Using stable isotopes 18O and 2H of lake water and biogeochemical analysis to identify factors affecting water quality in four estuarine Amazonian shallow lakes          下载免费PDF全文

Alan Cavalcanti da Cunha  Leonel da Silveira Lobo Sternberg 《水文研究》2018,32(9):1188-1201

Stable isotopes analyses of oxygen and hydrogen of lake water were used to estimate the effect of evaporation (E) on the water quality of four shallow lakes in the Amapá State coast—Amazon/Brazil. These lakes, with different size and hydrologic conditions, were sampled during the course of the 2015/2016 El‐Niño (record‐breaking warming/drought in the Amazon rainforest). Hydrometeorological and water quality parameters were simultaneously performed to the isotopic sampling. The results showed that the evaporation process and the water quality can be explained by climate season and distances from the Atlantic Ocean. Lake evaporation losses ranged from ≈0–22% during the wet season in April/2016 and ≈35.7% during the dry season in November/2015. As expected, the evaporation of lake water was greater during the dry season, but it was higher for lakes farther away from the Atlantic Ocean compared with more coastal lakes due to tidal preponderance and the influence of major river channels. The more inland estuarine lakes showed a lower level of salinity (0.00–0.03 ppt) compared with those closer to the Atlantic Ocean (0.01–0.08 ppt). The El Niño phenomenon, with a lower precipitation in the Amazon basin, may initiate salinization of lakes closer to the Atlantic Ocean. Furthermore, strong mean seasonal variations of evaporation (0.06 ≤ E ≤ 0.22) and other hydrologic parameters were observed (precipitation, water temperature, and water depth), with significant effects on the water quality such as salinity, dissolved oxygen, chlorophyll (p < .05). We conclude that the occurrence of the extreme climatic events can disrupt the biogeochemical and hydrological balance of these aquatic ecosystems and salinization of lakes closer to the Atlantic Ocean.  相似文献   

Quantification of sediment source contributions in two paired catchments of the Brazilian Pampa using conventional and alternative fingerprinting approaches     

Mirian Lago Valente  José Miguel Reichert  Cédric Legout  Tales Tiecher  Rosane Barbosa Lopes Cavalcante  Olivier Evrard 《水文研究》2020,34(13):2965-2986

The knowledge of the contribution of sediment sources to river networks is a prerequisite to understand the impact of land use change on sediment yield. We calculated the relative contributions of sediment sources in two paired catchments, one with commercial eucalyptus plantations (0.83 km²) and the other with grassland used for livestock farming (1.10 km²), located in the Brazilian Pampa biome, using different combinations of conventional [geochemical (G), radionuclide (R) and stable isotopes and organic matter properties (S)] and alternative tracer properties [spectrocolorimetric visible-based-colour parameters (V)]. Potential sediment sources evaluated were stream channel, natural grassland and oat pasture fields in the grassland catchment, and stream channel, unpaved roads and eucalyptus plantation in the eucalyptus catchment. The results show that the best combination of tracers to discriminate the potential sources was using GSRV tracers in the grassland catchment, and using GSRV, GSV and GS tracers in the eucalyptus catchment. In all these cases, samples were 100% correctly classified in their respective groups. Considering the best tracers results (GSRV) in both catchments, the sediment source contributions estimated in the catchment with eucalyptus plantations was 63, 30 and 7% for stream channel, eucalyptus stands and unpaved roads, respectively. In the grassland catchment, the source contributions to sediment were 84, 14 and 2% for natural grassland, stream channel and oats pasture fields, respectively. The combination of these source apportionment results with the annual sediment loads monitored during a 3-year period demonstrates that commercial eucalyptus plantations supplied approximately 10 times less sediment (0.1 ton ha⁻¹ year⁻¹) than the traditional land uses in this region, that is, 1.0 ton ha⁻¹ year⁻¹ from grassland and 0.3 ton ha⁻¹ year⁻¹ from oats pasture fields. These results demonstrate the potential of combining conventional and alternative approaches to trace sediment sources originating from different land uses in this region. Furthermore, they show that well-managed forest plantations may be less sensitive to erosion than grassland used for intensive livestock farming, which should be taken into account to promote the sustainable use of land in this region of South America.  相似文献   

Correction to: Spatiotemporal variability of vegetation due to drought dynamics (2012–2017): a case study of the Upper Paraíba River basin,Brazil     

da Silva  Glauciene Justino Ferreira  de Oliveira  Nádja Melo  Santos  Celso Augusto Guimarães  da Silva  Richarde Marques 《Natural Hazards》2020,102(3):965-965

Natural Hazards - This correction stands to support the updating of the original article for changing the name Glauciene Justino Ferreira to Glauciene Justino Ferreira da Silva. The author group...  相似文献   

Magnetite-hematite transformation: correlation between natural and synthetic features     

