The Seasonality of Nutrient Regeneration in an Organic-Rich Coastal Sediment: Kinetic Modeling of Changing Pore-Water Nutrient and Sulfate Distributions

• Published in: Limnology and oceanography Vol. 34; no. 3; pp. 559 - 577
• Main Authors: Klump, J. Val, Martens, Christopher S.
• Format: Journal Article
• Language: English
• Published: Waco, TX American Society of Limnology and Oceanography 01-05-1989
• Subjects: Adsorption; Bays; Diffusion coefficient; Earth sciences; Earth, ocean, space; Exact sciences and technology; Geochemistry; Marine; Methane; Phosphates; Porosity; Quaternary ammonium compounds; Sediments; Soil and rock geochemistry; Sulfates; Temperature dependence; ANW, USA, North Carolina, Cape Lookout Bight; ANW, USA, North Carolina, Cape Lookout; North Carolina; Consumption; Temperature; United States; Biogenic effects; Sulfates; Sediments; North America; Seasonal variations; Reduction; America; Production; Pore water; Nutrients; Coastal environment; Kinetics; Numerical models
• ISSN: 0024-3590; 1939-5590
• DOI: 10.4319/lo.1989.34.3.0559

Measured pore-water concentration profiles for dissolved ammonium, phosphate, total inorganic carbon, and sulfate show a distinct seasonal cycle in response to the temperature dependence of rates of microbially mediated organic matter oxidation in sediments at Cape Lookout Bight, N. C. The depth and temperature dependence of measured production and consumption rates, adsorption coefficients, apparent diffusion coefficients, and sediment porosities were combined to construct a diagenetic model of ammonium production, $\sigma CO_2$ production, and sulfate reduction that was time-temperature- and depth-dependent. Numerical predictions of pore-water concentrations from a set of initial spring conditions agree well with measured pore-water profiles through summer and fall-the period of greatest change in reaction rates in response to seasonal fluctuations in temperature. Modeling also indicates that inclusion of complex, porosity-dependent terms, even in the time-and temperature-dependent case, is probably unnecessary in these sediments; simpler, constant-porosity models give results that generally deviate <4% from the predictions of complex models.