The fate of Chernobyl radiocesium in the River Öre catchment,northern Sweden

A¹³⁷Cs-balance for the catchment of the River Öre in central northern Sweden which received about 30 kBq m^–2 of radiocesium from the Chernobyl accident was calculated for the period 1986–1991. Altogether, slightly less than 10% of the total deposition in the catchment was estimated to be exported from the terrestrial parts during this period of time. More than 90% of this loss is transported with the River Öre to the outer sea of the Gulf of Bothnia. The retention in Lake Örträsket which is the only lake along the river course and the Öre Estuary outside the river mouth was thus slightly less than 10%. Nearly all of the radiocesium deposited in the lake is permanently retained in the sediments and successively covered with less radioactive sediment. A considerable export of radiocesium from the estuary to the outer sea takes place due to resuspension and subsequent transport by wind and wave generated currents.     

Size and shape variation in the planktonic foraminiferHeterohelix striata (late cretaceous,southern Scandinavia)

The biserial planktonic foraminiferal species Heterohelix striata (Ehrenberg)has been analyzed by morphometric techniques from six sequential late Maestrichtian core samples from southern Sweden and one sample from the “Dania”quarry of Denmark. The study is based on measurements of number of chambers, size of test (length, width, and thickness),marginal angle, and chamber sizes. In addition, prolocular and apertural sizes were analyzed in the “Dania”quarry sample. The study includes analyses of the ontogenetic development of the tests, stratigraphic variation in size and shape, intrasample variability, and relationship between gross morphology of the test and prolocular and apertural dimensions.     

Characterization of sediments by high-frequency echo-sounding

A high-frequency echo-sounder (200 kHz) was used to characterize the sediments of the shallow Öre Estuary in the Gulf of Bothnia, northern Sweden. The acoustic signal patterns of the echogram were used to differentiate between fine-grained and coarse-grained sediment bottoms according to four major criteria: roughness of the line surface, line thickness, and occurrence of white line and double echo. The echogram characteristics were calibrated against physical properties of the sediment determined in the laboratory. It can be concluded that high-frequency echo-sounding offers an easily applied and reliable method for determining the spatial extent of different bottom sediments (e.g., fine-grained) in shallow waters.     

Multivariate normality tests of planktonic foraminiferal data

Data of a microfossil group, the planktonic foraminifera, have been tested to determine the conformity of various real data distributions to univariate and multivariate normality and the effects that standard transformations have upon the distributions. Studies of two bivariate samples, one trivariate sample, and two quadrivariate samples of size data indicate that distributions frequently deviate greatly from multivariate normality. Univariate distributions are generally positively skewed and show a tendency for leptokurtosis. A logarithmic transformation improved both univariate and multivariate distributions but the number of distributions conformable to normality increased only slightly—from zero to one in the multivariate case and from one to four in the univariate case (totally 15 distributions). Arcsine (p/100) ^1/2 transformations of percentage data in two samples including 16 and 23 species, respectively, decreased highly significant deviations from multivariate normality but distributions remained greatly non-normal. Although markedly positively skewed and leptokurtic univariate distributions were improved in most instances, the number of normal distributions (two) did not change. It follows that neither of the transformations caused significant increases in the number of normal distributions but if it is assumed that the consequences of non-normality are less severe as the deviation from normality decreases, the transformations are justified.     

Laboratory Tests on Shotcrete-Rock Joints in Direct Shear, Tension and Compression

Summary. A series of laboratory tests was performed on cemented shotcrete-rock joints to investigate the strength and stiffness of the interfaces, while simulating field conditions as close as possible. The direct shear test formed the core of the experimental work, while the tension and compression tests were complementary. To simulate loading conditions experienced in practical cases the direct shear tests were performed under fairly low normal stresses. In most practical cases when shotcrete is used with rock bolts, the normal load on shotcrete lining seldom exceeds 0.2 to 0.5 MPa. The direct shear test results show that, for such normal load range the shear strength is determined by the bond strength for genuinely bonded shotcrete-rock interfaces. For higher normal stresses (σ_n > 1.0 MPa), which rarely exist at the shotcrete-rock interface, the shear strength is largely influenced by friction resulting in the cohesive strength being less significant. Assessment of the shear surface revealed that the steel fibres in the shotcrete appeared to contribute significantly to the frictional component. The shear and normal stiffnesses of the interface were also determined, which were in principal the stiffnesses of the bond. An interesting observation was the complex interaction at the interface and the mechanisms that controlled the peak shear strength which depended on the surface roughness, the existence of natural flaws and the normal load.     

