Soluble pollutants, those that are dissolved in water, are carried within the runoff water by a weak attraction to water molecules. These pollutants are the most mobile because they essentially become part of the runoff water and flow where the water flows. Biological uptake will occur in ponds with extended holding times or permanent pools of water, and in soil when stormwater infiltrates into the soil. Pollutants transported in the sediment-bound or solid phase are either attached to or are part of soil or dust particles, organic matter, or are solids themselves. The mobility of sediment-bound pollutants depends on the transport of the sediment particles.
Sediment particles themselves have two methods of transport.
Larger sediment particles roll or hop along the land surfaces or stream bottoms from the force of the moving water. Thus, sediment-bound pollutants may be either up in the water with the small suspended particles or in the bottom sediment with the larger particles. Modes of Transport of Common Pollutants Pollutant Transport Mode Sediment Occurs as suspended particles or larger particles on the stream bottom Organic Matter Occurs as large particles and in soluble phase. Pollutants that are dissolved or are associated with suspended particles will be transported much farther than those associated with larger particles. These programs cover different areas of activity and set up different alternatives for stormwater pollution control.