Ligustrum lucidum Ait. f. tricolor (Rehd.) Rehd. in relation to atmospheric pollutants in Córdoba city, Argentina. The study area receives
regional pollutants and was categorized taking into account traffic level, industrial density, type of industry, location
of the sample point in relation to the street corner, treeless condition, and topographic level. Dried weight/fresh weight
ratio (DW/FW) and specific leaf area (SLA) were calculated, and concentrations of chlorophylls, carotenoids, total sulfur,
soluble proteins, malondialdehyde (MDA), and hydroperoxy conjugated dienes (HPCD) were determined in leaf samples. Sulfur
content correlates positively with traffic density and SLA correlates negatively with some combinations of the categorical
variables; MDA correlates positively with topographic level and total protein concentration correlates negatively with treeless
condition. On the basis of our results, traffic, location of trees, type of industry, situation of a tree with respect to
others, and topographic level are the environmental variables to bear in mind when selecting analogous sampling points in
a passive monitoring program. An approximation to predict tree injury may be obtained by measuring DW/FW ratio, proteins,
pigments, HPCD, and MDA as they are responsible for the major variability of data. 相似文献
The pathway for the flow of salt-marsh grass production into marsh food-webs is still not well defined. We compared the abilities
of three marsh macroinvertebrates [salt marsh periwinkles, Littoraria irrorata (Say) (=Littorina irrorata), salt-marsh coffee-bean snails, Melampus bidentatus (Say); and a talitrid amphipod, Uhlorchestia spartinophila Bounsfield and Heard] to access standing-dead leaves of smooth cordgrass (Spartina alterniflora Loisel). The invertebrates were incubated with naturally-decaying leaves, and the rates of removal of organic matter and
living fungal biomass (ergosterol) were measured. The impact of invertebrate activity upon fungal growth rates was measured
as rates of fungal-membrane synthesis (incorporation of radioacetate into ergosterol). The removal rates of organic leaf biomass
per mg individual biomass were highest for amphipods (700 μg mg−1 d−1) and lowest for periwinkles (90 μg mg−1 d−1), but the relatively large biomass of the snails made their removal rates per individual greater than those of amphipods.
Net removal of ergosterol by all three invertebrates was >50% for yellow-brown (early-decay) leaf blades. For fully-brown
(advanced-decay) blades, >50% removal of ergosterol was found only for periwinkles; exposure to coffee-bean snails and amphipods
resulted in a net ergosterol reduction of ≤20%. The lower net reduction of living fungal biomass by coffee-bean snails and
amphipods may have been due to fungal-growth stimulation (2.3-fold stimulation in coffee-bean snails and 1.5-fold stimulation
in amphipods). Grazing by periwinkles did not stimulate fungal growth, possibly because of its high intensity. Grazing by
these three salt-marsh shredders may affect marsh-grass shoot-decay in different ways. Periwinkles may abbreviate the period
of fungal production, and incorporate the decaying material relatively quickly into snail biomass and fecal-pellet rain to
the sediments. Coffee-bean snails and amphipods may enhance and prolong fungal production, along with the formation of fecal-pellet
rain. All three invertebrates fed preferentially on leaf blades rather than leaf sheaths, and feeding rates of gastropods
were higher during the night than during the day.
Received: 25 November 1998 / Accepted: 4 November 1999 相似文献
Environmental Science and Pollution Research - Due to human activities, there is an increasing presence of agrochemicals residues in water bodies, which could be attributed to an increased use of... 相似文献
Regional Environmental Change - By 2014 approximately 2.2 million km2 (~43%) of Brazil’s Legal Amazonia region had been incorporated into an extensive network of 718 protected areas, which... 相似文献
Plasticized starch (PLS) is a renewable, degradable, and inexpensive polymer, but it suffers from poor mechanical properties.
