Distribution and fluxes of metals in the St. Lawrence River from the outflow of Lake Ontario to Québec City     

Ken R. Lum  K. L. E. Kaiser  C. Jaskot 《Aquatic Sciences - Research Across Boundaries》1991,53(1):1-19

Six anchor stations in the St. Lawrence River from the outflow of Lake Ontario to Quebec City, were occupied for ca. 24 hours in June 1987 during low flow conditions. Samples of water and suspended particulate matter were separated by continuous-flow centrifugation, and were collected every two hours.During this sampling period, fluxes of dissolved forms of zinc, copper and nickel increased in Lac St. François and downstream relative to the sum of the fluxes for the two upstream stations at the outflow of Lake Ontario. Increases in the flux of dissolved zinc and copper were pronounced below Montreal and above Lac St. Pierre. For particulate forms of metals, all five metals show that there are significant inputs in the section of the St. Lawrence River between Lac St. François and the station just above the entrance to Lac St. Pierre.The average concentrations of dissolved cadmium, lead, zinc, copper and nickel ranged from 7–23 ng/l; 9–35 ng/l; 0.434–0.939 g/l; 0.15–0.89 g/l and 0.58–1.12 g/l respectively.Regression analysis of the dissolved and particulate metal concentrations suggests that the concentration of dissolved cadmium, lead, zinc and nickel can be predicted from the regression equation and the determination of particulate metal concentration. This prediction appears to be independent of the suspended particulate matter concentration which varies from ca. 1 to 10 mg/l from the outflow of Lake Ontario to Québec City.  相似文献   

Wind-induced eddy motion in the lower St. Lawrence Estuary     

G. Mertz  V.G. Koutitonsky  Y. Gratton  M.I. El-Sabh 《Estuarine, Coastal and Shelf Science》1992,34(6)

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Radiocarbon redating of contaminated samples from a tropical volcano: the Mansion ‘Series’ of St Kitts,West Indies     

D. D. Harkness  M. J. Roobol  A. L. Smith  J. J. Stipp  P. E. Baker 《Bulletin of Volcanology》1994,56(5):326-334

Heavy rainfall and dense vegetation on tropical volcanoes produce abundant carbonized wood in pyroclastic deposits, in addition to easy contamination of this wood by root systems and soluble humic material. Because the physical nature of the charcoal varies, some samples are more prone to contamination. Two independent studies of the same volcano, Mt Liamuiga on St Kitts in the Lesser Antilles, sometimes using samples from the same carbonized tree, yielded a systematic difference in radiocarbon ages. An exchange of samples and a re-investigation of three physically distinct types of charcoal yielded the following results. Rare, hard, dense charcoal, lacking contamination, which had yielded a spurious age of 2860 years bp, was redated at 1845±58 years bp. Common soft, friable charcoal with good cellular structure proved to be susceptible to contamination. A field decontamination technique utilized by one group seems significant as it yields older ages than when only routine laboratory pre-treatment was used, indicating that the latter technique only partly removes the dried and hard residue produced by the decomposition of modern plant rootlets. A previous date of 24870 years bp obtained from powdery charcoal in a horizon beneath the Mansion Series contradicted ages older than 41000 years bp from common friable charcoal in the lower Mansion Series. The soft powdery charcoal was re-investigated using a sample collected a few centimeters from the original, although field decontamination of this sample was not possible, more extensive laboratory treatment yielded an age of ca. 43000 years bp, again proving that routine laboratory pretreatments are inadequate. A revised geochronology for the Mansion Series is described and a cautionary discussion is presented for the benefit of investigators using radiocarbon ages to date volcanic deposits.  相似文献   

Source parameters of microearthquakes at Mount St Helens (USA)   总被引：1，自引：0，他引：1  

Giuseppina Tusa  Alfonso Brancato  Stefano Gresta  Stephen D. Malone 《Geophysical Journal International》2006,166(3):1193-1223

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A late quaternary record of eolian silt deposition in a maar lake, St. Michael Island, western Alaska     

Daniel R Muhs  Thomas A AgerJosh Been  J.Platt BradburyWalter E Dean 《Quaternary Research》2003,60(1):110-122

