Marine environment geochemistry

Until now, Mercury has only been studied more closely by one spacecraft (Mariner 10, 1974), since its nearness to the sun means that spacecraft approaching it are subject to particularly extreme conditions. NASA s MESSENGER (Mercury Surface, Space, Environment, Geochemistry and Ranging) was launched in 2004 and is planned to reach Mercury in March 2011, and then to orbit the planet. The main tasks of the MESSENGER mission are to map the planet, to make measurements of its magnetic field and to collect data relevant to its geological and tectonic history (Solomon, 2007). 

Vandenbroucke, M., Pelet, R., and Debyser, Y. (1985). Geochemistry of humic substances in marine environments. In Humic Substances in Soil, Sediment, and Water Geochemistry, Isolation, and Characterization, Aiken, G. R., McKnight, D. M., Wershaw, R. L., and Mac-Carthy, R eds., John Wiley Sons, New York, pp. 249-273. 

At this stage in the development of the subject of the geochemistry of sedimentary carbonates, we have dealt primarily with the mineralogy and basic physical chemistry of the carbon system and some of its important phases. In the following chapters, this information and additional data and interpretations are utilized to explain the behavior of sedimentary carbonates in shallow water and deep marine environments, and during early and late diagenesis. The... 

Sackett, W.M., Mo, T., Spalding, R.E., and Exner, M.E. (1973) A reevaluation of the marine geochemistry of uranium, in Radioactive Contamination of the Marine Environment (IAEA), Vienna. 

Tebo, B.M. and Emerson, S., Microbial manganese (II) oxidation in the marine environment A quantitative study, Bio geochemistry, 2, 149, 1986. 

Liu, K. K. (1979). Geochemistry ofinorganic nitrogen compounds in two marine environments The Sta Barbara Basin and the ocean offPeru. Ph.D. Thesis. University of Cahfomia, Los Angeles p. 354. 

Over the past several decades, the importance of trace elements in the marine environment has become apparent, with major regions of world s oceans now known to be affected by iron limitation, and with the first accurate measurements of incredibly scarce quantities of other essential metals. Yet, we understand little of how metal limitation manifests itself in the biochemistry of marine microorganisms or of the role of trace elements in the geochemistry of the oceans. But we now know enough to ask relevant questions at both the molecular and global scale, and are able to use novel experimental tools to help answer these questions. 

The chemistry of the carbonic acid system in seawater has been one of the more intensely studied areas of carbonate geochemistry. This is because a very precise and detailed knowledge of this system is necessary to understand carbon dioxide cycling and the deposition of carbonate sediments in the marine environment. A major concept applicable to problems dealing with the behavior of carbonic acid and carbonate minerals in seawater is the idea of a constant ionic medium. This concept is based on the observation that the salt in seawater has almost constant composition, i.e., the ratios of the major ions are the same from place to place in the ocean (Marcet s principle). Possible exceptions can include seawater in evaporative lagoons, pores of marine sediments, and near river mouths. Consequently, the major ion composition of seawater can generally be determined from its salinity. It has been possible, therefore, to develop equations in which the influence of seawater composition on carbonate equilibria is described simply in terms of salinity. 

Sackett W. M. (1989) Stable carbon isotope studies on organic matter in the marine environment. In Handbook of Environmental Isotope Geochemistry (eds. P. Fritz and J. C. Fontes). Elsevier, Heidelberg, vol. 3, pp. 139-169. 

Lawrence, J.R. (1989) The stable isotope geochemistry of deep-sea pore water. In Handbook of Environmental Isotope Geochemistry, Vol. 3 The Marine Environment (Eds Fritz, P. Fontes, J.Ch.), pp. 317-356.Elsevier, Amsterdam. 

E. R. Sholkovitz, The Geochemistry of Plutonium in Fresh and Marine Environments, Earth-Science Rev. 19 (1983) 95. 

The geochemistry of marine sediments is a major source of information about the past environment. Of the many measurements that provide such information, those of the U-series nuclides are unusual in that they inform us about the rate and timescales of processes. Oceanic processes such as sedimentation, productivity, and circulation, typically occur on timescales too short to be assessed using parent-daughter isotope systems such as Rb-Sr or Sm-Nd. So the only radioactive clocks that we can turn to are those provided by cosmogenic nuclides (principally or the U-series nuclides. This makes the U-series nuclides powerful allies in the quest to understand the past ocean-climate system and has led to their widespread application over the last decade. 

Cochran JK (1984) The fates of U and Th decay series nuclides in the estuarine environment. In The Estuary as a Filter. Kennedy VS (ed) Academic Press, London, p 179-220 Cochran JK (1992) The oceanic chemistry of the uranium - and thorium - series nuclides. In Uranium-series Disequilibrium Applications to Earth, Marine and Environmental Sciences. Ivanovich M, Harmon RS (eds) Clarendon Press, Oxford, p 334-395 Cochran JK, Masque P (2003) Short-lived U/Th-series radionuclides in the ocean tracers for scavenging rates, export fluxes and particle dynamics. Rev Mineral Geochem 52 461-492 Cochran JK, Carey AE, Sholkovitz ER, Surprenant LD (1986) The geochemistry of uranium and thorium in coastal marine-sediments and sediment pore waters. Geochim Cosmochim Acta 50 663-680 Corbett DR, Chanton J, Burnett W, Dillon K, Rutkowski C. (1999) Patterns of groundwater discharge into Florida Bay. Linrnol Oceanogr 44 1045-1055... 

Windom, H.L. and D.R. Kendall. 1979. Accumulation and biotransformation of mercury in coastal and marine biota. Pages 301-323 in J. 0. Nriagu (ed.). The Bio geochemistry of Mercury in the Environment. Elsevier/North-Holland Biomedical Press, NY. 

Schematic representation of manganese nodule end-member morphologies. The size of the arrows Indicates the proportion and direction of metal supply, (a) Typical situation In the open ocean with the nodules lying on an oxidized sediment substrate dominant mode of formation Is hydrogenous, (b) Typical situation In nearshore and freshwater environments with nodules lying on a sediment substrate that Is partly reducing In character. Dominant supply of metals Is via Interstitial waters from below the substrate surface. Source From Chester, R. (2003). Marine Geochemistry, 2nd ed. Blackwell, p. 425.

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