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81.
FANG Tao LI Daoji YU Lihua LI Yun 《中国地球化学学报》2008,27(2):161-170
We conducted ship-board incubation experiments to investigate changes in nutrient uptake of phytoplankton under different phosphate concentrations and irradiances in the Changjiang River Estuary and its adjacent waters in China. Under 100% natural irradiance the uptake rates of phosphate, silicate, and nitrate were accelerated at high phosphate levels (1.84 μM), while under low irradiance (about 50% natural irradiance) their uptake rates were restrained at the high but stimulated greatly at the intermediate phosphate concentrations (1.26 μM), as the growth of phytoplankton, changes in nitrite and ammonium uptake didn't follow an obvious pattern. Our results also showed that there were linear relationships between nitrate, silicate and phosphate uptake at different phosphate concentrations under low and high irradiances, and the growth period of phytoplankton was prolonged both at the high phosphate concentrations under high irradiance and at the intermediate concentrations under low irradiance, suggesting that the limitation of phytoplankton growth mainly reflected changes in its growth period, and because no such environment (low irradiance and low phosphate concentrations) actually existed in a high turbidity zone, phytoplankton blooms hardly occurred there. In the absence of irradiance, denitrification occurred readily and phytoplankton was kept decreasing, which resulted in phosphate regeneration. 相似文献
82.
83.
石笋流体包裹体中的惰性气体及其在重建长江中游古温度变化中的作用 总被引:2,自引:0,他引:2
文中讨论了一种评估古气温变化的新方法。我们成功地利用石笋流体包裹体所捕获的Xe/Ar比值,重建了末次冰盛期以来盛行东亚季风的长江中游地区的气候演化。一种表达成ln(CXe/CAr)的对数式被证明与冷暖周期变化具有密切的关系。从研究的石笋中所提出的δ13C与Mg/Ca曲线一般随区域古气温波动而变化,但不能排除其中有另类气候信号的叠加。我们的工作则明确地指出,流体包裹体所记录的Xe/Ar在各种反映温度变化的替代指标中可能是最好的一种。整体而言,ln(CXe/CAr)曲线与那些基本随暖期和冷期振荡的曲线保持一致。将稀有气体曲线与δ13C和Mg/Ca信号整合对比之后,我们在研究区划分出末次冰盛期以来8组暖/冷旋回。整合后的气温变化模式合理地解释了过去20000年里的区域环境变化。 相似文献
84.
本文以朱拉扎嘎金矿为例,应用遥感技术,对比分析朱拉扎嘎金矿遥感蚀变异常、化探异常的提取过程和分布特征,认为:1.遥感蚀变异常位于化探异常中心与矿体吻合关系好,可作为找矿标志,应用于化探异常筛选可增加其成矿有力度的判别;2.遥感蚀变异常定位精度高,异常范围小,更接近矿体,应用于化探异常查证可以提高查证效率.该方法技术适合于寻找与热液活动有关的金属矿产,在基岩出露好,植被稀少的干旱地区效果好,建议在我国西北部荒漠景观区开展应用遥感技术评价化探异常的找矿工作. 相似文献
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87.
针对陆相湖盆沉积特征,以T A Cross高分辨率层序地层学理论为指导,在大量岩心、测井和地震资料研究的基础上,定量研究了黄骅坳陷北大港构造带沙河街组沉积体系和沉积物源特征,确定了沙河街组沉积时期总体发育近岸水下扇、滩坝、深水重力流水道、扇三角洲前缘和滑塌浊积扇等主要沉积相类型。中期基准面旋回A-D层序沉积时期发育近岸水下扇和扇三角洲前缘—前扇三角洲—滑塌浊积扇沉积体系;中期基准面旋回E-F层序沉积期间发育有利于油气储集的近岸水下扇和滩坝砂体;中期基准面旋回G层序沉积时期主要发育重力流主水道—重力流水道侧缘以及近岸水下扇沉积砂体;中期基准面旋回H层序沉积时期主要发育重力流主水道—重力流水道侧缘沉积体系。最后,预测了有利岩性圈闭发育的沉积相带和地区。 相似文献
88.
89.
Rock magnetic record of Cenozoic lake sediments from the Linxia basin and aridification of the Asian inland 总被引:1,自引:0,他引:1
High resolution research of rock magnetic records and quartz sands from the Maogou Section in the Linxia basin reveals that
after a relatively stable environment between 13.07 Ma and 8.6 Ma, the basin was gradually influxed by eolian dusts at about
8.6 Ma, with two rapid increases at about 6.4 Ma and 5.3 Ma, respectively. The study suggests that drying of northwest China
began at 8.6 Ma and strengthened rapidly at about 6.4 Ma and 5.3 Ma.
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Translated from Marine geology & Quaternary geology, 2007, 27(4): 103–110 [译自: 海洋地质与第四纪地质] 相似文献
90.
Hualing Wei Nianqiao Fang Xuan Ding Lanshi Nie Xiuming Liu 《Frontiers of Earth Science》2008,2(2):162-169
This paper presents pelagic records of planktic foraminifera, as well as data of stable isotope stratigraphy and carbonate
stratigraphy since 3.5 Ma B.P. from site ODP758 in the Ninetyeast Ridge of the Indian Ocean. Based on these data, manifestations
and related mechanisms of major tectonic and environmental events such as the rapid uplift of the Himalaya Mountains, “middle
Pleistocene climatic transition” and “mid-Brunhes dissolution event” in the region are discussed. According to the analysis
and comparison of various indices and changes in terms of foraminifera assemblage, paleotemperature, paleosalinity and themocline
from site ODP758, the authors deduce that the paleoclimatic changes might correlate with the mid-Pleistocene transition at
1.4–1.7 Ma B.P. The changes of CaCO3, mass accumulation rates (MAR) of CaCO3 and non- CaCO3 MAR indicate that the loaded terrigenous sediments increased at 1.7 Ma, which is in agreement with the uplift history of
the Qinghai-Tibet plateau as shown by the available data. The last two changes coincide with the uplift of the Qinghai-Tibet
plateau, hence they are called “Qinghai-Tibet movement” (1.7 Ma), and the “Kunlun-Yellow River movement” (1.2–0.6 Ma). The
changes of the CaCO3 content, coarse fraction (> 150 μm) content and planktonic foraminifera biostratigraphy show that strong dissolution of abyssal
CaCO3 occurred in the study region during 0.5–0.4 Ma. The event was consistent with the “mid-Brunhes dissolution event” in the
sedimentary records of the Atlantic Ocean, Pacific Ocean, Indian Ocean and Nansha sea area of the South China Sea.
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Translated from Geological Bulletin of China, 2007, 26(12): 1627–1632 [译自: 地质通报] 相似文献