where Do is the diffusion coefficient corrected for temperature and pressure, n is the chemical species-specific constant, and φ is porosity. The value of n was set to 2.75 as this was found to be a reasonable fit for all chemical species examined [49]. The ionic states of each species at the average pH value of tubeworm-dominated sediments (7.78) were used for the determination of diffusion coefficients. Porosity was determined from the following function: