An evaluation of in situ microcosms for validating aquatic fate and transport models

The fates of two compounds, 2,4 Dichlorophenoxy Acetic Acid Butoxyethyl Ester (2,4-DBEE) and 1,4 Dichlorobenzene (1,4-DCB), were examined in in situ microcosms placed in a pond and compared with the fates in the pond itself. Results also were compared with predictions of an aquatic fate and transport model (EXAMS). Decay rates of 2,4-DBEE were not significantly different among the microcosms, pond and model predictions. The decay rate of 1,4-DCB in the microcosms was significantly lower than the rate for the pond, and lower than the rate predicted by the model. The low volatility of 1,4-DCB in the microcosms is attributed primarily to lack of water surface turbulence in the microcosms.     

城郊旅游的潜在市场特征及产品开发--以合肥市为例

城市郊区已成为旅游的热点区域,合肥市对行政区域进行划分后,正着手大力开发城郊旅游.为了使合肥城郊旅游业的发展更具科学性,在实地调查基础上,分析了合肥城郊旅游潜在的市场特征,得出其城郊旅游开发市场潜力巨大;在分析外来旅游者及市民的城郊旅游意向基础上探讨了合肥城郊旅游产品开发,认为新城郊区旅游功能可定位为水上休闲度假娱乐中心和生态农业观光园区;最后提出合肥城郊旅游科学开发的几点建议.     

VOC Emission Controls for Can End Sealing Compounds

Regulations require that emissions of VOC from the application of can end sealing compounds be limited to 440 grams per liter. One can manufacturer has investigated the cost and feasibility of a VOC capture/control system and the availability and efficacy of water-based and high solids end sealing compounds. After characterizing and optimizing VOC evaporation rates, a prototype VOC containment system was tested on one can end sealing compound line. An 83 percent VOC capture efficiency was obtained at approximately 950 acfm. A cost analysis for a full facility capture and control system gave cost-effectiveness values of $1.21 to $2.36 per pound of VOC controlled. An evaluation oflow-VOC end sealing compounds, including long term pack tests, produced a water-based compound that could be implemented on pet food can ends by early 1986. Continuation of pack tests could allow full facility conversion to zero VOC water-based compounds by mid- to late-1987. Using an innovative averaging technique, the can manufacturer has achieved equivalent compliance with the 440 grams per liter standard.     

TREE RING RECONSTRUCTIONS OF STREAMFLOW FOR THREE CANADIAN PRAIRIE RIVERS1

ABSTRACT: Information regarding long term hydrological variability is critical for the effective management of surface water resources. In the Canadian Prairie region, growing dependence on major river systems for irrigation and other consumptive uses has resulted in an increasing vulnerability to hydrological drought and growing interprovincial tension. This study presents the first dendrochronological records of streamflow for Canadian Prairie rivers. We present 1,113‐year, 522‐year, and 325‐year reconstructions of total water year (October to September) streamflow for the North Saskatchewan, South Saskatchewan, and Saskatchewan Rivers, respectively. The reconstructions indicate relatively high flows during the 20th Century and provide evidence of past prolonged droughts. Low flows during the 1840s correspond with aridity that extended over much of the western United States. Similarly, an exceptional period of prolonged low flow conditions, approximately 900 A.D. to 1300 A.D., is coincident with evidence of sustained drought across central and western North America. The 16th Century megadrought of the western United States and Mexico, however, does not appear to have had a major impact on the Canadian rivers. The dendrohydrological records illustrate the risks involved if future water policy and infrastructure development in the Canadian Prairies are based solely on records of streamflow variability over the historical record.     

Flash kinetics and spatial patterns of bioluminescence in the copepodGaussia princeps

Kinetics and local spatial patterns of bioluminescence in the mesopelagic copepodGaussia princeps (T. Scott), collected by net off the coast of southern California, USA, were investigated from 1986 to 1989. Luminescence elicited by single electrical stimuli began as a localized secretion from any of 16 widely distributed sites on the body. Appendage or body movements swept the particulate luminescent exudate away from the cuticle. Three types of single flashes were identified in response to single electrical stimuli, including a fast flash of ca. 2 s duration, a long flash of 7 s duration, and a 17 s slow flash. In addition, in 20% of the tests a fourth, two-component flash consisting of a fast or long component followed by a slow component was elicited. Frequency of the four flash types was dependent on the recovery time after collection. Shorter, less intense fast and long flashes occurred early in the recovery period, and longer, brighter slow and compound flashes became more common as recovery progressed. The laboratory handling protocol strongly affected total stimulable light (TSL). Strong handling resulted in a reduced TSL, which recovered to the original level upon termination of the stimulation. TSL and flash kinetics in the laboratory were highly dependent on the chronic laboratory stimulation protocol and represent an equilibrium between recovery of luminous reserves and re-stimulation. Flash kinetics and TSL were also affected by the frequency of stimulation. Higher stimulation rates resulted in greater temporal summation of the flashes, a decreased response duration, and a lower TSL. Stimulus frequency and duration therefore determine the nature of the bioluminescent response. Flash kinetics and TSL made with either in situ bathyphotometric measurements of laboratory measurements strongly depend on the extent of prestimulation, depletion of bioluminescent reserves, and the level of stimulation inherent with the particular device.     

