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dos Santos C.P.,Campus da Praia Vermelha | Coe H.H.G.,Campus da Praia Vermelha | Coe H.H.G.,State University of Rio de Janeiro | Borrelli N.,Institute Geologia Of Costas Y Del Cuaternario | And 5 more authors.
Brazilian Journal of Oceanography | Year: 2015

The Maricá restinga, located in the eastern part of the Rio de Janeiro State (Brazil), corresponds to one of the few remaining preserved areas of the state's coastal plain. This paper reports on a study of the Maricá restinga plant communities and also presents an identification of the main plant species present in each community, with the objective of establishing reference collections, by the methods of the proxies opal phytoliths and stable carbon isotopes, for paleoenvironmental reconstructions of this coastal area during the Quaternary. Six plant communities, distributed perpendicularly to the coast line over sandy barriers, lagoonal plain, lagoon margin and weathered basement were identified: halophile-psamophile, scrub, herbaceous swamp, slack, shrubby vegetation and dry forest. In general, the plant species analyzed in each community presented low productivity of opal phytoliths, as only the Poaceae, Cyperaceae and Arecaceae families produce a great amount and diversity of morphotypes of opal phytoliths. The results of the analysis of stable carbon isotopes in sediments indicated a predominance of C3 or a mixture of C3 and C4 plants, presenting a close correlation with the results found in plants collected in each community. In conclusion, it was verified that the carbon isotope analysis associated with that of the opal phytoliths are good proxies for the reconstruction of vegetation in the study area. © 2015, Universidade de Sao Paulo. All Rights Reserved.


Martinez D.,Institute Geologia Of Costas Y Del Cuaternario | Martinez D.,CONICET | Moschione E.,University of Buenos Aires | Bocanegra E.,Institute Geologia Of Costas Y Del Cuaternario | And 3 more authors.
Environmental Earth Sciences | Year: 2014

The impact of urbanization on groundwater quality is of special concern for water managers dealing with the provision of drinking water to large urban centers. Nitrate is one of the most common contaminants found in urban aquifers. This paper presents a case study aiming at evaluating the distribution and sources of nitrate in an urban aquifer in the city of Mar del Plata, Argentina. Four study zones under different land uses, including a pristine, a semi-rural, an intermediate, and an urban area, were evaluated as a part of this study. The three latter zones are linked by the groundwater flow system. The average nitrate concentration in the pristine area is 6.7 mg/L as nitrate and is over the permissible level of 50 mg/L for drinking water in the other areas. In the semi-rural area it ranges from 39.2 to 107.1 mg/L with an average value of 38.2 mg/L and the nitrate concentration tends to decrease in the intermediate zone to an average value of 38.2 mg/L; however, values above 60 mg/L are also observed there. Then the nitrate concentration in the urban area water is higher than that in the intermediate zonewater ranging from 48.2 to 100.3 mg/L with an average value of 67.3 mg/L. Data on the stable isotopes 15N and 18O in nitrate show that the main sources of nitrate in the study area are manure associated to agriculture uses and cesspools in the semi-rural area, and leakage of the sewage distribution network in the urban area, respectively. This is supported by a previous study which found that 20 % of the water flooding many underground structures in the city came from leakage of the sewage network. No evidence of nitrate attenuation by denitrification was found in the groundwater. This study has shown that aquifers in urban areas can be affected by agricultural activity in the upstream areas and leakage of the sewage network in the urban area. © 2014 Springer-Verlag Berlin Heidelberg.


Lourdes L.,Institute Geologia Of Costas Y Del Cuaternario | Lourdes L.,CONICET | Karina Z.,Instituto Nacional de Tecnologia Agropecuaria | Pedro L.,CONICET | And 2 more authors.
Procedia Environmental Sciences | Year: 2011

