A 4-year study of mercury in crude oil refined in the United States has found that, of the two major sources of U.S. fossil energy mined coal and crude oil crude oil contains much less toxic mercury, on average, than coal.
S. Mark Wilhelm and colleagues point out that extensive studies had been done on mercury in coal, the nation's other major fuel. Coal is the largest source of human-generated mercury emissions in the United States. Coal-fired power plants released about 48 tons of mercury annually, according to U. S. Environmental Protection Agency (EPA) data, a figure that would drop to 15 tons annually with implementation of new clean air regulations.
However, the amount of mercury present in crude oil, and thus potentially released into the air in automobile exhaust and other sources, remained uncertain due to a lack of accurate mercury concentration data for the wide range of crude oils produced domestically and imported into the U. S., the study noted.
To understand the mean concentration of mercury in oil processed by U.S. refineries, EPA employed two independent laboratories, each using different pre-qualified methods, to analyze oil streams arriving at U.S. refineries by tanker or pipeline. The samples included oil from the U. S. and 20 foreign countries. The total amount of mercury in crude oil processed in the U. S. annually is less than five percent of the amount contained in U. S. coal produced annually, the study concluded.
The article, "Mercury in Crude Oil Processed in the United States," is scheduled for publication in the July 1 issue of ACS Environmental Science & Technology.
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