Recent stratigraphic studies in central Alaska have yielded the unexpected finding that there is little evidence for full-glacial (late Wisconsin) loess deposition. Because the loess record of western Alaska is poorly exposed and not well known, we analyzed a core from Zagoskin Lake, a maar lake on St. Michael Island, to determine if a full-glacial eolian record could be found in that region. Particle size and geochemical data indicate that the mineral fraction of the lake sediments is not derived from the local basalt and is probably eolian. Silt deposition took place from at least the latter part of the mid-Wisconsin interstadial period through the Holocene, based on radiocarbon dating. Based on the locations of likely loess sources, eolian silt in western Alaska was probably deflated by northeasterly winds from glaciofluvial sediments. If last-glacial winds that deposited loess were indeed from the northeast, this reconstruction is in conflict with a model-derived reconstruction of paleowinds in Alaska. Mass accumulation rates in Zagoskin Lake were higher during the Pleistocene than during the Holocene. In addition, more eolian sediment is recorded in the lake sediments than as loess on the adjacent landscape. The thinner loess record on land may be due to the sparse, herb tundra vegetation that dominated the landscape in full-glacial time. Herb tundra would have been an inefficient loess trap compared to forest or even shrub tundra due to its low roughness height. The lack of abundant, full-glacial, eolian silt deposition in the loess stratigraphic record of central Alaska may be due, therefore, to a mimimal ability of the landscape to trap loess, rather than a lack of available eolian sediment.  相似文献   

Analysis of the interannual variability of annual daily extreme water levels in the St Lawrence River and Lake Ontario from 1918 to 2010          下载免费PDF全文

Ali A. Assani  Raphaëlle Landry  Stacey Biron  Jean‐Jacques Frenette 《水文研究》2014,28(13):4011-4022

We compared the interannual variability of annual daily maximum and minimum extreme water levels in Lake Ontario and the St Lawrence River (Sorel station) from 1918 to 2010, using several statistical tests. The interannual variability of annual daily maximum extreme water levels in Lake Ontario is characterized by a positive long‐term trend showing two shifts in mean (1929–1930 and 1942–1943) and a single shift in variance (in 1958–1959). In contrast, for the St Lawrence River, this interannual variability is characterized by a negative long‐term trend with a single shift in mean, which occurred in 1955–1956. As for annual daily minimum extreme water levels, their interannual variability shows no significant long‐term change in trend. However, for Lake Ontario, the interannual variability of these water levels shows two shifts in mean, which are synchronous with those for maximum water levels, and a single shift in variance, which occurred in 1965–1966. These changes in trend and stationarity (mean and variance) are thought to be due to factors both climatic (the Great Drought of the 1930s) and human (digging of the Seaway and construction of several dams and locks during the 1950s). Despite this change in means and variance, the four series are clearly described by the generalized extreme value distribution. Finally, annual daily maximum and minimum extreme water levels in the St Lawrence and Lake Ontario are negatively correlated with Atlantic multidecadal oscillation over the period from 1918 to 2010. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Fairtrade bananas in the Caribbean: Towards a moral economy of recognition     

《Geoforum》2016

Working through a Caribbean case study, this paper examines the networks and associations of Fair Trade bananas as they move both materially and morally from farms in St Vincent and the Grenadines to supermarkets and households in the United Kingdom. In doing so, the paper provides grounded empirical evidence of Fair Trade’s moral economy as experienced by banana producers in the Caribbean. The paper follows Nancy Fraser’s distinction between ways of framing justice to argue that, in order to transcend its complex postcolonial positionalities, the Fair Trade Foundation needs to include recognition in its moral economy as well as representation and redistribution. The paper compares the moral framework of Fair Trade as an ideology and social movement with the lived experience of certified Fairtrade banana farmers in the Windward Islands who work mostly for, rather than within, an idealized moral economy. The paper also contributes to several recent debates in the agri-food literature exploring the interconnections between production and consumption, the role of materiality in contemporary food networks, the historical and (post)colonial nature of food moralities, and links between political and moral economies of food. Following an outline of recent debates about the moral economies of food and its relation to Fair Trade as a movement, the paper dissects the moral economy of the Fairtrade Foundation, highlighting the historical and geographical, material and symbolic, gendered and generational ways that food producers in the Global South (in this case, banana farmers in St Vincent and the Grenadines) may be counterposed to ‘responsible’ consumers in the Global North. Despite the good intentions of those who promote the Fair Trade movement through the Fairtrade Foundation and the Fairtrade Labelling Organisation (FLO), our case study reveals a moral economy of non- (or partial) recognition, which has a range of unintended consequences and paradoxical effects.  相似文献   

