CARAIB陆地碳循环模型研究进展及其应用

陆地生态系统碳循环是全球变化研究中的重要组成部分,多种模型已用于陆地生态系统碳循环的模拟。文中着重论述了陆地生物圈碳循环模型CARAIB的原理、方法及其应用和最新进展。CARAIB模型主要是基于叶面光合作用子模型、冠层子模型和木质呼吸作用3个子模型的耦合,应用大气环流模式气候数据模拟出生态系统碳存储量和生物群区分布。介绍了欧洲利用植物数字化地理配准数据库重新划分植物群组(BAGs)的方法,比较BAGs与传统的植物功能型(PFTs)划分在方法上的差异,根据植物群组应用CARAIB模型进行生物群区分布模拟,并提出利用CARAIB模型模拟我国陆地碳循环和生物群区分布的可行性,为研究中国植被对气候变化的响应模型和预测提供区域尺度的新方法。     

贵州锦丰(烂泥沟)金矿床含砷黄铁矿和脉石英及其包裹体的稀土元素特征

贵州锦丰(烂泥沟)金矿是滇黔桂“金三角“目前已探明的最大的卡林型金矿床.含砷黄铁矿是该矿床最主要的载金矿物,脉石英是最显著的热液蚀变作用产物.含砷黄铁矿、脉石英及其包裹体具有相同的稀土元素特征,表现为轻重稀土分馏明显(LREE/HREE:7.95～31.77,(La/Yb)N:8.97～40.49);轻稀土有一定的分异((La/Sm)n:3.20～5.29),曲线右倾程度大;重稀土分异不明显((Gd/Yb)n:1.41～3.35),曲线平坦;负铕异常明显(δEu 0.59～0.71);微弱的铈负异常(δCe 0.97～0.98).代表成矿流体特征的脉石英包裹体稀土配分型式及特征值与区域上不同时代的幔源基性-超基性岩差别较大,而与矿床围岩、矿石、含砷黄铁矿及其包裹体稀土配分型式及特征值十分相似,具上部地壳普通沉积岩的特点,反映成矿流体主要不是来源于地幔,而是以壳源为主.Eu负异常反映了偏酸性(富CO2)、还原性的成矿环境;微弱的Ce负异常表明成矿流体来源于以沉积水和热脱水为主的盆地流体.     

2001年11月14日可可西里地震研究：远震数据和现场测量得到的破裂历史及几何形状

根据远震体波数据反演估计震源参数对2001年11月14日可可西里地震进行了研究。该地震使得东西向的昆仑走滑断层库赛湖西段发生破裂,表面破裂超过400km。这次矩震级为Mw7·8(Harvard CMT,2001)级地震事件后有中等而持续的地震活动。我们采用多次子事件反演复杂体波的方法(Kikuchi and Kanamori,1991)模拟波形,理解破裂过程。现场测量用来约束反演结果,并评估破裂过程的解。考虑到库赛湖段西部的复杂性,我们反演初始部分数据来模拟破裂的起始。发现破裂起始于布喀达坂峰西南的断层段上。虽然破裂主要向东传播,但一些子事件系统地出现于震中以西。尔后的完整体波波形反演表明破裂沿着库赛湖段的垂直断层单侧向东传播。     

地震早期预警优势周期估计的性质

近期的研究结果表明,利用地震P波最初几秒数据测量得到的平均"优势周期"τp,提供了对震级的快速近似估计,该方法能用于地震早期预警系统。尽管以往的研究说明了这种方法的经验价值,本文中我们仍将检测优势周期估计值的理论特性。我们指出,这种估计值是频谱振幅和周期的非线性函数,对大振幅和高频成分赋予了更大的权重。我们的结果还显示,通过递推关系计算得到的、与时间相关的τp最大值估计,在每次单独的测量中都存在固有的误差。在震级的优势周期估计中,尽管一些观测到的变化似乎是缘于局部场地效应,但本文结果表明,估计值的非理想特性也增加了结果的噪声。针对地震早期预警系统潜在的重要性,我们建议应对震级测定所依赖的初始P波数据的频谱特性进行更详细的分析,例如利用多锥形谱或小波方法,有助于设计更好的方法以实现系统性能的进一步优化。     

断层面粗糙度随滑距的演化

地震时大部分断层位移发生在断层带内的主滑动面上。虽然断层面形貌对地震和断层力学具有重要意义,但是在地震滑距尺度上几乎是未知的。我们使用新的基于激光技术的方法绘制了10μm～120m尺度范围内的暴露断层面。这些数据提供了首个定量证据显示断层面粗糙度随滑距递增而变化。长度在10μm到大于100m范围内的数千条剖面表明,在平行滑动方向上小滑距断层(滑距<1m)比大滑距断层(滑距为10m～100m或更大)粗糙。小滑距断层表面在全部观测尺度上都有凹凸体,而大滑距断层面是平滑的,且长达1～2m的纵剖面上均方根(RMS)值小于3mm。大滑距断层面表现为光滑的、拉长的、半椭圆状的、约1m高数米长的凸起。我们推断这些凸起随断层成熟进程不断演化。这种几何学上的差别显示,在相对成熟的断层上,地震的成核、发展和终止与新断层是根本不同的。     

