We developed a numerical simulation model of the decay and vertical transport of soil organic matter. Soil organic matter is divided into a number of compartments each with different decay rates but with similar migration parameters. Decay has been represented with first‐order processes. Two elementary forms of migration were explored: diffusive equations represent transport through soil mixing whereas translational convection simulates movement within the liquid phase. Coefficients of decay, diffusion, and convection were taken to be uniform with depth. Carbon input is both through the surface in the form of litter fall and directly underground from roots. Profiles of total C content and 14C content were measured for a temperate forest silt loam soil. Similar data for other forest soils, available in the literature, were also assembled. Statistical adjustment, through nonlinear regression, of decay, migration, compartment configuration, and plant production parameters, accurately simulated profiles of C and 14C. The rapidly decaying compartment was successfully likened to the 50‐ to 2000‐µm particle‐size fraction. Convection rates of ≈0.3 mm yr−1 and diffusion rates ranging from 1 to 15 cm2 yr−1 were obtained. Diffusive processes appear to be preponderant relative to convection. The model has proven sensitive to differences between temperate and tropical soils as well as textural variations.

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Purpose -The aim of this paper is to explore the rationale for teaching sustainability and engineering ethics within a decision-making paradigm, and critically appraise ways of achieving related learning outcomes. Design/methodology/approach -The paper presents the experience of the School of Civil Engineering at the University of Sydney in teaching environmental sustainability and engineering ethics to third-year undergraduate students. It discusses the objectives of the course and the merits and drawbacks of incorporating ethics and sustainability in the same teaching framework. In addition, it evaluates ways of incorporating theoretical and applied perspectives on sustainability. Findings -Ethics and sustainability overlap but do not coincide; incorporating them in the same engineering course can be effective, provided that points of linkage are clearly recognized in the syllabus, a suitable combination of theory and practical applications is drawn upon and adequate teaching methods, including decision-making case problems, are used. Research limitations/implications -While environmental sustainability, economic rationality and ethical reasoning can be easily fitted into the syllabus, social sustainability is more difficult to teach because it requires a significant conceptual departure from deep-seated preconceptions on the part of students and teachers, and does not lend itself easily to conventional classroom activity, such as lectures and weekly workshops. Further research on effective ways of incorporating social sustainability in engineering curricula is therefore needed. Originality/value -The paper evaluates sustainability issues within the context of civil engineering education.

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