Pb chronology and trace metal geochemistry at Los Tuxtlas, Mexico, as evidenced by a sedimentary record from the Lago Verde crater lake     

Ana Carolina Ruiz-Fernández  Claude Hillaire-Marcel  Federico Páez-Osuna  Bassam Ghaleb  Margarita Caballero 《Quaternary Research》2007,67(2):181-192

Lago Verde is a fresh-water maar found on the lower slopes of San Martin volcano, at the Sierra de Los Tuxtlas, Mexico, currently the northernmost remnant of the tropical rain forest in America. ²¹⁰Pb and ¹³⁷Cs analyzed in a sediment core were used to reconstruct the historical fluxes of Ag, Cd, Cu, Pb, Hg and Zn to the site during the last ∼ 150 yr. The ²¹⁰Pb_xs-derived sediment accumulation rates, the magnetic susceptibility, C/N ratios and δ¹³C data evidenced background conditions at the lake until 1960s, when enhanced erosion related to the clearing of large forested areas at Los Tuxtlas promoted higher accumulation rates of a heavier and more magnetic sedimentary material. Recent sediments from Lago Verde were found enriched by Pb (26-fold natural concentration level [NCLs]) and moderately enriched by Cd > Cu > Zn and Hg (6-, 5-, 4- and 4-fold corresponding NCLs, respectively). The fluxes of Cu, Hg, Pb and Zn have significantly increased since 1940s, with peak ratios of total modern to pre-industrial fluxes of 11, 11, 19 and 49, respectively. The lake occupies a relatively pristine, non-industrialized basin, and therefore the increased metal fluxes might be related to long-distance aeolian transport of trace metals.  相似文献   

PCBs and PAHs in surficial sediments from aquatic environments of Mexico City and the coastal states of Sonora,Sinaloa, Oaxaca and Veracruz (Mexico)     

Rossano Piazza  Ana Carolina Ruiz-Fernández  Mauro Frignani  Roberta Zangrando  Luca Giorgio Bellucci  Ivo Moret  Federico Páez-Osuna 《Environmental Geology》2008,54(7):1537-1545

Concentrations of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) were measured in 13 surficial sediment samples collected at three lacustrine locations in the surroundings of Mexico City and four coastal areas of the States of Sinaloa, Sonora, Oaxaca and Veracruz. Total PCB concentrations span the interval 3.18–621 ng g⁻¹. The highest values (63.7–621 ng g⁻¹) were found in Mexico City, which is a highly anthropogenically impacted area, whereas low concentrations (3.18–12.9 ng g⁻¹) were characteristic of seven places, some of them subject to intense hydrodynamics. In these latter cases, values increase by 18–73 times if normalised against the fine fraction (silt plus clay) content in sediment. Two samples from Mexico City exceed the ERM (Effect Range Median) guidelines and are likely to cause adverse effects. Samples contain only lower chlorinated PCBs (mainly 2-, 3- and 4-CB), thus suggesting that the most used PCB commercial mixture was Aroclor 1242. The homologue composition of the sample taken close to the nuclear power plant of Laguna Verde is identical to this commercial mixture. PAHs in the same samples have relatively low concentrations (14.9–287 ng g⁻¹), well below ERL (Effect Range Low) guidelines. The composition of PAH mixtures accounts for the influence of both petrogenic and pyrolitic sources, with these latter prevailing at some places in Mexico City.  相似文献   

The 2014 southeast Brazil austral summer drought: regional scale mechanisms and teleconnections     

Caio A. S. Coelho  Cristiano Prestrelo de Oliveira  Tércio Ambrizzi  Michelle Simões Reboita  Camila Bertoletti Carpenedo  José Leandro Pereira Silveira Campos  Ana Carolina Nóbile Tomaziello  Luana Albertani Pampuch  Maria de Souza Custódio  Lívia Marcia Mosso Dutra  Rosmeri P. Da Rocha  Amanda Rehbein 《Climate Dynamics》2016,46(11-12):3737-3752

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In Situ Surfactant Washing of Polychlorinated Biphenyls and Oils from a Contaminated Site   总被引：5，自引：0，他引：5  

A. S. Abdul  T. L. Gibson  Carolina C. Ang  Julie C. Smith  R. E. Sobczynski 《Ground water》1992,30(2):219-231

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Using a regional frequency analysis approach for calculating the Standardized Precipitation Index: an operational approach based on the two-parameter gamma distribution     

dos Santos Junior  Edimar Pereira  Xavier  Ana Carolina Freitas  Martins  Letícia Lopes  da Rocha Sobierajski  Graciela  Blain  Gabriel Constantino 《Theoretical and Applied Climatology》2022,148(3-4):1199-1216

Theoretical and Applied Climatology - The Standardized Precipitation Index (SPI) is a worldwide used probability-based drought index. Considering that the two-parameter gamma distribution (gam) is...  相似文献   

Present Limnological Conditions and Recent (ca. 340 yr) Palaeolimnology of a Tropical Lake in the Sierra de Los Tuxtlas, Eastern Mexico     