Multifrequency Polarization Variations in the Quasar 0917＋624

We present a detailed analysis of multi-frequency observations of linear polarization in the intraday variable quasar 0917+624 (z = 1.44). The observations were made in May 1989 at five frequencies (1.4, 2.7, 5.0, 8.3 and 15GHz) with the VLA and the Effelsberg 100 m-telescope and in December 1988 at two frequencies (2.7 and 5.0 GHz) with the latter. It is shown that the relationship between the variations of the polarized and total flux density is highly wavelength dependent, and the multi-frequency polarization behavior may be essential for investigating the mechanisms causing these variations. It is shown that the variations observed at 20 cm can be interpreted in terms of refractive interstellar scintillation. However, after subtracting the variation due to scintillation, three 'features' emerged in the light-curve of the polarized flux density, indicating an additional variable component. Interestingly, these features are shown to be correlated with the variations at 2-6 cm, thus indicating that thes     

Reduction in organic contaminant exposure and resultant hepatic hydropic vacuolation in winter flounder (Pseudopleuronectes americanus) following improved effluent quality and relocation of the Boston sewage outfall into Massachusetts Bay, USA: 1987-2003

Effluent upgrades for metropolitan Boston have included toxicant reduction, primary and secondary treatment and outfall extension. Between 1992 and 2003 winter flounder at five stations were surveyed annually for liver and muscle burden and chronic hepatic sub-lethal impacts of polynuclear and halogenated aromatic hydrocarbons, and metals. Trends in flounder availability and fin condition were also examined. In 1988 12% of the adult winter flounder in Boston Harbor exhibited hepatic neoplasms and up to 80% had hepatic hydropic vacuolation (HV). Tumor prevalence fell to 0-2% and HV to <50% by 1996. Since then tumors have been absent, while a steady prevalence of HV has persisted, consistent with lower hydrocarbon loading and tissue levels. Contaminants and HV also fell with distance from the Boston outfall. After the outfall extension was activated in 2000, there has been no significant change in flounder liver health at the new outfall site.     

The use of steroid markers to assess sewage contamination of the Black Sea

Analyses of faecal steroids in coastal sediments taken from throughout the Black Sea indicate chronic sewage contamination at some locations. These include Sochi, where concentrations of coprostanol up to 5400 ng g(-1) (dry wt) were recorded, and in the coastal areas adjacent to the Danube delta (2600 ng g(-1) dry wt). Comparatively high values of 5beta/(5beta+5alpha) isomeric ratios of cholestan-3-ol and cholestan-3-one are reported at these locations and are characteristic of sediments contaminated with sewage. Lower concentrations of coprostanol are reported for Bosphorus sediments (12-440 ng g(-1) dry wt) and in the region of Odessa (130-290 ng g(-1) dry wt). Isomeric ratios at these locations also confirm sewage as a significant contributor to steroids in the Bosphorus, but lower values of the ratios indicate only minor sewage inputs in Odessa. In contrast, steroid concentrations and compositions from most Ukrainian sites are characteristic of uncontaminated environments. To place these results into perspective, the range in levels of coprostanol in the Black Sea sediments compares to the lower to mid-range of concentrations reported for coastal sediments on a world-wide basis, with Black Sea sedimentary levels substantially below those previously reported for heavily impacted sites.     

Fate of DDT-related compounds in Bohai Bay and its adjacent Haihe Basin, North China

Concentrations of ten DDTs (2,2-bis-(chlorophenyl)-1,1,1-trichloroethane) of which p,p'-DDA (2,2-bis(chlorophenyl)acetic acid), p,p'-DDM (bis(chlorophenyl)methane) and p,p'-DBP (dichlorobenzophenone) are often neglected, were measured in 25 water and 25 sedimentary samples from Bohai Bay and its adjacent Haihe Basin. The ratio of o,p'-DDX/p,p'-DDX in the upper reaches of Yongdingxin River ranged from 0.71 to 2.44, suggesting that the potential source of pollution would be the manufacturing or use of dicofol near this river. While DDA accounted for 52-93% of the SigmaDDT concentration in water, DDA was only detected in three sedimentary samples. And DDM was found to be an important degradation product of DDT in water following DDA. It should be noted that DBP (0.60-3.30 ng/g) is a major metabolite comparable with DDE (2,2-bis(chlorophenyl)-1,1-dichloroethylene, nondetectable-1.80 ng/g) and DDD (2,2-bis-(chlorophenyl)-1,1-dichloroethane, nondetectable-2.86 ng/g) in sediment in Bohai Bay. Finally, the SigmaDDT concentration in sedimentary sample from Bohai Bay was found to be dependent on the TOC (total organic carbon) value.