Physicochemical properties of fine aerosols at Plan d'Aups during ESCOMPTE

The physical and chemical properties of aerosol particles were investigated at Plan d'Aups, one of the ESCOMPTE sites located in the St. Baume mountain area (700 m a.s.l.), 50 km east of Marseilles (France). The site is ideally located for assessing the vertical and horizontal extent of the pollution plume from the Marseilles–Berre area.Our study showed that polluted air masses from the Marseilles–Berre area are advected to Plan d'Aups in the early afternoon. Average daily concentration of particles reaches up to 40 μg m⁻³ while 1-h average particle number concentration is greater than 30,000 cm⁻³. Most of the particle mass is composed of SO₄²⁻ and organic carbon (OC). The chemical properties of the particles revealed that an additional source, possibly from the industrial area of Gardanne, contributes to the aerosol mass. This last source is characterised by significant emissions of elements, such as Zn, V, Al and Si.In addition to transport, we found that gas-to-particle conversion takes place at the interface between the free troposphere and the boundary layer. We estimated that on average, 30% of the particle number is accounted for by direct nucleation. This is potentially a major aerosol source to the free troposphere.     

苏北榴辉岩的岩石性质及其金红石的嵌布特征

苏北榴辉岩主要产于由角闪岩相变质的长英质片麻岩，根据其赋存部位划分为3类：Ⅰ类榴辉岩，通常形成独立块体，有时夹薄层片麻岩、片岩，岩石呈块状、条带状、斑杂状、条纹状和片麻状等；Ⅱ类榴辉岩，与超基性岩相伴，矿石主要呈块状和斑杂状；Ⅲ类榴辉岩，与大理岩整合接触，岩石呈块状、片麻状。3类榴辉岩在变晶矿物组合中具有一定的差异。面积测量法统计结果表明：Ⅰ类榴辉岩的晶间金红石占12．49%，间粒金红石占85．69％，包体金红石占1．81％；Ⅱ类榴辉岩的晶间金红石占36．40％，间粒金红石占44．17%，包体金红石占19．43％．Ⅲ类榴辉岩的晶间余红石占27．49％．间粒会红石占53．43%，包体金红石占19．09％。     

豫西东部黄土工程特性研究

豫西东部堆积了第四纪不同时期的风成黄土及冲积、冲洪积黄土状土,全新统黄土、上更新统黄土具有湿陷性,为弱—中等湿陷。中更新统黄土一般不具有湿陷性。黄土的微观结构与土的形成时代、成因类型关系密切,全新统黄土颗粒间为开放或次开放式架空结构,具有较高的湿陷性,上更新统黄土接近接触式胶结,存在粒间架空孔隙,潜在弱—中等湿陷性;中更新统黄土为不等粒基底胶结结构,存在骨架接触式孔隙,一般不具有湿陷性;同时,黄土的渗透性又具有各向异性。     

表层岩溶带调蓄系数定量计算--以湘西洛塔赵家湾为例

本文以湖南洛塔赵家湾表层岩溶系统为例,综合利用水位、降雨量、蒸发量及泉流量等长观资料,分别对不同降雨特征下的表层岩溶带调蓄系数进行了定量计算,并对影响表层岩溶带调蓄能力的因素进行了分析。计算得到丰水期赵家湾表层岩溶带调蓄系数为0 14～0 2 8,明显小于枯水期调蓄系数0 44 ;但丰水期久旱后表层岩溶带的调蓄能力接近于枯水期;在丰水期,场雨和连续降雨时的调蓄能力比间歇降雨时的小近1倍。实例计算表明:赵家湾表层岩溶带具有一定的调蓄能力,其地下迳流滞后于降雨至少3d ,调蓄系数确实可以用来定量评价表层岩溶带的调蓄能力。     

苏北潮滩湿地不同生态带碳、氮、磷分布特征*

通过对比苏北潮滩湿地不同生态带的表层以及柱状沉积物中总有机碳、总氮、总磷和有机磷含量,并结合不同植被不同植株部位中碳、氮、磷的含量变化,分析了潮滩沉积物中碳、氮、磷的垂向和水平分布特征与规律,探讨了不同生态带以及潮滩植被对碳、氮、磷等生源要素的富集作用。对比分析结果表明:苏北潮滩湿地各生态带对不同的测量指标有着不同的富集作用,互花米草滩的总有机碳、总氮和有机磷含量要远大于其他几个生态带,光滩沉积物中总磷的含量最高; 粒度效应是控制互花米草前缘地带以及互花米草滩沉积物中有机碳和氮分布的一个重要因素,盐蒿和芦苇滩中有机碳和氮的分布更多的是受粒度之外的其他因素影响; 不同生态带表层沉积物中的C/N比值分布,大致可反映其有机物来源的差异,而不同生态带中柱状沉积物中的C/N比值相对接近,很难根据C/N比值大小来对不同生态带中的有机物来源进行判断,这可能是埋藏在柱状沉积物中的有机物更多的受到了早期成岩作用造成的。植被对潮滩湿地中碳、氮、磷的分布有着重要影响,3种物质在互花米草、盐蒿和芦苇中的含量差别不是很大,因此潮滩植被对沉积物中上述3种物质的贡献差别主要是由不同植被的生物量和其所处环境的沉积动力差异造成的。     

Coseismic and post-seismic signatures of the Sumatra 2004 December and 2005 March earthquakes in GRACE satellite gravity

