model of Corcos and Sherman (J Fluid Mech 73:241–264, 1976) is used to explain the physics of these simulations prior to saturation of the KH billow, and also provide a computationally efficient prediction of the vortex dynamics of the instability. The DNS results show that the large-scale structure of the billow does not depend on the Reynolds number for sufficiently high Reynolds numbers. The billow structure reveals a less straightforward dependence on the Prandtl number. Predictions of the model of Corcos and Sherman (J Fluid Mech 73:241–264, 1976) improve as Reynolds number and Prandtl number increase. The small-scale structure of the vorticity and density fields vary with both Reynolds and Prandtl numbers. Three-dimensional DNS of KH flows and their transition to turbulence are used to study small length scales. Based on the thickness of the braid, a simple method is introduced to estimate the Batchelor scale, which can be used as a guide for the resolution required for the direct numerical simulation of two and three-dimensional Kelvin–Helmholtz flow fields. 相似文献
15.
In this paper, we propose a semiparametric survival model to investigate the pattern of spatial and temporal variation in
disease prevalence of chronic wasting disease (CWD) in wild deer in Wisconsin over the years 2002 and 2006. The semiparametric
survival model we suggested allows to build a more flexible model than the parametric model with fewer parametric assumptions
by modeling the baseline hazard using a Gamma process prior. Based on the proposed model, we investigate the geographical
distribution of CWD, and assess the effect of sex on disease prevalence. We use a Bayesian hierarchical framework where latent
parameters capture temporal and spatial trends in disease incidence, incorporating sex and spatially correlated random effects.
We also propose bivariate baseline hazard which change over age and time simultaneously to adopt different effects of age
and time on the baseline hazard. Inference is carried out by using MCMC simulation techniques in a fully Bayesian framework.
Our results suggest that disease has been spreaded mainly in the disease eradication zone and male deer show a significantly
higher infection probability than female deer. 相似文献
16.
Analysis of variations in water–soluble organic matter (WSOM) δ13C of leaves and phloem can efficiently describe the δ13C distributions within plants and identify the temporal variation of δ13C. In this study, WSOM δ13C values of both leaves and phloem (twig, stem, and root) of Platycladus orientalis were measured during seven sunny days, including 2–hour interval measurements at three days for diel pattern analysis and 6–hour interval measurements at the remaining four days for day–to–day variation analysis. Analysis of WSOM δ13C in different plant organs showed that 13C was generally depleted from leaves to twigs, then enriched in stems and subsequently depleted in roots. Stems were significantly 13C–enriched compared to twigs (p?<?0.05), while δ13C differences between stems and other organs and among leaves, twigs and roots were not significant (p?>?0.05). No clear diel patterns in δ13C of leaves and phloem were found. Daily average δ13C values indicated that all plant organs had more positive values on sunny days during the dry season than during the wet season. Both photosynthetic and post–photosynthetic fractionation influence variations in WSOM δ13C. These results have implications for research on plant physiology and plant water use. 相似文献
17.
Organic reactions in aqueous media are being developed because water is environmentally benign. The Horner–Wadsworth–Emmons reaction is a modified Wittig reaction for the synthesis of α,β-unsaturated ketones and other conjugated compounds. Here we prepared high molecular weight ketones by the Horner–Wadsworth–Emmons reaction of dimethyl-2-oxopropylphosphonate and various aldehydes in water at room temperature. The product was precipitated during the reaction process and was separated readily by a simple filtration in 90–99 % yield. 相似文献
18.
