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91.
Enhancement effect of water associated with natural organic matter (NOM) on organic compound-NOM interactions: a case study with carbamazepine 总被引:1,自引:0,他引:1
Natural organic matter (NOM) in soils and sediments is recognized to strongly affect environmental distributions of organic compounds. Water associated with NOM may have a significant impact on NOM-organic compound interactions. The objectives of this research were (1) to determine the effect of hydration of a model NOM sorbent on interactions with a probe organic compound, carbamazepine (CBZ), and (2) based on the comparison with the literature data, to evaluate the effect of organic compound structure on the cooperative participation of water molecules in organic sorbate-NOM interactions. CBZ is one of the most widely reported water pollutants from the pharmaceutical and personal care products family. Therefore, CBZ sorption on Pahokee peat was compared from water and from n-hexadecane, using solubility-normalized solute concentrations. CBZ-NOM interactions were enhanced by one to two orders of magnitudes when NOM became fully hydrated. This enhancement is associated with the distinct ability of CBZ to undergo strong, specific interactions with NOM which was revealed by comparing the transfer of CBZ and another model sorbate, phenanthrene, from solution in n-hexadecane to the hydrated NOM sorbent. The enhancing effect of NOM hydration on CBZ-NOM interactions was also observed when CBZ sorption was examined on partially hydrated NOM. In comparison with a smaller-size organic sorbate such as phenol, CBZ needs more NOM-associated water in order to demonstrate the strengthening of interactions with NOM. Therefore, for penetration of the larger sorbate molecules into the NOM interior, a greater number of water molecules are needed to compensate for the local NOM disintegration thus suggesting the greater extent of the cooperativity in an involvement of water molecules in the CBZ-NOM interactions. 相似文献
92.
D.Q. Kellogg A.J. Gold P.M. Groffman M.H. Stolt K. Addy 《Journal of the American Water Resources Association》2008,44(4):1024-1034
Abstract: Ground‐water flow paths constrain the extent of nitrogen (N) sinks in deep, stratified soils of riparian wetlands. We examined ground‐water flow paths at four forested riparian wetlands in deep, low gradient, stratified deposits subjected to Southern New England’s temperate, humid climate. Mid‐day piezometric heads were recorded during the high water table period in April/May and again in late November at one site. Coupling field data with a two‐dimensional steady‐state ground‐water flow model, flow paths and fluxes were derived to 3 m depths. April/May evapotranspiration (ET) dominated total outflux (44‐100%) while flux to the stream was <10% of total outflux. ET exerted upward ground‐water flux through shallow carbon‐rich soils, increasing opportunities for N transformations and diverting flow from the stream. Dormant season results showed a marked increase in flux to the stream (27% of the total flux). Riparian sites with deep water tables (naturally or because of increased urbanization or other hydrologic modifications) or shallow root zones may not generate ground‐water upwelling to meet evaporative demand, thereby increasing the risk of N movement to streams. As water managers balance issues of water quality with water quantity, they will be faced with decisions regarding riparian management. Further work towards refining our understanding of ET mediation of N and water flux at the catchment scale will serve to inform these decisions. 相似文献
93.
William G. Reay Daniel L. Gallagher George M. Simmons 《Journal of the American Water Resources Association》1992,28(6):1121-1134
ABSTRACT: Surface water, groundwater, and groundwater discharge quality surveys were conducted in Cherrystone Inlet, on Virginia's Eastern Shore. Shallow groundwater below agricultural fields had nitrate concentrations significantly higher than inlet surface waters and shallow groundwater underlying forested land. This elevated nitrate groundwater discharged to adjacent surface waters. Nearshore discharge rates of water across the sediment-water interface ranged from 0.02 to 3.69 liters·m?2·hr?1 during the surveys. The discharge was greatest nearshore at low tide periods, and decreased markedly with increasing distance offshore. Vertical hydraulic heads, Eh, and inorganic nitrogen flux in the sediments followed similar patterns. Nitrate was the predominant nitrogen species discharged nearshore adjacent to agricultural land use, changing to ammonium farther offshore. Sediment nitrogen fluxes were sufficient to cause observable impacts on surface water quality; nitrate concentrations were up to 20 times greater in areas of groundwater discharge than in the main stem inlet water. Based on DIN:DIP ratios, nitrogen contributions from direct groundwater discharge and tidal creek inputs appear to be of significant ecological importance. This groundwater discharge links land use activity and the quality of surface water, and therefore must be considered in selection of best management practices and water quality management strategies. 相似文献
94.