Paola F. Barbosa  Leonardo Lagoeiro  Ricardo Scholz  Leonardo M. Graça  Nelcy Mohallem 《Mineralogy and Petrology》2015,109(3):329-337

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Modern sedimentation processes in a wave-dominated coastal embayment: Espírito Santo Bay,southeast Brazil     

Alex Cardoso Bastos  Daphnne Moraes Costa Moscon  Dannilo Carmo  José Antonio Baptista Neto  Valéria da Silva Quaresma 《Geo-Marine Letters》2015,35(1):23-36

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Some remarks on the assessment of P-wave velocity in laboratory tests for evaluating the degree of saturation     

Astuto  Giuseppe  Molina-Gómez  Fausto  Bilotta  Emilio  Viana da Fonseca  António  Flora  Alessandro 《Acta Geotechnica》2023,18(2):777-790

Acta Geotechnica - This work stems from the need to validate a technique for a reliably measurement of the degree of saturation (Sr) in deposits composed of sandy soils to improve their...  相似文献   

Shear behaviour of subgrade soil with reference to varying initial shear stress and plasticity index     

Silva  Isabella Novais  Indraratna  Buddhima  Nguyen  Thanh Trung  Rujikiatkamjorn  Cholachat 《Acta Geotechnica》2022,17(9):4207-4216

Acta Geotechnica - The influence of stress anisotropy (K) (i.e. the ratio between effective horizontal and vertical stresses) on the shear behaviour of soils has received significant attention in...  相似文献   

Grain-scale analysis of proppant crushing and embedment using calibrated discrete element models     

Bandara  K. M. A. S.  Ranjith  P. G.  Zheng  W.  Tannant  D. D.  De Silva  V. R. S.  Rathnaweera  T. D. 《Acta Geotechnica》2022,17(11):4837-4864

Acta Geotechnica - Proppant crushing and embedment in hydraulically-induced fractures is a major drawback to the recovery of unconventional oil/gas and geothermal energy production. This study...  相似文献   

The origin of the near-IR line emission from molecular,low and high ionization gas in the inner kiloparsec of NGC 6240     

Gabriele da Silva Ilha  Marina Bianchin  Rogemar A. Riffel 《Astrophysics and Space Science》2016,361(6):178

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Timing of multiple hydrothermal events in the iron oxide–copper–gold deposits of the Southern Copper Belt,Carajás Province,Brazil     

Carolina?P.?N.?MoretoEmail author  Lena?V.?S.?Monteiro  Roberto?P.?Xavier  Robert?A.?Creaser  S.?Andrew?DuFrane  Gustavo?H.?C.?Melo  Marco?A.?Delinardo da Silva  Colombo?C.?G.?Tassinari  Kei?Sato 《Mineralium Deposita》2015,50(5):517-546

The Southern Copper Belt, Carajás Province, Brazil, hosts several iron oxide–copper–gold (IOCG) deposits, including Sossego, Cristalino, Alvo 118, Bacuri, Bacaba, Castanha, and Visconde. Mapping and U–Pb sensitive high-resolution ion microprobe (SHRIMP) IIe zircon geochronology allowed the characterization of the host rocks, situated within regional WNW–ESE shear zones. They encompass Mesoarchean (3.08–2.85 Ga) TTG orthogneiss, granites, and remains of greenstone belts, Neoarchean (ca. 2.74 Ga) granite, shallow-emplaced porphyries, and granophyric granite coeval with gabbro, and Paleoproterozoic (1.88 Ga) porphyry dykes. Extensive hydrothermal zones include albite–scapolite, biotite–scapolite–tourmaline–magnetite alteration, and proximal potassium feldspar, chlorite–epidote and chalcopyrite formation. U–Pb laser ablation multicollector inductively coupled mass spectrometry (LA-MC-ICP-MS) analysis of ore-related monazite and Re–Os NTIMS analysis of molybdenite suggest multiple Neoarchean (2.76 and 2.72–2.68 Ga) and Paleoproterozoic (2.06 Ga) hydrothermal events at the Bacaba and Bacuri deposits. These results, combined with available geochronological data from the literature, indicate recurrence of hydrothermal systems in the Southern Copper Belt, including 1.90–1.88-Ga ore formation in the Sossego–Curral ore bodies and the Alvo 118 deposit. Although early hydrothermal evolution at 2.76 Ga points to fluid migration coeval with the Carajás Basin formation, the main episode of IOCG genesis (2.72–2.68 Ga) is related to basin inversion coupled with Neoarchean (ca. 2.7 Ga) felsic magmatism. The data suggest that the IOCG deposits in the Southern Copper Belt and those in the Northern Copper Belt (2.57-Ga Salobo and Igarapé Bahia–Alemão deposits) do not share a common metallogenic evolution. Therefore, the association of all IOCG deposits of the Carajás Province with a single extensive hydrothermal system is precluded.  相似文献