TREE-RING RECORD OF SMELTER OPERATIONS AT PALMERTON, PA

In 1898 New Jersey Zinc began smelting (West Plant) ores, at Palmerton, PA, from the Franklin Furnace and Sterling Hill zinc mines. A second smelter (East plant) began operation in 1915. Smelting operations continued at these two plants until 1980. Electrostatic precipitators were installed in 1953. In 1954 the Franklin Furnace mine was closed and subsequent smelter operations only used ores from Sterling Hill. When operating, it was estimated that the smelters emitted 47 tons/yr of Cd, 95 tons/yr Pb, and 3,575 tons/yr Zn plus significant amounts of sulfur dioxide. The site of the abandoned smelters is now an EPA (Environmental Protection Agency) superfund site.

A tree ring core was extracted from an oak tree approximately 2 km downwind from the zinc smelters. The core encompasses approximately 150 years of history starting in 1860. Ten segments of this core (ranging in mass from 167 to 351 mg) were analyzed for 25 elements using Instrumental Neutron Activation Analysis (INAA).

Metals can be delivered to the tree either by deposition on the leaves or by cycling of the metals through the soil-root system. The metals are subsequently incorporated into the tree and are lodged in the ring wood. In principle a tree-ring core can provide a record of environmental change. The data from the tree ring sequence reveal the following: (1) by 2005 the concentration of most metals had returned to pre-smelter values, (2) Au, Co, Sb, and Zn increased throughout the period of smelter operation which suggests these metals were accumulating in the soils, (3) Sc, Se, and U values increased from the time that smelter operations started until around 1950 when their concentrations began to decline, (4) Na and Zn concentrations remained relatively constant, (5) K concentration declined throughout the period of smelter operation and (6) after a significant increase at the start of smelter operations, Sb showed a linear decrease. One interpretation of the post-1950 decrease in Sc, Se, and U is that these metals were delivered as particulates that were removed after installation of the electrostatic precipitators. The significant decrease in K may be due to the leaching of K from the soils in response to acid deposition. Thus, the tree ring record provides a relatively detailed history of smelter operations and the variations of contaminants in the environment.