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971.
Photodegradation of ethylenediaminetetraacetic acid (EDTA) and ethylenediamine disuccinic acid (EDDS) within natural UV radiation range. 总被引:4,自引:0,他引:4
The rate of photodegradation of two chelating agents, ethylenediaminetetraacetic acid (EDTA) and an isomeric mixture of ethylenediamine disuccinic acid (EDDS), was analysed in humic lake water and in distilled water using exposure to sunlight, and in the laboratory using lamps emitting UV radiation in the range 315-400 nm. Degradation was studied using Fe(III) complexes and sodium salts of chelates. Fe(III) complexes were illuminated at pH 3.1 and 6.5. The results demonstrated that the rate of photodegradation of Fe(III)-EDTA and Fe(III)-EDDS complexes seems to be pH dependent. In the laboratory experiments degradation occurred much faster when the original pH was 3.1 rather than 6.5. The photodegradation of the isomeric mixture of EDDS was markedly faster than the degradation of EDTA both in the laboratory and field experiments, and both in humic and distilled water. The results indicated that in natural waters photodegradation of EDDS is independent of initial speciation of EDDS, while degradation of EDTA is dependent on its existence as Fe(III)-EDTA species. 相似文献
972.
Concentrations of monosaccharides in humic substances in the early stages of humification. 总被引:8,自引:0,他引:8
Deteriorated liquid packaging board (LPB) and biowaste compost are matrices, mainly consisting of cellulose, in the early stages of humification. Degradative studies on these matrices allow an examination of the role of carbohydrates in the synthesis of humic substances. Samples of different age were collected and divided by extraction into hot water extract (HWE), bitumen, humic acid (HA), fulvic acid (FA) and humin or residual fibre fractions. The following monosaccharides were identified in these fractions: L-arabinose, D-ribose, D-xylose, L-fucose, D-mannose, D-fructose, D-galactose, D-glucose, L-rhamnose and xylitol. The main component in all fractions was glucose. The concentrations of monosaccharides in humic acids (HAs) of LPB ranged from 67 to 503 mg/g of organic matter, and the concentrations in HAs of compost from 52 to 101 mg/g. As a general trend, the concentrations of monosaccharides decreased during LPB degradation and composting in all fractions. At the same time the relative amounts of D-xylose, D-mannose and D-galactose increased in HAs of compost samples. 相似文献
973.
Many species of amphibians have experienced population and range reductions. It has been hypothesized that sensitivity to UV-B may contribute to the population declines of some amphibian species. We performed field experiments to measure the effects of solar UV-B on the hatching success of three Finnish anuran species, the common frog (Rana temporaria), moor frog (Rana arvalis) and common toad (Bufo bufo). Further, the effects of natural UV-B radiation on survival of the tadpoles of the same three species of anurans were tested. A significant percentage of R. temporaria and B. bufo embryos survived when exposed to and protected from solar UV-B and hatching success was not affected by solar radiation. Elimination of solar UV-B significantly increased the hatching success of R. arvalis, but embryonic mortality was high in both treatments. The data indicates that under natural conditions, solar UV-B radiation influences embryo survival in R. arvalis, but has no effect on R. temporaria and B. bufo. Solar UV-B radiation had no effect on R. temporaria and R. arvalis tadpoles, but elimination of UV-B significantly increased survival of B. bufo tadpoles. It seems that ambient UV-radiation levels have no effect on R. temporaria but may affect R. arvalis and B. bufo at different developmental stages. 相似文献
974.
