A GIS based approach to back trajectory analysis for the source apportionment of aerosol constituents and its first application     

Dominik van Pinxteren  Erika Brüggemann  Thomas Gnauk  Konrad Müller  Christian Thiel  Hartmut Herrmann 《Journal of Atmospheric Chemistry》2010,67(1):1-28

A new method has been developed to combine back trajectory statistics with a detailed land cover analysis. It provides numeric proxies for the residence times of sampled air masses above certain land cover classes (marine, natural vegetation, agricultural lands, urban areas, and bare areas), as well as further meteorological parameters (mean trajectory length, solar radiation along trajectory, and local height of the boundary mixing layer). The method has been implemented into a GIS-enabled database system to allow for an efficient processing of large datasets with low computational demands. A principal component analysis was performed on a dataset including the modelled residence times, the modelled meteorological parameters, some measured meteorological parameters (wind speed and temperature), and the concentrations of 10 particle constituents (inorganic ions and organic and elemental carbon) in 5 particle size ranges for 29 winter- and summertime samples at an urban background site in Leipzig, Germany. Six principal components could be extracted which together explained about 80% of the total variance in the dataset. The factors could be attributed to the influence of meteorology to continental background pollution, secondary formation processes in polluted air masses, wood burning, aged sea-salt, local traffic, and long-range transported crustal material. The modelled residence times and the meteorological parameters were generally consistent with the existing knowledge of specific particle sources and thereby facilitated and strengthened the interpretation of the factors. Moreover, they allowed for a clear distinction between continental background pollution and secondary formation processes, which has not been possible in previous source apportionment studies. The results demonstrate that the combined usage of back trajectory, land cover, and meteorological data by the presented method yields valuable additional information on the history of sampled air masses, which can improve the quality of source apportionment of atmospheric aerosol constituents.  相似文献   

Fragmented governance: Reconciling legal strategies for shark conservation and management     

Erika J. Techera  Natalie Klein 《Marine Policy》2011

Sharks play a critical role in the ocean environment yet many species are under threat. Over the last ten years, the international community has taken significant steps to protect shark species and address the threats to them through the adoption and implementation of international laws, plans and programmes. Nevertheless, despite the attention given to this issue, many shark species continue to deteriorate in numbers. While the reasons for this decline are complex and varied, regulatory fragmentation is one contributing factor. Legal regulation is a critical element in achieving effective conservation and management of sharks. This article considers the international laws, plans and programmes that seek to conserve shark species, explores the current fragmented regime and outlines possible strategies to overcome this challenge and enhance shark protection in the future.  相似文献   

Constraints on the origin of alkaline and calc-alkaline magmas from the Tuxtla Volcanic Field,Veracruz, Mexico   总被引：5，自引：0，他引：5  

S. A. Nelson  Erika Gonzalez-Caver  T. Kurtis Kyser 《Contributions to Mineralogy and Petrology》1995,122(1-2):191-211

 Lavas erupted in the Tuxtla Volcanic Field (TVF) over the last 7 Ma include primitive basanites and alkali basalts, mildly alkaline Hy-normative mugearites and benmoreites, and calc-alkaline basalts and basaltic andesites. The primitive lavas are silica-undersaturated, with high concentrations of both incompatible and compatible trace elements, variable La/Yb with constant Yb at 6 to 8 times chondritic, and low Sr and O and variable Pb and Nd isotopic ratios. The primitive magmas originated by increasing degrees of melting with pressure decreasing from greater than 30 kbar to 20 kbar, in the garnet stability field. Another group of alkali basalts and hawaiites has lower Ni and Cr concentrations and higher Fe/Mg ratios, and was derived from the primitive group by crystal fractionation at pressures of several kbar. Incompatible trace elements in these silica undersaturated lavas show depletion in high field strength elements (HFSE) relative to large ion lithophile elements, similar to subduction-related basalts. Ba/Nb ratios are nearly constant and thus the HFSE depletion cannot be the result of a residual HFSE-bearing phase in the source, but could be the result of generation from a source contaminated by fluids or melts from the subducted lithosphere. The silica-saturated mugearites and benmoreites, and the calc-alkaline basalts and basaltic andesites, were erupted only between 3.3 and 1.0 Ma. These have incompatible element concentrations generally lower than in the silica-undersaturated lavas, and thus could not have been derived by crystal fractionation from the silica-undersaturated alkaline magmas. Magmas parental to the silica-saturated magmas originated by higher degrees of melting at lower pressures than the primitive magmas. Melting may have been promoted by an influx of fluid from the subducted lithosphere. Trace element and Sr, Nd, Pb and O isotopic data suggest that three components are involved in the generation of TVF magmas: the mantle, a fluid from the subducted lithosphere, and continental crust. TVF alkaline lavas are similar to those erupted in the back-arc region of the MVB and Japan, and show characteristics similar to alkaline magmas erupted in the southern Andean volcanic arc. These low degree melts reach the surface along with calc-alkaline lavas in the TVF due to an extensional stress field that allows their passage to the surface. Received: 15 September 1994/Accepted: 14 February 1995  相似文献   

