Tuesday, November 14, 2006

Assessment of Soil Microbial Communities in Surface Applied Mixtures of Illinois River Sediments and Biosolids.

John Kelly and Emmanuel Favila. 6525 N Sheridan Rd, "Loyola University Chicago, Biology", Loyola University Chicago, Biology Department, Chicago, IL 60626

Restoration of the Illinois River and its backwater lakes involves the removal of millions of cubic meters of sediment, and the relocation of this dredged sediment is a significant challenge. Beneficial use of sediment as landscaping soil on brownfields, strip mines, highway borders and other areas is a potential use for large quantities of this material, as sediments have some desirable soil characteristics, including a favorable texture for plant growth and good water holding capacity. Previous research has demonstrated that weathered Illinois River sediments readily support plant growth in greenhouse and field environments. The addition of biosolids to Illinois river sediments has the potential to increase the organic and nutrient content of the sediments and thus to make these sediments more useful for the reclamation of damaged soils. The goal of the current study was to assess the impact of biosolids addition on soil physical/ chemical characteristics and on soil microbial communities. Field plots containing various sediment/biosolids mixture were established and examined one year after application. Results indicated that biosolids addition had significant positive effects on soil organic matter, total nitrogen, and total phosphorous, as well as microbial biomass and microbial activity. However, PLFA analysis revealed that biosolids addition also resulted in shifts in microbial community composition, with relative increases in Gram negative bacteria and relative decreases in Gram positive bacteria, fungi, and actinomycetes. These data suggest that a mixture of sediment and biosolids is preferable to either sediment or biosolids alone.