Selection effects of air pollution on gene pools of Norway spruce, European silver fir and European beech. 总被引:1,自引:0,他引:1
R Longauer D G?m?ry L Paule D F Karnosky B Manikovská G Müller-Starck K Percy R Szaro 《Environmental pollution (Barking, Essex : 1987)》2001,115(3):405-411
The effects of industrial pollution on allelic and genotypic structures of Norway spruce. European silver fir and European beech were investigated by means of isozyme analysis. In a mixed Norway spruce-silver fir forest stand in an area heavily polluted by sulphur dioxide and heavy metals in the region of Spis (eastern Slovakia), pairs of neighbouring damaged and apparently healthy trees were selected in two replicates (44 and 69 pairs in a heavily and moderately damaged stand, respectively). Pairwise sampling of trees with contrasting vitality was applied to reduce potential effects of site heterogeneity on the vitality of sampled trees. No significant differences in allelic and genotypic frequencies were found between sets of healthy and declining trees. There were differences in the single-locus heterozygosities, but these were not consistent between the replicates. However, the set of damaged trees exhibited higher levels of genetic multiplicity and diversity, possibly due to the deleterious effect of rare alleles under the conditions of air pollution. Consequently. following the decline of pollutant-sensitive trees, the remaining stand will be depleted of a part of alleles with unknown adaptive value to future selection pressures. 相似文献
975.
976.
Virginia E. Villafañe Paul J. Janknegt Marco de Graaff Ronald J. W. Visser Willem H. van de Poll Anita G. J. Buma E. Walter Helbling 《Marine Biology》2008,154(6):1021-1029
During austral summer 2006, experiments were carried out to evaluate the effects of ultraviolet radiation (UVR, 280–400 nm)
on carbon fixation of natural phytoplankton assemblages from Patagonia (Argentina). Surface water samples were collected (ca.
100 m offshore) at mid morning using an acid-cleaned (1 N HCl) dark container. The short-term impact of UVR (measured as radiocarbon
incorporation) was immediately assessed by exposing samples to three artificial illumination treatments: PAR (400–700 nm),
PAR + UV-A (320–700 nm), and PAR + UV-A + UV-B (280–700 nm). Pico-nanoplankton characterized the assemblages, and taxon-specific
pigment fingerprinting combined with CHEMTAX and supplemented with microscopic observations showed varied proportions of diatoms,
chlorophytes, and cyanobacteria throughout January–February 2006. Photosynthetic efficiency, as assessed through assimilation
numbers, was high [between 4.4 and 10.4 μg C (μg chl-a)−1 h−1], and it was probably favored by the supply of inorganic nutrients from the Chubut River. UVR-induced photoinhibition appeared
to be related to the taxonomic composition: in general, higher photoinhibition was observed when diatoms dominated, whereas
this was lower when samples were dominated by chlorophytes. Our data suggest that xanthophyll pigments might have provided
only limited protection in these already highlighted acclimated assemblages. 相似文献
977.
18S rRNA phylogeny of sea spiders with emphasis on the position of Rhynchothoracidae 总被引:2,自引:1,他引:1
Koichiro?Nakamura Yasunori?KanoEmail author Nobuo?Suzuki Takashi?Namatame Akinori?Kosaku 《Marine Biology》2007,153(2):213-223
The phylogenetic relationships among all living families of sea spiders (Arthropoda: Pycnogonida) are investigated using nearly
complete 18S rRNA sequences from 57 ingroup species and five chelicerates under the Bayesian and maximum likelihood methods.
Monophyly of Colossendeidae, Pycnogonidae, Phoxichilidiidae, Endeidae and Pallenopsidae is consistently supported. However,
the genera formerly classified in the family Ammotheidae are split up into two distantly related groups. The genera Ascorhynchus and Eurycyde (here recognized as Ascorhynchidae) are possibly an early offshoot of sea spiders, whereas other ammotheids constitute a
robust terminal clade with Pallenopsidae, Phoxichilidiidae and Endeidae. This topology also opposes the prevalent assumption
of successive losses and simplification of three kinds of cephalic appendages like in a previous cladistic analysis. At least
three independent losses are suggested for palps by the inferred topology, and both chelifores and female ovigers may have
been lost twice. Our knowledge of early ontogeny and internal anatomy is more congruent with the present 18S rRNA data. The
families Callipallenidae and Nymphonidae with unique “attaching larvae” are grouped together in present molecular trees, suggesting
that extended paternal care of offspring evolved only once in Pycnogonida. Confident clustering of Pycnogonidae and Rhynchothoracidae
indicates that the number of female genital pores is an evolutionary conservative character. 相似文献
978.
