Geochemistry, past, present and future

Geochemical Perspectives, a new quarterly journal of the European Association of Geochemistry, recently published its fourth issue, which is entirely devoted to the life and scientific work of Gordon Brown, Chair of the Department of Geological & Environmental Sciences, and his long-time scientific collaborator, Professor Georges Calas, of the Université Pierre et Marie Curie  – Paris VI.

Each issue of the journal is a single book-length article presenting an in-depth view on the past, present, and future of a geochemical field, “as seen through the eyes of highly respected members of our community.” The articles include personal insights into the author’s scientific career, along with opinions regarding the direction the field is – or ought to be – headed.

Brown joined the Stanford faculty in 1973 and has devoted much of his career to studying the geochemistry of mineral surfaces and their reactivity with aqueous solutions, along with the environmental fate of heavy metals. In doing so, he pioneered the use of extremely intense x-rays from synchrotron radiation sources, particularly the Stanford Synchrotron Radiation Lightsource (SSRL) at SLAC National Accelerator Laboratory, to probe the molecular-level environments of atoms and molecules in many different types of Earth materials.  Following is a Q&A with Brown about the recent publication in Geochemical Perspectives.

How did the book come about?

The 260-page book is part of a new series started by the European Association of Geochemistry in 2012, and the editorial board selected certain individuals – me being one of them – to approach and write about their work in and perspectives on a particular field of geochemistry. 

The people they have chosen usually are older, have been working in that area for many years, and have helped develop that field.  I received an invitation to do one of these perspectives on a topic of interest to me.

I chose the topic that is the title of the book, “Mineral-Aqueous Solution Interfaces and Their Impact on the Environment”.  This area represents much of the research that I have been doing with my group for the last 28 years.

The editors of this new series allow each author the option of choosing one coauthor, and I invited a longtime collaborator of mine, Georges Callas, to join me in this effort.

How did you decide on an approach?

 The editors did not want this book to be a review--a dry scientific document--but to have more of a personal touch, so they asked me to include my life history, and for Georges to include his.  As a result, there is a chapter on “The Life and Times of Gordon Brown” and also one on Georges Calas’ life.

The editors also wanted our perspectives, so we wrote a short piece at the end of each of the first 21 chapters to highlight key discoveries.  It was fun to write this book, but it was not the normal type of scientific writing that I am used to. 

The first part of the book highlights some of my scientific heroes who helped develop this field in its very earliest stages - people like Nobel Laureates Linus Pauling, arguably the most influential chemist of the 20^th century, and Irving Langmuir, the father of surface chemistry, but also others who are probably are not terribly well known.  Two of these lesser-known people were Victor Goldschmidt, the father of geochemistry, and Konrad Krauskopf, one of the most influential American geochemists who was also a professor at Stanford University and Chair of the Department of Geology when I first arrived here.   

The second part of the book consists of scientific stories about areas in which I have worked as well as a couple of areas in which Georges Calas has worked.

The very last chapter of the book is an extended perspective on this field in general which outlines some of the key problems remaining to be solved by the next generation of geochemists.

How did you come to collaborate with your coauthor, Georges Calas?

Our collaboration started back in 1984, when I was awarded a French government fellowship and was invited to spend a sabbatical leave at the University of Paris VI.  When first asked to spend 6-months in Paris, I stupidly said, “No, I can’t do this.  I have a wife who is working and I have two kids in school.  I also have no place to live in Paris.”

But my French hosts persisted and said they’d find us a place to live, which they did, so my family and I went to Paris for six wonderful months.  We all had a very nice time learning about French food, wines, culture, and language.  In spite of these distractions, I got a lot of work done while there.

Georges and I had known each other before this visit, but we struck up a scientific collaboration while I was there, which blossomed into a lifelong friendship.  I’ve been working with him for almost 30 years, and we have published over 30 papers together.

In 1997 I received an honorary doctorate from the University of Paris, in a very nice ceremony with ermine robes in the old Sorbonne.  Since that 1984 sabbatical I’ve had 9 or 10 postdocs from Paris, each of whom was outstanding and has returned to France where they are gainfully employed in industry, universities, and CNRS .  The most recent one just arrived at Stanford in March.

What are two or three developments in geochemistry that you feel are most significant?

One of the big ones is the availability of large user facilities like the synchrotron x-ray source that I use at SLAC National Accelerator Laboratory.  These devices have revolutionized the way we do science, including the field of geochemistry, and allow us to do things we could never have dreamed of doing before they became available.  I was fortunate to have arrived at Stanford in 1973 because SSRL began user operation in 1974.

Another huge development has been the rapid evolution of computers, not only in terms of more memory, but also speed.  I remember the Digital Equipment Corporation PDP 11/32 computer that I set up in 1970, which had a 25-kbyte hard disk and 8-kbytes of memory.  My G4 iPhone is much more powerful than this early computer. 

My group now uses super computers to look at how atoms bond to one another, what sort of geometries they might form, and how water and aqueous complexes interact with the surface of a mineral, for example.

A third development is new theories that allow us to understand chemical processes at a deeper, totally different level.  Development of some of these new theories would not have occurred without the parallel development of synchrotron radiation sources that produce new data with which to test the predictions of new theories, and the incredible advances in computational power.   

What’s in your crystal ball for geochemistry in the future?

The environmental implications of nanotechnology will be a big issue. 

We now use nanoparticles for many important applications, such as carbon nanotubes to make lightweight, high-strength composite materials and silver nanoparticles, which are widely used for their antibacterial properties.  One of the big questions is, what will be the long-term impact of nanoparticles on our environment? 

It took about 20 years to demonstrate the cause and effect between the burning of fossil fuels and the production of acid rain, which has damaged forest ecosystems in the northeastern US.  And with DDT, a very effective pesticide used to kill mosquitoes, it took about 20 years to understand that it was also killing birds.

We really don’t know yet what the long-term effects of nanoparticles will be, but it’s becoming an important topic that has led to the development of a new field known as environmental nanotechnology.  An important issue in this new field is gaining a more fundamental understanding of the surface chemistry of nanoparticles, which controls their chemical reactivity and their impact on the health of organisms. My research group is part of a national center funded by a grant from the National Science Foundation that allows us to study the structure-property relationships of these nanomaterials, both natural as well as manufactured ones.

In addition to the area of environmental nanotechnology, I think there is also a huge amount left to do in the area of natural catalysis, which converts one chemical compound into another.  In our labs here, for example, several of my Stanford colleagues and I are looking at the potential to use catalytic reactions of CO₂ on natural iron oxide surfaces to convert this potent greenhouse gas into other hydrocarbons.

So natural catalytic reactions on metal oxide surfaces is a big area that should be explored by the next generation of geochemists.

There is a 1942 quotation from Winston Churchill that I used to end the book, which I think nicely expresses the idea that much is left to be done in this field of interface geochemistry. “Now this is not the end, it is not even the beginning of the end, but it is perhaps the end of the beginning.”

This sums up how I feel about this whole area of science. There are many unanswered questions.

Making further progress in this area will require new experimental methods, faster computers, and new user facilities. But 30 years ago, when I first started my work in this area, there wasn’t a lot known at the molecular level.  Now we know a lot about how these chemical interactions between aqueous species and mineral surfaces work.  You can go a long way in 30 years if you have good ideas, the right facilities, the right collaborators, and good luck.

Louis Bergeron is a freelance science writer.