Remeasurement of weathering rates,St. Paul's Cathedral,London     

S. T. Trudgill  H. A. Viles  R. J. Inkpen  R. U. Cooke 《地球表面变化过程与地形》1989,14(3):175-196

Remeasurements of weathering rates at six sites on the base of the balustrade of St. Paul's Cathedral gave substantially lower mean results (0.06 mm a^?1, 1980–1985) than for earlier results (0.14 mm a^?1, 1980–1981). Statistical analysis of the data showed that for five of the sites there were no significant differences between the measurement periods. The only significant spatial difference was for the southwest (exposed) site which was greater than the other sites for 1980–1981, but not at later times. This site also showed the only significant decrease over time. If this site is included in the statistical analysis, the whole set shows a significant decrease over time; omitting this site from the data removes any significant differences over time. The results for this one site for 1980–1981 thus have significant bias on the data body as a whole. Methodological problems, such as rock erosion by the probe and temperature effects, are thought to have minimal effect on the interpretation of the data. Calibrations showed that measurements were accurate to ±0.006 mm and that only results of a change ≥ 0.02 mm were reliably interpretable as different. Remeasurements of the Lead Plug Index (LPI) for the top of the balustrade in 1987 gave a mean rate for 1718–1985 of 0.081 mm a^?1. This is not significantly different from the 1718–1980 mean rate of 0.078 mm a^?1 but the data are not directly comparable, the 1987 sample being smaller than the 1980 set. For the 1987 data, the only statistically significant differences are for the southeast rate ≧ northeast and for a rise in rate in the northeast quadrant. The LPI data are comparable to most of the 1980–1985 MEM data. The conclusion is that most erosion rates have neither increased nor decreased significantly in the measurement time, except for a significant decrease at one (southwest) site from 1980–1981 to 1981–1982. Such a sustained level of erosion gives cause for concern in the context of stone conservation. Causative factors of air quality are discussed and while SO₂ levels have decreased, NO₂ and smoke levels show increases. An overall decrease in stone decay in association with the decrease in SO₂ levels is thus not in evidence.  相似文献   

St. Vincent and the Grenadines     

Mills AP 《Marine pollution bulletin》2001,42(12):1208-1220

Saint Vincent and the Grenadines conjures up images of a yachting haven and a quiet tourists' paradise. The conflicting demands of a growing population, a middle-income economy dominated by fishing, plantation agriculture and tourism, and environmental and social concerns, all contribute to marine stress on the limited, precious, but internationally important resources. While the vision exists to manage effectively coastal and offshore resources, the institutional, financial and social capital to achieve that vision is limited. Development of the fledgling partnerships between local communities, national governmental structures and the international research, government and donor organisations seems the best hope to conserve the environment and coastal livelihoods of the islands.  相似文献   

Suspended sediment load transport in the Mississippi River basin at St. Louis: temporal scaling and nonlinear determinism     

Bellie Sivakumar  Ji Chen 《地球表面变化过程与地形》2007,32(2):269-280

This study investigates the dynamic behavior of suspended sediment load transport at different temporal scales in the Mississippi River basin. Data corresponding to five successively doubled temporal scales (i.e. daily, two‐day, four‐day, eight‐day and 16‐day) from the St. Louis gaging station in Missouri are analyzed. The investigation is focused on identifying possible low‐dimensional deterministic behavior in the suspended sediment load transport dynamics, with an aim towards reduction in model complexity. The correlation dimension method is used to identify low‐dimensional determinism. The suspended sediment load dynamics are represented through phase‐space reconstruction, and the variability is estimated using the (proximity of) reconstructed vectors in the phase space. The results indicate the presence of low‐dimensional determinism in the suspended sediment load series at each of the five temporal scales, with the variables dominantly governing the dynamics in the order of three or four. These results not only suggest the appropriateness of relatively simpler models but also hint at possible scale invariance in the suspended sediment load transport dynamics. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献