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71.
72.
A study was conducted to quantitatively screen the Inner Harbor Navigation Canal of Lake Pontchartrain for the presence of EPA priority pollutants and any other pollutants detected in significant concentration. Water column samples were collected at different depths and on the flood and ebb tides. Compounds identified include aliphatic and aromatic hydrocarbons, phthlates, phenols, alcohols, amines, pesticides, herbicides, aldehydes, quinolines, fatty acids, carboxylic acids. These compounds were detected at the parts-per-trillion level. The concentrations of the individual organics detected on the flood and ebb tides were not significantly different. The data derived from samples taken at two different depths suggest that the distribution of organics in the water column was homogeneous. 相似文献
73.
A. Ann Sorensen Tana M. Busch S. Bradleigh Vinson 《Behavioral ecology and sociobiology》1985,17(3):191-198
Summary Temporal subcastes in the fire ant, Solenopsis invicta Buren were selectively starved to determine if foragers could assess the nutritional status of their nestmates and respond accordingly. We found that starved foragers increase the honey entering the colony (Fig. 1). When nurses are starved more oil and liquid egg yolk enters the colony (Figs. 2, 3) and when both reserves and nurses are starved, more egg yolk powder is brought in by the foragers (Fig. 4). When queens are starved, more liquid egg yolk and oil enters the colony (Figs. 2, 3). Starved larvae increase the oil in the colony (Fig. 2) and when held with nurses for 24h before feeding, increase the egg yolk powder brought in and receive significantly more of it than other subcaste members (Fig. 5). We conclude that foragers can respond to the nutritional needs of their nestmates. Based on our behavioural observations, the quantity of food brought in by the foragers is regulated via discriminatory solicitation by reserves in response to the nutritional needs of the nurses. 相似文献
74.
Overview of case studies on recovery of aquatic systems from disturbance 总被引:13,自引:2,他引:13
Gerald J. Niemi Philip DeVore Naomi Detenbeck Debra Taylor Ann Lima John Pastor J. David Yount Robert J. Naiman 《Environmental management》1990,14(5):571-587
An extensive review of the published literature identified more than 150 case studies in which some aspect of resilience in
freshwater systems was reported. Approximately 79% of systems studied were lotic and the remainder lentic. Most of the stressor
types were chemical with DDT (N=29) and rotenone (N=15) the most common. The most common nonchemical stressors were logging
activity (N=16), flooding (N=8), dredging (N=3), and drought (N=7).
The variety of endpoints to which recovery could be measured ranged from sparse data for phytoplankton (N=13), periphyton
(N=6), and macrophytes (N=8) to relatively more data for fish (N=412) and macroinvertebrates (N=698). Unfortunately the same
characteristics were rarely measured consistently among sites. For example, with respect to fish, more than 30 different species
were studied and recovery was measured in many ways, most commonly on the basis of: (1) first reappearance of the species,
(2) return time of predisturbance densities, and (3) return time of predisturbance average individual size. Based on these
criteria, all systems in these studies seem to be resilient to most disturbances with most recovery times being less than
three years. Exceptions included when (1) the disturbance resulted in physical alteration of the existing habitat, (2) residual
pollutants remained in the system, or (3) the system was isolated and recolonization was suppressed. 相似文献
75.
William F. Schillinger Ann C. Kennedy Douglas L. Young 《Agriculture, ecosystems & environment》2007,120(2-4):345-358
The tillage-based winter wheat (Triticum aestivum L.)-summer fallow (WW-SF) cropping system has dominated dryland farming in the Pacific Northwest USA for 125 years. We conducted a large-scale multidisciplinary 8-year study of annual (i.e., no summer fallow) no-till cropping systems as an alternative to WW-SF. Soft white and hard white classes of winter and spring wheat, spring barley (Hordeum vulgare L.), yellow mustard (Brassica hirta Moench), and safflower (Carthamus tinctorius L.) were grown in various rotation combinations. Annual precipitation was less than the long-term average of 301 mm in 7 out of 8 years. Rhizoctonia bare patch disease caused by the fungus Rhizoctonia solani AG-8 appeared in year 3 and continued through year 8 in all no-till plots. All crops were susceptible to rhizoctonia, but bare patch area in wheat was reduced, and grain yield increased, when wheat was grown in rotation with barley every other year. Remnant downy brome (Bromus tectorum L.) weed seeds remained dormant for 6 years and longer to heavily infest recrop winter wheat. There were few quantifiable changes in soil quality due to crop rotation, but soil organic carbon (SOC) increased in the surface 0–5 cm depth with no-till during the 8 years to approach that found in undisturbed native soil. Annual no-till crop rotations experienced lower average profitability and greater income variability compared to WW-SF. Yellow mustard and safflower were not economically viable. Continuous annual cropping using no-till provides excellent protection against wind erosion and shows potential to increase soil quality, but the practice involves high economic risk compared to WW-SF. This paper provides the first comprehensive multidisciplinary report of long-term alternative annual no-till cropping systems research in the low-precipitation region of the Pacific Northwest. 相似文献
76.
