Seasonal changes in iron transport and nature of dissolved organic matter in a humic river in northern Finland

Changes in the concentration of iron and dissolved organic matter (DOM), and in the colour and fluorescence properties in the River Kiiminkijoki were investigated as functions of the seasonal flow regime over a two-year period. The iron concentration in filtrates and the ratio of Fe to DOC in the river increased under low flow conditions and decreased during the flood periods. The colour of the dissolved organic matter increased with increasing iron content, the effect being more pronounced during the warm period of the year than in winter. The ratio of fluorescence to DOC increased during the warm period of the year but not in winter, and decreased rapidly with discharge at the beginning of the flood period in autumn. The results give indications of the origin, formation, nature, and fate of the DOM in the river water. Temperature-dependent microbiological processes in the formation and sedimentation of iron-organic colloids seem to be important. Estimates are given for the amounts and transport rates of iron discharged into the Gulf of Bothnia by the river.     

Geomagnetic field variations as determined from bulgarian archaeomagnetic data

The archaeomagnetic determinations obtained from the collections of archaeological materials, dated in the last 2000 years are summarized. The review describes the materials used, the methodology applied, the local database organization, the principles of data processing and smoothing procedures. Errors evaluation at different levels of analysis of the experimental results are described. Special attention is paid to the archaeointensity determinations. Some rock magnetic properties studied in connection with the difficulties in the Thellier method are summarised. The curves of geomagnetic field elements variations for the last 2000 years for Bulgaria are shown. The Bauer plots, VGP path and VDM curve are also discussed, the latter confirming the general decrease in the strength of the geomagnetic field from the beginning of this era to the present. Westward drift of the geomagnetic field non-dipole part cannot be considered proved yet for the time interval 7th to 13th Centuries AD from the Bulgarian directional data.     

地磁场Sq的经度效应和UT变化

使用国际地球物理年（ＩＧＹ）和国际地球物理合作年（ＩＧＣ）期间全球地磁台网的资料和中国台站的同期地磁记录，对地磁场太阳日变化Ｓ_ｑ的经度效应和ＵＴ变化进行了分析研究．将适用于瞬时全球磁场的球谐分析法与适用于平均场的双调和分析法相结合，提出了一种分析Ｓ_ｑ磁场的新方案，得到了（θ，Ｔ，ｔ）坐标系中组成Ｓ_ｑ场的三个部分，即仅随地方时ＬＴ变化的部分Ｓ_ＬＴ，仅随世界时ＵＴ变化的部分Ｓ_ＵＴ以及既随ＬＴ变化又随ＵＴ变化的部分Ｓ_ＬＵＴ．从全球来看，在ＩＧＹ／ＩＧＣ期间，这三部分的强度之比分别为：Ｘ分量１．０：０．２：０．３，ｙ分量１．０：０．１：０．６，Ｚ分量１．０：０．４：１．０．Ｓ_ｑ的经度效应和ＵＴ变化虽然表现了同一物理过程，但它们有不同的表达形式，其决定因素是地磁轴对地理轴的倾斜，地磁场的非偶极子成分（即区域性异常）和地球内部电性的横向不均匀性（包括海陆分布、地壳上地幔电导率的区域差异）     

由扰动位确定核幔起伏

地表和外空的重力场决定于地球内部的密度分布，地核、地幔具有明显的密度差，同时核－幔边界还存在较大的起伏，无疑，它对地面及外空产生一定的重力效应．本文基于这一前提，并假定两者有-一对应的关系，从而求出被压缩的球壳上的异常密度的分布及所相应的起伏，并讨论了核－幔边界起伏的大小、扰动位应取的阶数等问题．     

On geophysical explanation of some irregular variations of the mean latitudes of latitude stations

Mean latitude variations computed by Orlovs or other filters have some irregular variations in addition to secular ones. These are of the order of ±0.05 to ±0.1, they can last several years and sometimes show regional similarities. In looking for an explanation of such latitude variations several physical mechanisms have been investigated. The most probable one is the mechanism of stress propagation in the lithosphere and asthenosphere. The consequent gravitational and deformational effects could explain both the magnitude and the time dependance of the irregular latitude variations.     

