- © 2000. AAPG/DEG
Dissolved manganese affects the aesthetic quality of groundwater used for domestic purposes. Reducing conditions created by natural biodegradation of petroleum hydrocarbons in contact with groundwater can cause manganese to dissolve from aquifer sediments. However, the reaction is reversible by chemical oxidation downgradient of the bioremediation shadow. Geochemical modeling (MINTEQA2) predicts the redox conditions for manganese to precipitate from groundwater back to aquifer sediments. The reaction rate for manganese precipitation is related to the advective and dispersive transport of dissolved oxygen in groundwater. At a petroleum release site in central California, the reaction rate was observed to follow first-order kinetics. By knowing the site-specific aqueous geochemistry and reaction kinetics, measures can be taken with reasonable certainty to construct water supply wells to avoid producing water containing unacceptable levels of manganese.
Leslie A. Klinchuch is an earth scientist with Chevron U.S.A. Production Company located in Bakersfield, California. She received her B.S. degree in geology from the University of California, Los Angeles in 1983 and joined Chevron in 1985 after postgraduate study at the Colorado School of Mines. Mrs. Klinchuch specializes in hydrogeology and geochemistry. She is a Certified Hydrogeologist in California and a Registered Geologist in California, Idaho, and Oregon. She is also a National Ground Water Association Certified Ground Water Professional.
Thomas A. Delfino received B.S. and M.S. degrees in chemical engineering from the University of California, Berkeley. Mr. Delfino currently is a principal of Geomatrix Consultants, Inc., an environmental and engineering consulting firm. He has more than 18 years of experience in chemical process engineering, chemistry, and statistics. Mr. Delfino leads Geomatrix Consultants’ Resource Optimization practice.