College of Fellows Distinguished Lecture Series Speaker

Barbara Bekins headshot

Barbara Bekins
US Geological Survey
United States of America
Primary Affiliation: Hydrology

Overview

Groundwater provides drinking water for 38% of the US population – more than 130 million people. The quality of groundwater is affected by both human activities and by geochemical reactions between water and geologic materials. Human-source contaminants come from chemical spills, agriculture, pipeline and underground storage tank leaks, road salt, unlined landfills, and other inadequate disposal practices. Geologic-source contaminants that impair groundwater quality are called geogenic contaminants, and they can be mobilized into water through natural processes or through processes caused by human activities.


Biography

Bekins studied geology and mathematics at the University of California, Los Angeles, and graduated summa cum laude in 1975. While working in computer support at the U.S. Geological Survey’s Seismology Branch, she studied applied mathematics part time at San Jose State University. She completed her master’s degree in 1988 and moved to the University of California, Santa Cruz,  where she performed doctoral research under the supervision of Shirley J. Dreiss. The research used numerical modelling to understand pore fluid pressures in subduction zones and the biodegradation of creosote contaminants in groundwater. In 1993 she was appointed as a United States Environmental Protection Agency (US EPA) postdoctoral research associate to model the biodegradation of groundwater contaminants in collaboration with the United States Geological Survey (USGS). 

In 1997 Bekins joined the staff at the USGS, where she combines field research with computer models to understand the biotransformation of contaminants in groundwater. In 1998 she was appointed to the National Research Council Intrinsic Remediation committee, with whom she co-wrote the book Natural Attenuation for Groundwater Remediation. 

In 1983, the USGS established a project to understand the natural attenuation of petroleum hydrocarbons at a research site where a high-pressure crude-oil pipeline ruptured near Bemidji, Minnesota, in 1979. Bekins research has evaluated the attenuation of the contaminants in both the crude-oil source zone and the groundwater contaminant plume. Natural Source Zone Depletion (NSZD) describes the change in composition of oil or fuel that occurs naturally due to volatilization, biodegradation, or dissolution. Biodegradation by a combination of fermentation and methanogenesis is the main NSZD process at the Bemidji site. Biodegradation is faster in areas where groundwater recharge is focused by surface runoff into topographic depressions. The biodegradation produces carbon dioxide, primarily by the oxidation of the biogenic methane, that can be measured at the surface as CO2 efflux. By monitoring and modelling, Bekins has shown that the main organic carbon in the groundwater contaminant plume is comprised of partial transformation products of the crude oil compounds. These compounds are quantified by measuring the concentrations of non-volatile dissolved organic carbon (NVDOC). Most of this NVDOC has biodegraded by around 200 m from the source, but some remains up to 300 m away. 

Bekins also has studied the effect of pore fluid pressure on the strength of faults. To investigate pore fluid pressure in subduction zones, she served as an onboard scientist for several Ocean Drilling Program expeditions to the northern Lesser Antilles, the Peru margin, and the Mariana Convergent margin. Using modelling she estimated pore pressure and fluid flow rates in subducted seafloor sediments. Her results demonstrate the importance of sediment compaction and dehydration of clay minerals in generating high pore pressures at different depths along subduction faults.   

Her awards and honors include: Fellow of the Geological Society of America (2004), Fellow of the American Geophysical Union (2019), and Member of the National Academy of Engineering (2020).