The Dulce Creek Basin (1000 km 2) is situated in the Buenos Aires's Sate and flows into the Mar Chiquita lagoon, (MAB Biosphere Reserve - UNESCO). While land cover on the upper basin is dominated by field crops, the low basin is mostly occupied by livestock grazing systems. The increased use of inputs (agricultural intensification), and a high degree of riverside vegetation's degradation in the grazing zone, represent an increasing pollution risk for surface water bodies and groundwater. The aim of this work was to find suitable driving factors for a dynamic land cover simulation model (Dyna-CLUE) since1997 to 2005 using logit regression models. Land cover change (Crop, Pasture, Grassland, and Others) was simulated using eleven driving factors accounting for geographic, climatic and soil and infrastructure features. We assessed multicolinearity from the Pearson correlation matrix, and only uncorrelated variables were applied in the logistic regression. Waterlogging, altitude, geomorphology and soil productivity were the main driving factors for the predictions of land cover dynamics, as selected from logistic models. The land-cover simulation model was run according to the actual trends of agricultural expansion. The accuracy of predictive models was tested using receiver operating characteristic (ROC) curves and the good fit showed by the Dyna-CLUE model to data, support its suitability for simulation of land cover dynamics of the Dulce Creek Basin. The expected trajectory of land cover according to current trends warns about a progressive decrease of grasslands cover, and the associated loss of their ecosystem services. Further simulations upon alternative scenarios can help land use planning for production and conservation objectives. © 2010 Published by Elsevier Ltd.


Alvarez M.F.,CONICET | Alvarez M.F.,Institute Geologia Of Costas Y Del Cuaternario | Osterrieth M.L.,Institute Geologia Of Costas Y Del Cuaternario | del Rio J.L.,Institute Geologia Of Costas Y Del Cuaternario
Environmental Earth Sciences | Year: 2012

Organic matter is a fundamental factor in the biogeochemical cycle of carbon; it influences the chemical, physical, and biological properties of the soil. The aim of this paper is to determine the organic fractions in the three predominant morphologies of aggregates found in Typical Argiudolls of the Buenos Aires southeastern area and to link them to different soil uses, as possible indicators of soil quality. The study was carried out in the basin de Los Padres Pound (General Pueyrredón, Buenos Aires). We analyzed the first 5 cm of mollic epipedons of plots with different soil uses: (a) cultivated plots, (b) pine and eucalyptus forests, (c) pastures, and (d) a natural plot in the de Los Padres Pound Reserve as a reference. The percentage of soil organic carbon (SOC), light organic carbon (LOC), fulvic acids (FA), humic acids (HA), and humins (H) in elongated, quadrangular and spherical aggregates were determined. The results show slight variations in SOC (7. 2-8. 6%) in the spherical aggregates of all the plots and a greater variability in elongated and quadrangular aggregates (5.6-10% and 6.9-13.6%, respectively). HA are minimal in the agroecosystems with extreme values of 0.02% in the spherical aggregates of cultivated plots, and maximal in the elongated and quadrangular aggregates of natural plots (0.3-0.5%). Fulvic acids display a similar behavior, while H decrease slightly with the morphologies and the different practices. The substantial decrease of humic substances in cultivated plots translates into a lower biologic activity; this, in turn, influences the aggregation, thus lowering the structural stability of these plots, which have been under agro-horticultural management for more than 50 years. © 2011 Springer-Verlag.


Borrelli N.,Institute Geologia Of Costas Y Del Cuaternario | Borrelli N.,CONICET | Alvarez M.F.,Institute Geologia Of Costas Y Del Cuaternario | Alvarez M.F.,CONICET | And 2 more authors.
Journal of Soils and Sediments | Year: 2010

