Models of Ground Deformation and Eruption Magnitude from a Deep Source at Popocatepetl Volcano,Central Mexico

Popocatepetl volcano in Central Mexico entered its latest stage of activity in late 1994. Due to the nature of its eruptive history and its location in a heavily populated area, it constitutes the highest risk in the cuntry. For this reason the volcano is currently under continuous surveillance; yet the interpretation of the information is carried out mostly on empirical basis and an integrating working model is lacking, at the present. In this paper, models of elastic deformation and mass erupted are developed to estimate the mass erupted according to the observed deformation patterns. We present results obtained from input based upon a gravimetric model of the volcano's internal structure and reasonable physical parameters of the volcanic system. These results are helpful in the planning of deformation and gravimetric observations aimed to forecast a major eruption.     

Distribution of hydrocarbons in the oyster,Pinctada margaratifera,along the coast of Kuwait

Concentrations of total hydrocarbons within the boiling point range of the alkanes n-C₁₄ and n-C₃₂ were determined in oysters, Pinctada margaratifera, from coastal waters of Kuwait. Levels of petroleum-derived hydrocarbons were highest in an area adjacent to the major oil loading facilities. Whether the use of dispersants to treat minor spills increases levels of incorporation of petroleum compounds into the food webs could not be concluded from the data of this study. Levels of total petroleum-type hydrocarbons in the oysters at this site were equivalent to those in mussels, Mytilus sp., from harbours, bays and urban coastal areas of California. The Kuwaiti oysters lacked a C₂₈ pentacyclic triterpane that was present in extracts of mussels from southern California that had been recently exposed to a minor spill or to a natural seepage. Levels of DDE and PCB were comparable to those in relatively unpolluted areas of North America.     

Electrical triggering of earthquakes: results of laboratory experiments at spring-block models

Recently published results of field and laboratory experiments on the seismic/acoustic response to injection of direct current(DC) pulses into the Earth crust or stressed rock samples raised a question on a possibility of electrical earthquake triggering. A physical mechanism of the considered phenomenon is not clear yet in view of the very low current density(10~(-7)–10~(-8) A/m~2) generated by the pulsed power systems at the epicenter depth(5–10 km) of local earthquakes occurred just after the current injection. The paper describes results of laboratory‘‘earthquake' triggering by DC pulses under conditions of a spring-block model simulated the seismogenic fault. It is experimentally shown that the electric triggering of the laboratory ‘‘earthquake'(sharp slip of a movable block of the spring-block system) is possible only within a range of subcritical state of the system, when the shear stress between the movable and fixed blocks obtains 0.98–0.99 of its critical value. The threshold of electric triggering action is about 20 A/m~2 that is 7–8 orders of magnitude higher than estimated electric current density for Bishkek test site(Northern Tien Shan, Kirghizia) where the seismic response to the man-made electric action was observed. In this connection, the electric triggering phenomena may be explained by contraction of electric current in the narrow conductive areas of the faults and the corresponding increase in current density or by involving the secondary triggering mechanisms like electromagnetic stimulation of conductive fluid migration into the fault area resulted in decrease in the fault strength properties.     

Selecting best mapping strategies for storm runoff modeling in a mountainous semi‐arid area

Accurate runoff and soil erosion modeling is constrained by data availability, particularly for physically based models such as OpenLISEM that are data demanding, as the processes are calculated on a cell‐by‐cell basis. The first decision when using such models is to select mapping units that best reflect the spatial variability of the soil and hydraulic properties in the catchment. In environments with limited data, available maps are usually generic, with large units that may lump together the values of the soil properties, affecting the spatial patterns of the predictions and output values in the outlet. Conversely, the output results may be equally acceptable, following the principle of equifinality. To studyhow the mapping method selected affects the model outputs, four types of input maps with different degrees of complexity were created: average values allocated to general soil map units (ASG1), average values allocated to detailed map units (ASG2), values interpolated by ordinary kriging (OK) and interpolated by kriging with external drift (KED). The study area was Ribeira Seca, a 90 km² catchment located in Santiago Island, Cape Verde (West Africa), a semi‐arid country subject to scarce but extreme rainfall during the short tropical summer monsoon. To evaluate the influence of rainfall on runoff and erosion, two storm events with different intensity and duration were considered. OK and KED inputs produced similar results, with the latter being closer to the observed hydrographs. The highest soil losses were obtained with KED (43 ton ha^{? 1} for the strongest event). To improve the results of soil loss predictions, higher accurate spatial information on the processes is needed; however, spatial information of input soil properties alone is not enough in complex landscapes. The results demonstrate the importance of selecting the appropriate mapping strategy to obtain reliable runoff and erosion estimates. Copyright © 2013 John Wiley & Sons, Ltd.     

