The 4.45 m-thick pure ice lens have been discovered firstly at depth from 19.81 -24.26 m in the bore No.6, which locates in north bank of the Ngoring Lake. In source region of the Huanghe (Yellow) River, 14C dating, X...The 4.45 m-thick pure ice lens have been discovered firstly at depth from 19.81 -24.26 m in the bore No.6, which locates in north bank of the Ngoring Lake. In source region of the Huanghe (Yellow) River, 14C dating, X -ray diffraction, pollen analysis, micropalaeontology, chemical components, environmental isotope 2H, 3H, 18O and freezing point of the ice and water samples from the bore have been tested and microorganism in the ice have been also appraised with microscope. Combined with the research on geomorphy and Quaternary around the lake, the ice lens are determined as a kind of deep-buried lake ice, formed in 35,030-45,209 yr.B.P., and annual mean air temperature was about -10℃ during that time.展开更多
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 me...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.展开更多
An integrated satellite precipitation estimation dataset, namely, the Climate Prediction Center morphing method (CMORPH), was used to analyze precipitation regimes across Equatorial Africa between 3<span style=&quo...An integrated satellite precipitation estimation dataset, namely, the Climate Prediction Center morphing method (CMORPH), was used to analyze precipitation regimes across Equatorial Africa between 3<span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"="">°</span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">S - 1</span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"=""><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"="">°</span></span></span><span style="font-family:Verdana;">N and 24</span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"=""><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"="">°</span></span></span><span style="font-family:Verdana;">E - 42</span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"=""><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"="">°</span></span></span><span style="font-family:Verdana;">E from 2000 to 2014. This region includes the Rift Valley, part of the Congo Forest, and the Lake Victoria (LV) basin, the second largest lake in the area of the world. Hovm<span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"=""><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">ö</span></span>ller diagrams were obtained for all organized convective systems to estimate their spans, duration, and phase speeds. The analysis included 33,189 episodes of westward propagating convective systems. Within the study area, lake and land breezes tend to trigger convection and precipitation over LV as well as mountain-valley circulation trigger thunderstorms over the mountains east of LV and western Rift Valley. The statistics of convective systems streaks on longitude-time diagrams were obtained for yearly frequencies of starting and ending longitudes and times among other morphologic variables. Results indicate organized precipitation episodes tend to move westward across Rift valley and Congo forest with an average phase speed of 10.3 <span style="white-space:normal;font-family:Verdana;">m<span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#f7f7f7;"="">·</span>s</span><sup style="white-space:normal;"><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;background-color:#f7f7f7;"=""><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span></span></span><span style="font-family:Verdana;">1</span></sup></span><sup><span style="font-family:Verdana;"></span></sup><span style="font-family:Verdana;">. More than 50% of them are triggered over LV and propagate more than 600 km at an average phase speed of 12.1 m<span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#f7f7f7;"="">·</span>s</span><sup><span style="font-family:Verdana;"><span style="white-space:normal;color:#4F4F4F;font-family:-apple-system, " font-size:16px;background-color:#f7f7f7;"=""><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span></span><span style="font-family:Verdana;white-space:normal;"></span></span><span style="font-family:Verdana;">1</span></sup><span style="font-family:Verdana;">. These convective systems tend to produce high rainfall rates hundreds of kilometers away into the Congo Forest. Half of all episodes of organized convection analyzed have phase speeds between 8 <span style="white-space:normal;font-family:Verdana;">m<span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#f7f7f7;"="">·</span>s</span><sup style="white-space:normal;"><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;background-color:#f7f7f7;"=""><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span></span></span><span style="font-family:Verdana;">1</span></sup></span><sup><span style="font-family:Verdana;"></span><span style="font-family:Verdana;"></span></sup><span style="font-family:Verdana;"> and 16 <span style="white-space:normal;font-family:Verdana;">m<span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#f7f7f7;"="">·</span>s</span><sup style="white-space:normal;"><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;background-color:#f7f7f7;"=""><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span></span></span><span style="font-family:Verdana;">1</span></sup></span><sup><span style="font-family:Verdana;"></span><span style="font-family:Verdana;"></span></sup><span style="font-family:Verdana;">, lasting 8 hr to 16 hr. Most precipitating systems start east of LV and west of Rift Valley in the afternoon to early morning and propagates less than 400 km. Finally, hourly precipitation accumulation and lightning density analysis indicate three preferable regions for convective initiation: 1) The mountain range east of LV;2) Midwest of LV, and;3) The Congo Forest mountain range.</span></span></span></span>展开更多
1 Introduction Many of the stratified lakes are characterized by the presence of large populations of cryptomonads in their chemocline zones(Reynolds,1992;Gervais et al,2003;Pedro’s-Alio’et al.,1995).These populatio...1 Introduction Many of the stratified lakes are characterized by the presence of large populations of cryptomonads in their chemocline zones(Reynolds,1992;Gervais et al,2003;Pedro’s-Alio’et al.,1995).These populations are adapted to low light intensity and high sulfide concentration;they have a mixotrophic ability and form the so-called"deep chlorophyll maxima"(Gervais,1998;Marsha"and Laybourn-Parry,2002).A similar Cryptomonas sp.展开更多
文摘The 4.45 m-thick pure ice lens have been discovered firstly at depth from 19.81 -24.26 m in the bore No.6, which locates in north bank of the Ngoring Lake. In source region of the Huanghe (Yellow) River, 14C dating, X -ray diffraction, pollen analysis, micropalaeontology, chemical components, environmental isotope 2H, 3H, 18O and freezing point of the ice and water samples from the bore have been tested and microorganism in the ice have been also appraised with microscope. Combined with the research on geomorphy and Quaternary around the lake, the ice lens are determined as a kind of deep-buried lake ice, formed in 35,030-45,209 yr.B.P., and annual mean air temperature was about -10℃ during that time.
