ARS | Publication request: Bacterial populations within copper mine tailings: long-term effects of amendment with Class A biosolids

Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 5, 2012
Publication Date: September 1, 2012
Repository URL: http://handle.nal.usda.gov/10113/55665
Citation: Pepper, I.L., Zerghi, H.G., Bengson, S.A., Iker, B.C., Banerjee, M.J., Brooks, J.P. 2012. Bacterial populations within copper mine tailings: long-term effects of amendment with Class A biosolids. Journal of Applied Microbiology. 113:569-577.

Interpretive Summary: Coal mining operations can reduce soil quality when waste products, such as mine tailings, associated with the process are surface disposed. This was particularly a problem with older mining sites, in which regulations and restrictions were not in place to govern the disposal of these waste products. As such, the mine tailing sites lack the nutrient and organic matter necessary to support crop or forage growth. This study investigated the use of municipal biosolids land application on reclaiming land lost to mining operations in the desert southwestern United States. Land application occurred in 1998 with the final application in 2006. Applications occurred in a manner in which to over supplement and replace the organic content of the soil, thus supporting microbial life, followed by replacement of the natural flora of the surrounding areas. Various measurements were made over the course of the study with soils monitored for enzymatic, cultural, and microbial diversity. Sites demonstrated a time-based effect in which microbial diversity was initially high during early observations, lulled, then slowly increased to background microbial levels. Overall, microbial diversity returned to the surrounding soil quality following the 10 year period, which was indicative of returning to baseline levels. This study demonstrated the utility of using an organic-rich material to supplement and reestablish a previously inhospitable environment.

Technical Abstract: This study evaluates the effect of surface application of dried Class A biosolids on microbial populations within copper mine tailings. Methods and Results: Mine tailing sites were established at ASARCO Mission Mine close to Sahuarita, Arizona. Site 1 (Dec. 1998) was amended with 248 tons ha-1 of Class A biosolids. Sites 2 (Dec. 2000) and 3 (April 2006) were amended with 371 tons ha-1 and 270 tons ha-1, respectively. Site D, a neighboring native desert soil acted as a control for evaluation of soil microbial characteristics. Surface amendment of Class A biosolids showed a 4 log10 increase in HPCs compared to unamended tailings, with the increase being maintained for a 10 year period. Microbial activities such as nitrification, sulfur oxidation and dehydrogenase activity were also sustained throughout the study period. 16S rRNA clone libraries obtained from community DNA suggest that mine tailings amended with biosolids achieve diversity and bacterial populations similar to native soil bacterial phyla, ten years post-application. Conclusion: Addition of Class A biosolids to copper mine tailings in the desert southwest increased soil microbial numbers, activity and diversity relative to unamended mine tailings. Significance and Impact of the Study: the amended tailings resulted in a functional soil with respect to microbial characteristics which were sustainable over a ten year period.