Srinivas K. Saidapur Dheeraj K. Veeranagoudar Ningappa C. Hiragond Bhagyashri A. Shanbhag 《Chemoecology》2009,19(1):21-28
Predator–prey relationship was studied in three sympatric species of anuran tadpoles. The study design consisted of allowing
predaceous Hoplobatrachus tigerinus tadpoles to devour prey tadpoles (Sphaerotheca breviceps and Bufo melanostictus) placed in a plastic tub (five tadpoles of each species, stage ~27) in 30 min. In trials without refugia, more tadpoles of
Bufo fell prey compared to Sphaerotheca. In contrast, provision of refugia using hydrilla plant reversed predation risk of the two species. The swimming speed (V
max = 64.55 ± 1.45 cm/s) of Hoplobatrachus tadpoles was much higher compared to the prey species (Bufo: 3.6 ± 0.4 cm/s; Sphaerotheca: 27.6 ± 1.6 cm/s). Poor swimming ability may account for the observed vulnerability of the Bufo tadpoles to predation especially in clear waters; refugia overcame predation to some extent. On the other hand, Sphaerotheca tadpoles that swim faster than the toad tadpoles were less vulnerable in open areas; refugia actually hindered swimming and
increased predation. Experiments with association choice tests show that predaceous tadpoles detect prey based on both visual
and chemical cues. On the other hand, the prey tadpoles detected predator based exclusively on chemical rather than visual
cues. The antipredator defense strategy of the toad tadpoles is manifested in the form of reduced movements, remaining still
for longer times and, increased burst speed. The present findings also suggest that in both prey species predator detection
has a genetic basis since naive tadpoles with no prior exposure to predators exhibit fright response on first encounter with
them. 相似文献
19.
A. Terán F. J. Gonzalez-Vila J. A. Gonzalez-Perez 《Environmental Chemistry Letters》2009,7(4):301-308
Pyrolysis coupled with gas chromatography–mass spectrometry (Py–GC–MS) has been previously proved to be an appropriate tool for the screening of organic contaminants in sediments. In this work the double-shoot pyrolysis technique has been applied to assess the contamination degree of sediment samples from Castro Marim Natural Park (South Portugal) and the Ria of Huelva (SW Spain). Compounds released both by thermodesorption at sub-pyrolysis temperatures (250–280°C) and subsequent pyrolysis (300–500°C) revealed information on the origin of the sedimentary organic matter and the occurrence of organic contamination in the sediments. Thermal desorption was found to be effective in releasing organic contaminants from spiked samples. However, in real sediments samples, higher pyrolysis temperatures (>300°C) were necessary to detect the occurrence of organic contaminants. Particularly polycyclic aromatic hydrocarbons (PAHs) and linear alkylbenzenes (LABs) were detected in variable proportions in most sediment samples. 相似文献
20.
Patrick J. Lyons 《Behavioral ecology and sociobiology》2013,67(5):737-745
Obligate mutualists are predicted to benefit more from mutualism than facultative mutualists and harbor traits that help derive this extra benefit. I tested these predictions with a shrimp–goby mutualism. Individual shrimp (Alpheus floridanus) construct burrows that are shared with individual gobiid fishes that warn shrimp when emergence from burrows is unsafe. The benefit to gobies is refuge from predation. I compared predator avoidance performance of obligate (Nes longus) and facultative (Ctenogobius saepepallens) shrimp-associated gobies with access to a shell, a shrimp burrow, or no shelter. The two gobies performed similarly with shells and no shelter, but N. longus outperformed C. saepepallens with shrimp burrows. Thus, N. longus benefits more from mutualism than C. saepepallens. Also, N. longus has four behavioral traits that likely allow it to benefit from mutualism more than does C. saepepallens: (1) diving into the nearest shrimp burrow when confronted with predators, (2) long flight initiation distance, (3) long time-until-re-emergence after taking refuge, and (4) remaining close to shelter. The latter three likely come with a cost to foraging or mate acquisition as they limit searching range outside the burrow and detract from time spent outside burrows. Thus, N. longus likely harbors traits that allow it to deal with these costs. I discuss a framework for determining whether traits crucial to obligate association with shrimp (both for reaping benefits and dealing with costs) are pre-adaptations or are created through coevolution with shrimp. 相似文献