Functional attributes of epilithic diatoms for palaeoenvironmental interpretations in South-West Greenland lakes     

Suzanne McGowan  Hazel V. Gunn  Erika J. Whiteford  N. John Anderson  Vivienne J. Jones  Antonia C. Law 《Journal of Paleolimnology》2018,60(2):273-298

Benthic diatoms are commonly used for palaeoenvironmental reconstruction in Arctic regions, but interpretation of their ecology remains challenging. We studied epilithic diatom assemblages from the shallow margins of 19 lakes from three areas (coast-inland-ice sheet margin) along a climate gradient in Kangerlussuaq, West Greenland during two periods; shortly after ice-off (spring) and in the middle of the growth season (summer). We aimed to understand the distribution of Arctic epilithic diatoms in relation to water chemistry gradients during the two seasons, to investigate their incorporation into lake sediments and to assess their applicability as palaeoenvironmental indicators. Diatoms were correlated with nutrients in the spring and alkalinity/major ions in the summer, when nutrients were depleted; approximately half of the variance explained was independent of spatial factors. When categorised by functional attributes, diatom seasonal succession differed among regions with the most obvious changes in inland lakes where summer temperatures are warmer, organic nutrient processing is prevalent and silicate is limiting. These conditions led to small, motile and adnate diatoms being abundant in inland lakes during the summer (Nitzschia spp., Encyonopsis microcephala), as these functional attributes are suited to living within complex mats of non-siliceous microbial biofilms. Seasonal succession in silica-rich lakes at the coast was less pronounced and assemblages included Tabellaria flocculosa (indicating more acidic conditions) and Hannaea arcus (indicating input from inflowing rivers). The nitrogen-fixing diatom Epithemia sorex increased from the coast to the ice sheet, negatively correlating with a gradient of reactive nitrogen. The presence of this diatom in Holocene sediment records alongside cyanobacterial carotenoids during arid periods of low nitrogen delivery, suggests that it is a useful indicator of nitrogen limitation. Nitzschia species appear to be associated with high concentrations of organic carbon and heterotrophy, but their poor representation in West Greenland lake sediments due to taphonomic processes limits their palaeoenvironmental application in this region. Proportions of epilithic taxa in lake sediment records of coastal lakes increased during some wetter periods of the Holocene, suggesting that snowpack-derived nutrient delivery may offer diatom taxa living at lake margins a competitive advantage over planktonic diatoms during the “moating” ice melt period. Thus, further research investigating linkages between epilithic diatoms, snowpack and nutrient delivery in seasonally frozen lakes is recommended as these taxa live on the ‘front-line’ during the spring and may be especially sensitive to changes in snowmelt conditions.  相似文献   

Silicate and carbonate mineral weathering in soil profiles developed on Pleistocene glacial drift (Michigan, USA): Mass balances based on soil water geochemistry     

Lixin Jin  Erika L. Williams  Lynn M. Walter 《Geochimica et cosmochimica acta》2008,72(4):1027-1042

