Melissa, This month Chemical Geology has a Special Issue on the Global Carbon Cycle. There are several papers on 13C in rivers. There are two papers, one on the Ottawa River and the other on the St. Lawrence, published by our group. Another one on the Indus River will be published soon in a sp. issue of the same journal. In this paper we report low concentrations and close to zero or positive d13C for some headwater tributaries. Ajaz - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Ajaz Karim, Ph.D. Department of Earth Sciences University of Ottawa, Ottawa Ontario, Canada K1N 6N5 Tel: (613) 562-5800 ext 6639 Fax: (613) 562-5192 http://www.science.uottawa.ca/~users/karim/default.htm