Self cleansing
Scientists have discovered that nature may be slowly scrubbing the lower portion of the river Hudson of its pollution. During a year long study of the river's lower estuary, scientists from the Institute of Marine and Coastal Sciences at Rutgers and the State University of New Jersey, USA, found that contaminants do not lie immobile on the river bottom. Instead, tidal forces, storms, rain and spring runoff power a cycle in which polluted sediment is stirred up and suspended in the water column, then re-deposited on the river floor. Repeated over and over again, the process ultimately washes away many contaminants, thereby, cleaning the river (www. edie.net , November 9, 2001).