Chemical Mechanism Development: Laboratory Studies and Model Applications

Within the German Tropospheric Research Programme (TFS) numerous kinetic and mechanistic studies on the tropospheric reaction/degradation of the following reactants were carried out: oxygenated VOC, aromatic VOC, biogenic VOC, short-lived intermediates, such as alkoxy and alkylperoxy radicals.At the conception of the projects these selected groups were classes of VOC or intermediates for which the atmospheric oxidation mechanisms were either poorly characterised or totally unknown. The motivation for these studies was the attainment of significant improvements in our understanding of the atmospheric chemical oxidation processes of these compounds, particularly with respect to their involvement in photooxidant formation in the troposphere. In the present paper the types of experimental investigations performed and the results obtained within the various projects are briefly summarised. The major achievements are highlighted and discussed in terms of their contribution to improving our understanding of the chemical processes controlling photosmog formation in the troposphere.     

Lumbering operations,lake humification and consequences for the structure of the lake foodweb: A case study using the LakeWeb-model for Lake Stora Kröntjärn,Sweden

This work presents a scenario to demonstrate how a given lake (Lake Stora Kröntjärn, Sweden) would respond to changes in colour related to lumbering operations in its watershed. The questions posed are: How would lake colour values increase, for how long would such increases last and how would this influence the production and biomasses of key functional organisms in the lake? The work is based on a comprehensive lake ecosystem model, LakeWeb, which accounts for production, biomasses, predation, abiotic/biotic interactions of nine key functional groups of organisms, phytoplankton, bacterioplankton, two types of zooplankton (herbivorous and predatory), two types of fish (prey and predatory), as well as zoobenthos, macrophytes and benthic algae. The LakeWeb-model has been calibrated and critically tested using empirical data and regressions for many lakes and it can capture typical functional and structural patterns in lakes. To obtain results like these by traditional field-work in one or more lakes would be very demanding (in terms of money, persons and time). It has been shown that single tributary peaks in colour concentrations are often "drowned" in weekly mean lake values. The lumbering operations must be extensive and continue for a long time to cause significant increases in tributary colour values in order to significantly influence fundamental lake foodweb structures. This means that it is often realistic to assume that lumbering activities do not strongly influence lake foodweb structures. The LakeWeb-model with the given mass-balance model for lake colour can be a useful tool to assess situations when this might not be valid.     

Fifteen days of continuous activity survey at Stromboli volcano, Italy, in late September 2000: Doppler radar, seismicity, infrared, soil humidity, and mapping of the crater region

The intention of our study was to gain new insight into the complex interplay between different types of eruption of the Stromboli volcano by combining detailed field observation with different geophysical methods. We recorded more than 600 eruptions by use of continuous Doppler radar measurements. We detected the onset of the seismic precursor and the beginning of the visible eruption by use of seismic and infrared data. Two soil samples per day were used to monitor the effect of humidity on the eruptive style. We mapped the crater region as a reference base for the long-term morphological changes of the active region and for the exact positions of our measurement systems. Two distinct types of eruption were distinguished from each other on the basis of seismic and radar data - short, wide-angle Strombolian explosions and pulsating, sharp angle fountain-like eruptions. Data and visual observations imply that weather conditions significantly effect volcanic activity. We also interpret the intensification of eruptive activity during our field study as replenishment of the reservoir with a new batch of magma in late September 2000.     

The termination of the last major phase of aeolian sand movement,coastal dunefields,Denmark

Optically stimulated luminescence (OSL) dating of sand samples from stabilized (or inactive) coastal dunes in Denmark provides information on the age of the termination phase of the last major aeolian activity period. A total of 26 sand samples were taken from four different coastal dunefields around the North Sea, Skagerrak and Kattegat coasts of Denmark. The OSL dates indicate that the last major phase of aeolian activity terminated between ad 1860 and 1905. Most of the dunes examined in this study were active around 1820, during a period documented to have been very stormy. A dune management scheme started around 1792, and this no doubt was a major cause of dunefield stabilization, but an overall decline of storminess, particularly spring and summer storminess, around the end of the 19th century must also have contributed to the increasing inactivity of coastal dunes. The new OSL dates on aeolian sand movement agree well with historical data and data from topographic maps on dune movement. This agreement supports the observation from earlier work that OSL dating of recent aeolian sand movement is accurate over the last few decades to centuries. Copyright © 2005 John Wiley & Sons, Ltd.     

