GEOCHEMICAL SIGNATURES OF POWER PLANT EMISSIONS IN SOILS AND SEDIMENTS OF THE NORTHEAST U.S

Particulate (fly ash) emissions from coal combustion represent a potential regional pollutant. These emissions may have been a particularly important component of toxic air releases, prior to the Clean Air Act of 1970. To test this hypothesis, we took sediment cores and nearby soil samples from two reservoirs located in northern West Virginia downwind from a concentration of coal-fired power plants. Sediments were analyzed for major-minor-trace elements, lead isotopes, magnetic properties, PAH’s, and ¹³⁷Cs. The temporal distributions of sedimentary As, Pb, Zn, Hg, Ge, combustion PAH’s and magnetite show pronounced and well-correlated peaks dated about 1969. Lead isotope data on samples from the 1969 lead peak match data from Appalachian Basin coal, and are dissimilar to gasoline lead. Spherical magnetite with internal metallographic texture, indicative of combustion rather than rock-derived origin, dominates the magnetic properties of the sediment. The simultaneous decline after 1970 of the correlated trace element, PAH, and magnetite peaks in the study area suggests that the amount of power plant particulate emissions has decreased since the initial implementation of the Clean Air Act. Despite this decrease, A-horizon soil samples collected from the vicinity of the two reservoirs are strongly enriched in As, Pb, and Zn relative to local bedrocks, indicating potential accumulation of trace elements in soils over time.

Although the drainages studied are quite small, regional geochemical data suggest that the fly ash component may be identifiable in surficial materials from a significantly larger area. Much of the Ohio River valley is elevated in arsenic in both stream sediments (based on extensive USGS regional stream sediment geochemical data) and on a published USGS national soil geochemical map. The enrichment coincides with a large concentration of bituminous coal-fired power plants along the Ohio River.