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Osterrieth M.,Institute Geologia Of Costas Y Del Cuaternario Igcyc | Osterrieth M.,CONICET | Borrelli N.,Institute Geologia Of Costas Y Del Cuaternario Igcyc | Borrelli N.,CONICET | And 5 more authors.
Environmental Earth Sciences | Year: 2016

In salt marshes, the hydrodynamics and the availability of iron, organic matter and sulphate, influence the formation and/or dissolution of iron sulfides and iron oxyhydroxides. Therefore, they constitute key factors affecting the iron biogeochemical processes in these environments. The aim of this work is to evaluate the physico-chemical and mineralogical variations associated to iron biogeochemistry in palaeo and actual salt marshes in the area of influence of the Mar Chiquita coastal lagoon, Pampean Plain, Argentina. In soils of exhumed palaeo marshes, the iron contents are 56–95 μmol g−1, whereas these contents decrease to 36–75 μmol g−1 in actual marsh soils. The presence of framboidal and poliframboidal pyrites associated with gypsum, barite, calcite, halite and iron oxyhydroxides defines the conditions of the pedosedimentary sequences of the Holocene paleomarshes. Sequences of pyrite formation (sulfidization) and degradation (sulfuricization) were observed. These processes were evidenced by a sequential extraction, reflecting that the largest proportion of iron is in the form of crystalline iron oxides (28–76 %) and lepidocrocite (6–16 %); while the proportion associated with ferrihydrite and pyrite is low (0–9 and 1–17 %, respectively). These facts could be partly explained by the complex redox processes characteristic of these environments, such as aeration generated by the rhizosphere and intense bioturbation by invertebrates. These iron biomineralizations have been useful because they allow paleoenvironmental interpretations and characterization of paleomarshes, and environmental inferences related to the management of actual salt marshes. © 2016, Springer-Verlag Berlin Heidelberg.

Borrelli N.,Institute Geologia Of Costas Y Del Cuaternario Igcyc | Borrelli N.,CONICET | Osterrieth M.,Institute Geologia Of Costas Y Del Cuaternario Igcyc | Romanelli A.,Institute Geologia Of Costas Y Del Cuaternario Igcyc | And 5 more authors.
Environmental Earth Sciences | Year: 2012

Although phytoliths constitute part of the wetland suspended load, there are few studies focused on the quantification of them in the biogenic silica (BSi) pool. So, the aim of this paper is both to determine BSi content (diatoms and phytoliths) and its relationship with dissolved silica in surface waters, and the influence of soil and groundwater Si biogeochemistry in Los Padres wetland (Buenos Aires Province, Argentina). In the basin of the Los Padres wetland, dissolved silica (DSi) concentration is near 840 ± 232 μmol/L and 211.83 ± 275.92 μmol/L in groundwaters and surface waters, respectively. BSi represents an 5.6-22.1% of the total suspension material, and 8-34% of the total mineralogical components of the wetland bottom sediments. DSi and BSi vary seasonally, with highest BSi content (diatoms specifically) during the spring-summer in correlation to the lowest DSi concentration. DSi (660-917.5 μmol/L) and phytolith (3.35-5.84%) concentrations in the inflow stream are higher than in the wetland and its outflow stream (19. 1-113 μmol/L; 0.45-3.2%, respectively), probably due to the high phytolith content in soils, the high silica concentration in the soil solution, and the groundwater inflow. Diatom content (5-16.8%) in the wetland and its outflow stream is higher than in the inflow stream (0.45-1.97%), controlling DSi in this system. The understanding of the groundwater-surface water interaction in an area is a significant element for determining the different components and the role that they play on the local biogeochemical cycle of Si. © 2011 Springer-Verlag.

Glok Galli M.,CONICET | Glok Galli M.,Institute Geologia Of Costas Y Del Cuaternario Igcyc | Martinez D.E.,CONICET | Martinez D.E.,Institute Geologia Of Costas Y Del Cuaternario Igcyc | And 6 more authors.
Environmental Earth Sciences | Year: 2014

Mar Chiquita is a coastal lagoon located in the Argentine Buenos Aires province in South America. The aim of this study was to perform a hydrochemical and stable isotopes characterization in order to better the understanding of the hydrology of the Mar Chiquita lagoon’s catchment and its water budget. Groundwater samples were taken from 144 wells and 21 samples from main streams, and seven lagoon water samples were also collected. Chemical analyses were carried out using standard laboratory methods, and isotopic determinations were made through laser spectroscopy using a DLT-100 liquid–water isotope analyzer. Hydrochemical analysis permits a general classification of groundwater and streamwater as sodium bicarbonate waters, while the lagoon chemical composition shows an evolution toward seawater composition, from the north to its mouth, which is located southerly. Isotopic data show a source of aquifer recharge from rainfall and a groundwater domain into the streams’ flow. Three main components can be recognized as end members in a plot of electrical conductivity (EC) versus δ18O: seawater, streamwater and groundwater. Obtained EC values for groundwater in the discharge zone (EC average value = 3,516 μS/cm) allow minimizing its direct contribution and to take into consideration two dominating end members: streamwater and seawater. Mar Chiquita lagoon’s water falls close to the line between streamwater and seawater end members according to its EC and δ18O. The obtained seawater proportion for these samples ranges from 84 % in the lagoon’s mouth to around 0 % in the more distal area. © 2014, Springer-Verlag Berlin Heidelberg.

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