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81.
Taxodium distichum (L.) Rich.]. The study site, a swamp in St. Martin Parish, Louisiana, has received municipal wastewater for the last 40 years.
Growth chronologies from 1920 to 1992 were developed from cross-dated tree core samples taken from treated and control sites
with similar size and age classes. Mean diameter increment (DINC) and mean basal area increment (BAI) chronologies were constructed
separately for each stand. These chronologies were then summarized by tree and stand into seven nine-year intervals resulting
in three pretreatment intervals from 1926 to 1952 and four treatment intervals from 1953 to 1988. Significant differences
in growth response between sites showed a consistent pattern of growth enhancement in the treated site coincident with the
onset of effluent discharge. The ratio of treated to control baldcypress growth rates (computed from DINC) averaged 0.74 during
the pretreatment period and 1.53 during the treatment period. Over the period of study, control DINC decreased from 77 mm
to 29 mm/nine-year interval, while treatment DINC increased slightly from 40 mm to 47 mm/nine-year interval. Control BAI did
not increase significantly and averaged 192 cm2/nine-year interval. There was a significant increase in treatment BAI from 129 to 333 cm2/nine-year interval over the period of record. These results clearly demonstrate sustained long-term baldcypress growth enhancement
throughout 40 years of municipal effluent discharge. 相似文献
82.
Abstract: Populations of wolves were estimated for the states of Gujarat and Rajasthan, India, based on interviews and surveys. The wolf range is continuous. The total number of wolves in Gujarat is between 190 and 270 and in Rajasthan is between 253 and 350. Recommendations for a wolf conservation strategy include: (1) encouraging public support and education, (2) enforcing legal protection, (3) paying compensation for wolf-killed livestock, (4) conducting surveys of wolf populations and research on the dynamics of select populations, (5) protecting breeding habitats, and (6) eradicating feral dogs from wolf conservation areas. It is not too late to save the wolf if such a conservation strategy is implemented immediately. 相似文献
83.
This article summarizes and interprets estimates, by the US Bureau of Mines and others, of the availability of silver from primary and secondary sources in market economy countries. Despite conservative measurements, ample silver to support expansion of its use in industrial applications was found to exist. Supply from only portions of this resource base can be expected to respond to changes in silver demand, because factors other than price are the major determinant of the flow of silver from large segments of its resource base. 相似文献
84.
Effects of the Interaction between Genetic Diversity and UV-B Radiation on Wood Frog Fitness 总被引:1,自引:0,他引:1
Abstract: Genetic diversity may buffer amphibian populations against environmental vicissitudes. We hypothesized that wood frogs ( Rana sylvatica ) from populations with lower genetic diversity are more susceptible to ultraviolet-B (UV-B) radiation than those from populations with higher diversity. We used RAPD markers to obtain genetic diversity estimates for 12 wood frog populations. We reared larval wood frogs from these populations and exposed experimental groups of eggs and larvae to one of three treatments: unfiltered sunlight, sunlight filtered through a UV-B-blocking filter (Mylar), and sunlight filtered through a UV-B-transmitting filter (acetate). In groups exposed to UV-B, larval mortality and deformity rates increased significantly, but egg mortality did not. We found a significant negative relationship between genetic diversity and egg mortality, larval mortality, and deformity rates. Furthermore, the interaction between UV-B treatment and genetic diversity significantly affected larval mortality. Populations with low genetic diversity experienced higher larval mortality rates when exposed to UV-B than did populations with high genetic diversity. This is the first time an interaction between genetic diversity and an environmental stressor has been documented in amphibians. Differences in genetic diversity among populations, coupled with environmental stressors, may help explain patterns of amphibian decline. 相似文献
85.
Trisorny 18 mosaicism was found in multiple primary cultures of amniotic fluid cells and subsequently confirmed by chromosome analysis of several tissues derived from the aborted fetus. The overall frequency of the minority cell line was 25 per cent in the amniotic fluid cultures and 28 per cent in the fetal tissues although much intertissue variations were noted. 相似文献
86.
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88.
J. A. Brink JR. B. B. crocker 《Journal of the Air & Waste Management Association (1995)》2013,63(11):449-454
“Rules of thumb” for stack design have been developed for use on problems where extensive studies cannot be justified or where quantitative design data are unavailable. The application of these rules to a practical stack design problem is discussed. The IBM 704 computer has been used for rapid yet rigorous stack design studies. The computer procedures for design are discussed and its application to a practical problem is described in detail. 相似文献
89.
There has been a recent increase in the use of silver nanoparticles (Ag NPs) in a wide range of consumer products due to their highly effective antimicrobial properties. However, Ag NPs give cause for concern since their wide use makes them likely to be released into aquatic ecosystems and potentially affect natural bacterial communities. In this study marine biofilms were grown in situ in a coastal site (Singapore Harbour) and exposed in the laboratory for a further 24 h to 0-2000 μg L−1 of well characterised Ag NPs. Increasing concentrations of Ag NPs caused a significant decrease in biofilm volume and biomass, and Ag uptake by biofilms per unit of volume was also dependent on concentration. Terminal fragment length polymorphisms and subsequent cluster and phylogenetic analysis showed the presence of major bacterial groups in biofilms irrespective of treatment with Ag NPs. This implies that even at the highest concentrations studied these taxonomic groups were not displaced. Nevertheless, biofilm succession was impeded on Ag NP treated biofilms, affecting the relative abundance of major bacterial groups in the biofilm community, with potential longer term effects on biofilm development and function. 相似文献