Preparation and After-Treatment of BaMgAl10 O17 ：Mn^2＋

INTRODUCTION The properties of phosphor usedin a plasma dis-play panel (PDP) affect the performance of the PDP(Okazaki et al .,2000 ; Rao and Devine ,2000) . Theluminescent properties of the phosphor are decided bythe morphology ,particle size and size distribution ofthe powder ,sothe requirements for the powder mor-phology are high in a color PDP which belongs to ahigh resolution display apparatus (I m et al .,2005 ;Yang et al ., 2005) . Studies have shown that withsmall particle si…     

从PM10的测量推测成都市区汞污染的来源

通过2007年5—6月期间测量成都市若干条剖面上大气可吸入颗粒物（PM10）中的汞含量，来推测成都市大气中汞的来源。结果表明：在12个点的测量范围内，成都市PM10的质量平均浓度为210．8μg／m^3；PM10中汞的质量平均浓度为0．36ng／m^3。公园和郊区PM10浓度和其中汞浓度均较少，可能与植被茂盛有关。由PM10中汞的分布可知，在热电厂、停用的生活垃圾堆放场和寺庙附近出现最高值。说明热电厂和生活垃圾堆放场是大气汞污染的重要次生来源。寺庙附近出现的高汞值，推测与寺庙的礼仪活动如香烛燃烧有关。     

地铁隧洞带水作业施工技术

以在建的北京地铁十号线双井一劲松区间暗挖隧道为例，通过分析北京特殊地层在带水条件下单洞结构单线隧道台阶法的施工工艺，洞悉浅埋暗挖正台阶法施工中超前预加固、开挖时空顺序、台阶长度等工艺对围岩稳定性的影响程度。     

兰州市取暖期可吸入颗粒物中单颗粒矿物组成特征

为研究兰州市2005年冬季大气可吸入颗粒物(PM10)中单颗粒的矿物组成,用能谱扫描电镜识别和统计了兰州市区(东方红广场)和郊区(榆中县)两个采样点的单矿物颗粒。结果在市区样品中识别出方解石、伊/蒙混层、石英、斜长石、伊利石、石膏、绿泥石、高岭石、浊沸石和钾长石等21种矿物,前7种占统计总量的75%以上;郊区样品中识别出20种矿物,以方解石、石英、伊利石、绿泥石、斜长石和伊/蒙混层为主(占70%以上),与市区相比缺少钾石膏、金红石和水铝酸钙而增加了硫酸镁和磷灰石。总体来看,大气PM10中的矿物颗粒可分为粘土类、长石类、碳酸盐类、硫酸盐类、氧化物类和其他六类,以粘土类和碳酸盐类矿物为主(约占60%);冬季市区颗粒物表面的“硫化”现象较郊区严重;这些矿物颗粒主要来自地表土,人为排放和大气中二次化学反应生成的矿物的贡献较小。     

2004年春季中国沙尘天气特征分析

利用全国681个站的沙尘天气观测资料分析得出,2004年春季中国北方的沙尘天气明显偏少、偏弱,主要表现在：（1）2004年春季681个站累计的沙尘天气日数2 080 d,相当于历史平均值的46.9%,是近四十余年中第三个偏少年份。沙尘暴的总面积约190万km2,仅为历史平均值的37.3%。（2）危害性较大的沙尘暴和强沙尘暴过程6次,不足2001年的一半。（3）4月和5月沙尘天气明显偏少导致整个春季显著偏少。沙尘天气出现时,PM10浓度相对增加,空气质量恶化,但与历史上较典型的强沙尘暴个例相比,PM10浓度增加的幅度不大。进一步分析表明,2004年春季沙尘天气偏少、偏弱的主要原因是大气动力条件不足,是比较特殊的一个年份。     

Determination of predevelopment denudation rates of an agricultural watershed (Cayaguás River, Puerto Rico) using in-situ-produced Be in river-borne quartz

Accurate estimates of watershed denudation absent anthropogenic effects are required to develop strategies for mitigating accelerated physical erosion resulting from human activities, to model global geochemical cycles, and to examine interactions among climate, weathering, and uplift. We present a simple approach to estimate predevelopment denudation rates using in-situ-produced cosmogenic ¹⁰Be in fluvial sediments. Denudation processes in an agricultural watershed (Cayaguás River Basin, Puerto Rico) and a matched undisturbed watershed (Icacos River Basin) were compared using ¹⁰Be concentrations in quartz for various size fractions of bed material. The coarse fractions in both watersheds bear the imprint of long subsurface residence times. Fine material from old shallow soils contributes little, however, to the present-day sediment output of the Cayaguás. This confirms the recent and presumably anthropogenic origin of the modern high denudation rate in the Cayaguás Basin and suggests that pre-agricultural erosional conditions were comparable to those of the present-day Icacos.     

