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1.
The S and O isotopic composition of dissolved SO4, used as a tracer for SO4 sources, was applied to the water of the Llobregat River system (NE Spain). The survey was carried out at 30 sites where surface water was sampled on a monthly basis over a period of 2a. The concentration of dissolved SO4 varied from 20 to 1575 mg L−1. Sulphur isotopic compositions clustered in two populations: one – 93% of the samples – had positive values with a mode of +9‰; the other had negative values and a mode of −5‰. Data for δ18OSO4 showed a mean value of +11‰, with no bi-modal distribution, though lower values of δ18O corresponded to samples with negative δ34S. These values can not be explained solely by the contribution of bedrock SO4 sources: that is, sulphide oxidation and the weathering of outcrops of sulphates, though numerous chemical sediments exist in the basin. Even in a river with a high concentration of natural sources of dissolved SO4, such as the Llobregat River, the δ34S values suggest that dissolved SO4 is controlled by a complex mix of both natural and anthropogenic sources. The main anthropogenic sources in this basin are fertilizers, sewage, potash mine effluent and power plant emissions. Detailed river water sampling, together with the chemical and isotopic characterisation of the main anthropogenic inputs, allowed determination of the influence of redox processes, as well as identification of the contribution of natural and anthropogenic SO4 sources and detection of spatial variations and seasonal changes among these sources. For instance, in the Llobregat River the input of fertilisers is well marked seasonally. Minimum values of δ34S are reported during fertilization periods – from January to March – indicating a higher contribution of this source. The dual isotope approach, δ34S and δ18O, is useful to better constrain the sources of SO4. Moreover, in small-scale studies, where the inputs are well known and limited, the mixing models can be enhanced and the contribution of the different sources can be quantified to some extent. 相似文献
2.
A. Plewka T. Gnauk E. Brüggemann C. Neusüss H. Herrmann 《Journal of Atmospheric Chemistry》2004,48(2):131-156
Inorganic ions, organic carbon (OC), elemental carbon (EC) and a variety of organic single species in airborne particles have been determined at the research station of the Leibniz – Institut für Troposphärenforschung (IfT) in Melpitz (Germany) in autumn 1997.Samples of eight selected measurement events were divided in two groups in order to investigate differences in the chemical composition of particles originating from southwesterly (SW – developed EU countries) or from easterly directions (E – less developed eastern countries). Differences between these two groups were tested statistically by Student's t-test.Five stage cascade impactor samples show nitrate as most abundant in the accumulation mode in the SW group. EC and sulphate show the most abundant mass fractions in the E group. That can be considered as a consequence of domestic coal heating and coal-fired power plant emissions in the region of westerly Poland, northern Czech Republic and easterly Germany. Higher nitrate concentrations in the SW group can be explained by stronger NO
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emissions caused by the leeward plume of the conurbation of Leipzig, as well as by the still higher traffic density in western Germany.The methane sulphonic acid (MSA) mass fraction was higher for SW air masses in accumulation mode particles, probably indicating marine origin. Succinic acid also showed higher mass fractions for the SW group. This could be caused by primary emission in automobile exhaust gases and photochemical formation during transport from SW. Indeed, during SW sampling, solar radiation intensity was higher than during E sampling.The observed differences in the particle composition are an expression of the still existing technology gradient in Europe. Future campaigns could show the development to a joint economy with smaller differences in anthropogenic emissions. 相似文献
3.
Abstract Knowledge of the processes that control nitrate migration and its geochemical evolution in the subsurface are fundamental for the regional management of polluted aquifers. In this paper, the spatial distribution and transient variations of nitrate concentrations, associated with manure fertilization, are used to depict hydrogeological dynamics within the sedimentary aquifer system of la Plana de Vic in the Osona region of Spain. Flow systems are identified from geological, hydraulic head, hydrochemical and isotopic data, and by considering nitrate itself as a tracer that indicates how flow paths are modified by human pressures. In this area, nitrates move through fractured aquitards in flows induced by groundwater pumping. Moreover, the lack of casing in the boreholes permits a mixing of groundwater from distinct layers inside the wells, which negates any benefits from the low-nitrate groundwater found in the deepest aquifer layers. Therefore, impacts on groundwater quality are related to intensive manure fertilization as well as to inadequate well construction and exploitation strategies. Citation Menció, A., Mas-Pla, J., Otero, N. & Soler, A. (2011) Nitrate as a tracer of groundwater flow in a fractured multilayered aquifer. Hydrol. Sci. J. 56(1), 108–122. 相似文献
4.