基金funded by the projects PICT 2005-33838 and PICT 2007-00393, Agencia Nacional de Promoción Científica y Tecnológica (Argentina), and by IAEA TCPARG7007
文摘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.
文摘An integrated satellite precipitation estimation dataset, namely, the Climate Prediction Center morphing method (CMORPH), was used to analyze precipitation regimes across Equatorial Africa between 3<span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"="">°</span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">S - 1</span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"=""><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"="">°</span></span></span><span style="font-family:Verdana;">N and 24</span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"=""><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"="">°</span></span></span><span style="font-family:Verdana;">E - 42</span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"=""><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"="">°</span></span></span><span style="font-family:Verdana;">E from 2000 to 2014. This region includes the Rift Valley, part of the Congo Forest, and the Lake Victoria (LV) basin, the second largest lake in the area of the world. Hovm<span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"=""><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">ö</span></span>ller diagrams were obtained for all organized convective systems to estimate their spans, duration, and phase speeds. The analysis included 33,189 episodes of westward propagating convective systems. Within the study area, lake and land breezes tend to trigger convection and precipitation over LV as well as mountain-valley circulation trigger thunderstorms over the mountains east of LV and western Rift Valley. The statistics of convective systems streaks on longitude-time diagrams were obtained for yearly frequencies of starting and ending longitudes and times among other morphologic variables. Results indicate organized precipitation episodes tend to move westward across Rift valley and Congo forest with an average phase speed of 10.3 <span style="white-space:normal;font-family:Verdana;">m<span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#f7f7f7;"="">·</span>s</span><sup style="white-space:normal;"><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;background-color:#f7f7f7;"=""><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span></span></span><span style="font-family:Verdana;">1</span></sup></span><sup><span style="font-family:Verdana;"></span></sup><span style="font-family:Verdana;">. More than 50% of them are triggered over LV and propagate more than 600 km at an average phase speed of 12.1 m<span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#f7f7f7;"="">·</span>s</span><sup><span style="font-family:Verdana;"><span style="white-space:normal;color:#4F4F4F;font-family:-apple-system, " font-size:16px;background-color:#f7f7f7;"=""><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span></span><span style="font-family:Verdana;white-space:normal;"></span></span><span style="font-family:Verdana;">1</span></sup><span style="font-family:Verdana;">. These convective systems tend to produce high rainfall rates hundreds of kilometers away into the Congo Forest. Half of all episodes of organized convection analyzed have phase speeds between 8 <span style="white-space:normal;font-family:Verdana;">m<span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#f7f7f7;"="">·</span>s</span><sup style="white-space:normal;"><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;background-color:#f7f7f7;"=""><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span></span></span><span style="font-family:Verdana;">1</span></sup></span><sup><span style="font-family:Verdana;"></span><span style="font-family:Verdana;"></span></sup><span style="font-family:Verdana;"> and 16 <span style="white-space:normal;font-family:Verdana;">m<span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#f7f7f7;"="">·</span>s</span><sup style="white-space:normal;"><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;background-color:#f7f7f7;"=""><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span></span></span><span style="font-family:Verdana;">1</span></sup></span><sup><span style="font-family:Verdana;"></span><span style="font-family:Verdana;"></span></sup><span style="font-family:Verdana;">, lasting 8 hr to 16 hr. Most precipitating systems start east of LV and west of Rift Valley in the afternoon to early morning and propagates less than 400 km. Finally, hourly precipitation accumulation and lightning density analysis indicate three preferable regions for convective initiation: 1) The mountain range east of LV;2) Midwest of LV, and;3) The Congo Forest mountain range.</span></span></span></span>
基金supported by Russian Foundation for Basic Research (RFBR) No. 13-04-01514Integrative Project of Siberian Branch of Russian Academy of Sciences No. 56
文摘1 Introduction Many of the stratified lakes are characterized by the presence of large populations of cryptomonads in their chemocline zones(Reynolds,1992;Gervais et al,2003;Pedro’s-Alio’et al.,1995).These populations are adapted to low light intensity and high sulfide concentration;they have a mixotrophic ability and form the so-called"deep chlorophyll maxima"(Gervais,1998;Marsha"and Laybourn-Parry,2002).A similar Cryptomonas sp.
