The characterization and composition of bacterial communities in soils blended with spent foundry sand

Abstract

The purpose of this research was to characterize the structure and composition of bacterial communities in sandy loam and silty clay soils amended with 30% spent sand from iron, aluminum, and steel foundries. All spent foundry sand (SFS) blends were grown with or without perennial ryegrass and samples were collected at 4 weeks and 6 months. Regions of the 16S rRNA gene were amplified using PCR and subsequently analyzed by DGGE and sequenced for bacterial identification and phylogenetic classification. Cluster analyses of PCR-DGGE banding patterns revealed that SFS blends from week 4 and month 6 produced unique clusters, with most ryegrass treatments clustering away from those without ryegrass. The diversity of the bacterial community revealed that it was generally higher in the SFS blends without ryegrass. By month 6 in treatments without ryegrass, the diversity in the sandy loam blends was similar to the control, while the diversity in all silty clay blends was greater than the control. Phylogenetic analysis of bacterial isolates (total of 309) from the SFS blends showed that they were dominated by Actinobacteria (46%), Proteobacteria (29%), and Bacilli (20%), with fewer numbers belonging to Bacteroidetes (5%). While the addition of SFS to soil does bring about bacterial community level changes, these changes are similar to that of blending soil with clean silica sand.