Mytilus californianus as an indicator of heavy metals on the northwest coast of Baja California, Mexico.

Samples of Mytilus californianus were analyzed to determine the spatial and temporal distribution of Ag, Al, Cd, Cr, Cu, Mn, Pb and Zn concentrations on the northwest coast of Baja California and to compare the results with levels reported for California, USA. The samples were collected at eight sites from the US-Mexican border to San Quintín, BC (300 km south of the border) in February and July 1982 and 1994. During both years, north-south gradients in the concentration of Ag and Pb were observed, with the highest values close to the US-Mexican border (Ag = 0.60-1.54 and Pb = 0.21-2.89 micrograms g-1) and the lowest in the southern part of the study area (Ag = 0.05-0.10 and Pb = not detectable-0.03 microgram g-1). The Ag and Pb gradients suggest that their distributions are affected by anthropogenic activities close to the US-Mexican border. South-north gradients in the concentration of Cd (minimum = 0.59-2.16 and maximum = 2.61-12.93 micrograms g-1), for both 1982 and 1994, were observed. The geographic annual means of Pb for California (average of six stations along the entire state) were significantly higher than those of this study (average of the eight sampling sites) in 1982 and 1994. Cu in California was significantly greater than that of this study only in 1994. Cluster analyses on all metals indicate three similar geographic zones in 1982 and 1994, suggesting a relative consistency in the processes that determine the spatial variability of the concentration of some metals in M. californianus on the northwest coast of Baja California.     

A catastrophe progression approach based index sensitivity analysis model for the multivariate flooding process

Flood mitigation should deal with those most sensitive flooding elements to very efficiently release risks and reduce losses. Present the most concerns of flood control are peak level or peak discharge which, however, may not always be the most sensitive flooding element. Actually, along with human activities and climate change, floods bring threats to bear on human beings appear in not only peak level and peak discharge, but also other elements like maximum 24-h volume and maximum 72-h volume. In this paper, by collecting six key flooding intensity indices (elements), a catastrophe progression approach based sensitivity analysis algorithm model is developed to identify the indices that mostly control over the flood intensity. The indices sensitivity is determined through a selected case study in the Wujiang River, South China, based on half a century of flow record. The model results indicate that there is no evident relationship of interplay among the index sensitivities, but the variability of the index sensitivity is closely related to the index variability and the index sensitivity increases with the decrease of index value. It is found that peak discharge is not the most influential flooding factor as is generally thought in this case. The sensitivity value of the maximum 24-h volume is the greatest influential factor among all the other indices, indicating that this index plays a leading role in the flood threat of the Wujiang River, South China. It is inferred that, for the purpose of flood warning and mitigation, the peak flood discharge is not always the most sensitive and dominant index as opposed to the others, depending on the sensitivity.     

A direct scaling analysis for the sea level rise

The estimation of long-term sea level variability is of primary importance for a climate change assessment. Despite the value of the subject, no scientific consensus has yet been reached on the existing acceleration in observed values. The existence of this acceleration is crucial for coastal protection planning purposes. The absence of the acceleration would enhance the debate on the general validity of current future projections. Methodologically, the evaluation of the acceleration is a controversial and still open discussion, reported in a number of review articles, which illustrate the state-of-art in the field of sea level research. In the present paper, the well-proven direct scaling analysis approach is proposed in order to describe the long-term sea level variability at 12 worldwide-selected tide gauge stations. For each of the stations, it has been shown that the long-term sea level variability exhibits a trimodal scaling behaviour, which can be modelled by a power law with three different pairs of shape and scale parameters. Compared to alternative methods in literature, which take into account multiple correlated factors, this simple method allows to reduce the uncertainties on the sea level rise parameters estimation.     

Analysis of the Characteristics of Low-Latitude GPS Amplitude Scintillation Measured During Solar Maximum Conditions and Implications for Receiver Performance

Ionospheric scintillations are fluctuations in the phase and/or amplitude of trans-ionospheric radio signals caused by electron density irregularities in the ionosphere. A better understanding of the scintillation pattern is important to make a better assessment of GPS receiver performance, for instance. Additionally, scintillation can be used as a tool for remote sensing of ionospheric irregularities. Therefore, the study of ionospheric scintillation has both scientific as well as technological implications. In the past few years, there has been a significant advance in the methods for analysis of scintillation and in our understanding of the impact of scintillation on GPS receiver performance. In this work, we revisit some of the existing methods of analysis of scintillation, propose an alternative approach, and apply these techniques in a comprehensive study of the characteristics of amplitude scintillation. This comprehensive study made use of 32?days of high-rate (50?Hz) measurements made by a GPS-based scintillation monitor located in S?o José dos Campos, Brazil (23.2°S, 45.9°W, ?17.5° dip latitude) near the Equatorial Anomaly during high solar flux conditions. The variability of the decorrelation time (τ₀) of scintillation patterns is presented as a function of scintillation severity index (S ₄). We found that the values of τ₀ tend to decrease with the increase of S ₄, confirming the results of previous studies. In addition, we found that, at least for the measurements made during this campaign, averaged values of τ₀ (for fixed S ₄ index values) did not vary much as a function of local time. Our results also indicate a significant impact of τ₀ in the GPS carrier loop performance for S ₄?≥?0.7. An alternative way to compute the probability of cycle slip that takes into account the fading duration time is also presented. The results of this approach show a 38% probability of cycle slips during strong scintillation scenarios (S ₄ close to 1 and τ₀ near 0.2?s). Finally, we present results of an analysis of the individual amplitude fades observed in our set of measurements. This analysis suggests that users operating GPS receivers with C/N ₀ thresholds around 30?dB-Hz and above can be affected significantly by low-latitude scintillation.     