Bioluminescence spectra of shallow and deep-sea gelatinous zooplankton: ctenophores, medusae and siphonophores

We have examined the variability and potential adaptive significance of the wavelengths of light produced by gelatinous zooplankton. Bioluminescence spectra were measured from 100 species of planktonic cnidarians and ctenophores collected between 1 and 3500 m depth. Species averages of maximal wavelengths for all groups ranged from 440 to 506 nm. Ctenophores (41 species) had characteristically longer wavelengths than medusae (34 species), and the wavelengths from siphonophores (25 species) had a bimodal distribution across species. Four species each produced two different wavelengths of light, and in the siphonophore Abylopsistetragona these differences were associated with specific body regions. Light from deep-dwelling species had significantly shorter wavelengths than light from shallow species in both ctenophores (p = 0.010) and medusae (p = 0.009). Although light production in these organisms was limited to the blue-green wavelengths, it appears that within this range, colors are well-adapted to the particular environment which the species inhabit. Received: 27 April 1998 / Accepted: 27 October 1998     

Spectral composition of bioluminescence of epipelagic organisms from the Sargasso Sea

The spectral characteristics of single identified epipelagic sources of bioluminescence from the western Sargasso Sea were measured with an optical multichannel analyzer (OMA) system during the April, 1985, Biowatt cruise. The emission spectra of specimens representing 45 species from 8 phyla were measured. Peak bioluminescence emissions typically occurred between 440 and 500 nm, in the blue region of the visible spectrum. Three exceptions involved emission in the green, yellow, and red spectral regions. Intraspectific variability in spectra, was noted in several species. One shrimp species exhibited two modes of light emission, each with different emission spectra. Other cases involved dynamic color shifts of 10 to 14 nm; the source of the spectral variability is unknown, but may involve optical filtering or differences in the color of luminescence from multiple sites of light emission. Measurements from independent samples of unsorted plankton revealed different spectral distributions. This suggests that the spectral emissions of bioluminescence in the upper water column will vary, based on species assemblage.     

Draining us dry: scarcity discourses in contention over bottled water extraction

Water scarcity is a highly contested concept. The dominant narratives of water scarcity in policy debates have been criticised for prioritising purely quantitative metrics and eliding questions of inequality and power. While much scholarship on water scarcity examines contexts in the global South where potable water infrastructures do not reach most residents, this article examines conflict over commercial water extraction in a Northern setting where access to potable tap water is nearly universal, yet local water supplies are increasingly constrained. It addresses three main questions: (1) How are narratives or discourses of water scarcity mobilised by a range of actors in local conflicts over groundwater extraction for water bottling?; (2) To what extent do these discourses invoke biophysical versus socially produced scarcity, current versus future scarcity, and local versus regional or global scales of scarcity?; and (3) What are the implications of the findings for efforts by environmental advocates and communities to protect local water supplies? We explore these questions by analysing a local case study of conflict over groundwater extraction by the leading bottled water firm, Nestlé Waters, in southwestern Ontario, Canada. We find that the scarcity narratives deployed by local residents, activists, public officials, and bottling industry representatives illustrate the use of several forms of figurative conflation involving geographic and temporal scales of water scarcity, and economic and volumetric forms of scarcity. We argue that this conflation illuminates deeper issues of economic and social justice at the heart of the conflict, which transcend reductionist hydrological assessments of scarcity or abundance.     

Temporal adaptations in visual systems of deep-sea crustaceans

The temporal characteristics of the visual systems of deep-sea crustaceans were examined at varying light levels. Experimental organisms were collected off Hawaii and southern California in 1991 and 1992, and continually maintained in the dark. At the University of California Santa Barbara Marine Laboratory, the temporal components of both visual interneuron activity and electroretinograms (ERGs) of adult Gnathophausia ingens were tested at threshold and with background light levels up to 6 log units above threshold. To compare these responses with those of mid-water organisms inhabiting shallower depths, the temporal characteristics of the ERGs of Oplophorus spinosus and juvenile G. ingens were assessed. Adults of both species showed little or no change in the time components of their responses when light-adapted, except for the response latency. There was also no evidence of a circadian rhythm in visual sensitivity. O. spinosus, a vertical migrator, and juvenile G. ingens, which inhabit a shallower depth than the adults, exhibited more rapid responses than adult G. ingens. These varying responses are considered adaptations to the differences in light levels at the characteristic depths of the organisms.