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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Early life on Earth : the microbial fractionation of iron isotopes

Leighton, Emma M. January 2005 (has links)
No description available.
42

The role of terrestrial ice in global geochemical cycles

Jones, Ian Wyn January 2002 (has links)
No description available.
43

The biogeochemical cycling of ammonium and methylamines in intertidal sediments

Dawit, Mekibib David January 2006 (has links)
The methylamines (MAs) are chemical analogues of ammonia and contain one, two or three methyl groups. This study looked at their occurrence in inter-tidal sediments and at changes in their abundance during tidal cycling, including forced and naturally occurring sediment resuspension. Two sites in the UK, Burnham Overy Staithe (BOS) and the Thames Estuary (TE), and the Ria Formosa (RF), Portugal, were chosen for the study. The MAs were abundant in all samples collected. MA concentrations were compared to NH ₄⁺ at BOS and TE. A consistent trend emerged, with NH ₄⁺ more abundant in the pore-waters and the MAs dominating the solid phase. Most NH ₄⁺ and MAs were found on the solid-phase, and the general magnitude of adsorption was: TMA > DMA > MMA > NH ₄⁺. This was inconsistent with their pKb values but could be explained by the ability of each cation to form hydrogen bonds with water. Pore-water MA concentrations at BOS were compared with salinity but no correlation was observed. However, the clam Ruditapes decussatus (L.) released TMA during tidal inundation. The mechanism of release is unclear as these organisms do not osmoregulate, but the calculated TMA loss from these sediments (169 mmol m⁻² per tide) could be increasing dissolved organic nitrogen concentrations in the Ria Formosa. TE sediments were used in desorption experiments. Desorption of NH ₄⁺ was more rapid than the MAs and their mean chemical response times were 15 and 25 minutes, respectively. Increases in concentrations of dissolved NH ₄⁺ and MAs over a tidal cycle were coincident with remobilisation of seabed sediments. Desorption of NH ₄⁺ and MAs from the remobilised sediments accounted for approximately 50% and > 90% of the increase, respectively. The results are proposed as a predictor for the sorption behaviour of other ON compounds and emphasise the importance of sediment resuspension as a mechanism of ON release to the water column.
44

The geochemistry of wallrock alteration in West Cornwall, with particular reference to the Mount Wellington Mine

Cotton, Malcolm Terry January 1972 (has links)
No description available.
45

Geochemistry of fossil formation waters : rates of water-rock interaction

Thurlow, James January 1996 (has links)
No description available.
46

The role of the North Atlantic water masses in the draw down of anthropogenic CO←2

Soler, Iris January 2002 (has links)
No description available.
47

Geochemical investigations at Dun Moss

Tervet, David John January 1976 (has links)
No description available.
48

Radon release from granites in south-west England

Poole, Jason January 2001 (has links)
No description available.
49

High precision transition metal isotope analysis by plasma-source mass spectrometry and its implications for low temperature geochemistry

Mason, Thomas Frederick David January 2003 (has links)
No description available.
50

Geochemical controls on the acidity of crude oils

Meredith, Will January 2001 (has links)
No description available.

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