The Tri-State Mining District of Missouri, Kansas and Oklahoma was the site of large-scale mining operations for lead, zinc, and other heavy metals until the mid-1950s. Although mining across the area has ceased, high concentrations of heavy metals remain in the region’s soil and water systems. The town of Picher, OK lies within this district and was included in the Tar Creek Superfund Site by the US Environmental Protection Agency in 1980 due to extensive contamination. In order to elucidate the extent of heavy-metal contamination, a soil chemistry survey of the town of Picher in Ottawa County, Oklahoma was conducted. Samples (n=111) were collected from mine tailings, locally known as chat, in Picher and along cardinal-direction transects within an 8.05-km radius of the town in August 2015 and analyzed for soil metal content using Inductively Coupled Plasma Optical Emission Spectrometry, pH, and moisture content. Phospholipid Fatty Acid (PLFA) analyses, Next-Generation Sequencing (NGS) of prokaryotic 16S rRNA genes and qPCR calculations of total Bacteria and Archaea have been used in a systems biology approach to compare soil chemistry to microbial community structure in these contaminated soils.
Results/Conclusions
ICP-OES analyses of 20 metals showed high concentrations of lead (>1000 ppm), cadmium (>40 ppm) and zinc (>4000 ppm) throughout the sampled region. Soil moisture content ranged from 0.30-35.9%, and pH values ranged from 5.14-7.42. MANOVA analysis of metal profiles determined that soils collected from the north transect were significantly different (p=0.001) than other sampled directions. Lead, cadmium and zinc were correlated with one another, moisture content was significantly correlated with cadmium (p=0.016) and pH was significantly correlated with aluminum (p<0.001) and zinc (p=0.049). These data show an unequal distribution of contamination surrounding the Picher mining site. Analysis of total bacteria using qPCR indicated a positive and significant correlation with moisture content, but negative and significant correlations with lead, cadmium, zinc and magnesium. Total numbers of archaea did not correlate significantly with any measured variables. Illumina sequencing of 16S rRNA genes was used to elucidate changes in community structure. A significant proportion of variation in these data were explained by pH (12.5%), lead (0.07%), cadmium (0.06%) and zinc (0.08%). Mapping the distribution of heavy-metal contamination and microbial communities in these soils represents the first step in understanding the effects of heavy-metal contamination at a basic trophic level.