The ability of the earth to heal itself of damage caused by our 20th-century industrial society is the topic of a special session at the spring meeting of the American Geophysical Union, May 26-29, in Boston, Mass. Papers presented at the session on the "Natural Restoration of Contaminated Aquifers" will describe natural processes that reduce the concentration of ground-water contaminants, such as sewage, hydrocarbons, metals, agricultural chemicals, and chlorinated compounds. Scientists from the U.S. Geological Survey (USGS) and others will discuss whether these naturally occurring processes can be relied on, by themselves or in conjunction with engineered systems, to restore contaminated aquifers for future use.
Several presentations by USGS scientists will focus on natural restoration of a Cape Cod aquifer. Treated sewage was discharged into the aquifer for 60 years at the Massachusetts Military Reservation. The USGS has been monitoring the natural changes in hydrology and ground-water quality that have taken place since the discharges were discontinued in 1995.
USGS hydrologist Denis LeBlanc will describe how the ground-water system responded immediately after the cessation of the sewage discharges. Within one week, the 4-centimeter-high mound in the water table caused by infiltration of the sewage disappeared and the direction of ground-water flow changed. Clean ground water is now flowing through the area previously contaminated by sewage, flushing away contaminants such as boron and dissolved organic carbon from beneath the old infiltration beds.
Not all the effects of natural restoration are beneficial. Other USGS
scientists will describe how natural biological and chemical processes can
cause the concentration of some contaminants to increase at first along the
propagating cleanup front. Natural changes in the acidity of the ground
water, for example, might cause metals on the Cape Cod sediments to be
released and, thus, increase the di
Contact: Kathryn Hess
United States Geological Survey