Sediment Flux Modeling of Nutrients and Organic Pollutants
nutrients and persistent organic pollutants (POPs) in water systems destroy ecosystem
balance and prevent the beneficial use of water bodies. One important but often
neglected and sometimes underestimated source is the internal loadings from the
sediments. As such, accurate estimation of sediment-water flux is critically important
to surface water quality modeling. In this th... read moreesis, the importance of the water side and
sediment side controlling mechanisms on sediment-water flux was evaluated using a
steady-state analytical model. It was found that diffusive boundary layer (DBL) poses
big resistance to the transport of highly adsorptive chemicals such as PCBs. In view of
the importance of DBL in controlling mass transfer, I zoomed in to study the impact of
periodic flows (i.e., seiches and tides) on DBL and proposed a method using effective
DBL thickness corresponding to the time averaged friction velocity to estimate the mean
sediment-water fluxes of both organic pollutants and nutrients. In addition, a widely
used Sediment Oxygen Demand (SOD) model was modified to incorporate the effect of DBL.
The modified SOD model was capable describing the correlation between flow velocity and
SOD seen in experimental datasets. Finally, a comprehensive diagenesis model named
Huni2K (湖泥2K) was developed to numerically simulate nutrient fluxes. The
software can produce steady-state and transient concentration profiles of 14 state
variables in the sediments, including particulate organic matters (carbon, nitrogen and
phosphorus) and dissolved constituents (oxygen, ammonium, nitrate, phosphate, and
methane). The nutrient fluxes are calculated incorporating both sediment side kinetics
and water side DBL effect. In addition, the flux of the methane gas can be obtained. The
model can accurately simulate the inhibition of methane formation by overlying water
sulfate concentration, which was a phenomenon poorly characterized in existing
Thesis (Ph.D.)--Tufts University, 2017.
Submitted to the Dept. of Civil Engineering.
Advisors: Steve Chapra, and Eric Adams.
Committee: Wayne Chudyk, and Andrew Ramsburg.
Keywords: Environmental engineering, and Water resources management.read less