Effects of red mud on marine animals

Red mud is a waste product in the reduction of bauxite in the production of aluminium. The exact composition of red mud depends on the source of the bauxite and its treatment during production. This variation has been responsible for conflicting reports about the damage caused by dumping red mud at sea.     

Environmental study of the disposal of red mud waste

Alkaline red mud is a waste product of extracting alumina from bauxite and it is produced in large quantities. This report examines the ecological consequences of red mud waste during the first 18 months of operation of a refinery in the Northern Territory of Australia.     

Terrestrial heat flow in Hungary

Summary The geothermal gradient in the Carpathian Basin lies between 40–70 C/km. According to careful measurements in shafts the value of terrestrial heat flow in the southern part of Hungary is (2.055–3.066)·10^–6 cal/cm² sec. These measurements are believed the first ever attempted in continental Europe. Systematic heat flow measurement are being extended to other part of this country.     

Comparison of two extensometric stations in Hungary

Quartz-tube extensometers are used to measure rock deformations in two geodynamic observatories in Hungary in order to contribute to the investigation of recent tectonic movements on the area of the Pannonian Basin. One of the observatories is situated on the border of the Alps at Sopronbánfalva and is set in the metamorphic (gneiss) material of the mountains. The other station is in the basically karstic environment of the Mátyáshegy (Mátyás Hill) near Budapest. The aim of this paper is to investigate how the local conditions, such as structure of the observatory, topography or geologic features of the surrounding rocks, lead to additional or modified deformations of the extensometric stations. Data collected over eight years were processed and analysed to compare the observatories taking into account geologic, lithologic and topograpic properties of the measurement sites. Tidal and coherence analysis of the continuous strain measurements revealed that the instrument at Sopronbánfalva is more sensitive to atmospheric pressure loading than the extensometer at Mátyáshegy. Signal to noise values from the data processing of the short period variations support the higher stability of tidal strain measurements at Mátyáshegy. The strain rates measured by extensometers in both observatories are in good agreement with the strain rates inferred from GPS measurements of the Hungarian GPS Geodynamic Reference Network and the Central European GPS Reference Network.     

Deep-sea foraminifera from the Cassidaigne Canyon (NW Mediterranean): Assessing the environmental impact of bauxite red mud disposal

Benthic foraminiferal assemblages were investigated from two sites along the axis of the Cassidaigne Canyon (NW Mediterranean Sea). Both areas are contaminated by bauxite red mud enriched in iron, titanium, vanadium and chromium. These elemental enrichments are related to bauxite-derived minerals and various amorphous phases. At the shallowest station located very close to the pipe outlet, the benthic living foraminiferal community is characterised by a very low diversity and by an unusual dominance of Gyroidina umbonata and Bulimina marginata. The mechanical stress related to downslope transport of red mud is a likely source of hydro-sedimentary pollution precluding the settlement of diverse fauna. The living and dead foraminiferal faunas from the deepest site are typical of oligo-mesotrophic conditions prevailing in natural environments. There, bauxite residues have obviously no environmental impact on foraminiferal faunas. The bioavailability of trace metals is likely low as elemental enrichments were not observed in foraminiferal test chemistry.     

Spatial heterogeneity in estuarine mud dynamics

The fate of mud in an estuary over an entire year was unravelled using complementary, independent, spatially explicit techniques. Sequential ERS-2 SAR and Envisat MERIS-FR data were used to derive synoptic changes in intertidal bottom mud and suspended particulate matter (SPM) in the top of the water column, respectively. These satellite data were combined with in situ measurements and with a high resolution three-dimensional cohesive sediment model, simulating mud transport, resuspension, settling and deposition under the influence of tides, wind, waves and freshwater discharge. The spatial distribution of both bottom mud and SPM as observed by in situ and satellite techniques was largely explained by modelled estuarine circulation, tidal and wind-induced variations in vertical mixing and horizontal advection. The three data sources also showed similar spring-neap and seasonal variations in SPM (all factor 1.5 to 2), but semi-diurnal tidal variations were underestimated by the model. Satellite data revealed that changes in intertidal bottom mud were spatially heterogeneous, but on average mud content doubled during summer, which was confirmed by in situ data. The model did not show such seasonal variation in bed sediment, suggesting that seasonal dynamics are not well explained by the physical factors presently implemented in the model, but may be largely attributed to other (internal) factors, including increased floc size in summer, temporal stabilisation of the sediment by microphytobenthos and a substantially lower roughness of the intertidal bed in summer as observed by the satellite. The effects of such factors on estuarine mud dynamics were evaluated.     

Climatic effects on the runoff conditions in Hungary

Using runoff and climatic observations from 37 small watersheds in Hungary a regional climate-runoff relationship has been established. This non-linear relationship is a modification of Budiko's similar equation and can be used to estimate the effect of climate changes on long-term average runoff. The degree of change in runoff depends not only on changes in precipitation and temperature, but also on the present climate characteristics. The regional relationship is verified only within a relatively narrow range of precipitation and temperature and this fact limits its use in climate impact assessment. Model calculations show that a relatively slight shift in climate, an increase in annual temperature by 0.5°C, and a decrease of annual rainfall by 0.08 mm d^?1 may lead to a decrease of runoff by 25-30 per cent in small watersheds of Hungary.     

