Acceptance speech for the 1999 Schenck Award
A chemical engineer lost in the realm of organic geochemistry
(19th International Meeting on Organic Geochemistry,
Istanbul, 10 September, 1999)
Stefan Schouten
Netherlands Institute for Sea Research, PO Box 59, 1790 AB Den Burg, The Netherlands
Ladies and Gentlemen,
It is with many feelings that I accept the Schenck award for young organic geochemists. First of all, the circum-stances in which this conference and the award ceremony takes place: Turkey has suered a great tragedy and I am sure I speak for many people when I wish the Turkish people a speedy recovery. I also have many scienti®c and per-sonal feelings on accepting this award. On the news of the nomination for this award I was very curious to know who the other nominees were. Looking at recent publications and presentations I feel there is an enormous pool of young talented organic geochemists out there, many of whom deserve to be nominated or to win the Schenck award. On a personal level, I think about all the people who have helped develop the little skills I have and turned me into a somewhat respectable scientist. I will mention a few names during this speech, but there are many, many more people responsible for the scienti®c work I did in the past. Finally, this award made me think of my ``sabbatical'' leave at the University of California, Davis, last year. It showed me what a wonderful place California is and that chemical engi-neering and material science is a fascinating ®eld with many unexpected applications. But it also showed that my heart belongs to organic geochemistry.
When the chairman of the award committee, Joan Grimalt, asked me to prepare a speech summarizing the highlights of my research I had great trouble writing it. There have been so many nice studies in which I have been lucky enough to be involved that it is dicult to choose what to talk about today. Possibly the best thing to do is to tell some stories in more or less chronological order. It all started when I did an oral examination in organic geochemistry after taking the class taught by Jan de Leeuw at the Technical University of Delft. I think it was his ®rst year of teaching the course since Professor Schenck had become dean of the University. After the successful completion of the exam, in which I got the only A of my studies, he kindly oered me (out of pity?) to do an undergraduate project in his group. I could either work on so-called resistant biopolymers or organic sulfur compounds. These are the kind of decisions that seem unimportant at the time but turn out to have quite some consequences later on. I started out under the supervision of Math Kohnen, now working at Shell, and Jaap Sinninghe DamsteÂ, working on samples from the sulfur-rich immature Vena del Gesso basin. Some preliminary work had already been done on other samples from this basin and a range of interesting organic sulfur compounds (OSC) were found, including di- and trisul®des which indicated the incorporation of polysul®des into functionalized lipids. We analyzed some bituminous marl layers, a stromatolite layer and a gypsum layer for free and sulfur-bound compounds and noted that several compound classes could be distinguished: carbon skeletons which were only occurring free, intramolecularly sulfur-bound or intermolecularly sulfur-bound (or combi-nations). This phenomenon could be clearly linked with the number and type of functionalities in the precursors of these compounds. I found it very exciting do this kind of research and the results were even part of some papers. I also distinctly remember that Math asked me to prepare some of the fractions I had isolated, since he was going to the United States to analyze them by a new technique; something called ``compound-speci®c stable carbon isotope analysis (CSIA)'' or so and the technique was only available at a university in Indiana, in a little town called Bloomington. I also remember that when he came back he showed me all these nice negative values he had measured for the com-pounds and what it all meant. To tell you the truth, I did not have a clue what he was talking about: free phytane is
0146-6380/00/$ - see front matter#2000 Elsevier Science Ltd. All rights reserved. P I I : S 0 1 4 6 - 6 3 8 0 ( 9 9 ) 0 0 1 3 9 - 4
Organic Geochemistry 31 (2000) 143±145
ÿ32 per mil...what does that mean? Now, 8 years later, I do now understand what he was talking about...but I still
do not have any idea why phytane isÿ32 per mil!