George I. Solish Hugo W. Moser Laura D. Ringer Ann E. Moser Carol Tiffany Edward Schutta 《黑龙江环境通报》1985,5(1):27-34
The prenatal diagnosis of the cerebro-hepato-renal syndrome of Zellweger (CHRS) was made by assaying the levels of very long chain fatty acids (VLCFAs) in amniotic fluid cell cultures, obtained by amniocentesis at 16 1/2 weeks of pregnancy. The family-at-risk, because they had previously borne a child with CHRS, accepted these results as indications of an affected fetus, and chose to terminate the pregnancy at 20 1/2 weeks of gestation. The diagnosis was confirned by the phenotype of the aborted fetus and the presence of markedly elevated levels of VLCFAs in fetal liver homogenates. The prenatal diagnosis of CHRS, which can now readily be determined from amniotic fluid cell cultures, is an important step in genetic counselling of families-at-risk for this disease. 相似文献
77.
A complex chromosome rearrangement, apparently a balanced translocation involving chromosomes 4,6, 15 and 16, was found in cultured cells of amniotic fluid from a 32–year-old primigravida who requested amniocentesis for prenatal diagnosis because of a family history of mental retardation. Chromosome analysis of peripheral blood from both parents were normal. The couple was counselled for the prenatal diagnosis of this de novo complex translocation and, subsequently, elected to terminate the pregnancy. Post-mortem examination revealed a 23–week fetus with intrauterine growth retardation. The identical chromosome rearrangement was subsequently confirmed in cultured fibroblasts from skin and cord obtained from the abortus. To our knowledge, this is the first report where routine prenatal diagnosis revealed a fetus with a balanced complex chromosomal rearrangement involving four chromosomes of de novo origin. 相似文献
78.
应对不确定性:呼吁建立新的科学政策论坛 总被引:4,自引:1,他引:4
Ann Kinzig David starrett Kenneth Arrow Sara Aniyar Bert Bolin Partha Dasgupta Paul Ehrlich Carl Folke Michael Hanemann Geoff Heal Michael Hoel AnnMari Jansson Bengt-Owe Jansson Nils Kautsky Simon Levin Jane Lubchenco Karl-Gran Miler Stephen W.Pacala Stephen H.Schneider Domenico Siniscalco Brian Walker 《Ambio-人类环境杂志》2003,32(5):330-335
科学界和政策界具有不同的目标,这就自然导致了对构成某种变化或现象的"检验"标准的差异,以及用不同的方法去描述不确定性和风险的持性及传达不确定性和风险.这些差异可能损害科学家、决策者和公众之间的有效沟通,同时也限制了科学家所愿意研究的社会紧迫问题的类型.本文主要回顾了一系列处理不确定性问题的方法,阐述了当科学和政策不能很好协调时所可能引起的一些错误.并在此基础上,特别针对解决不确定性问题提出了一些具体建议,包括重构科学规范,建立由科学、政策两方面领导广泛参加的科学政策论坛. 相似文献
79.
Persistence of carbofuran in marine sand and water 总被引:4,自引:0,他引:4
Marine sand and seawater samples were collected in March 2002 from Laysan Island in the Hawaiian Islands National Wildlife Refuge, where a small area was contaminated by the carbamate insecticide carbofuran. Carbofuran was still detected at microg g(-1) levels in the Laysan sand after its identification in 1998 and initial observation of the toxicity in 1988. The persistence of carbofuran in the marine sand was investigated in the dark in a 30 degrees C oven, and in distilled deionized water and seawater samples exposed to artificial 300 nm light and to direct sunlight. The laboratory study showed a half-life (t1/2) of approximately 40 days for carbofuran in the native sand and in Ottawa sand. The photolysis of carbofuran was faster in seawater than in distilled deionized water when it was exposed to 300 nm light (t1/2, 0.1 vs. 3.1 h) and to direct sunlight (t1/2, 7.5 vs. 41.6 h). The large difference between the laboratory results and the field observation of carbofuran dissipation suggests that carbofuran degradation at the remote, undisturbed marine site may be governed by its unique environmental factors. 相似文献
80.
Kinzig A Starrett D Arrow K Aniyar S Bolin B Dasgupta P Ehrlich P Folke C Hanemann M Heal G Hoel M Jansson A Jansson BO Kautsky N Levin S Lubchenco J Mäler KG Pacala SW Schneider SH Siniscalco D Walker B 《Ambio》2003,32(5):330-335
The scientific and policy worlds have different goals, which can lead to different standards for what constitutes "proof" of a change or phenomena, and different approaches for characterizing and conveying uncertainty and risk. These differences can compromise effective communication among scientists, policymakers, and the public, and constrain the types of socially compelling questions scientists are willing to address. In this paper, we review a set of approaches for dealing with uncertainty, and illustrate some of the errors that arise when science and policy fail to coordinate correctly. We offer a set of recommendations, including restructuring of science curricula and establishment of science-policy forums populated by leaders in both arenas, and specifically constituted to address problems of uncertainty. 相似文献