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41.
An automated method for the indirect determination of fluoride by inductively coupled plasma atomic emission spectrometry using discontinuous-flow analysis has been developed. A modified flow injection analysis system was used for sample preparation. The method is based on the determination of excess cerium(III) ion after precipitation of CeF3. Separation of the precipitate is performed online on a syringe membrane filter that is cleaned each analysis cycle by 1 M nitric acid, ensuring a long life-time for the filter. As a result of the short reaction time, a detection limit of 9.5 mg L?1 was obtained. The precision (RSD) of the proposed method is 1.02% at fluoride concentration of 28 mg L?1. The applicability of the technique for groundwater monitoring of fluoride-contaminated area is demonstrated. 相似文献
42.
Breda Jakovac-Strajn Katarina Pavšič-Vrtač Igor Ujčič-Vrhovnik Anton Vengušt Gabrijela Tavčar-Kalcher 《毒物与环境化学》2013,95(8):1551-1563
This study was aimed at investigating the contamination of grains, which are grown and used for animal diets by Slovene farmers. A total of 107 samples were examined for mesofilic aerobic molds and yeasts. The leading contaminants among molds were from Fusarium spp., detected in 73 samples, mostly in maize (50). In accordance with the European Feed Microbiology Organisation criteria, 68% of all tested samples were of the quality level I, with normal microbiological flora, and 9% of samples were estimated as quality level IV and not suitable for animal feed. Using liquid and gas chromatography methods, the presence of various mycotoxins (expressed as 12% of moisture content) was found in 77% of all samples; mostly deoxynivalenol (71%) in concentration of 150–14,420 µg kg?1, followed by zearalenone (32%, 20–640 µg kg?1), fumonisin B1 (31%, 10–4863 µg kg?1), fumonisin B2 (22%, 10–1629 µg kg?1), while HT-2 and T-2 toxins were found in low concentration in two samples, and aflatoxin B1 and ochratoxin A in one sample. By statistical evaluation, significant positive correlations were noted between the presence of deoxynivalenol and zearalenone as well as between fumonisin B1 and B2. 相似文献
43.
Pesticides are chemicals used in agriculture but are known to produce adverse effects on humans. In this study, blood activities of superoxide dismutase (SOD), catalase (CAT), aspartate transaminase (AST), alanine transaminase (ALT), gamma-glutamyl transaminase, lactate dehydrogenase (LDH), and levels of malondialdhyde (MDA) were determined in 44 greenhouse workers (24 tomato workers, 20 clove workers) and in tomato (24 samples) and clove (20 samples) products. At the end of this study, blood MDA levels and activities of ALT, AST, and LDH levels in greenhouse workers were significantly increased while SOD and CAT activity levels fell significantly. Pesticide residues were not found in agricultural worker blood. Malathion residues (average 0.8?ppm) were detected in tomatoes (8 samples) in these greenhouses. Data suggest that the health of the greenhouse workers may be adversely affected by pesticides. 相似文献
44.
The influence of rainfall, air temperature and soil moisture on the vertical mobility in the soil of fuel oil hydrocarbons (HC) was investigated in a field experiment. A controlled spreading of fuel oil (nC10‐nC25) was performed at a rate of 5 L HCm‐2 on an agricultural soil in summer and in winter. Concentration, chemical composition of HC and soil moisture were regularly determined at different soil depths between 0 and 140 cm, 1 h, 3, 8and 15 days (d) after the spreading of oil. Sorption of hydrocarbons onto the organo‐mineral matrix of the soil was studied in laboratory experiments. The results showed that in summer, with an air temperature of 24°C and without water leaching in the soil profile, 65% of the initial HC remained trapped in the 0–140 cm soil layer, about 20% of the HC volatilized and around 15% migrated deeper. A vertical selective migration of the lightest (nC10‐nC15) HC (naphthas) was shown lSd after the spreading of fuel oil. Naphthas progressively reached the 120–140 cm soil layers whereas the heavy fractions of oil (nC17‐nC25) migrated and concentrated in the 0–60 cm soil layers. In winter, when soil was regularly watered by rainfalls and at low air temperatures, only 47% of the initial HC remained in the 0–140 cm profile after 15 d. A fast vertical infiltration of naphthas occurred within the first 3 d. After 15 d, all HC were detected in the same relative amounts as in the initial oil in the whole profile. Volatilization was negligible in winter and an increase in the migration of total oil at depth in the soil profile was shown. As inferred from the laboratory experiments, the high soil moisture led to the decrease in HC sorption on the organo‐mineral matter of the soil. 相似文献
45.