Numerical investigation of fluid mud motion using a three-dimensional hydrodynamic and two-dimensional fluid mud coupling model

A water-fluid mud coupling model is developed based on the unstructured grid finite volume coastal ocean model (FVCOM) to investigate the fluid mud motion. The hydrodynamics and sediment transport of the overlying water column are solved using the original three-dimensional ocean model. A horizontal two-dimensional fluid mud model is integrated into the FVCOM model to simulate the underlying fluid mud flow. The fluid mud interacts with the water column through the sediment flux, current, and shear stress. The friction factor between the fluid mud and the bed, which is traditionally determined empirically, is derived with the assumption that the vertical distribution of shear stress below the yield surface of fluid mud is identical to that of uniform laminar flow of Newtonian fluid in the open channel. The model is validated by experimental data and reasonable agreement is found. Compared with numerical cases with fixed friction factors, the results simulated with the derived friction factor exhibit the best agreement with the experiment, which demonstrates the necessity of the derivation of the friction factor.     

鼻咽非霍奇金淋巴瘤的影像诊断

目的:探讨鼻咽非霍奇金淋巴瘤(NHL)的影像学特征。材料与方法:回顾性分析经病理证实的28例鼻咽NHL的MR或CT表现,其中22例行CT检查,6例行MR检查。观察肿块的形态、有无坏死、邻近结构及颈部淋巴结浸润的特点。结果:16例表现为鼻咽粘膜对称性或大致对称性弥漫性增厚,12例表现为鼻咽顶后壁和(或)一侧壁局限性增厚,形成软组织肿块,并突向鼻咽腔。25例密度(信号)强化均匀。病灶累及口咽壁者14例,其中腭或(和)舌根扁桃体浸润4例;累及喉咽2例;累及鼻腔4例;枕骨斜坡受侵并累及颅底肌肉1例。17例患者合并颈部淋巴结肿大,其中4例内出现坏死。结论:鼻咽NHL常侵犯鼻咽多个侧壁,病灶及淋巴结坏死少见,很少累及颅底骨质,易向下蔓延至咽淋巴环其他部位。影像学检查对其诊断、鉴别诊断及病灶范围的判断有重要价值。     

结节性硬化症的影像学表现

目的 分析结节性硬化症的影像学表现。材料与方法 回顾性分析30例临床和病理证实的结节性硬化症的影像学表现。结果 CT发现25例室管膜下钙化,2例实质内钙化,1例合并巨细胞星形细胞瘤及梗阻性脑积水。MRI发现3例室管膜下未钙化结节。B超发现2例双肾多发血管平滑肌脂肪瘤,其中1例同时有肝血管瘤。结论 室管膜下和/或皮质钙化、未钙化结节及双肾多发血管平滑肌脂肪瘤是非常重要的诊断结节性硬化的征象,结合临床三联征能准确诊断。     

防震减灾科普示范学校建设的现状和应注意把握的几个环节

防震减灾科学技术教育是基础教育的重要组成部分,是构建和谐社会的一个重要内容。而搞好防震减灾科普示范学校建设就是贯彻落实《中华人民共和国防震减灾法》的有力举措,以达到教育一个孩子、带动一个家庭、影响整个社会的目的,推动全社会防震减灾意识的形成和增强。但由于防震减灾科普示范学校建设仍处于探索阶段,经验普遍比较缺乏,再加上有的指导思想不明确、工作措施不到位、方法形式简单,     

Critical erosion profiles in macro-tidal estuary sediments: Implications for the stability of intertidal mud and the slope of mud banks

Vertical profiles of the critical erosion threshold (τ_crit) in sediment have been measured at 11 stations along the axis of the Tamar Estuary and at a single station in a tributary of the Tamar at St. John's Ford. The τ_crit of surface sediment increased from 0.04 Pa in the upper, brackish estuary to 0.09 Pa in the lower estuary. In the upper estuary τ_crit only increased slightly with depth whereas in the marine estuary τ_crit increased rapidly from 0.09 Pa at the surface to 0.25 Pa at 15 cm below the sediment surface. The results showed that the relationship between τ_crit and bulk density (ρ_b) obtained previously for surface sediment was also applicable to sediments from depths of 10–15 cm and probably deeper. Profiles of ρ_b were measured to depths of 70 cm using a corer. In the lower (marine) estuary ρ_b increased with depth in the sediment from 1580 kg m⁻³ at the surface to 1720 kg m⁻³ at 70 cm. In the upper estuary ρ_b values were lower at 1170–1200 kg m⁻³ and profiles were almost homogeneous indicating that consolidation was not occurring. The mid-estuary was transitional between these two situations. These results are consistent with the seasonal accumulation and loss of ‘mobile’ sediment observed previously in the upper estuary with changes in river flow, and with the apparent stability of intertidal mud in the lower marine estuary deduced from historical bathymetric survey records. The slopes of the intertidal mud banks ranged from 1–2% in the lower estuary to 20–25% in mid-estuary but, instead of continuing to increase in steepness towards the head as the estuary became narrower, the measured slopes actually decreased. It is speculated that the lack of consolidation through continual mobilisation and settlement cycles combined with an increase in silt content in the upper estuary resulted in sediment that lacked the mechanical strength to maintain steep slopes.     