Having gotten a little ¯avor of the stable carbon isotope technique I still pushed onwards with the organic sulfur geochemistry. Jan and Jaap thought I did not do too bad a job with my undergraduate project and oered me a Ph.D. project on organic sulfur compounds. Besides developing a few chemical degradation techniques, still my most cited work, I quickly became involved in the Cooperative Monterey Organic Geochemistry project set-up by Caroline Isaacs at the USGS. In collaboration with Maria de Loureiro of the University of Rio de Janeiro we analysed a sequence in the Monterey Formation for free and sulfur-bound biomarkers. Although some nice results came out of this work we felt at that time that CSIA was needed to improve the interpretation of the biomarker data. Fortunately, help came along in the form of Martin Schoell, Chevron, and Roger Summons, Australian Geological Survey, to perform these kind of analyses. I was lucky to spend some time in Martin's lab doing CSIA and getting experience with an irm-GC± MS with the aid of Bob Dias, currently at the USGS. Every analysis of a Monterey sample turned out to be so exciting that I could hardly wait to ®nish the analyses. Compounds like dinorhopane vary by up to 8 per mil in the Monterey Formation while compounds like steranes vary only by 1 per mil. Since CSIA was usually done on limited samples at that time, it showed that wide isotopic variations can occur in stable carbon isotopic compositions of compounds in sedimentary sequences, even if they are known to be derived from one organism. We later extended these data by taking more samples from the Monterey Formation on a separate ®eld trip. Those samples turned out to be extremely worthwhile since we also discovered several OSC with carbon skeletons unknown until then. The Monterey Formation is still my favorite sample site and I think there is still a lot of organic geochemistry left in it.
When I neared the end of my Ph.D. project I carefully looked around to see what I would do next. Organic geo-chemistry had a ®rm grip on me and I was keen to go on in the ®eld, pretty much in anything: organic sulfur, bio-markers or carbon isotopes. Luckily the decision was made for me. At that time the lab moved to The Netherlands Institute for Sea Research, Jaap Sinninghe Damste was awarded a big grant by the Dutch Science Foundation and Shell donated money to buy an irm-GC±MS. Since I was one of the few persons with CSIA experience, and I did not get too much in the way of people, Jaap asked me to stay on for another 3 years as a postdoc working on the new irm-GC±MS. In those years I developed a love±hate relationship with the machine, something probably familiar to most people doing CSIA. You hate it when the chromatography goes bad and you just cannot get it right, but you love that sound of the Epson dot matrix printer when it spits out another nice set of isotope data. I became involved with a lot of projects of Ph.D. students and postdocs and I felt like a spider in a web. Some very nice work had come out of the lab at that time, for instance Heidy van Kaam-Peter's work on the Kimmeridge Clay and the Toarcian shales, Martin Koopman's work on aromatic carotenoids, and many, many more excellent studies. Exciting also was the discovery that Archaeal lipids are abundantly present in sediments, something which has become even more obvious from some of the talks presented here at this conference. However, the more we measured stable carbon isotopic compositions of sedimentary compounds, the more I felt that there was a fundamental lack of knowledge on the eects of carbon acquisition mechanisms, and biosynthesis, on the stable carbon isotopic composition of lipids. Fortunately a couple of oces away at the NIOZ Wim Klein Breteler was continuously culturing a number of algae to keep his copepods healthy and happy. Kliti Grice, now at Curtin University, took full advantage of this situation by determining the fractionation eects of compounds when they passed through the guts of copepods. Fortunately, these eects turned out to be nearly zero. However, when we examined the dierent lipids of the algae we found widespread variation in the isotopic composition of lipids, up to 8 per mil. Indeed recent research presented at this conference by John Volk-man and others, indicate even larger variations depending on growth conditions. Clearly, we need to learn a lot more about biosynthetic eects on the13C-contents of lipids, research that I hope to pursue in the future. Also very recent
ments in our lab: the construction of brand new lab facilities next year and the arrival of a new irm-GC±MS capable of compound-speci®c hydrogen measurements.
As I said, there are many people I would like to thank for all their support and help and I have mentioned a number of names during my speech. To name everyone, however, would be impossible since it would take me at least another hour and I would miss my plane and you would fall asleep. I would like to give a special mention to a few people though. I would like to thank Jan de Leeuw for having faith in my development as a scientist and his continuous supply of thought-provoking ideas. A career in organic geochemistry is made easy for you when you work with Jaap Sinninghe DamsteÂ, a former Schenck award winner himself. His continuous drive to do more, better and focused research and his brilliant interpretation of data is inspiring and awesome at the same time. His enthusiasm for the ®eld seems to have no boundaries and, together with Jan de Leeuw, he has made the group what it is today. Thanks Jaap, for helping me through my career and making me the scientist I am today (I hope you take that as a compliment). Finally, I would like to thank Ellen for all the support she has given and the enormous sacri®ce she has made. If it was not for your courage then I would not be standing here today accepting this award. I know you still think organic geochemistry is ``digging in mud'', but I consider it as my ultimate revenge that you have turned from being a food chemist into a ``mud digger''.
