Gordon Brown of Standford University will present two talks during the 7th annual Environmental Chemistry Student Symposium:

Friday's talk will be addressed to a general audience. We invite all disciplines to attend! The talk is entitled: "From Subduction to Mercury in Tuna: Mercury Mining and Contamination in the California Coast Range, USA"

Description: This first talk will explore mercury as a significant environmental contaminant, particularly in the San Francisco Bay area and California Coast Range, as a result of mercury mining in the Coast Range and placer gold mining activities in the Sierra Nevada foothills, where elemental mercury was used to amalgamate gold. Following a review of the magnitude of the problem and the associated health effects, the geology of the two major mercury deposits in North America (New Almaden, CA and New Idria, CA) will be reviewed via an "armchair" field trip to these deposits, including a discussion of acid mine drainage at the New Idria Mine and a sidebar on microbial oxidation of pyrite, which is one of the main processes producing acidic mine waters. We will then examine the various pathways that mercury takes in its journey from these deposits to surface waters such as drinking water reservoirs and San Francisco Bay. Details of the mineralogy and geochemistry of mercury will be highlighted as will the transport mechanisms of mercury, its molecular level speciation, sorption processes, and transformations into potentially bioavailable forms. The talk will conclude with a study of atmospheric emissions of mercury, which is based on measurements made at various mining sites in the western U.S. and correlated with mercury mineralogy at these sites.

Saturday's talk concerns a more specialized research subject. All are invited to attend. The talk is entitled: "Environmental Interfaces, Heavy Metals, Microbes, and Plants: Applications of Synchrotron Radiation Methods to Environmental Science at the Molecular Level"

Description: This second talk will focus on recent applications by my group and others of synchrotron radiation-based methods to environmental processes and problems. Following a brief introduction to synchrotron radiation (SR) and some of the SR methods now being used to examine complex environmental samples, we will examine a number of case studies aimed at addressing specific environmental processes and problems, including heavy metal sorption processes at mineral/aqueous solution interfaces, factors controlling the reactivity of mineral surfaces in contact with water, the role of microbial biofilm and natural organic matter coatings on mineral surfaces in heavy metal sequestration, Pb contamination at Leadville, CO, Zn contamination in soils in northern France, Cr and U contamination problems in the vadose zone at Hanford, Washington, and As contamination problems in Bangladesh.