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71.
The deep, ultraoligotrophic piedmont lakes of Northern Patagonia (Argentina) are located in pristine and barely impacted areas, along a wide latitudinal range. Several studies have reported moderate to high total mercury (Hg) concentrations and contrasting methylmercury (CH3Hg+) production in different lake compartments. Sources of Hg for western Patagonian terrestrial and aquatic ecosystems are still not clear; while point sources can be ruled out and atmospheric deposition is a plausible source, along with contribution from active volcanic areas of the Andes. In this investigation, we reported a noticeably seasonal, spatial (between lake branches), and vertical (between water column strata) heterogeneity in the total Hg concentrations found in the pelagic zone of Lake Moreno. Sterile water samples taken in a depth profile of the lake showed moderate to high concentrations of CH3Hg+ in autumn with a decreasing trend with depth. Our results indicated that Hg is largely allocated in the plankton fraction between 10–53 μm; which dominated within the euphotic (epilimnetic) zone of the lake due to the high densities attained by two species of the dinoflagellate Gymnodinium. The 53–200 μm planktonic size fraction (comprising rotifers, ciliates and immature stages of crustaceans) and the 200 μm fraction (calanoid copepods and cladocerans) were found to bear strikingly lower total Hg concentrations, suggesting that the magnification of Hg at the planktonic consumer level is negligible. 相似文献
72.
Mar′?a Arrib′ere Mar′?a C Di′eguez Sergio Ribeiro Guevar Claudia P Queimali?nos Vesna Fajon Mariana Reissig Milena Horvat 《环境科学学报(英文版)》2010,22(8):1171-1178
The deep, ultraoligotrophic piedmont lakes of Northern Patagonia (Argentina) are located in pristine and barely impacted areas,
along a wide latitudinal range. Several studies have reported moderate to high total mercury (Hg) concentrations and contrasting
methylmercury (CH3Hg+) production in di erent lake compartments. Sources of Hg for western Patagonian terrestrial and aquatic
ecosystems are still not clear; while point sources can be ruled out and atmospheric deposition is a plausible source, along with
contribution from active volcanic areas of the Andes. In this investigation, we reported a noticeably seasonal, spatial (between lake
branches), and vertical (between water column strata) heterogeneity in the total Hg concentrations found in the pelagic zone of Lake
Moreno. Sterile water samples taken in a depth profile of the lake showed moderate to high concentrations of CH3Hg+ in autumn with
a decreasing trend with depth. Our results indicated that Hg is largely allocated in the plankton fraction between 10–53 m; which
dominated within the euphotic (epilimnetic) zone of the lake due to the high densities attained by two species of the dinoflagellate
Gymnodinium. The 53–200 m planktonic size fraction (comprising rotifers, ciliates and immature stages of crustaceans) and the > 200
m fraction (calanoid copepods and cladocerans) were found to bear strikingly lower total Hg concentrations, suggesting that the
magnification of Hg at the planktonic consumer level is negligible. 相似文献
73.
74.
Luo Ai-Min Li Wan-Chun Wu Zong-Zhi 《Journal of Loss Prevention in the Process Industries》2008,21(6):642-645
The relative importance of the vapor cloud explosion (VCE) hazard has grown in recent years. Many of large disasters were attributed to the VCE. This article introduced an explosion accident of solvent vapor in a ring partition of floating roof in detail. Source of explosive materials and ignition reason were analyzed, and the blast equivalency in ring partition was estimated in the specific conditions. The case would provide a reference for preventing the similar accident. 相似文献
75.
人工浮岛在丁香湖水质改善中的应用 总被引:1,自引:0,他引:1
针对丁香湖水体恶化产生蓝藻的问题,在湖中设置人工浮岛对水质进行改善,浮岛植物以凤眼莲为主,辅以美人蕉等搭配.人工浮岛运行后,对水体中TN、TP指标净化效果良好,TN的去除率为48.1%~52.1%,TP的去除率为55.0%~64.4%,而且具有一定的景观效果. 相似文献
76.
77.
叙述了RF内星轮塑性变形的工艺分析,提出了RF内星轮制造的(闭式)精密温锻工艺,阐明了新技术取代旧工艺的优点. 相似文献
78.
79.
80.
From 1935 to 2000, the net open water area of Inle Lake in Central Shan State, Myanmar decreased from 69.10 to 46.69 km2, a loss of 32.4% during this 65-year period. Local beliefs are that losses in lake area have been even greater within the
last 100–200 years. Various activities, including timber removal, shifting agriculture in the uplands by various ethnic groups,
and unsustainable cultivation practices on the low- and mid-level hillslopes around the lake, have been blamed for both historical
and ongoing sedimentation. We take issue with attributing loss of lake area to these activities, and propose instead that
ongoing “in-lake” and “near-lake” agricultural practices are the main sources of contemporary sediment and loss of open water
area. About 93% (i.e., 20.84 km2) of the recent loss in open water area of the lake is due to the development of floating garden agriculture, largely along
the west side of the lake. Direct environmental impacts associated with this practice and with other agriculture activities
within the wetlands and margins of the lake include sedimentation, eutrophication, and pollution. Whilst the sustainability
of hillslope agriculture and past forestry practices can indeed be questioned, a more urgent need is to address these "in-lake"
and "near-lake" practices. 相似文献