Groundwater response to climate variability in Mediterranean type climate zones with comparisons of California (USA) and Portugal

Hydrogeology Journal - Aquifers are a fundamental source of freshwater, yet they are particularly vulnerable in coastal regions with Mediterranean type climate, due to both climatic and...     

Oscillatory behavior of monsoon rainfall over Sri Lanka during the late 19th and 20th centuries and its relationships to SSTs in the Indian Ocean and ENSO

Summary In this study, we have analyzed the temporal oscillations of precipitation in meso-scale zones of Sri Lanka to examine potential existence of periodic oscillatory behavior in rainfall. Only a few statistically significant cycles were identified: a 3.5-year cycle in most of central Sri Lanka during the January–March rainfall regime and a cycle of the same length in southwestern Sri Lanka during the October regime. A 2.1-year cycle marks the northeastern parts of Sri Lanka during the December/April contrast rainfall regime. This cycle is shown to be strongly related to Quasi-Biennial Oscillation. October and November rainfall are found to be coupled with ENSO fluctuations, and on average, more than 900 mm more rainfall is observed per month over all stations during El Ni?o than during La Ni?a years. Analysis of relationships between the observed meso-scale rainfall regions and the Sea Surface Temperatures (SSTs) in the Indian Ocean north of the Equator showed that the northern Indian Ocean can be divided into three particular regions based on similarity in the SST fluctuations: (a) a region with cool upwelling water, (b) non upwelling water, and (c) the Indian Ocean Warm Pool. We found that there are no statistically significant relationships between the observed SST regions in the Indian Ocean and the meso-scale precipitation patterns in Sri Lanka.     

Multivariate analysis of environmentally controlled variation in Lagena: Late Maastrichtian,Sweden

Costate forms of Lagena (benthonic foraminifer) have been studied in an uppermost Maastrichtian bore-hole core sequence (28 levels) from southern Sweden. Analysis of a large sample shows that consistent assignment to previously described “species” of costate Lagena is not possible. This observation is supported by multivariate analysis of five morphologic variables which indicates that there are no distinct clusters of specimens along principal component axes associated with general size, number of costae, and relationships between roundness of test/length and number of costae. Specimens with a basal ring differ from specimens with an apical spine and those with no basal structure with regard to average number of costae. They also differ from specimens with no basal structure with regard to relationships between roundness of test/length and number of costae. These characters grade into each other thus preventing them from being used as taxonomic criteria.Mean ratios of benthonic foraminifers to total benthonic and planktonic formaminifers determined individually for each level are inversely related to mean relative frequencies of costate Lagena and directly related to mean general sizes of costate Lagena. The benthonic/planktonic ratio has been suggested by other workers to represent a paleobathymetric index across a continental slope and shelf when open marine conditions prevailed. If this were so in the Danish basin at the end of the Cretaceous, costate Lagena would have been relatively less frequent and larger at shallower depths.As a result of the study, the analyzed specimens are considered as representing a single morphospecies of the costate species Lagena sulcata. Between-level variation is regarded as ecophenotypic, and within-level variation as natural biologic variation of no taxonomic significance. A total of about 1000 species of Lagena has been described in the literature which is probably many orders of magnitude too great for a genus with such a simple morphology as Lagena. A revision of the taxonomy of Lagena is, therefore, probably necessary on a wide scale.     

Size and shape variation in the planktonic foraminiferHeterohelix striata (late cretaceous, southern Scandinavia)

The biserial planktonic foraminiferal species Heterohelix striata (Ehrenberg)has been analyzed by morphometric techniques from six sequential late Maestrichtian core samples from southern Sweden and one sample from the Daniaquarry of Denmark. The study is based on measurements of number of chambers, size of test (length, width, and thickness),marginal angle, and chamber sizes. In addition, prolocular and apertural sizes were analyzed in the Daniaquarry sample. The study includes analyses of the ontogenetic development of the tests, stratigraphic variation in size and shape, intrasample variability, and relationship between gross morphology of the test and prolocular and apertural dimensions.