Soil Trace Metals Concentrations in A Mining Impacted Agricultural Watershed: Comparison of Analytical Methods, Geospatial Distribution, and Evaluation of Risk
Abstract
This study investigated four aspects surrounding lead, zinc, and cadmium soil trace metals concentrations within a mining impacted watershed: (1) a comparison of three soil trace metal quantification methods relating measurements from field portable X-ray fluorescence spectroscopy (XRFS) in in situ and laboratory environments, and inductively coupled plasma-optical emission spectrometry (ICP-OES), (2) distribution of soil trace metals in riparian terraces of a creek, (3) distribution of soil trace metals in an upland environment, (4) analysis of trace metals uptake into white-tailed deer (Odocoileus virginianus) and the human health risk associated with consuming said deer. This study was conducted within the Elm Creek watershed, located in Ottawa County in northeastern Oklahoma, and situated to the west and south of the Tar Creek Superfund Site, part of the historic Tri-State Lead-Zinc Mining District (TSMD). Trace metals contamination has been documented in Elm Creek, however, questions remain about broader impacts in the Elm Creek watershed. Elm Creek watershed properties purchased by the Grand River Dam Authority (GRDA), a public power provider, are designated to be used as offsite mitigation for fish and wildlife impacts under the Pensacola Dam Hydropower License under the Federal Energy Regulatory Commission. This study found: (1) In situ XRFS analysis on soils with less than 10% moisture content yielded statistical similarities to laboratory XRFS concentrations for lead and zinc when the samples were homogenized, dried and sieved, while samples with moisture continents exceeding 20% showed no similarities. Organic contents greater than 10% caused underreporting of lead XRFS values when compared to ICP concentrations and ICP and laboratory XRFS concentrations were not statistically different for lead but were for zinc (p < 0.05). The XRFS overreported zinc concentrations when compared to ICP values. (2) The creek branch with headwaters originating within the Tar Creek Superfund Site had the most influence on downstream soils concentrations and concentrations of trace metals within creek terraces decreased with increasing distances from the headwaters. (3) Areas with elevated trace metals concentrations within upland environments were located closest to the stream at lower elevations suggesting that the creek is depositing contaminated material during flood events. Creek terraces and upland soils within 100 m of the creek reflected background soil concentrations 11.5 km downstream from the headwaters of the branch originating within the Tar Creek Superfund Site. (4) Uptake of trace metals into white-tailed deer tissues were accurate for lead and cadmium, and conservative estimates of risk to humans from consumption of white-tailed deer found no associated human health risk (HI < 1). This study highlights the differences in trace metals detection methods and impacts of trace metals within a mining impacted agricultural watershed. The results of this study will influence long-term land use in the watershed.
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- OU - Theses [2090]