NITROGEN CHANGES AND DOMAIN BACTERIA RIBOTYPE DIVERSITY IN SOILS OVERLYING THE CENTRALIA, PENNSYLVANIA UNDERGROUND COAL MINE FIRE

Abstract

In this study, changes to soil chemistry and domain bacteria diversity were analyzed in a near-surface environment recently impacted by the Centralia, Pennsylvania anthracite coal mine fire. As this underground fire expands into new areas, land collapses are common as hot gases vent to the surface, causing rapid changes in surface soil temperatures and chemistry. To determine how these environmental changes are affecting the resident microbial populations, surface soil samples (at a depth of 0-20 cm) were taken from boreholes at eight locations that spanned both newly affected and unaffected areas. Soil temperature, pH, and chemical composition were analyzed at each borehole. Terminal restriction fragment length polymorphism analysis of domain bacteria 16S rRNA genes was utilized to monitor the associated changes in soil microbial diversity. Over a 1-year period, the maximum surface soil temperatures in this site increased from 47.0 °C to 75.7 °C. Whereas ribotype diversity did decrease significantly within individual boreholes as temperatures increased, no significant correlation was observed between overall temperature increases and either soil chemistry or domain bacteria ribotype diversity. Unweighted pair group means analysis of Jaccard ribotype similarity coefficients indicated that soil bacterial community diversity clustered well with trends in temperature, ammonium, and nitrate levels. Since significantly elevated ammonium and nitrate levels were seen in several of the affected boreholes, polymerase chain reaction with primers specific for ammonia-oxidizing bacteria and Tap-terminal restriction fragment length polymorphism analysis of the ribotype profiles were performed. These analyses provided evidence that nitrifying bacteria were present throughout the site.