| Study of Dissolved Chlorofluorocarbons in Lake Washington |
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| 作者姓名： | 韩丽君 |
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| 作者单位： | [1]InstituteofOceanology,ChianeseAcademyofSciences,Qingdao266071,China [2]NationalOceanicandAtmosphericAdministrationPacificMarineEnvironmentalLaboratory,SeattleWA98115,USA |
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| 基金项目： | ContributionNo.4 5 0 9fromInstituteofOceanology,ChineseAcademyofSciences. Project 2 0 0 1AA62 0 5 0 3supportedbyHTRDPC . |
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| 摘 要： | Measurements of three chlorofluorocarbons(CFCs) :trichlorofluoromethane (CFC-11),dichlorodifluoromethane (CFC-12) and trichlorotrifluoroethane (CFC-113), along with methyl chloroform (CH3CCl3) and carbon tetrachloride (CCl4) were made in water samples from Lake Washington,using Electron Capture-Gas Chromatography (EC-GC).The samples were collected in mid-autumn, a period when the lake‘‘‘‘‘‘‘‘s upper layer undergoes rapid cooling,At the time of sam-pling,a strong vertical temperature gradient was present in the lake,with surface temperatures of -14℃,and near bottom(50 meters) temperatures of -8℃ ,The concentrations of dissolved CFC-12 and CFC-11 increased with depht ,as expected from the higher solubilities of these gases at lower temperatures ,Atmospheric measurements made at the sampling site at the time of the cruise ,showed that CFC-11 and CFC-12 saturations in the near surface samples were 100% and 106%,respectively,For the deepest sample (52 meters)CFC-11 and CFC-12 saturations were 102% and 126%,Because the surface layer of the lake respondes to changes in atmospheric CFCs on a time scale of several weeks ,the highere than equilibrium concentrations of CFC-12 observed at the time of sampling may reflect earlier episodes of elevated levels of atmospheric CFC-12 in this urban area.High concentrations of dissolved CFCs in runoff or industrial effluent might also lead to elevated CFC levels in the lake. The cold ,deep water of Lake Wahington is realtively isolated from the effects of surface gas exchange except during winter ,and the supersaturations observed in the deep layer may reflect pe-riods of elevated atmospheric CFC-12 levels from the previous winter season.These results were compared to summertime profiles of CFC-11 and CFC-12 made in 1994.
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| 关 键 词： | 氯氟碳化物 二氯二氟甲烷 三氯氟甲烷 三氯三氟代乙烷 华盛顿湖 电子俘获气相色谱法 溶解度 饱和度 |
| 收稿时间： | 10 October 2001 |
| 修稿时间： | 5 April 2002 |
Study of dissolved chlorofluorocarbons in Lake Washington |
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| Han?Lijun,John?L.?Bullister,David?P.?Wisegarver.Study of Dissolved Chlorofluorocarbons in Lake Washington[J].Chinese Journal of Oceanology and Limnology,2003,21(2):171-179. |
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| Authors: | Han Lijun John L Bullister David P Wisegarver |
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| Institution: | (1) Institute of Oceanology, Chinese Academy of Sciences, 266071 Qingdao, China;(2) National Oceanic and Atmospheric Administration Pacific Marine Environmental Laboratory, 98115 Seattle, WA, USA |
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| Abstract: | Measurements of three chlorofluorocarbons (CFCs): trichlorofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12) and trichlorotrifluoroethane
(CFC-113), along with methyl chloroform (CH3CCl3) and carbon tetrachloride (CCl4) were made in water samples from Lake Washington, using Electron Capture-Gas Chromatography (EC-GC). The samples were collected
in mid-autumn, a period when the lake's upper layer undergoes rapid cooling. At the time of sampling, a strong vertical temperature
gradient was present in the lake, with surface temperatures of ∼14°C, and near bottom (50 meters) temperatures of ∼8°C. The
concentrations of dissolved CFC-12 and CFC-11 increased with depth, as expected from the higher solubilities of these gases
at lower temperatures. Atmospheric measurements made at the sampling site at the time of the cruise, showed that CFC-11 and
CFC-12 saturations in the near surface samples were 100 % and 106 %, respectively. For the deepest sample (52 meters) CFC-11
and CFC-12 saturations were 102 % and 126 %. Because the surface layer of the lake responds to changes in atmospheric CFCs
on a time scale of several weeks, the higher than equilibrium concentrations of CFC-12 observed at the time of sampling may
reflect earlier episodes of elevated levels of atmospheric CFC-12 in this urban area. High concentrations of dissolved CFCs
in runoff or industrial effluent might also lead to elevated CFC levels in the lake.
The cold, deep water of Lake Washington is relatively isolated from the effects of surface gas exchange except during winter,
and the supersaturations observed in the deep layer may reflect periods of elevated atmospheric CFC-12 levels from the previous
winter season. These results were compared to summertime profiles of CFC-11 and CFC-12 made in 1994.
Contribution No. 4509 from Institute of Oceanology, Chinese Academy of Sciences.
Project 2001 AA620503 supported by HTRDPC. |
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| Keywords: | chlorofluorocarbons(CFCs) solubilities saturations Electron Capture-Gas Chromatography (EC-GC) |
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