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1.
Two different test methods for assessing the toxicity of aminotriazole to Selenastrum capricornutum are compared. Growth medium composition is demonstrated to have a significant effect on the toxicity of aminotriazole. 相似文献
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A new, higher dam was installed at Kerkini Reservoir in 1982, causing habitat and landscape disruption. A decrease in the
area of grassland and shallow water areas, the rapid disappearance of reedbeds, the appearance of beds ofNymphaea, and the disappearance of half the forest area were all observed between 1982 and 1991. With the new hydrological regime,
a lacustrine system was created, with an extensive, rather deep (4–8 m), pelagic zone favorable for the development of coarse
fish species throughout the year. After 1982, an increase in fishing effort and a change in the relative abundance of fish
species in the catch, including the disappearance of eels and wels, were observed. The impact of the rise in the water level
of breeding aquatic birds led to a general decline in species typical of marshy habitats in favor of species preferring deeper
open water habitats. A decrease was recorded in bird species that feed largely on invertebrates and to a lesser extent fish
(e.g., glossy ibis) and that require extensive shallow feeding areas. There was a decline in geese, whose nests were regularly
flooded, and a major increase in piscivorous birds, particularly diving birds (e.g., cormorants), which prefer deeper open
water and benefitted directly from the large increase in coarse fish biomass. The disappearance of birds breeding in flooded
meadows (e.g., black-winged stilts) and of those restricted to reedbeds (e.g., marsh harrier) occurred from 1983. Over the
same period, the changes in populations of wintering birds at Kerkini were different from those occurring in other wetlands
in northern Greece. The changes recorded in the populations of wintering birds at Kerkini did not therefore result from overall
regional trends but from the major habitat modifications that occurred to this wetland. As for breeding birds, strictly piscivorous
species increased greatly as a result of the increased availability of fish, but also due to the appearance of many suitable
night roosting sites (flooded trees) and to the great increase in the area of open water greater than 2 m deep. Today, Kerkini
has become the most important breeding site in Greece for a majority of colonial waterbirds. In contrast, wintering shorebirds
practically disappeared. The many changes recorded in the status of breeding and wintering birds at Kerkini can mostly be
explained by the changes that occurred in the functioning of the ecosystem and in the habitat structure following the inauguration
of the new hydrological regime. These changes did not all occur at the same time: some were immediate and others required
a delay before they could be detected. 相似文献
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The octachlorodibenzo-p-dioxin (OCDD) concentrations have been determined in aged samples of commercial pentachlorophenol (PCP), in wood protection formulations containing PCP and in wood treated with PCP as a preservative or as an anti-sapstain treatment. The concentrations of OCDD found in the various samples are within the range expected from the amount of commercial PCP initially present in the samples. In view of the known stability of OCDD the results are interpreted as indicating that the formulation, treatment and ageing processes have not led to any substantial conversion of PCP to OCDD; although one result indicates that outdoor exposure of treated samples increased the OCDD concentration by a factor of approximately 2 after years. Analysis of aged samples of treated wood indicate that OCDD is lost much less rapidly from the wood than PCP. 相似文献
5.
To understand the consequences of the invasion of the nonnative rainbow trout Oncorhynchus mykiss on the native marble trout Salmo marmoratus, we compared two distinct headwater sectors where marble trout occur in allopatry (MTa) or sympatry (MTs) with rainbow trout
(RTs) in the Idrijca River (Slovenia). Using data from field surveys from 2002 to 2009, with biannual (June and September)
sampling and tagging from June 2004 onwards, we analyzed body growth and survival probabilities of marble trout in each stream
sector. Density of age-0 in September over the study period was greater for MTs than MTa and very similar between MTs and
RTs, while density of trout ≥age-1 was similar for MTa and MTs and greater than density of RTs. Monthly apparent survival
probabilities were slightly higher in MTa than in MTs, while RTs showed a lower survival than MTs. Mean weight of marble and
rainbow trout aged 0+ in September was negatively related to cohort density for both marble and rainbow trout, but the relationship
was not significantly different between MTs and MTa. No clear depression of body growth of sympatric marble trout between
sampling intervals was observed. Despite a later emergence, mean weight of RTs cohorts at age 0+ in September was significantly
higher than weight of both MTs and MTa. The establishment of a self-sustaining population of rainbow trout does not have a
significant impact on body growth and survival probabilities of sympatric marble trout. The numerical dominance of rainbow
trout in streams at lower altitudes seem to suggest that while the low summer flow pattern of Slovenian streams is favorable
for rainbow trout invasion, the adaptation of marble trout to headwater environments may limit the invasion success of rainbow
trout in headwaters. 相似文献
6.
The results of analyses for polychlorodibenzofuran (PCDF) content in two samples of polychlorobiphenyl (PCB) from used electrical transformers are presented and discussed. In neither sample was there evidence for enhanced PCDF concentrations even though one of them had been subjected to overheating while in service. 相似文献
7.
Results of analyses of eight samples of technical pentachlorophenol conducted by three different analytical methods are presented and discussed. 相似文献
8.
The floodplain of the river Strymon at Kerkini (northern Greece) was transformed into an irrigation reservoir by the construction
of a dam in 1932 and subsequently enlarged in 1982. The aims of this study were to quantify the changes occurring in the various
habitat types following raising of the waterlevel and to assess the stability of the plant communities present at this Ramsar
site. The current hydrological regime, which has been stable since 1986, is typified by an increase in mean annual reservoir
level of 2.2 m and by an increase in the annual range in level of 1.3 m. Landsat (1980, 1981, 1984, 1986, and 1988) and SPOT
(1990) satellite images show a decrease in the area of grassland and shallow water areas, the very rapid disappearance of
reedbeds, the appearance of beds ofNymphaea and the disappearance of half the forest area.
The flooded forest, dominated bySalix alba, is a key habitat contributing to the biological richness of this wetland of international importance. The decrease in the
forested area will continue because of the death of standing trees, the absence of regeneration under the new regime, the
felling of trees and grazing. Management could be undertaken to ensure the survival of forested habitat and reedbeds at Kerkini,
but this would require that the authorities take into account nature conservation and the protected status of the site and
not raise the water level again. 相似文献
9.
The activity of a chemical in solution determines its tendency to move into other media. At low concentrations (<0.01M) it is generally considered to be linearly related to concentration. A hypothetical model based on the structure of liquid water is discussed which could cause deviations from this linearity in the ppb region, a concentration much lower than that normally investigated thermodynamically, but one of great importance environmentally. Headspace experiments are reported with carbon tetrachloride and chloroform in water at concentrations down to ~10?3 ppb but no such deviations were discerned. 相似文献
10.
Wood samples treated with technical pentachlorophenol (PCP), technical sodium pentachlorophenoxide (NaPCP) and octachlorodibenzo-p-dioxin have been exposed outdoors for periods up to years. Analysis of extracts from the samples show that photolytic reductive dechlorination of highly chlorinated dibenzo-p-dioxins to less chlorinated isomers occurs. However there is no discernible increase in polychlorodibenzo-p-dioxin concentrations in the technical PCP treated wood presumably because further photolytic reactions and volatilisation compete effectively with the photolytic formation. There is no evidence for formation of octachlorodibenzo-p-dioxin (OCDD) in technical PCP treated wood in this study, probably because photolytic destruction and volatilisation compete effectively with formation reactions when the initial OCDD concentration is relatively high. 相似文献