Links between bacterial communities in marine sediments and trace metal geochemistry as measured by in situ DET/DGT approaches

Our current view about the relationship between metals and bacteria in marine sediments might be biased because most studies only use ex situ approaches to quantify metals. The aim of the present research was to compare ex situ and in situ methods of metal measurement (DET and DGT--diffusive equilibration or diffusive gradients in thin-films) and relate the results with two commonly used microbiological variables (bacterial biomass and bacterial diversity as revealed by DGGE). No previous studies have used such in situ approaches in microbial ecology. For biomass and most of the investigated trace metals (Ag, Cd, Sn, Cr, Ni, Cu, Pb, and Al) no significant correlations were found. The exceptions were Fe, Mn, Co, and As which behave like micronutrients. For bacterial diversity, no relevant relationships were found. We conclude that in situ methods are more adapted tools for microbial ecologists but that ex situ approaches are still necessary.     

星际分子云平均寿命的研究

本文叙述一项分子云平均寿命的实测研究结果。采用分子云的云-云碰撞生长模型,从~(13)CO的银道面(l=27°.85-40°,b=0°)观测资料得出的分子云的质量谱导出了星际分子云平均寿命的下限,其值为1×10~9年。     

EFFECTS OF WATER MANAGEMENT ON SEDIMENT TRANSPORT IN CHINA''''s YELLOW RIVER, WITH COMPARISONS FROM THE UNITED STATES

1 INTRODUCTION Too much sediment and too little water are related problems in China抯 Yellow River Basin. Sediment yield in the basin averages about 2,100 t/(km2a), greatest of the world抯 large rivers although the Yellow River ranks 31st in mean streamflow. A quarter of the sediment is deposited in the 780-km lower reach, causing bed levels to rise an average of a meter per decade (Wang et al., 1997). Sediment aggradation along this reach is concentrated between dikes, resulting in a…     

阿坝藏族羌族自治州土地资源特征

四川省阿坝藏族羌族自治州(简称自治州)地处青藏高原东南缘,南北长414公里,东西宽约360公里,平均海拔3000米以上,属川西北高寒地区,是四川省林牧业重要基地。全州总土地面积为834.26万公顷(12513.93万亩)。其中,草地面积为421.90万公顷,占土地总面积的50.6％;林地304.94万公顷,占36.3％;耕地仅9.93万公顷,占1.2％;水域5.94万公顶,占0.7％。草地、林地、耕地和水域用地比值为71.0:51.0     

黑云母中氯的含量

前言在"盆地"和"山区"构造区,有许多从花岗岩到闪长岩的深成岩体(主要是岩株).铜、铅、锌和其它金属的矿床在空间上与这些深成岩体有关,但也有许多岩体不含矿.含矿和不含矿侵入体之间在地球化学上     

美国大规模调水的经济效益问题

Ⅰ.现有的与予计的调水情况美国的降水分布是很不均匀的。粗略地说,这个国家的东部水资源丰沛而西部则干旱少雨。所以,毫不足怪,东部的水质问题比较突出,而高部水量问题则占首要地位。因而,西部地区对跨流域调水抱有极大的兴趣。     

Effects of oil spill on seawater infiltration and macrobenthic community in tidal flats

Tidal flat ecosystem simulators are used to clarify the effects of stranded fuel oil on tidal flat ecosystems. Results show that oil spills increase the periphyton on sediment by decreasing the predation stress caused by deposit feeders. About a month after an oil spill, the total population density of the macrobenthos recovered. The oxidation-reduction potential in the surface sediment drops to a negative value after the oil spill, and the anaerobic condition throughout the sediment seems to be responsible for the decrease in the population density of the macrobenthos. The infiltration volume of seawater into the oil-stranded sediment decreases to a third of that without the oil spill. The recovery of infiltration volume after about a month coincides with the recovery of the population density of the macrobenthos. This result suggests that the macrobenthic population is highly dependent on the infiltration of seawater.     

热带气旋的结构和能量学

用西北太平洋10年的无线电探空测风资料,分析研究热带气旋的大尺度结构。分析风暴内的各个区域的温度、高度、湿度、风和垂直运动场,从台风眼到半径12°(纬距,下同)内的平均探测情况。讨论了半径4°以内区域的降水特征。还使用了台风飞机探测资料来分析核心部分。发现了许多重要的特点。在风暴的结构上,特别是在大的半径处,存在强的持续的非对称性。风暴环流水平范围十分宽广,好象不管内部核心的强度怎么样,总是保持常定的尺度。对流层中层的入流主要地是来自4°以外。在4～6°半径带存在一个平均下沉区。内区湿度非常之高,眼的外面处处存在条件不稳定。降水和温度的日变化明显。