青藏高原东部全新世冬夏季风变化的高分辨率泥炭记录

在建立了全新世泥炭沉积物高分辨率冬夏季风代用指标时间序列的基础上, 发现青藏高原若尔盖地区全新世冬夏季风的变化具有此消彼长和同时消长两种基本的模式, 冬季风与夏季风在不同时间尺度上两种模式又相互嵌套. 由冬夏季风指标叠加效应合成的气候状况却有与全球同步的规律性, 表现出千年-百年尺度的不稳定性, 6.2 ka的季风突然减弱事件要比8.0 ka的事件更显著, 反映了亚洲季风的区域特点或它本身就是全球气候的一个窗口.     

Facies characteristics, morphology and depositional models of clay-slide deposits in terraced fjord valleys, Norway

Many bedrock-confined fjord valleys along the Norwegian coast contain thick accumulations of fine-grained sediments that were deposited during and after the last deglaciation. The deposits gradually emerged above sea level due to glacioisostatic uplift, and fjord marine sedimentation was gradually followed by shallow marine and fluvial processes. During emergence terraces and river-cut slopes were formed in the valleys. Subsequent leaching of salt ions from the pore water in the marine deposits by groundwater has led to the development of quick clay. The deposits are subject to river erosion and destructive landslides involving quick clay. Most slides are of prehistoric age. Others are known from modern observations as well as from historic records.Landforms such as distinct slide scars or the hummocky terrain of slide deposits may be strongly modified by secondary processes. In addition, deposits from the most liquid part of quick clay slides may have planar surfaces. Clay-slide deposits on a fluvial or deltaic terrace, therefore, are not always easily recognized from morphology, and only exposures may reveal their internal structures and allow them to be distinguished from overbank flood sediments. Detailed sedimentological work shows that slide deposits in such setting consist of distinct facies containing reworked marine sediments. We propose three facies successions of clay-slide deposits that form a continuum. The dominant components of these succession types are: slightly deformed blocks of laminated clay and silt (A), highly deformed clay and silt with gravel clasts (B) and massive to stratified clay and silt with scattered clasts (C). We suggest that in many cases a basal muddy diamicton is a characteristic, and possibly diagnostic feature. Processes and depositional models are interpreted from the different succession types. The results may be relevant for identifying clay-slide deposits elsewhere and may be useful during general mapping of fjord marine deposits and characterization of slide-prone areas as well as during identification of prehistoric slides.     

Stellar forensics — II. Millisecond pulsar binaries

We use the grid of models described in Paper I to analyse those millisecond pulsar binaries whose secondaries have been studied optically. In particular, we find cooling ages for these binary systems that range from < 1 to ∼ 15 Gyr. Comparison of cooling ages and characteristic spin-down ages allows us to constrain the initial spin periods and spin-up histories for individual systems, showing that at least some millisecond pulsars had sub-Eddington accretion rates and long magnetic field decay times.     

Evaluation of Multi-Frequency-Microwave-Radiometer-System performance for oceanography

A technique is presented for constructing a mathematical model of a Multi-Frequency Microwave Radiometer System. The technique combines the different responses of microwave radiometers with models of the sea surface, the effects of the Earth's atmosphere and of the sky emission. A linear perturbation method and a more accurate non-linear method are outlined for processing of data simultaneously collected by the radiometers. The mathematical model of the Radiometer System combined with the linear data-processing method is useful for predicting in-flight sensor performance. Based on a chosen performance function, an evaluation of a spaceborne Multi-Frequency Microwave Radiometer System is given.     

Industrial minerals and rocks, aggregates and natural stones in the Nordic countries

The Nordic countries, including Greenland, have a long tradition in mining. The industrial minerals sector is expanding in most Nordic countries and extensive development has taken place during the last few years. The main commodities mined are carbonate rocks, quartz, feldspar, apatite, olivine and talc.
A number of diferent types of dimension stones are quarried in all countries. Rock aggregates are increasingly important, replacing sand and gravel aggregate as construction materials in some countries due to the need to protect ground water supplies.     

A discrete particle representation of hillslope hydrology: hypothesis testing in reproducing a tracer experiment at Gårdsjön,Sweden

Despite the long history of the continuum equation approach in hydrology, it is not a necessary approach to the formulation of a physically based representation of hillslope hydrology. The Multiple Interacting Pathways (MIPs) model is a discrete realization that allows hillslope response and transport to be simultaneously explored in a way that reflects the potential occurrence of preferential flows and lengths of pathways. The MIPs model uses random particle tracking methods to represent the flow of water within the subsurface alongside velocity distributions that acknowledge preferential flows and transition probability matrices, which control flow pathways. An initial realization of this model is presented here in application to a tracer experiment carried out in Gårdsjön, Sweden. The model is used as an exploratory tool, testing several hypotheses in relation to this experiment. Copyright © 2011 John Wiley & Sons, Ltd.