基于GEE的地表覆盖与气候状态关联研究

为探究地表覆盖与气候状态间的关联性,本文选取2019年的Landsat影像数据,结合温度、降水量、PM_2.5浓度3种气候指标,利用GEE平台,结合NDVI、MNDWI、NDBI,采用SVM、RF、CART方法进行地表覆盖分类,探究气候指标与地表覆盖类型分布的关联性;提出了使用3种气候指标构建分类特征进行地表覆盖分类的方法,并通过消融试验分析了气候指标对地表覆盖分类精度的影响。结果表明:①RF有较好的分类结果,总体精度为96.0%;②3种气候指标均能提高地表覆盖分类精度,其中PM_2.5浓度效果最好;③温度与植被、水体关联性较大,PM_2.5浓度与城区、植被关联性较大,降水量与耕地关联性较大。     

2013年河北中南部PM_(10)和PM_(2.5)浓度时间变化特征及其影响气象条件分析

对2013年河北省中南部的石家庄、保定、沧州、衡水、邢台和邯郸6个地市市区各站点逐小时PM10和PM2.5监测资料及相应气象资料分析结果表明:6个地市中邢台年污染日数最多,对应其年平均风速最小;沧州的最少,年平均风速最大。各地市各个级别污染日数不同,五、六级重污染天气均集中在10月—次年3月。首要污染物主要是PM10和PM2.5,但比例不尽相同。特殊的地理位置、污染源差异和气象条件的差异造成各地市污染日数、级别的差异。6个地市污染天气过程时段大都相同,区域性污染明显。各地市PM10和PM2.5浓度平均最大值均出现在冬季,PM10浓度平均最小值均出现在夏季,各市PM2.5浓度平均最小值出现的季节不同。6个地市PM10和PM2.5浓度值的月变化趋势相似。不同季节各地市PM10和PM2.5浓度日变化趋势不同,极值出现的时间也各不相同,极值出现的时间与气象条件和人类活动关系密切。秋、冬季各地市PM10和PM2.5浓度日较差多大于春、夏季的。各地市PM10和PM2.5浓度日均值与当地的日均气温、风速、能见度呈负相关关系,与相对湿度呈正相关关系且相关性比较显著。     

Minimum Bedrock Exposure Ages and Their Implications: Larsemann Hills and Neighboring Bolingen Islands, East Antarctica

<正>Considerable controversy exists over whether or not extensive glaciation occurred during the global Last Glacial Maximum(LGM) in the Larsemann Hills.In this study we use the in situ produced cosmogenic nuclide ~(10)Be(half life 1.51 Ma) to provide minimum exposure ages for six bedrock samples and one erratic boulder in order to determine the last period of deglaciation in the Larsemann Hills and on the neighboring Bolingen Islands.Three bedrock samples taken from Friendship Mountain(the highest peak on the Mirror Peninsula,Larsemann Hills;～2 km from the ice sheet) have minimum exposure ages ranging from 40.0 to 44.7 ka.The erratic boulder from Peak 106(just at the edge of the ice sheet) has a younger minimum exposure age of only 8.8 ka.The minimum exposure ages for two bedrock samples from Blundell Peak(the highest peak on Stornes Peninsula,Larsemann Hills;～2 km from the ice sheet) are about 17 and 18 ka.On the Bolingen Islands(southwest to the Larsemann Hills;～10 km from the ice sheet),the minimum exposure age for one bedrock sample is similar to that at Friendship Mountain(i.e.,44 ka).Our results indicate that the bedrock exposure in the Larsemann Hills and on the neighboring Bolingen Islands commenced obviously before the global LGM(i.e.,20-22 ka),and the bedrock erosion rates at the Antarctic coast areas may be obviously higher than in the interior land.     

Periglacial climate at the 2.5 Ma onset of Northern Hemisphere glaciation inferred from the Whippoorwill Formation, northern Missouri, USA

The Whippoorwill Formation is a gleyed diamicton that is present locally within bedrock depressions beneath the oldest glacial till in northern Missouri, USA. Stratigraphy, paleomagnetism, and cosmogenic-nuclide burial ages show that it was deposited between the Matuyama-Gauss magnetostratigraphic boundary at 2.58 Ma and the first advance of the Laurentide ice sheet into Missouri at 2.47 ± 0.19 Ma. High cosmogenic-nuclide concentrations also show that the constituents of the Whippoorwill Formation experienced long exposure at a stable landscape surface with erosion rates of 1-2 m/Ma. However, cosmogenic-nuclide concentrations are invariant with depth below the Whippoorwill Formation surface, indicating active mixing of the soil profile shortly before burial by till. The Whippoorwill Formation retains numerous features indicative of cryoturbation. Therefore, we interpret it as a buried Gelisol, a soil formed under periglacial conditions in the presence of permafrost. At the onset of Northern Hemisphere glaciation, climate cooling established permafrost conditions and accelerated erosion by inducing landscape instability. Thus, weathered regolith materials were mobilized and redeposited by gelifluction shortly before the ice sheet overrode the landscape.