Ore-forming fluid and mineralization of Caijiaying and Dajing polymetallic ore deposits

Fluid inclusions from the Dajing and Caijiaying deposits have nearly the same ho-mogenization temperature. Correlation between temperature and salinity shows that both Sn-and Cu-bearing fluids Sn and Cu were present in the Dajing deposit but only one kind of fluids continuously evolved in the Caijiaying deposit. Study on rare earth elements (REE) in ancient fluid from the inclusions indicates that the fluid of Sn mineralizing stage in Dajing was derived from remelting magma of the continental crust, and the fluid of Cu-Pb-Zn mineralizing stage in the Dajing deposit and the fluid of Cu-Pb-Zn mineralization in the Caijiaying deposit were derived from the mantle. It is concluded that the Cu-Pb-Zn mineralizations in the Dajing and Caijiaying deposits resulted from the identical tectono-thermal event of magma-fluids induced by Mesozoic tectonic transition and extension in the eastern part of North China Craton.     

Criteria for defining and recognizing the various orders of sequences in outcrop sequence stratigraphy

Sequence stratigraphy which began in the late seventies of the previous century has not only enriched and widened the scope of stratigraphy, but also has been widely used in sedimentary geology, basin analy-sis, exploration of oil and gas, and other fields of ge-ology. In the last two decades and more, sequence stratigraphy, as a new branch of stratigraphical disci-pline, has become a cornerstone of modern stratigra-phy, and has produced more profound influences than all others. The currently …     

Synthesis of todorokite by refluxing process and its primary characteristics

Todorokite is one of the common manganese ox-ides in manganese ore deposits, weathering product of manganese-bearing rocks, soils and sediments. It is also an important component in the abundant marine manganese nodules. Since todorokite was firstly found in Japanese Todoroki mine in 1934, its properties and origination have appeared to be very interesting to many researchers[1—3]. It has a stable structure similar to porous molecular sieves, constructed of triple MnO6 octahedral chains. Th…     

Geospatial-temporal analysis of land-use changes in the Yellow River Delta during the last 40 years

Research on land use/land cover changes (LUCC)has been the core project of the Global EnvironmentalChanges since the 1990s[1—6]. Scientists at home andabroad have been laying emphasis on integrationstudies on land-use change by “space and process”features[7—10] as researches on LUCC are in a greatdeal. It is of paramount important for us to studyLUCC at various spatial-temporal scales and build aquantitative assessment of land-use conversion by in-tegrated spatial-temporal features. …     

Mean and eddy motion in the Skagerrak/northern North Sea: insight from a numerical model

Insight regarding the mean and eddy motion in the Skagerrak/northern North Sea area is gained through an analysis of model-simulated currents, hydrography, kinetic energy and relative vorticity for the 2 years 2000 and 2001. In this a -coordinate ocean model is used. Since the tidal currents are generally strong in the area, care is exercised to distinguish the mesoscale (eddy) motion from higher-frequency motion such as tides, before computing the mean and eddy kinetic energy. The model-simulated response is first compared with available knowledge of the circulation in the area, and when available, also with sea-surface temperature obtained from satellite imagery. It is concluded that the model appears to faithfully reproduce most of what is known, in particularly the upper mixed layer circulation. An analysis of the mean and eddy kinetic energy reveals that many of the mesoscale structures found in the area are recurrent. This is particularly true for the structures off the southern tip of Norway. Also in general, areas of strong mean and eddy kinetic energy are co-located. The exception is the area off the southern tip of Norway, where the eddy kinetic energy is much larger than its mean counterpart. An analysis of the relative vorticity reveals that the variability found is due to the occurrence of recurrent anticyclonic eddies. It is hypothesized that these eddies are generated due to an offshore veering of the Norwegian coastal current (NCC) as it reaches the eastern end of the Norwegian Trench plateau. Here it becomes a free jet, which is then vulnerable to either barotropic instability caused by the horizontal shear in the jet-like structure of the NCC at this point, or a baroclinic (frontal) instability. The latter may come into play when the NCC veers offshore and its relatively fresh water meets the inflowing saline water of Atlantic origin, a frontogenesis that may become strong enough for cyclogenesis to take place. Due to the depth-independent nature of the model-generated eddies, the barotropic instability is the most likely candidate. It remains to resolve the reason for the offshore veering of the NCC. The most likely candidate mechanisms are vortex squeezing or simply that the coastline curvature is large enough for the NCC to separate from the coast in a hydraulic sense.Responsible Editor: Phil Dyke