ASSESSMENT OF SEDIMENTS WITHIN THE PINE FOREST MINE ANOXIC LIMESTONE DRAIN TREATMENT SYSTEM IN ST. CLAIR (SCHYULKILL COUNTY), PA

The purpose of this study was to analyze the composition of sediments deposited within the settling ponds of the Pine Forest Anoxic Limestone Drain (ALD) Treatment System along Little Wolfe Creek in St. Clair, PA. In a concurrent study, Dalbo et al. examined the water chemistry before, after, and throughout the treatment system. The purpose of the system is to raise alkalinity and pH while removing iron, aluminum, and manganese from the mine discharge. Water exits the ALD through two grates, then enters a series of settling ponds where oxic conditions promote the precipitation of iron and settling of other heavy metals. Ferrous iron (Fe²⁺) exiting the ALD oxidizes to form ferric iron (Fe³⁺) upon interaction with oxygen. This inorganic chemical precipitation of iron is greatly aided by iron-precipitating bacteria such as Gallionella sp. and Leptothrix sp. in slightly acidic AMD such as occurs at Pine Forest Treatment System.

On November 2, 2018, we collected both water and sediment samples at Pine Forest. Several types of sediment samples were collected including a 14 cm sediment core from the ponded area above the grates exiting the ALD, rocks coated with iron precipitate at each water sampling site, and cattail roots from wetland ponds three and four as well as adjacent to where we collected the core. Cattail roots and coatings from rock surfaces were imaged on a portable scanning electron microscope with energy dispersive X-ray spectrometer. Abundant Leptothrix and Gallionella were revealed in the SEM images, especially prevalent at the top of the core. Distinct horizons of the sediment core were dried and analyzed using the Niton XL3t Goldd XRF for elemental composition. XRF results for the sediment core reveal the primary composition to be Al, Mn, Fe, Ca, S, Si, and Cl. Concentrations of all elements increase towards the top of the core with the exception of Mn. This core sample was taken down flow of a large cattail filled zone with evident upwelling water. The high concentration of Mn in the bottom of the core may indicate that Mn is being taken up by the cattail roots as water upwells and escapes the cap covering the ALD. This idea is supported by the reduced manganese concentration in water from the upwelled area as compared to water going through the ALD.