The GRACE satellite mission has been measuring the Earth's gravity field and its temporal variations since 2002 April. Although these variations are mainly due to mass transfer within the geofluid envelops, they also result from mass displacements associated with phenomena including glacial isostatic adjustment and earthquakes. However, these last contributions are difficult to isolate because of the presence of noise and of geofluid signals, and because of GRACE's coarse spatial resolution (>400 km half-wavelength). In this paper, we show that a wavelet analysis on the sphere helps to retrieve earthquake signatures from GRACE geoid products. Using a wavelet analysis of GRACE geoids products, we show that the geoid variations caused by the 2004 December ( M _w= 9.2) and 2005 March ( M _w= 8.7) Sumatra earthquakes can be detected. At GRACE resolution, the 2004 December earthquake produced a strong coseismic decrease of the gravity field in the Andaman Sea, followed by relaxation in the area affected by both the Andaman 2004 and the Nias 2005 earthquakes. We find two characteristic timescales for the relaxation, with a fast variation occurring in the vicinity of the Central Andaman ridge. We discuss our coseismic observations in terms of density changes of crustal and upper-mantle rocks, and of the vertical displacements in the Andaman Sea. We interpret the post-seismic signal in terms of the viscoelastic response of the Earth's mantle. The transient component of the relaxation may indicate the presence of hot, viscous material beneath the active Central Andaman Basin.     

High-resolution structures of the Landers fault zone inferred from aftershock waveform data

High-frequency body waves recorded by a temporary seismic array across the surface rupture trace of the 1992 Landers, California, earthquake were used to determine fault-zone structures down to the seismogenic depth. We first developed a technique to use generalized ray theory to compute synthetic seismograms for arbitrarily oriented tabular low-velocity fault-zone models. We then generated synthetic waveform record sections of a linear array across a vertical fault zone. They show that both arrival times and waveforms of P and S waves vary systematically across the fault due to transmissions and reflections from boundaries of the low-velocity fault zone. The waveform characteristics and arrival-time patterns in the record sections allow us to locate the boundaries of the fault zone and to determine its P - and S -wave velocities independently as well as its depth extent. Therefore, the trade-off between the fault-zone width and velocities can be avoided. Applying the method to the Landers waveform data reveals a low-velocity zone with a width of 270–360 m and a 35–60 per cent reduction in P and S velocities relative to the host rock. The analysis suggests that the low-velocity zone extends to a depth of ∼7 km. The western boundary of the low-velocity zone coincides with the observed main surface rupture trace.     

Soil erosion along a long slope in the gentle hilly areas of black soil region in Northeast China

Characteristics of soil erosion change along a long slope in the gentle hilly areas in black soil region in Northeast China are discussed. A simplified slope model based on seg-ments was used to analyze the runoff data and soil erosion data observed between 2003 and 2004 over 10 field plots with different slope length in Heshan Farm, Heilongjiang Province. We found that soil erosion rate over long slopes in the black soil region changed alternatively along the slope and creates alternative zones of intensive erosion and week erosion.The exact place of each zone is different for different rainfall conditions. In a year with less and mild precipitation, rill cannot happen within the top 50 m, while in a year with large and inten-sive precipitation, rill can be formed starting even at 15 m from the top of the slope.     

Mass movements in cave sediments: investigation of a ∼40,000-year-old guano mudflow inside the entrance of the Great Cave of Niah, Sarawak, Borneo

The West Mouth of the Great Cave at Niah in Sarawak, northwest Borneo and the North Passage that leads to the West Mouth contain large deposits of guano. The main deposit, several metres thick in places, forms the sloping floor of the entire North Passage. A mass movement deposit identified in the West Mouth, having a volume of 600 m³, originated as a guano mudflow up the North Passage in the order of 40,000 years ago. This failure of the guano slope was investigated to determine whether particular conditions or events could be identified as the most likely causes. The physical, hydrological and geotechnical properties of samples of the material were determined so that the stability of the slope could be assessed. Stability analyses showed that shearing failure of the slope would require inputs of water to the slope in quantities for which no feasible explanation can be suggested. However, the properties of the guano are similar to those of loess, indicating a high susceptibility to ‘hydrocollapse’. Very shallow failure of the slope, possibly as several smaller mudflows, could therefore have occurred due to additional water in quantities that could realistically be supplied as rainwater spray, possibly with a seismic trigger. The climate must therefore have been wetter than it is at present. These findings have implications for the interpretation of sediment deposits in other relict caves.     

Structural and fabric analyses of basal slip zone of the Jin’nosuke-dani landslide, northern central Japan: its application to the slip mechanism of decollement

We describe in detail the deformation structures and textures of a large-scale landslide body that developed in the Betto-dani Valley in northern central Japan. We studied the shape-preferred orientation of clasts and clay flakes and the development of internal shear planes within the slip zone of the landslide. The slip has an average rate of 5–10 cm/year under the overburden pressure of approximately 1.6 MPa; these values are similar to those of the proto-decollement zone of the Nankai accretionary prism in SW Japan. The anisotropy of magnetic susceptibility of samples obtained from the slip zone reveals that the long axes of clay flakes define an imbricate structure. The slip was due to a long-term periodical creep, which occurs during the thaw seasons with an average slip rate of 0.16–0.32 μm/min. During the creep, the long axes of grains including clay flakes in the slip zone are developed from parallel to perpendicular to the slip direction. The observed textures provide a clue to elucidate the deformation textures and process in the decollement zone of the Nankai prism.