A. Jason Hill Vincent S. Neary 《Journal of the American Water Resources Association》2007,43(6):1373-1382
Abstract: This study used measured diurnal surface‐water cycles to estimate daily evapotranspiration (ET) and seepage for a seasonally flooded sinkhole wetland. Diurnal surface‐water cycles were classified into five categories based on the relationship between the surface‐water body and the surrounding ground‐water system (i.e., recharge/discharge). Only one class of diurnal cycles was found to be suitable for application of this method. This subset of diurnal cycles was used to estimate ET and seepage and the relative importance of each transfer process to the overall water budget. The method has limited utility for wetlands with erratic hydrologic regimes (e.g., wetlands in urban environments). This is due to violation of the critical assumption that the inflow/outflow rate remains constant throughout the day. For application to surface‐water systems, the method is typically applied with an assumed specific yield of 1.0. This assumption was found to be invalid for application to surface‐water systems with a noncylindrical pond geometry. An overestimation of ET by as much as 60% was found to occur under conditions of low pond stage and high water loss. The results demonstrate the high ET rates that can occur in isolated wetlands due to contrasting roughness and moisture conditions (oasis and clothesline effects). Estimated ET rates ranged from 4.1 to 18.7 mm/day during the growing season. Despite these large ET rates, seepage (recharge) was found to be the dominant water loss mechanism for the wetland. 相似文献
95.
Antoine?O.H.C.?Leduc Maud?C.O.?Ferrari Jocelyn?M.?Kelly Grant?E.?BrownEmail author 《Chemoecology》2004,14(2):107-112
Summary. Recent studies have demonstrated that under
weakly acidic conditions (pH 6.0), many prey fishes, including
juvenile rainbow trout (Onchorhynchus mykiss), do not
exhibit overt antipredator responses to conspecific chemical
alarm cues. In laboratory trials, we investigated the potential
effects of reduced pH on the ability of hatchery reared, predator
naïve juvenile rainbow trout to acquire the recognition of
a novel predator (yellow perch, Perca flavenscens). Initially,
we exposed trout to the odour of a predatory yellow perch,
buffered to pH 6.0 (weakly acidic) or pH 7.0 (neutral) paired
with conspecific skin extracts (also buffered to pH 6.0 or 7.0)
or a distilled water control. Juvenile trout exhibited significant
increase in antipredator behaviour when exposed to neutral
skin extract (pH 7.0). When retested 48 hours later to perch
odour alone (pH 7.0), only trout initially conditioned with
neutral skin extracts (pairs with either neutral or acidic perch
odour) exhibited a learned recognition of perch odour as a
predator risk. Those initially exposed to weakly acidic skin
extract or the distilled water control did not show a learned
response to predator odour. These results demonstrate that the
ability to acquire the recognition of novel predators is
impaired under weakly acidic conditions, as would occur in
natural waterways affected by acidic precipitation. 相似文献
96.
Summary. Plants attacked by herbivorous insects emit a blend of volatile compounds that serve as important host location cues for parasitoid
wasps. Variability in the released blend may exist on the whole-plant and withinplant level and can affect the foraging efficiency
of parasitoids. We comprehensively assessed the kinetics of herbivore-induced volatiles in soybean in the context of growth
stage, plant organ, leaf age, and direction of signal transport. The observed patterns were used to test the predictions of
the optimal defence hypothesis (OD). We found that plants in the vegetative stage emitted 10-fold more volatiles per biomass
than reproductive plants and young leaves emitted >2.6 times more volatiles than old leaves. Systemic induction in single
leaves was stronger and faster by one day in acropetal than in basipetal direction while no systemic induction was found in
pods. Herbivore-damaged leaves had a 200-fold higher release rate than pods. To some extent these findings support the OD:
i) indirect defence levels were increased in response to herbivory and ii) young leaves, which are more valuable, emitted
more volatiles. However, the fact that reproductive structures emitted no constitutive or very few inducible volatiles is
in seeming contrast to the OD predictions. We argue that in case of volatile emission the OD can only partially explain the
patterns of defence allocation due to the peculiarity that volatiles act as signals not as toxins or repellents. 相似文献
97.
Meaghan A. Vavrek Chris K. Elvidge Robert DeCaire Brenna Belland Christopher D. Jackson Grant E. Brown 《Chemoecology》2008,18(4):255-261
Summary. Several freshwater invertebrate and vertebrate prey species rely on chemosensory cues, including non-injury released disturbance
cues, to assess and avoid local predation threats. The prevailing hypothesis is that a pulse of ammonia released by disturbed
or stressed prey functions as the disturbance cue. Here, we test this hypothesis in two phylogenetically distant freshwater
prey fishes, convict cichlids and rainbow trout. In our first experiment, we measured NH4
+ concentration in tanks containing shoals of cichlid or trout before and after exposure to a realistic model predator (or
left undisturbed). We failed to find an increase in ambient NH4
+ concentration for either cichlids or trout. In our second experiment, we exposed cichlids or trout to NH4
+ at 0.1 or 0.5 mg L−1 (or a distilled water control) and measured the change in antipredator behaviour (time moving, foraging rate and area use).