Margarita Caballero  Gabriela Vázquez  Socorro Lozano-García  Alejandro Rodríguez  Susana Sosa-Nájera  Ana Carolina Ruiz-Fernández  Beatriz Ortega 《Journal of Paleolimnology》2006,35(1):83-97

The Sierra de Los Tuxtlas is a recently active volcanic field, with eruptions in 1664 and 1792. It holds one of the reserves of tropical evergreen forest in Mexico, as well as several maar lakes. One of them, Lago Verde, was chosen for a three-fold study (1) on its present limnological conditions, (2) on the algal community living in the water column and preserved in the surface sediments; and (3) on its recent history (ca. 340 yr). The palaeolimnological study was based on multiproxy analyses on core material dated by ²¹⁰Pb, ¹³⁷Cs and ¹⁴C. Lago Verde is a small, shallow lake with dilute, slightly alkaline water (CO₃²⁻ + HCO₃⁻ > Cl⁻ > SO₄²⁻, Na⁺ + K⁺ > Ca²⁺ > Mg²⁺). It is turbid, eutrophic, with high phosphorus levels. It is a warm polymictic lake, with thermal and oxygen stratification establishing by midday during the warm months. The lake does not stratify in winter. Diatoms dominate the phytoplankton community in the cold ‘nortes’ season, Cyanobacteria in summer, and Chlorophyta in autumn. Cyanobacteria (Chroococcales) are not well preserved in the surface sediments while Chlorophyta are better preserved. Sedimentary diatoms are well preserved, dominated by the three most abundant species in the water column: Achnanthidium minutissimum, Fragilaria capucina and Aulacoseira granulata. The base of the studied sequences is constrained by the historic eruption of 1664. The period from 1664 to 1963 is characterised by a meso-eutrophic lake. Tropical Forest vegetation reaches maximum values between ca. 1800 and 1963. Between ca. 1785 and 1885 the lake was slightly shallower than in the rest of the 1664–1963 period, probably recording climatic variability. An early pulse of anthropogenic disturbance was recorded by ca. 1921 and after ca. 1963 intense forest clearance and high erosion rates led to a more turbid, more productive, nutrient-rich lake. The highest anthropogenic impact was reached by ca. 1988; afterwards the lake and its basin reached a new balance, with the establishment of the present modern conditions.  相似文献   

In Situ Surfactant Washing of Polychlorinated Biphenyls and Oils from a Contaminated Field Site: Phase II Pilot Study   总被引：1，自引：0，他引：1  

Abdul S. Abdul  Carolina C. Ang 《Ground water》1994,32(5):727-734

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Vapor Extraction of Volatile Organic Compounds from Clay Soil: A Long-Term Field Pilot Study     

Thomas L. Gibson  Abdul S. Abdul  William A. Glasson  Carolina C. Ang  Dallas W. Gatlin 《Ground water》1993,31(4):616-626

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Potential responses of oligochaetes (Annelida, Clitellata) to global changes: Experimental fertilization in a lowland stream of Argentina (South America)     

Laura Armendáriz  Carolina Ocón  Alberto Rodrigues Capítulo 《Limnologica》2012,42(2):118-126

One of the possible consequences of climatic change for streams and rivers in the pampean region of South America is an increment in nutrient loads. To analyze this possible perturbation on a biological scale, the response of oligochaetes to an experimental eutrophication of the La Choza Stream, Argentina was studied. We proposed that the addition of nutrients could increase the abundance, biomass, and species composition of the stream. Two stretches (Control and Treatment sites) were selected, with bimonthly samples being taken (March 2007 through February 2009) in two habitat types: the sediments and the aquatic vegetation. On each sampling occasion the environmental variables were measured. The nutrient addition consisted in the continuous dissolution of a commercial fertilizer. The oligochaete mean density and total biomass, the taxonomic richness, the Shannon diversity (H′), and the evenness (E) were calculated and the BACI ANOVA design used to compare the differences between the sites. Thirty-three species of the families Naididae (Naidinae, Pristininae, Tubificinae, and Rhyacodrilinae), Opistocystidae, Enchytraeidae plus Aphanoneura Aeolosomatidae were collected. The oligochaete abundance and biomass increased significantly in the sediments and on the aquatic vegetation, especially among the Naidinae and Pristininae during their asexual reproductive phase. The diversity and evenness varied significantly in the sediments with the nutrient addition. Significant differences in the species richness and diversity were found on the aquatic vegetation, with both increasing at the treatment site after the fertilization. A significant correlation (Spearman) was observed between the oligochaete density in the sediments and the NO₃-N and NH₄-N concentration in the water. The increment in the naidines resistant to the fertilizer throughout the experiment could be explained by the greater nutrient availability, their mode of reproduction, and their short life cycles. The results of our study suggested that the incorporation of nutrients modified the composition of the oligochaete assemblage in favor of herbivores and detrivores. The usefulness of these indicator organisms in monitoring freshwater systems is subsequently discussed.  相似文献   

Erratum     

Carolina Mallol  Eudald Carbonell I Roura 《Geoarchaeology》2008,23(2):321-321

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