We simulate the satellite constellations of two Global Navigation Satellite Systems: Galileo (EU) and GPS (USA). Satellite motions are described in the Schwarzschild space-time produced by an idealized spherically symmetric non rotating Earth. The trajectories are then circumferences centered at the same point as Earth. Photon motions are described in Minkowski space-time, where there is a well known relation, (Coll et al. in Class. Quantum Gravit. 27:065013, 2010a), between the emission and inertial coordinates of any event. Here, this relation is implemented in a numerical code, which is tested and applied. The first application is a detailed numerical four-dimensional analysis of the so-called emission coordinate region and co-region. In a second application, a GPS (Galileo) satellite is considered as the receiver and its emission coordinates are given by four Galileo (GPS) satellites. The bifurcation problem (double localization) in the positioning of the receiver satellite is then pointed out and discussed in detail. 相似文献
5.
Neus Garcias-Bonet Timothy D. Sherman Carlos M. Duarte Núria Marbà 《Estuaries and Coasts》2011,34(6):1161-1168
The presence of the pathogenic protist Labyrinthula sp., the causative agent of seagrass wasting disease and mass mortality events, was assessed in 18 seagrass meadows in the
Balearic region (western Mediterranean). This protist was found in 70% of seagrass meadows investigated and in all seagrass
species present in the region (i.e., Posidonia oceanica, Cymodocea nodosa, and Zostera noltii). Labyrinthula spp. cultures isolated from seven P. oceanica and one Thalassia testudinum meadows were used as inocula to perform cross-infection experiments in order to test seagrass vulnerability to Labyrinthula spp. infection. These isolates produced lesions on P. oceanica and other seagrass species (Zostera marina, Z. noltii, and C. nodosa). P. oceanica and Z. noltii, both species autochthonous to the Mediterranean Sea, were the seagrasses most vulnerable to infection by the tested isolates.
One of the P. oceanica isolates of Labyrinthula sp. also infected the Atlantic seagrass Z. marina, and all of the Mediterranean seagrasses were infected by Labyrinthula sp. isolated from the T. testudinum, native to the Caribbean and Gulf of Mexico. This work confirms that Labyrinthula sp. is commonly found on seagrasses of the Mediterranean Sea and demonstrates that Labyrinthula sp. can infect seagrasses in different genera, in contrast to previous studies where Labyrinthula sp. was considered to be genus-specific. This finding points out the broadly pathogenic nature of some Labyrinthula sp. isolates. Finally, this work identifies Labyrinthula sp. as a possible detrimental agent for P. oceanica. 相似文献
6.
Jordi Llorca Marc Campeny Neus Ibez David Allepuz Josep Maria Camarasa Josep Aurell‐Garrido 《Meteoritics & planetary science》2020,55(4):705-725
On Christmas Day 1704, at 17 h (UT), a meteorite fell in Terrassa (about 25 km NW of Barcelona). The meteorite fall was seen and heard by many people over an area of several hundred kilometers and it was recorded in several historical sources. In fact, it was interpreted as a divine sign and used for propaganda purposes during the War of the Spanish Succession. Although it was believed that meteorite fragments were never preserved, here we discuss the recent discovery of two fragments (49.8 and 33.7 g) of the Barcelona meteorite in the Salvador Cabinet collection (Botanic Institute of Barcelona). They are very well preserved and partially covered by a fresh fusion crust, which suggests a prompt recovery, shortly after the fall. Analysis of the fragments has revealed that the Barcelona meteorite is an L6 ordinary chondrite. These fragments are among the oldest historical meteorites preserved in the world. 相似文献
7.
Global navigation satellite systems use appropriate satellite constellations to get the coordinates of an user—close to Earth—in an almost inertial reference system. We have simulated both GPS and GALILEO constellations. Uncertainties in the satellite world lines lead to dominant positioning errors. In this paper, a detailed analysis of these errors is developed inside a great region surrounding Earth. This analysis is performed in the framework of the so-called relativistic positioning systems. Our study is based on the Jacobian (J) of the transformation giving the emission coordinates in terms of the inertial ones. Around points of vanishing J, positioning errors are too large. We show that, for any 4-tuple of satellites, the points with J=0 are located at distances, D, from the Earth centre greater than about 2R/3, where R is the radius of the satellite orbits which are assumed to be circumferences. Our results strongly suggest that, for D-distances greater than 2R/3 and smaller than 105 km, a rather good positioning may be achieved by using appropriate satellite 4-tuples without J=0 points located in the user vicinity. The way to find these 4-tuples is discussed for arbitrary users with D<105 km and, then, preliminary considerations about satellite navigation at D<105 km are presented. Future work on the subject of space navigation—based on appropriate simulations—is in progress. 相似文献
8.