An isopycnal view of the Nordic Seas hydrography with focus on properties of the Lofoten Basin

Few basins in the world exhibit such a wide range of water properties as those of the Nordic Seas with cold freshwaters from the Arctic in the western basins and warm saline waters from the Atlantic in the eastern basins. In this study we present a 50-year hydrographic climatology of the Nordic Seas in terms of depth and temperature patterns on four upper ocean specific volume anomaly surfaces. This approach allows us to better distinguish between change due to variations along such surfaces and change due to depth variations of the stratified water column. Depth variations indicate changes in the mass field while property variations along isopycnals give insight into isopycnal advection and mixing, as well as diapycnal processes. We find that the warmest waters on each surface are found in the north, close to where the isopycnal outcrops, a clear indication of downward mixing of the warmer, more saline waters on shallower isopycnals due to convective cooling at the surface. These saline waters come from the Norwegian Atlantic Slope Current by means of a very high level of eddy activity in the Lofoten Basin.The isopycnal analyses further show that the principal water mass boundary between the waters of Arctic origin in the west and Atlantic waters in the east aligns quite tightly with the Jan Mayen, Mohn, Knipovich Ridge system suggesting little cross-ridge exchange. Instead, the main routes of exchange between the eastern and western basins appear to be limited to the northern and southern ends of ridge system: Atlantic waters into the Greenland Sea in the Fram St and Artic waters into the southern Norwegian Sea just north of the Iceland-Faroe Ridge.Analysis of a representative isopycnal in the main pycnocline shows it to be stable over time with only small variations with season (except where it outcrops in winter in the Greenland and Iceland Seas). However, two very cold winters, 1968–1969, led to greater than average heat losses across the entire Lofoten Basin that eroded away much of the Lofoten eddy and induced the greatest temperature anomaly in the entire 50-year record. Interannual variations in isopycnal layer temperature correlate with the NAO index such that waters in the Iceland Sea become warmer than average with warming air temperatures and conversely in the Lofoten Basin.     

In situ experimental study of reed leaf decomposition along a full salinity gradient

An experimental study on Phragmites australis leaf litter decomposition was conducted in the estuarine environment, Ria de Aveiro, Western Portugal, using the leaf-bag technique, with fine- (1 mm) and coarse-mesh (5 mm) bags. The leaf bags were placed in the field sites at day 0, covering a complete salinity gradient, and replicates were collected over time, at days 3 (leaching), 7, 15, 30 and 60. The biomass loss through the leaching phase, about 20% of the initial leaf mass, was independent of both the salinity and the bag mesh size. The biomass decay pattern along the salinity gradient varied through time and presented strong similarities between the two mesh sizes, with the remaining biomass always lower in the 5 mm mesh-size bags. At days 7 and 15, the lowest remaining biomass was observed at the head of the estuary, the preferential distribution area of P. australis. At day 30, the remaining biomass was higher in the marine area and diminished under a direct relationship with salinity, reaching the lowest value in the freshwater environment, with values ranging from 66% to 44% of the initial weight in 5 mm bags, and from 79% to 51% in 1 mm bags. The largest heterogeneity in the remaining biomass among the study areas positioned along the salinity gradient was found close to days 30 (5 mm) and 40 (1 mm). The overall results indicate that the relationship between leaf decay rate and salinity depends on the decay time considered (k₁₅, k₃₀ or k₆₀) and, for the later stages (k₆₀), also on the leaf-bag mesh size. This implies that the use of leaf litter decay rates as a functional indicator in transitional waters will need to take into consideration the factor location in the salinity gradient and leaf litter stage at which the decay rate is determined. The differences between the decay rates with the mesh size acted mainly at the level of the absolute k value and not at the level of the pattern along the salinity gradient. Even so, the data obtained at the mouth of the estuary, in the area closest to a fully marine environment, indicated that after the initial biomass loss through leaching, P. australis decayed either very slowly, in the 5 mm, or not at all, in the 1 mm mesh bags.     