The mechanical properties can be improved by blending PLS with polyolefins, nonetheless, at high PLS content, the mechanical
properties remain poor. Here we show that addition of clay can greatly improve the mechanical properties of PLS/polypropylene
blends at high starch content. Unmodified and organically modified montmorillonite clays, MMT and Cloisite 30B respectively,
were added to blends of glycerol-plasticized starch and polypropylene, compatibilized using maleated polypropylene. TEM indicates
that MMT is well dispersed in the PLS phase of the blends, while Cloisite 30B is located both within the PLS phase as well
as at the interface between PLS and PP. At high PLS content, the addition of clay increased the tensile strength and tensile
modulus by an order of magnitude, while reducing the ultimate elongation only slightly. Such improvements are attributable
to both the addition of clay as a reinforcing component, as well as to the change in the two phase morphology due to addition
of clay. 相似文献
Rodent outbreaks affect many farmland areas worldwide and the negative environmental impacts of control campaigns cause intense social tensions. In such conservation conflicts, understanding stakeholders’ viewpoints is critical to promote ecologically sustainable management. We used Q-methodology, a framework standing between qualitative and quantitative social research, to investigate human subjectivity and understand conflicts caused by rodent outbreaks in Spain. We interviewed farmers, conservationists, hunters, and governmental agencies, and identified five main discourses about the origins and consequences of the conflictive situation. Finding sustainable management is impaired by opposing views about causes and consequences of vole outbreaks and their management, which are at the root of the conflict. Social tensions will likely remain until the underlying conflicts between people holding different views are also managed. Decision-making should therefore focus on mitigating underlying conflicts. Using trained independent mediators would help the effective resolution of conservation conflicts caused by rodent outbreaks and their management.
AbstractThe main objective of this study is the degradation of a synthetic solution of atrazine by a modified vermiculite catalyzed ozonation, in a rotating packed bed (RPB) reactor. A 0.5?L RPB reactor was used to perform the experiments, using a Central Composite Design (CCD) response surface to construct the quadratic model based on the factors: pH, catalyst concentration and reactor rotation frequency. The response variable was the removal of the organic load measured in terms of Chemical Oxygen Demand (COD). After the complete quadratic model was constructed through the response surface, the COD degradation process had an optimal removal of 41% under the following conditions: pH 8.0, rotation of 1150?rpm and catalyst concentration 0.66?g L?1. 相似文献
Sediment cores from oxygen depleted zones of lake Léman (lake of Geneva) and from anoxic surface sediment from Voua de la Motte (France) were analyzed for their sterol compositions. 4-methylstanols were found to be major sterols in Motte lake sediment, which is rich in organic matter. In lake Léman, the relative abundances of the same 4-methylstanols increase with the depth in the core, but they remain always minor compounds. An extensive search for a possible external source for these compounds included the analysis of water, of the plankton and of the surrounding soil material. All these results, along with those of an in situ incubation experiment, give strong evidence in favor of their in situ bacterial biosynthesis. 相似文献
Seven complete clutches of Morelet's crocodile (Crocodylus moreletii) eggs were collected in northern Belize and examined for organochlorine (OC) pesticide residues. The primary OC detected, p,p-DDE, was found in every egg analyzed (n=175). Other OCs detected included p,p-DDT, p,p-DDD, methoxychlor, aldrin, and endosulfan I. Concentrations of individual OCs ranged from 4 ppb (ng chemical/g egg wet weight) to greater than 500 ppb. A statistical evaluation of p,p-DDE levels in three complete clutches was used to derive the minimum number of eggs needed from a clutch to precisely determine the mean p,p-DDE concentration representative of that clutch. Sample sizes of 8 (80% confidence level) and 11 (90% confidence level) were determined to yield an accurate estimate of contaminant levels in a full clutch of eggs. The statistically recommended sample size of 11 eggs (at 90% confidence level) was successfully tested on the four additional clutches. 相似文献
Degradation rates and removal efficiencies of Metronidazole using UV, UV/H2O2, H2O2/Fe2+, and UV/H2O2/Fe2+ were studied in de-ionized water. The four different oxidation processes were compared for the removal kinetics of the antimicrobial pharmaceutical Metronidazole. It was found that the degradation of Metronidazole by UV and UV/H2O2 exhibited pseudo-first order reaction kinetics. By applying H2O2/Fe2+, and UV/H2O2/Fe2+ the degradation kinetics followed a second order behavior. The quantum yields for direct photolysis, measured at 254 nm and 200-400 nm, were 0.0033 and 0.0080 mol E(-1), respectively. Increasing the concentrations of hydrogen peroxide promoted the oxidation rate by UV/ H2O2. Adding more ferrous ions enhanced the oxidation rate for the H2O2/Fe2+ and UV/H2O2/Fe2+ processes. The major advantages and disadvantages of each process and the complexity of comparing the various advanced oxidation processes on an equal basis are discussed. 相似文献