We found no consistent increase in antipredator behaviour in response to NH4
+. In our third study, we exposed cichlids and trout to the disturbance cues of cichlids or trout (versus the odour of undisturbed
donors). We found significant increases in antipredator behaviour, regardless of donor species, for both cichlids and trout.
Thus, the results of our first two experiments do not support the hypothesis that ammonium functions as a disturbance cue
in prey fishes. However, the results of our final experiment do confirm the use of disturbance cues in convict cichlids and
rainbow trout and support that hypothesis that the disturbance cue is indeed some generalized metabolic byproduct. 相似文献
98.
Summary. To exploit biologically active compounds from white clover (Trifolium repens L.) for suppressing weeds and soil-borne diseases, either as isolated products (biopesticides) or through cultivars with
enhanced production of these compounds, the biologically active compounds must be identified, plant content measured, and
their fate in soil known. The present review summarizes the published knowledge needed for such exploitation; providing essential
information on structure and concentration of flavonols, flavones, condensed tannins, isoflavones, isoflavanones, pterocarpans,
coumestans, cyanogenic glucosides, and saponins in healthy and stressed white clover plants. Various stresses and particular
cultivars affect the concentrations of several of the compounds. Information on biological effects and the degradation/transformation
of these compounds in plants or by microorganisms is available. There is no information on the degradation pathway in soil,
the mechanisms of exudation and leaching of compounds from plants, and soil sorption properties of the compounds. The clover
soil fatigue problem is increasing in grasslands and causes problems especially in organic farming. Research efforts focused
on biological elements of clover soil fatigue have not explained it, and the influence of secondary metabolites has not been
investigated. There are few investigations into the interaction between beneficial fungi/fungal-diseases and the occurrence
of biologically active secondary metabolites in white clover plants. Such studies are critical to better understand beneficial
fungi and pathogens. 相似文献
99.
Factors Mediating Co‐Occurrence of an Economically Valuable Introduced Fish and Its Native Frog Prey
Habitat characteristics mediate predator–prey coexistence in many ecological systems but are seldom considered in species introductions. When economically important introduced predators are stocked despite known negative impacts on native species, understanding the role of refuges, landscape configurations, and community interactions can inform habitat management plans. We measured these factors in basins with introduced trout (Salmonidae) and the Cascades frog (Rana cascadae) to determine, which are responsible for observed patterns of co‐occurrence of this economically important predator and its native prey. Large, vegetated shallows were strongly correlated to co‐occurrence, and R. cascadae larvae occur in shallower water when fish are present, presumably to escape predation. The number of nearby breeding sites of R. cascadae was also correlated to co‐occurrence, but only when the western toad (Anaxyrus boreas) was present. Because A. boreas larvae are unpalatable to fish and resemble R. cascadae, they may provide protection from trout via Batesian mimicry. Although rescue‐effect dispersal from nearby populations may maintain co‐occurrence, within‐lake factors proved more important for predicting co‐occurrence. Learning which factors allow co‐occurrence between economically important introduced species and their native prey enables managers to make better‐informed stocking decisions. Factores que Median la Co‐Ocurrencia de un Pez Introducido con Valor Económico y su Presa, una Rana Nativa 相似文献
100.
Golden Eagle fatalities and the continental‐scale consequences of local wind‐energy generation 下载免费PDF全文
Todd E. Katzner David M. Nelson Melissa A. Braham Jacqueline M. Doyle Nadia B. Fernandez Adam E. Duerr Peter H. Bloom Matthew C. Fitzpatrick Tricia A. Miller Renee C. E. Culver Loan Braswell J. Andrew DeWoody 《Conservation biology》2017,31(2):406-415
Renewable energy production is expanding rapidly despite mostly unknown environmental effects on wildlife and habitats. We used genetic and stable isotope data collected from Golden Eagles (Aquila chrysaetos) killed at the Altamont Pass Wind Resource Area (APWRA) in California in demographic models to test hypotheses about the geographic extent and demographic consequences of fatalities caused by renewable energy facilities. Geospatial analyses of δ2H values obtained from feathers showed that ≥25% of these APWRA‐killed eagles were recent immigrants to the population, most from long distances away (>100 km). Data from nuclear genes indicated this subset of immigrant eagles was genetically similar to birds identified as locals from the δ2H data. Demographic models implied that in the face of this mortality, the apparent stability of the local Golden Eagle population was maintained by continental‐scale immigration. These analyses demonstrate that ecosystem management decisions concerning the effects of local‐scale renewable energy can have continental‐scale consequences. 相似文献