Effect of diffusion and resuspension on nutrient release from submerged sediments

Abstract

Nutrient release from a coarse-sand (CS) and a fine-sand (FS) estuarine sediment into the overlying water column was studied under static (diffusion-controlled) and dynamic (resuspension) conditions. Resuspension increased the amounts of

and P released from the sediment cores compared to those released by diffusion alone due to direct release of these nutrients from the readily available pore-water and ion exchange fractions. The average effective

and P diffusion coefficients (D _e) were found to be similar for both sediments, and did not vary significantly between static and dynamic conditions. Values of D _e were typically of the order of 10⁻⁵ to 10⁻⁶ cm² s⁻¹. The average daily

and P diffusive flux density from CS and FS into the overlying water column of the study area was estimated to be 24.6, 0.02 and 0.39 mg m⁻² d⁻¹, and 66.9, 0.017 and 0.002 mg m⁻² d⁻¹, respectively. These fluxes suggest that nutrient release from the sediments via diffusion and small-scale resuspension events may represent only a minor source of

and P to the water column of the study area.

Keywords:

• Nitrogen
• phosphorus
• effective diffusion coefficient
• resuspension
• nutrient release

Acknowledgement

The authors wish to thank the Co-operative Research Centre for Sustainable Tourism for funding this project (Project No. 22004).