Toward the application of ecological concepts in EU coastal water management

The EU Water Framework Directive demands the protection of the functioning and the structure of our aquatic ecosystems. The defined means to realize this goal are: (1) optimization of the habitat providing conditions and (2) optimizing the water quality. The effects of the measures on the structure and functioning of the aquatic ecosystems then has to be assessed and judged. The available tool to do this is 'monitoring'. The present monitoring activities in The Netherlands cover target monitoring and trend monitoring. This is insufficient to meet the requirements of the EU. It is, given the EU demands, the ongoing budget reductions in The Netherlands and an increasing flow of unused new ecological concepts and theories (e.g. new theoretical insights related to resource competition theory, intermediate disturbance hypothesis and tools to judge the system quality like ecological network analysis) suggested to reconsider the present monitoring tasks among governmental services (final responsibility for the program and logistic support) and the academia (data analyses, data interpretation and development of concepts suitable for ecosystem modelling and tools to judge the quality of our ecosystems). This will lead to intensified co-operation between both arena's and consequently increased exchange of knowledge and ideas. Suggestions are done to extend the Dutch monitoring by surveillance monitoring and to change the focus from 'station oriented' to 'area oriented' without changing the operational aspects and its costs. The extended data sets will allow proper calibration and validation of developed dynamic ecosystem models which is not possible now. The described 'cost-effective' change in the environmental monitoring will also let biological and ecological theories play the pivotal role they should play in future integrated environmental management.     

A sensitive method for measuring atmospheric concentrations of sulfur dioxide

A new sensitive method for measuring atmospheric concentrations of sulfur dioxide is presented. Samples are obtained using the mist chamber, which collects highly water-soluble gases with high efficiency, and concentrates them in a small volume of water. Particles are removed from the sampled air stream with a teflon filter, before it enters the mist chamber. After collection, the pH of the water is raised above pH 10 using sodium carbonate, then hydrogen peroxide (H₂O₂) is added to oxidize sulfur that may be present in the sulfur (IV) oxidation state, to sulfate. After a reaction time of at least 16 hours, the sulfate concentration is measured by ion chromatography. From the sulfate concentration, the water volume used in the mist chamber, and the volume of air sampled, the atmospheric concentration of SO₂ is computed. The method is not sensitive to other atmospheric sulfur gases such as DMS, SC₂, H₂S, COS, or MSH. The estimated overall precision of the method is 10%. The detection limit at the present stage of technique development is approximately 20 ppt (parts per trillion, or 10^-12 mol · mol^-1) for a 45 minute sampling time, with lower concentrations being detectable with lower precision.     

Geochemical and mineralogical distinctions between Bonnin and Morris (Philadelphia, 1770–1772) porcelain and some contemporary British phosphatic wares

The major element compositions of 15 ceramic sherds from the Bonnin and Morris factory site were determined by electron microprobe. Thirteen samples are phosphatic; the others consist of (a) “soapstone” (magnesian/plombian) and (b) true porcelain, and are interpreted as exotic artifacts, as is one compositionally distinct (relatively SiO₂‐poor, P₂O₅+CaO‐rich) phosphatic sample. Although long considered to be virtually indistinguishable from Bow porcelain (London: ca. 1747–1776), the phosphatic Philadelphia wares have a relatively low mean CaO/P₂O₅ ratio (3.3 versus 3.8; molecular proportions) and high alumina content (6.6 versus 5.4 wt % Al₂O₃). Furthermore, unlike Bow, the Bonnin and Morris samples contain calcic plagioclase (bytownite), and in some instances, an orthoclase‐rich ternary feldspar. The preservation of calcic plagioclase indicates that Philadelphia porcelain was fired at (rather than above) the thermal minimum in the An‐SiO₂‐C₃P system, although the presence of Na (and other fluxes) in these wares precludes the exact determination of the maximum firing temperature from this phase diagram. These wares are also distinctive insofar as the phosphate and melt phases can contain small amounts of lead; they have bulk lead contents of approximately 0.1–1.2 wt % PbO. This component has not been detected in the body of Bow or other contemporary British phosphatic porcelains. Their principal similarity lies in the fact that both wares contain sulfate. In addition, the glazes on Bonnin and Morris porcelain (e.g., PbO ∼ 35–50 wt %; SnO₂ ∼ 1–2%) compositionally resemble those used at Bow. If feldspar is formed at all, then Al‐poor phosphatic porcelain (or those with low CaO/P₂O₅ ratios) will have comparatively low modal calcic plagioclase contents, thereby allowing the rapid depletion of this mineral via resorption by the melt phase during vitrification. Such appears to have been the case for analyzed Bow porcelain, which is therefore interpreted to have been overfired (sensu lato) relative to its Philadelphia counterpart. Conceivably, calcic plagioclase could be preserved in low‐Al wares that were fired only briefly at vitrification temperatures. Given the role of firing history in governing the mineralogy of porcelain, compositional criteria are more reliable for distinguishing these wares. © 2001 John Wiley & Sons, Inc.