A method-of-lines code for carbon and nutrient diagenesis in aquatic sediments

In a remarkable example of independent convergence of interests and perception of needs, there has been a recent flurry of new numerical models for OM-nutrient diagenesis (Dhakar and Burdige, 1996; Van Cappellen and Wang, 1995, in press; Wang and Van Capellen, in press; Soetaert, Herman and Middleburg, in press). This paper similarly presents an independently developed, public-domain, interactive, FORTRAN code for calculating transient or steady-state diagenesis of OM, nutrients (NO sub(3) super(-), capital sigma PO sub(4), capital sigma NH sub(4)), oxidants (O sub(2), NO sub(3) super(-), MnO sub(2), Fe(III)-solid, and SO sub(4) super(=)), reduced by-products (Mn super(2+), Fe super(2+), capital sigma NH sub(4), capital sigma H sub(2)S, CH sub(4), and FeS,) acid-base speciation (carbonate, ammonia, sulfide and phosphate species), and pH in aqueous sediments. It was given the acronym CANDI for carbon and nutrient diagenesis. It is a highly stable, accurate, and general code that includes all the standard reactions and transport processes thought to affect this system. It is not limited to any particular redox condition (i.e. oxic, suboxic sulfidic are all included), nor are there any particular limitations on the depth dependence of biotrubation, irrigation, or porosity, although minor modification of the code will be needed if new functional forms are desired. Nevertheless, even in its present form, it is quite flexible.