Attila?HettyeyEmail author J.?Dale?Roberts 《Behavioral ecology and sociobiology》2007,61(8):1303-1310
In species where males use alternative reproductive tactics and male phenotypes are confronted with different risks of sperm
competition, theory predicts that between-male-type differences in sperm expenditure may evolve. In the frog Crinia georgiana big males can monopolize females, whereas small males often engage in polyandrous matings. Consequently, big males may experience
a lower risk of sperm competition than do small males. We tested if the predictions from theoretical models can be applied
to the mating system of C. georgiana. Our results showed that small males do not have larger testes relative to their body size compared to their larger counterparts
and that the efficiency with which sperm number, size, motility, and longevity are produced by the testes does not differ
between small and large males in the predicted way. These results are not in alignment with predictions from a loaded raffle
model of sperm competition on sperm expenditure in males with alternative phenotypes. The plasticity in mating tactics used
by C. georgiana males and a high intraseasonal variation in male densities may have prevented the evolution of enhanced sperm performance
in smaller males. A fair raffle in the sperm competition game played by C. georgiana males could also explain the observed patterns in sperm traits. Future investigations determining the parameters responsible
for the deviation from theoretical predictions in this system will test the degree to which current theoretical models can
indeed be applied to species with plastic reproductive tactics. 相似文献
979.
Byela Tibesigwa Martine Visser Mark Collinson Wayne Twine 《Sustainability Science》2016,11(2):193-214
This paper examines the impact of agriculture-related shocks on consumption patterns of rural farming households using 3 years of data from South Africa. We make two key observations. First, agriculture-related shocks reduce households’ consumption. Second, natural resources and informal social capital somewhat counteract this reduction and sustain dietary requirements. In general, our findings suggest the promotion of informal social capital and natural resources as they are cheaper and more accessible coping strategies, in comparison to, for example, insurance, which remains unaffordable in most rural parts of sub-Saharan Africa. However, a lingering concern centres on the sustainability of these less conventional adaptation strategies. 相似文献
980.
Hg transfer from contaminated soils to plants and animals 总被引:1,自引:0,他引:1
S. M. Rodrigues B. Henriques A. T. Reis A. C. Duarte E. Pereira P. F. A. M. R?mkens 《Environmental Chemistry Letters》2012,10(1):61-67
Understanding the transfer of mercury (Hg) from soil to crops is crucial due to Hg toxicity and Hg occurrence in terrestrial
systems. Previous research has shown that available Hg in soils contributes to plant Hg levels. Plant Hg concentrations are
related to soil conditions and plant characteristics. Mechanistic models describing such soil–plant interactions are however
difficult to quantify. Here we performed a field study in agricultural, mining and industrial areas in Portugal to evaluate
potential food chain risks. The uptake of Hg by Italian ryegrass, ryegrass, orchard grass, collard greens and rye was measured
to calculate daily intakes (DI) of Hg for cows and sheep grazing. A total of 136 soil samples and 129 plant samples were analysed.
Results show that total Hg concentrations ranged from 0.01 to 98 mg kg−1 in soils; 0.01–5.4 mg kg−1 in shoots and 0.01–42 mg kg−1 in roots. Calculated DI ranged from 0.18 to 132 mg d−1 for cows, and from 0.028 to 23 mg d−1 for sheep. In 27 grassland sites, daily intakes exceeded the acceptable daily intake of both cows and sheep in view of food
safety considering Hg in animal kidneys evidencing potential risks to human health. The transfer of Hg from soil to crops
was described using empirical Freundlich-type functions. For ryegrass, orchard grass and collard greens, the soil-to-root
or soil-to-shoot transfer of Hg appeared to be controlled by the total soil Hg concentration and levels of Alox and Feox. Empirical functions allowed us to obtain realistic estimates of Hg levels in crops and can be used as an alternative to
mechanistic models when evaluating food chain risks of Hg contamination in agricultural soils. 相似文献