Geochemistry of soil, soil water, and soil gas was characterized in representative soil profiles of three Michigan watersheds. Because of differences in source regions, parent materials in the Upper Peninsula of Michigan (the Tahquamenon watershed) contain only silicates, while those in the Lower Peninsula (the Cheboygan and the Huron watersheds) have significant mixtures of silicate and carbonate minerals. These differences in soil mineralogy and climate conditions permit us to examine controls on carbonate and silicate mineral weathering rates and to better define the importance of silicate versus carbonate dissolution in the early stage of soil-water cation acquisition.Soil waters of the Tahquamenon watershed are the most dilute; solutes reflect amphibole and plagioclase dissolution along with significant contributions from atmospheric precipitation sources. Soil waters in the Cheboygan and the Huron watersheds begin their evolution as relatively dilute solutions dominated by silicate weathering in shallow carbonate-free soil horizons. Here, silicate dissolution is rapid and reaction rates dominantly are controlled by mineral abundances. In the deeper soil horizons, silicate dissolution slows down and soil-water chemistry is dominated by calcite and dolomite weathering, where solutions reach equilibrium with carbonate minerals within the soil profile. Thus, carbonate weathering intensities are dominantly controlled by annual precipitation, temperature and soil pCO₂. Results of a conceptual model support these field observations, implying that dolomite and calcite are dissolving at a similar rate, and further dissolution of more soluble dolomite after calcite equilibrium produces higher dissolved inorganic carbon concentrations and a Mg²⁺/Ca²⁺ ratio of 0.4.Mass balance calculations show that overall, silicate minerals and atmospheric inputs generally contribute <10% of Ca²⁺ and Mg²⁺ in natural waters. Dolomite dissolution appears to be a major process, rivaling calcite dissolution as a control on divalent cation and inorganic carbon contents of soil waters. Furthermore, the fraction of Mg²⁺ derived from silicate mineral weathering is much smaller than most of the values previously estimated from riverine chemistry.  相似文献   

Al-Mg systematics of chondrules in a primitive CO chondrite     

Erika Kurahashi  Noriko T. Kita  Hiroko Nagahara 《Geochimica et cosmochimica acta》2008,72(15):3865-3882

We have conducted systematic investigations of formation age, chemical compositions, and mineralogical characteristics of ferromagnesian chondrules in Yamato-81020 (CO3.05), one of the most primitive carbonaceous chondrites, to get better understanding of the origin of chemical groups of chondrites. The ²⁶Al-²⁶Mg isotopic system were measured in fourteen FeO-poor (Type I), six FeO-rich (Type II) and two aluminum-rich (Al-rich) chondrules using a secondary ion mass spectrometer. Excesses of ²⁶Mg in plagioclase (1.0-13.5‰) are resolved with sufficient precision (mostly 0.4-6.6‰ at 2σ level) in all the chondrules studied except one. Chemical zoning of Mg and Na in plagioclase were investigated in detail in order to evaluate the applicability of ²⁶Al-²⁶Mg chronometer. We conclude that the Al-Mg isotope system of the chondrules in Y-81020 have not been disturbed by parent-body metamorphism and can be used as chronometer assuming homogeneous distribution of ²⁶Al. Assuming an initial ²⁶Al/²⁷Al ratio of 5 × 10⁻⁵ in the early solar system, ²⁶Al-²⁶Mg ages were found to be 1.7-2.5 Ma after CAI formation for Type I, 2.0-3.0 Ma for Type II and 1.9 and 2.6 Ma for Al-rich chondrules.The formation ages of ferromagnesian chondrules in Y-81020 are in good agreement with those of L and LL (type 3.0-3.1) chondrites in the literature, which indicates that common chondrules in the CO chondrite were formed contemporaneously with those in L and LL chondrites. The concurrent formation of chondrules of CO and L/LL chondrites suggests that the chemical differences between CO and L/LL chondrites might be caused by spatial separation of chondrule formation environments in the protoplanetary disk.  相似文献   

Experimental phase relations of a low MgO Aleutian basaltic andesite at XH2O = 0.7–1     

Erika L. Rader  Jessica F. Larsen 《Contributions to Mineralogy and Petrology》2013,166(6):1593-1611

