Answer. Colloids are microscopic particles ranging in size from 1 to 0.01 m. Because of their small size, they are influenced by Brownian motion and minor currents in the bulk of the solution and do not settle out of suspensions. Colloids are important in the transfer of nutrients and pollutants in the environment over both short and long distances. Colloids, for example, can transport nutrients such as phosphate through soil channels to deeper horizons as well as much longer distances in surface waters. Colloids can be known as the primary vehicle for the transport of chemical species that are strongly bound to soil. Understanding and accurately modelling the relevant processes requires knowledge of both the physical and chemical composition of environmental colloids involved in nutrient and pollutant transport.