Erosion rate of sand and mud mixtures

Erosion of mixed cohesive and noncohesive sediments is studied using the erosion test instrument SEDFlume. The sediment mixtures are composed of well-sorted quartz sand (0.25–0.5 mm) and one of the three used muds: kaolinite, kaolinite-bentonite and Mississippi River muds. The mud contents cover from 0 to 100%. The measured data of erosion rate and bed shear stress are used to examine the segmented linear, nonlinear, and exponential erosion models. The parameters of each erosion model are related to the physical properties of sediment mixtures, including clay fraction, mud fraction, mixture dry density, and mud dry density. It is found that the three models can fit well with the data, and their parameters have strong relations with the mud fraction and mud dry density, to a less extent with the clay fraction, but not with the mixture dry density.     

Geotechnical properties of the Cassino Beach mud

Knowledge of the marine soils properties, together with hydrodynamic and climatic data, plays an important role for a better understanding of the dynamic behavior of sandy and muddy coasts. This paper deals with reporting and basic interpretation of two campaigns of exploration and characterization of the mud of Cassino Beach, southern Brazil, carried out during the years of 2004 and 2005. Samples were obtained by means of cores collected at some locations offshore, and were submitted to various laboratory geotechnical tests, including determination of the physical index, grain size distribution, Atterberg limits, and shear resistance by both triaxial and shear vane tests. Results confirm the existence of a very soft soil deposit offshore Cassino Beach, highly plastic, compressible, and viscous, forming an important database for further studies.     

Modelling sand–mud morphodynamics in the Friesche Zeegat

The objective of the study presented in this paper is to investigate the predictive capabilities of a process-based sand–mud model in a quantitative way. This recently developed sand–mud model bridges the gap between noncohesive sand models and cohesive mud models. It explicitly takes into account the interaction between these two sediment fractions and temporal and spatial bed composition changes in the sediment bed [Van Ledden (2002) 5:577–594, Van Ledden et al. (2004a) 24:1–11, Van Ledden et al. (2004b) 54:385–391]. The application of this model to idealized situations has demonstrated a good qualitative agreement between observed and computed bed levels and bed composition developments. However, in real-life situations, a realistic quantitative prediction of the magnitude and timescale of this response is important to assess the short-term and long-term impacts of human interventions and/or natural changes. For this purpose, the Friesche Zeegat in the Wadden Sea (the Netherlands) is used as a reference to hindcast the morphological response in the period 1970–1994. Due to the closure of the Lauwerszee in 1969, the tidal prism of this tidal basin was reduced by about 30%. Significant changes in the bed level and bed composition have occurred in the decades following the closure to adjust to the new hydrodynamic conditions. We modeled the long-term bed level and bed composition development in the Friesche Zeegat in the period 1970–1994 starting with the geometry of 1970 by using a research version of Delft3D, which incorporates the sand–mud formulations proposed by [Van Ledden (2002) 5:577–594].The computed total net deposition in the tidal basin in the period 1970–1994 agrees well with the observations, but the observed decrease of the import rate with time is not predicted. The model predicts net deposition in the deeper parts and at the intertidal area in the basin and net erosion in between, which resembles the observations qualitatively. Furthermore, the computed distribution of sand and mud in the basin of the Friesche Zeegat appears to be realistic. Analysis of the results shows that the absence of the decreasing import rate in the basin is caused by a poor quantitative prediction of the changes in the hypsometry of the basin. Because of this, the computed velocity asymmetry in the main channel tends toward flood dominance, whereas the observations indicate that the system is ebb-dominant in 1992. Although the sand–mud model needs to be further improved and verified, the results presented in this paper indicate that the model can be applied as a first step to estimate the effects of human interventions on the large-scale bed level and bed composition changes in tidal systems with sand and mud.     

Sand–mud morphodynamics in a short tidal basin

The influence of sand and mud transport on the morphological behaviour of a short tidal basin is investigated in this paper. For this purpose, a morphological model is applied in which sand and mud transport are included and the temporal and spatial bed composition variations are taken into account. Initially, the morphological development shows a sand wave near the entrance of the basin and a mud deposition wave more landward. A quasi equilibrium bed level profile is found after a long period (order century) with a sandy bed surface over almost the entire basin and only a small muddy area near the landward end. The dimensionless ratio between the deposition and erosion flux turns out to be a crucial parameter for the understanding of the observed behaviour. Comparison with previous studies on short tidal basins for sand indicates only that the presence of mud in a combined sand mud model does not change the equilibrium bed level profile considerably for the applied parameter settings herein, but drastically decreases the morphological time scale. Comparison between model results and field data of the Wadden Sea suggests that the obtained bed level and bed composition profile are realistic, indicating that the process-based sand mud model is a first step towards a better understanding of sand mud distributions in tidal basins.Responsible Editor: Jens Kappenberg