We conducted melting experiments on a low MgO (3.29 wt.%) basaltic andesite (54.63 wt.% SiO₂) from Westdahl volcano, Alaska, at XH₂O = 0.7–1 and fO₂ ~ Ni–NiO, at pressures = 0.1–180 MPa and temperatures = 900–1,200 °C. We examine the evolution of the melt along a liquid line of descent during equilibrium crystallization at high H₂O and fO₂ conditions, starting from a high FeOt/MgO, low MgO basaltic andesite. Ti-magnetite formed on the liquidus regardless of XH₂O, followed by clinopyroxene, plagioclase, amphibole, and orthopyroxene. We observe slight but significant differences in the phase stability curves between the XH₂O = 1 and 0.7 experiments. Early crystallization of Ti-magnetite and suppression of plagioclase at higher pressures and temperatures resulted in strongly decreasing melt FeOt/MgO with increasing SiO₂, consistent with a “calc-alkaline” compositional trend, in agreement with prior phase equilibria studies on basalt at similar H₂O and fO₂. Our study helps quantify the impact of small amounts of CO₂ and high fO₂ on the evolution of melts formed during crystallization of a low MgO basaltic andesite magma stored at mid- to shallow crustal conditions. Like the prior studies, we conclude that H₂O strongly influences melt evolution trends, through stabilization of Ti-magnetite on the liquidus and suppression of plagioclase at high P–T conditions.  相似文献   

Depositional evolution of a lower Paleozoic portion of the Southalpine domain: the Mt. Pizzul area (Carnic Alps,Italy)     

Monica Pondrelli  Carlo Corradini  Luca Simonetto  Maria Giovanna Corriga  Erika Kido  Angelo Mossoni  Claudia Spalletta  Thomas J. Suttner  Nicola Carta 《International Journal of Earth Sciences》2015,104(1):147-178

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Lateglacial environmental and climatic changes at the Maloja Pass,Central Swiss Alps,as recorded by chironomids and pollen     

Boris Ilyashuk  Erika Gobet  Oliver Heiri  André F. Lotter  Jacqueline F.N. van Leeuwen  Willem O. van der Knaap  Elena Ilyashuk  Florencia Oberli  Brigitta Ammann 《Quaternary Science Reviews》2009,28(13-14):1340-1353

Chironomids and pollen were studied in a radiocarbon-dated sediment sequence obtained from a former lake near the Maloja Pass in the Central Swiss Alps (1865 m a.s.l.) to reconstruct the Lateglacial environment. Pollen assemblages imply a vegetation development around the Maloja Pass from shrub tundra at the beginning of the Allerød to coniferous forest during the early Holocene with a lowering of the timberline during the Younger Dryas. Chironomid assemblages are characterized by several abrupt shifts in dominant taxa through the Lateglacial. The occurrence of taxa able to survive hypoxia in the second part of the Allerød and during the Preboreal, and their disappearance at the onset of the Younger Dryas cold phase suggest summer thermal stratification and unfavourable hypolimnetic oxygen conditions in the palaeo-lake during the warmer periods of the Lateglacial interstadial and early Holocene. Mean July air temperatures were reconstructed using a chironomid-temperature transfer function from the Alpine region. The pattern of reconstructed temperature changes agrees well with the Greenland δ¹⁸O record and other Lateglacial temperature inferences from Central Europe. The inferred July temperatures of ca 10.0 °C during most of the Allerød were slightly lower than modern values (10.8 °C) and increased up to ca 11.7 °C (i.e., above present-day values) at the end of the Allerød. The first part of the Younger Dryas was colder (ca 8.8 °C) than the second part (ca 9.8 °C). During most of the Preboreal, the temperatures persisted within the limits of 13.5–14.5 °C (i.e., ca 3 °C above present-day values). The amplitudes of temperature changes at the Allerød–Younger Dryas–Preboreal transitions were ca 3.5–4.0 °C. The temperature reconstruction also shows three short-lived cooling events of ca 1.5–2.0 °C, which may be attributed to the centennial-scale Greenland Interstadial events GI-1d and GI-1b, and the Preboreal Oscillation.  相似文献   

Understanding and Managing the Potential By-Products of PFAS Destruction     

John Horst  Jeffrey McDonough  Ian Ross  Erika Houtz 《Ground Water Monitoring & Remediation》2020,40(2):17-27

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