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Adsorption and availability of phosphorus in response to humic acid rates in soils limed with CaCO3 or MgCO3 Ciência e Agrotecnologia
Maluf,Henrique José Guimarães Moreira; Silva,Carlos Alberto; Curi,Nilton; Norton,Lloyd Darrell; Rosa,Sara Dantas.
ABSTRACT Humic acid (HA) may reduce adsorption and increase soil P availability, however, the magnitude of this effect is different when Ca2+ prevails over Mg2+ in limed soils. The objective of this study was to evaluate the effects of HA rates and carbonate sources on the adsorption, phosphate maximum buffering capacity (PMBC), and P availability in two contrasting soils. Oxisol and Entisol samples were firstly incubated with the following HA rates: 0, 20, 50, 100, 200 and 400 mg kg-1, combined with CaCO3 or MgCO3, to evaluate P adsorption. In sequence, soil samples were newly incubated with P (400 mg kg-1) to evaluate P availability. The least P adsorption was found when 296 mg kg-1 of HA was added to Oxisol. Applying HA rates decreased maximum...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Organic ligands; Liming; Humic acid-metal-P complexes; Langmuir isotherm; Phosphate maximum buffering capacity..
Ano: 2018 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1413-70542018000100007
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Chemical Speciation of Copper in a Salt Marsh Estuary and Bioavailability to Thaumarchaeota ArchiMer
Whitby, Hannah; Hollibaugh, James T.; Van Den Berg, Constant M. G..
The concentrations of dissolved copper (Cu-d), copper-binding ligands, thiourea-type thiols, and humic substances (HScu) were measured in estuarine waters adjacent to Sapelo Island, Georgia, USA, on a monthly basis from April to December 2014. Here we present the seasonal cycle of copper speciation within the estuary and compare it to the development of an annually occurring bloom of Ammonia Oxidizing Archaea (AOA), which require copper for many enzymes. Two types of complexing ligands (L-1 and L-2) were found to dominate with mean complex stabilities (log K'(cuL)) of 14.5 and 12.8. Strong complexation resulted in lowering the concentration of free cupric ion (Cu2+) to femtomolar (fM) levels throughout the study and to sub-fM levels during the summer...
Tipo: Text Palavras-chave: Copper speciation; Cathodic stripping voltammetry; Humic substances; Thiols; Thiourea; Organic ligands; Thaumarchaeota; Ammonia-oxidizing archaea.
Ano: 2017 URL: https://archimer.ifremer.fr/doc/00616/72834/72735.pdf
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Trace element behaviour at cold seeps and the potential export of dissolved iron to the ocean ArchiMer
Lemaitre, Nolwenn; Bayon, Germain; Ondreas, Helene; Caprais, Jean-claude; Freslon, Nicolas; Bollinger, Claire; Rouget, Marie-laure; De Prunele, Alexis; Ruffine, Livio; Olu-le Roy, Karine; Sarthou, Geraldine.
Seawater samples were collected by submersible above methane seeps in the Gulf of Guinea (Regab and Baboon pockmarks) in order to investigate the behaviour of iron (Fe), manganese (Mn) and rare earth elements (REE) during fluid seepage. Our aim was to determine whether cold seeps may represent potential sources of dissolved chemical species to the ocean. Dissolved (<0.45 μm filtered samples) and total dissolvable (unfiltered samples) concentrations were determined over ∼50 m long vertical transects above the seafloor and at various discrete locations within the pockmarks. We show that substantial amounts of Fe and Mn are released into seawater during seepage of methane-rich fluids. Mn is exported almost quantitatively in the dissolved form (more than...
Tipo: Text Palavras-chave: Iron; Rare earth elements; Cold seeps; Seawater; Organic ligands; Iron-sulfide nanoparticles.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00211/32190/30704.pdf
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