[L&O Featured Article]Vol 47, Issue 2 (Mar 2002)

[lo-feature-admin@aslo.org]

The featured article in the March 2002 issue of L&O is:

Quigley, Matthew S., Peter H. Santschi, Chin-Chang Hung, Laodong Guo, and Bruce 
D. Honeyman. 2002. Importance of acid polysaccharides for 234Th complexation to 
marine organic matter. Limnol. Oceanogr. 47(2): 367-377. It can be read online 
or downloaded by clicking here. 

          http://aslo.org/lo/toc/vol_47/issue_2/0367.pdf

Instructions for reading PDF files are located on the ASLO web page: 

          http://aslo.org/help/loonline.html 

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Introductory comments by Ray Hesslein (the Associate Editor for this paper)

About 20 years ago I had the pleasure of working with one of the authors, Peter 
Santschi, and a Swiss colleague, Urs Nyffeler, on the fate of metal radiotracers 
added to a lake at the Experimental Lakes Area (Hesslein et al. 1980, Nyffeler 
et al. 1986, Santschi et al 1986). In both field and laboratory studies the rate 
at which the metals moved from dissolved to particulate phase was too slow to be 
accounted for by collision theory. We hypothesized that there was a dissolved 
(colloidal) organic molecule that acted as an intermediary in the process; the 
metal sorbed to the organic molecule which then stuck to the particle. In the 
past decade a large body of knowledge on this topic has been developed using a 
number of new techniques. Most of this work now centers on the ocean, where 
there are more geochemists and more research resources. I think it is fair to 
say that this work has redefined the concept of "particle-reactive."

Quigley et al. have developed novel applications of gradient gel electrophoresis 
to very specifically investigate the characteristics of the strong binding 
ligand for Th(IV) in sea water. They have shown that this ligand has a size of 
about 13kDa and strong acidic functional groups. Other aspects of the 
investigation strongly support its identification as a polysaccaride. 
Polysacarride enriched colloidal organic matter had the highest partition 
coefficient of any sorbant for 234Th. This enriched material also had enhanced 
partition coefficients for many other metals.

The reviewers clearly recognized that the significant implications of this work. 
The use of natural and enhanced levels of radio-tracers in the oceans is 
critical to the interpretation of rates of water and particle movements, which 
are fundamental ocean processes. Variations in the abundance of these 
polysaccarides could help explain variability in previous studies. Researchers 
looking at metals in effluents also will have interest in this work as natural 
and introduced polysaccarides could have important influence on the fate of 
those metals. The tools developed by Quigley et al. significantly advance 
understanding the role of organic molecules in the distribution of metals in 
natural systems. It is clearly time to again look at the abundant organic matter 
in lakes with these sophisticated techniques.

References

Hesslein, R.H., W. S. Broecker and D.W Schindler. 1980. Fates of metal 
radiotracers added to a whole lake. Can. J. Fish. Aquat. Sci. 37:378-386.

Nyffeler, U.P, P.H. Santschi and Y.H. Li. 1986. The relevance of scavenging 
kinetics to modeling sediment-water interactions in natural waters. Limnol. 
Oceanogr. 31(2), 277-292.

Santschi, P.H., U.P Nyffeler, R.F. Anderson, S.L. Schiff, P. O'Hara, and R.H. 
Hesslein. 1986. Response of radiotracers to acid base titrations of controlled 
experimental ecosystems: Evaluation of transport parameters for application to 
whole-lake radiotracer experiments. Can. J. Fish. Aquat. Sci. 43: 60-77.