Gerhard?LammelEmail author Thomas?Engelhardt Adrian?Leip Christian?Neusü? Andreas?R?hrl Birgit?Wehner Alfred?Wiedensohler Paul?Wieser 《Journal of Atmospheric Chemistry》2005,51(1):95-117
The change of the chemical composition of the near-ground level atmospheric aerosol was studied during two summer episodes by a Lagrangian type of experimental approach. Bulk and single-particle chemical analyses of ions and elements in the particulate phase were deployed. N(-III) and N(V) components were also measured in the gas-phase. The measurements were completed by particle size distributions.Secondary inorganic aerosols (SIA) and fine particles of ≈0.2–0.4 μm size were still elevated 50 km downwind of the city. The direct comparison of transport over the city in contrast to transport over the surrounding areas showed that SIA was formed from emission from the city within less than 3 h. Relative increases, i.e., enrichment during transport were observed for primary and secondary aerosol components. The degree of mixing on the individual particle level increased significantly during transport in the area. In particular, newly emitted carbonaceous particles became internally mixed within hours with pre-existing sulphate particles. Mostly due to secondary aerosol formation the average particle size (mass median diameter) of major constituents of the aerosol was significantly decreased while being transported over 13 h. Given recent insights which link fine particles number and mass concentrations with health risks, the results suggest that rural populations in areas which frequently are located within an urban plume might run an elevated health risk relative to populations in areas not affected by urban plumes. 相似文献
9.
Núria Marbà Carlos M. Duarte Marianne Holmer Maria Ll. Calleja Elvira Álvarez Elena Díaz-Almela Neus Garcias-Bonet 《Estuarine, Coastal and Shelf Science》2008
The relationship between sedimentary Fe inputs and net seagrass population growth across a range of Posidonia oceanica meadows growing in carbonate Mediterranean sediments (Balearic Islands, Spain; SE Iberian Peninsula, Spain; Limassol, Cyprus; Sounion, Greece) was examined using comparative analysis. Sedimentary Fe inputs were measured using benthic sediment traps and the net population growth of P. oceanica meadows was assessed using direct census of tagged plants. The meadows examined ranged from meadows undergoing a severe decline to expanding meadows (specific net population growth, from −0.14 yr−1 to 0.05 yr−1). Similarly, Fe inputs to the meadows ranged almost an order of magnitude across meadows (8.6–69.1 mg Fe m−2 d−1). There was a significant, positive relationship between sedimentary iron inputs and seagrass net population growth, accounting for 36% of the variability in population growth across meadows. The relationship obtained suggested that seagrass meadows receiving Fe inputs below 43 mg Fe m−2 d−1 are vulnerable and in risk of decline, confirming the pivotal role of Fe in the control of growth and the stability of seagrass meadows in carbonate sediments. 相似文献
10.
Environmental isotopes (N, S, C, O, D) to determine natural attenuation processes in nitrate contaminated waters: Example of Osona (NE Spain) 总被引：1，自引：0，他引：1
Nitrate-contaminated groundwater from an aquifer in the Osona region (NE Spain) was chemically and isotopically (δ15NNO3,δ18ONO3,δ34SSO4,δ18OSO4, δD, δ18OH2O and δ13CDIC) characterized. Diffuse- contamination reached values of 366 mg/L. Nearly 75% of the 37 sampled sites had higher concentrations than the 50 mg/L in limit for drinking water. To identify the source of pollution δ15NNO3 and δ18ONO3 were used with results, for most samples, in the range of pig manure . Nitrification processes were evaluated by means of the δ18O of and water. Isotopic data suggested that natural attenuation of was taking place. This process was confirmed using the δ18ONO3 coupled with the ratio, avoiding the influence of continuous inputs. A further insight on denitrification processes was obtained by analyzing the ions involved in denitrification reactions. Although the role of organic matter oxidation could neither be confirmed nor discarded, this approach showed a link between denitrification and pyrite oxidation. Therefore, in areas with no adequate infrastructure (e.g. multipiezometers), such as the one studied, this approach could be useful for implementing better water management. 相似文献