GEOCHEMICAL CHARACTERIZATION OF STEEL PLANT EMISSIONS BY LICHEN BIOMONITORING

Steel production is one of the most energy and material intensive industries, which results in the formation of large quantities of pollutant such as SO₂, NO_x, and dust. Dust is released during various steel production steps and contributes to the particulate matter (PM) pollution in surrounding residential areas. Based on numerous epidemiological studies, exposure to PM is associated with several adverse health effects ranging from cardiovascular diseases to respiratory problems and neurological disorders [1; 2; 3]. Middletown works, a leading steel plant in the US, is located in Middletown, Ohio. According to EPA’s toxic release inventory, this steel plant releases 48,865 pounds of nitrate, Mn, Ba, Cu, and Ni compounds into the atmosphere annually [4]. However, no study to date has evaluated the impact of steel production on air quality in Middletown.

To assess the degree and nature of air pollution and relative contributions of the steel plant and other potential sources (i.e., traffic and coke plant) to the atmospheric toxic metal load in Middletown, we collected lichen and atmospheric particulate matter (PM). We analyzed these samples for their elemental and Pb isotopic compositions by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and Thermal Ionization Mass Spectrometry (TIMS), respectively.

Lichen samples have elevated metal concentrations relative to the background. The highest and the lowest Pb concentrations are observed in samples collected within 2 Km North of the steel plant and in samples collected from green areas and parks located 0.1 Km East and 4 km Northeast of the steel plant, respectively. Cr, Ni, Pb, Mn, and REE concentrations decrease with increasing distance from the steel plant. An atmospheric PM sample collected adjacent to the steel plant exhibits the highest Fe, Pb, Co, and As concentrations. The coke plant PM contains the highest V, Cr, and Mn; and the highest Cu, Mo, Cd, and Zn concentrations are measured in traffic PM. ²⁰⁶Pb/²⁰⁴ Pb values in lichen samples range from 18.59 to 19.08 and ²⁰⁸Pb/²⁰⁴ Pb values range from 38.24 to 38.70. Three endmember mixing between the steel plant, background, and less radiogenic traffic related emissions explains the compositional variations in lichen samples.