Purpose: Little is known on the silica biogeochemical cycle in terrestrial environments. The aim of this work is to assess phytolith's role on the biogeochemical cycle of Si in Typical Argiudolls under different vegetation of the Pampean Plain, Argentina. Materials and methods: The work has been developed in three plots with different vegetal cover: grasses and shelter-belt plantations of Acacia melanoxylon-Celtis tala and Eucalyptus globulus-C. tala. The heavy liquid separation in the soil samples was realized with sodium polytungstate. The silica concentration of the soil solution and groundwaters was determined by UV-VIS spectrophotometry. Results and discussion: Acacia and eucalyptus do not produce phytoliths; instead, Dactylis glomerata (grass) is a silica-accumulating species, and their phytolith assemblage is composed basically by oblong and crenate, smooth elongate, rectangular and prickles within isolated phytoliths, and smooth long cells articulated. Phytolith content in soils decreases with depth. Total stock of phytoliths represents 5.9 to 12.9 wt.% and is higher in the arboreal plots. In the A horizons, phytolith fraction represents about 59.6 × 103 to 103.5 × 103 kg/ha. In these horizons, 90.7-94.4% of the phytolith content constitutes the labile pool and 9.3-5.6% the stable pool. In the arboreal plots, SiO2 content in soil solution is higher (406-1,106 μmol/L) and decreases with depth, while in the grass plot, SiO2 content is lesser (421-777 μmol/L) and increases with depth; probably because of differences in the nutritional requirements and root design between vegetal species, therefore, in the different depth uptake from the soil solution. In groundwaters, silica content is very high (932 μmol/L). Conclusions: Phytoliths are very representative in Typical Argiudolls and show a great degree of weathering so they could be into account in the biogeochemical studies since they could contribute with silica content in the soil solution, affecting the terrestrial silica biogeochemical cycle. © 2010 Springer-Verlag.


Alvarez M.F.,CONICET | Alvarez M.F.,Institute Geologia Of Costas Y Del Cuaternario | Osterrieth M.L.,Institute Geologia Of Costas Y Del Cuaternario | Del Rio J.L.,CONICET
Soil and Tillage Research | Year: 2012

Over the last few years, the increase of agriculture in the Pampean plains has led to a significant degradation of the most fertile soils in the country. The aim of our work is to define the effect of soil use on the stability of aggregates, bulk density and penetration resistance, and, especially, on the morphology and roughness of aggregates for their evaluation as possible soil quality indicators of Typical Argiudolls of south-eastern Buenos Aires. Mollic epipedons of plots with different soil use were analyzed: cultivated, pasture, and natural plots.The results indicated that bulk density values (>1.2g/cm 3) and penetration resistance (2-4.4MPa) values were significantly higher (p<0.05) in the cultivated sites when compared to natural soil (1g/cm 3 and 1.5-3MPa respectively). Aggregate stability was significantly lower (p<0.05) in the cultivated plots with respect to the natural plot, showing stable aggregates with values of 60-80% (crop intensive) and 85-100% (crop extensive). Moreover, these areas showed a greater percentage of spherical aggregates, and less rough than those in the natural plots. All of the properties were affected by soil use. The morphology and roughness of aggregates are effective indicators to help in the evaluation the quality of Typical Argiudolls of south-eastern Buenos Aires. © 2012 Elsevier B.V.


Borrelli N.,Institute Geologia Of Costas Y Del Cuaternario | Borrelli N.,CONICET | Fernandez Honaine M.,Institute Geologia Of Costas Y Del Cuaternario | Fernandez Honaine M.,CONICET | And 2 more authors.
Aquatic Botany | Year: 2011

Calcium oxalate crystal and silicophytolith assemblages were investigated in leaves of eleven aquatic species from habitats of the Argentinean Pampean Plain. Calcium oxalate druses and raphide bundles mainly occurred in leaf parenchyma and aerenchyma. Druses were observed in Alternanthera philoxeroides, Ludwigia peploides, Polygonum hydropiperoides and Rumex crispus; and raphide bundles in L. peploides and Typha latifolia. No calcium oxalate crystals were observed in Bidens laevis, Mikania parodii, Solanum glaucophyllum, Ranunculus apiifolius or the Juncaceae family. Druse density ranged between 14.62±3.09 (R. crispus) to 39.6±7.2crystalsmm-2 (P. hydropiperoides), and raphide bundle density ranged between 7.55±1.36 (L. peploides) to 20.55±5.19crystalsmm-2 (T. latifolia). Silicification mainly occurred in epidermal cells and xylem. Juncus spp., S. glaucophyllum, B. laevis, M. parodii and R. apiifolius produced abundant and diverse phytolith morphotypes. The rest of the species produced very few (L. peploides, P. hydropiperoides, A. philoxeroides) or no identifiable phytoliths (T. latifolia, R. crispus). Silica content ranged from 0.07 (T. latifolia) to 4.7% dry weight (S. glaucophyllum). © 2010 Elsevier B.V.

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