Julie Marmet Beno?t Pisanu Jean-Louis Chapuis Gwena?l Jacob Emmanuelle Baudry 《Behavioral ecology and sociobiology》2012,66(11):1449-1457
While sexual selection in mammals with female defense systems has historically received considerable attention, much less is known about the factors affecting reproductive success in mammalian species with scramble competition mating systems. Using mark–recapture techniques and DNA microsatellite loci to assign parentage, we examined the mating system and factors affecting the variation of the annual reproductive success in an introduced population of the Siberian chipmunk, Tamias sibiricus, a small, monomorphic, solitary squirrel. Our analyses showed that breeding females were spatially dispersed, setting the stage for a scramble competition mating system. Male reproductive success was positively associated with the size of the home range. The strength of sexual selection on this behavioral trait was very strong, equaling previous estimates for morphological traits in female defense mating systems. These findings suggest that a behavioral trait, space use, strongly influences the annual reproductive success in males, which is consistent with expectations in a scramble competition mating system. In both sexes, reproductive success was influenced by habitat, with twice as many juveniles produced in semi-open than in closed habitat, possibly due to differences in food availability between the two habitats. 相似文献
46.
T.?C.?IngsEmail author M.-Y.?Wang L.?Chittka 《Behavioral ecology and sociobiology》2012,66(3):487-496
Predators hunting for cryptic prey use search images, but how do prey search for cryptic predators? We address this question using the interaction between bumblebees and the colour-changing crab spider Misumena vatia which can camouflage itself on some flowers. In laboratory experiments, we exposed bumblebees to an array of flowers concealing robotic predators (a trapping mechanism combined with a 3D life-sized model of a crab spider or a circle). Groups of bees were trained to avoid either cryptic yellow spiders or yellow circles (equal area to the spiders) or remained predator naive. The bees were then exposed to a new patch of white flowers containing some cryptic predators (either white spiders, white circles or a mixture of both). We monitored individual foraging choices and used a 3D video tracking system to quantify the bees’ flight behaviour. The bees trained to avoid cryptic spiders, chose 40% fewer spider-harbouring flowers than expected by chance, but were indifferent to cryptic circles. They also aborted a higher proportion of landings on flowers harbouring spiders, ultimately feeding from half as many ‘dangerous’ flowers as naive bees. Previous encounters with cryptic spiders also influenced the flight behaviour of bees in the new flower patch. Experienced bees spent more time inspecting the flowers they chose to reject (both with and without concealed spiders) and scanned from side to side more in front of the flowers to facilitate predator detection. We conclude that bees disentangle shape from colour cues and thus can form a generalised search image for spider shapes, independent of colour. 相似文献
47.
Cristea Adorján Pustan Marius Bîrleanu Corina Dudescu Cristian Floare Călin Gabriel Tripon Andreea-Melisa Banciu Horia Leonard 《Journal of Polymers and the Environment》2022,30(1):424-430
Journal of Polymers and the Environment - Poly(3-hydroxybutyrate) (PHB) is a natural and biodegradable polyester which represents an alternative to replace conventional plastics in the packaging... 相似文献
48.
Environmental Modeling & Assessment - Lucas–Washburn equation is a fundamental expression which is used to describe capillary rise in porous materials according to average pore radius,... 相似文献
49.
In mammalian polygynous mating systems, male reproductive effort consists mainly of male–male competition and courting of
females, which entail substantial somatic costs. Males are thus expected to adjust their reproductive effort according to
their age and condition. In this study, we examined how activity budgets of male mountain goats (Oreamnos americanus), a polygynous ungulate, varied with age in a marked population over two periods: (1) summers 1995–2006 and (2) ruts 2004–2006.
We then assessed if the proportions of time spent in male–male competition and courtship behaviors were influenced by age-specific
body mass and social rank during the rut. Males spent most of their time foraging and resting during summer, and rested more
and foraged less with increasing age. During the rut, pronounced shifts in activity budgets occurred as juveniles (1–2 years)
increased time spent foraging, whereas adults (≥3 years) increased standing and time spent in social interactions at the expense
of foraging. At old age, reproductive effort either stabilized or decreased slightly, providing weak support for the ‘mating
strategy–effort’ hypothesis, predicting that courtship behaviors should peak in prime-aged males. Age-specific body mass did
not affect time spent in male–male competition, but was positively related with time spent in courtship behaviors, providing
support for the ‘individual quality’ hypothesis, predicting that males with more resources at the start of the rut should
spend more time in mating-related activities. Age-specific social rank did not affect reproductive effort. Surviving to prime
age while increasing mass each year should thus allow male ungulates to gain greater ability to court estrus females. 相似文献
50.
Combined archaeological and ecological investigations in a large ancient oak forest in Central France have revealed a dense network of ancient human settlements dating from the Roman period. We demonstrate a strong correlation between present-day forest plant diversity patterns and the location of Roman farm buildings. Plant species richness strongly increases toward the center of the settlements, and the frequency of neutrophilous and nitrogen-demanding species is higher. This pattern is paralleled by an increase in soil pH, available P, and delta(15)N, indicating the long-term impact of former agricultural practices on forest biogeochemical cycles. These extensive observations in a forested region on acid soils complement and confirm previous results from a single Roman settlement on limestone. Ancient Roman agricultural systems are increasingly being identified in contemporary French forests; the broad extent and long-lasting effects of previous cultivation shown in this study require that land-use history be considered as a primary control over biodiversity variations in many forest landscapes, even after millennia of abandonment. 相似文献