Lanthanide marine pore water

The pore water composition of lanthanides is poorly characterized. Low concentrations and small volumes of pore water samples (typically 10-50 ml) combine to make detection difficult. Only the lanthanide-enriched pore waters of anoxic coastal and estuarine sediments have been measured at a few sites (sect. 6). Currently, the pore water chemistry of lanthanides in non-coastal marine sediments is unknown. The field of lanthanide pore water chemistry remains an important challenge. 

The objective of this section is to describe the major features of lanthanides in the water column of anoxic basins and briefly discuss the mechanisms responsible for spatial and temporal variations. Two examples will be used, the Black Sea and Chesapeake Bay. The next subsection on lanthanides in pore waters follows naturally in that many of the processes operating in anoxic water columns occur in marine sediments. 

This handbook article combines an up-to-date tabulation of the lanthanide composition of the ocean with a description of lanthanide distributions in the context of physical, chemical and biogeochemical processes controlling these distributions. The focus of this chapter is water column biogeochemistry. While pore waters and hydrothermal waters will be considered in this article, the extensive literature on the lanthanide geochemistry of minerals and marine sediments will not be discussed. 

Lanthanide cycling in anoxic marine basins, pore waters and hydrothermal waters... 

What are pore waters and why are their compositions important with respect to the marine geochemistry of the lanthanides The term pore waters (or alternatively, interstitial waters) refers to the waters contained within the pores of sediments. Pore waters are extracted by different types of procedures. Centrifugation and squeezing of sediments are two common methods. The latter is accomplished by using hydraulic systems or gas pressure systems. In all methods the extracted waters are rapidly filtered (typically 0.22 or 0.45 [xm pore size) to yield dissolved matter for analysis. 

There is only one paper with data on the pore water composition of deep ocean sediments deposited under oxygenated water (Ridout and Pagett 1984). This paper mostly deals with extraction methods and provides poorly documented lanthanide data for a single sample. It is fair to state the lanthanide composition and chemistry of oxic marine sediments is unknown. 

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