Phosphorus models for eutrophic lakes

A model is developed for a highly eutrophic lake (White Lake, Michigan) which incorporates both the water and sediment systems and considers two forms of phosphorus--particulate and dissolved. Dynamic interactions of phosphorus between sediments and water are quantified by taking account particulate phosphorus sinking to the sediment-water interface and diffusion of dissolved phosphorus across the interface. Other model mechanisms include vertical eddy diffusion in the water; phosphorus transformation between the particulate form and the dissolved form in both the water and the sediment, diffusion of phosphorus in the interstitial water, and sedimentation in the sediments.Extensive field data have been used to determine the coefficients and parameters defined in the model formulations. Close agreement between the model calculations and the observed data is obtained, especially for the upper layers of the sediment. Sensitivity analysis for the model further substantiates the model calculations. It is found that two separate forms of phosphorus are necessary to gain detailed insight into the dynamics of phosphorus cycling in White Lake. The model also explains significant releases of phosphorus during anaerobic periods from the sediment to the hypolimnion of White Lake in summer. The general applicability of the model to lakes having different degrees of eutrophication must be determined by an examination and analysis of data from other systems.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/21923/1/0000330.pd

Self-catheterization of urinary bladder complicated with extraperitoneal abscess that mimics an infected bladder diverticulum

AbstractFor patients who are suffering from neurogenic lower urinary tract dysfunction, intermittent urinary catheterization is an efficient way to empty the bladder.1 However, the method may result in various complications. Herein we present a rare complication of extraperitoneal abscess owing to intermittent urinary catheterization in a 62-year-old male who had cervical spine injury and was treated with intermittent urethral catheterization for neurogenic lower urinary tract dysfunction. Treatment and a literature review are also described

Modeling Of Phosphorus Sediment - Water Interactions In White Lake, Michigan.

PhDCivil engineeringEnergyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/180565/2/7609447.pd

Pollutant Flux Estimation in an Estuary Comparison between Model and Field Measurements

This study proposes a framework for estimating pollutant flux in an estuary. An efficient method is applied to estimate the flux of pollutants in an estuary. A gauging station network in the Danshui River estuary is established to measure the data of water quality and discharge based on the efficient method. A boat mounted with an acoustic Doppler profiler (ADP) traverses the river along a preselected path that is normal to the streamflow to measure the velocities, water depths and water quality for calculating pollutant flux. To know the characteristics of the estuary and to provide the basis for the pollutant flux estimation model, data of complete tidal cycles is collected. The discharge estimation model applies the maximum velocity and water level to estimate mean velocity and cross-sectional area, respectively. Thus, the pollutant flux of the estuary can be easily computed as the product of the mean velocity, cross-sectional area and pollutant concentration. The good agreement between the observed and estimated pollutant flux of the Danshui River estuary shows that the pollutant measured by the conventional and the efficient methods are not fundamentally different. The proposed method is cost-effective and reliable. It can be used to estimate pollutant flux in an estuary accurately and efficiently