Carbon dioxide in cave atmospheres. New results in belgium and comparison with some other countries

More than 600 measurements of the carbon dioxide content of cave air in Belgium lead up to the conclusion that the main factors of its distribution are: (1) a flow originating from the biomass and diffusing in the soil and the voids of bedrock; (2) a trend, discernible in very still air only, to go down by density; (3) in some caves, draughts caused, for instance, by a swift underground stream. Results in Belgium are compared with published and unpublished data from other countries, showing that CO₂ is often less abundant in cold climate caves and in caves of semi-arid regions (influence of the biomass). Special attention is paid to human contamination during analyses: the influence of people passing through the cave nearby the operator, but also the influence of the operator himself are discussed, and the use of special precautions (including a CO₂-absorbing mask) in defined critical situations is stressed.     

Spectroscopic measurements of atmospheric carbon monoxide and methane. 2: Seasonal variations and long-term trends

A spectroscopic technique for measuring CO and CH₄ contents is described and the latitudinal distributions of these gases are presented. Carbon monoxide abundance decreases southward, having two local maxima: in midlatitudes and in the tropics. The slope of latitude dependence varies according to the season of the year. The difference in CH₄ content does not exceed the accuracy of the method (±8%).     

龙海风压时空分布特征

利用龙海1959~2005年地面10 m in平均年最大风速资料,计算分析了历年地面最大风压的年际分布及同期内的极大风压的垂直分布,结果表明:离地面10 m高处的极大风压为49.0 kg/m2;50 m高处风压可增大到93.3 kg/m2;100 m高处风压可达到123.2 kg/m2,相当于44 m/s强风暴的破坏力。     

Time-lapse resistivity investigations for imaging saltwater transport in glaciofluvial deposits

Five intersecting resistivity sections have been measured in glaciofluvial deposits hosting an aquifer of regional importance situated along a heavy traffic highway in Sweden. The winter salt spreading has caused a regular salinity increase through the years. For imaging the transport of saltwater in the aquifer, the sections were measured exactly in the same location before and after winter, and interpreted using a time-lapse inverse procedure. Some auger drilling and RCPT data were available for correlation. After winter, the resistivity had generally decreased under the water table and increased above it. The decrease in resistivity in the saturated zone is interpreted as a plume of more saline groundwater created by de-icing salt from the road. The increase in the upper layer can be explained by changes in temperature and soil moisture. The study shows that time-lapse resistivity investigations has potential for imaging hydraulic pathways in complex hydrogeological environments.     

Stratigraphic evidence for millennial-scale temporal clustering of earthquakes on a continental-interior fault: Holocene Mississippi River floodplain deposits, New Madrid seismic zone, USA

The earthquake cycles that characterize continental-interior areas that are far from active plate boundaries have proven highly cryptic and difficult to resolve. We used a novel paleoseismic proxy to address this issue. Namely, we reconstructed Holocene Mississippi River channels from maps of floodplain strata in order to identify channel perturbations reflective of major displacement events on the high-hazard and mid-plate Reelfoot thrust fault, New Madrid seismic zone, U.S.A. Only three discrete slip events are currently documented for the Reelfoot fault ( AD 900,  AD 1450, and AD 1812). This study extends this record and, thus, illustrates the utility of stratigraphic proxies as paleoseismic tools. We concurrently offer here some of the first quantified response times for tectonically induced channel pattern changes in large alluvial rivers.

We identified at least two cycles of pervasive meandering that were interrupted by channel-straightening responses occurring upstream of the Reelfoot fault scarp. These straightening responses initiated at 2244 BC +/− 269 to 1620 BC +/− 220 and  AD 900, respectively, and each records initiation of a period of Reelfoot fault slip after millennia of relative tectonic quiescence. The second (or New Madrid) straightening response was triggered by the previously known  AD 900 fault slip event, and this initial low sinuosity has been protracted until the modern day by the latter  AD 1450 and AD 1812 events. The first (or Bondurant) straightening response began a period of several hundred to  1400 years of low river sinuosity which evidences a similar period of multiple recurrent displacement events on the Reelfoot fault. These Bondurant events predate the existing paleoseismic record for the Reelfoot fault.

These data offer initial evidence that slip events on the Reelfoot fault were temporally clustered on millennial scales and, thus, offers the first direct evidence for millennial-scale clustering of earthquakes on a continental-interior fault. This carries additional ramifications. Namely, faults that have been quiescent and non-hazardous for millennia could re-enter an enduring period of recurrent hazardous earthquakes with little warning. Likewise, the Reelfoot fault also reveals evidence of temporal clustering of earthquakes on short-term cycles (months), as well as evidence for longer-term reactivation cycles (10⁴–10⁶ years). This introduces the possibility that temporal clustering could be hierarchical on some continental-interior faults.