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Title: BLENDING FOUNDRY SANDS WITH SOIL: EFFECT ON DEHYDROGENASE ACTIVITY

Author
item Dungan, Robert - Rob
item Kukier, Urszula
item Lee, Brad

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2005
Publication Date: 3/15/2006
Citation: Dungan, R.S., Kukier, U., Lee, B. 2006. Blending foundry sands with soil: effect on dehydrogenase activity. Science of the Total Environment. 357(1-3):221-230.

Interpretive Summary: Each year U.S. foundries landfill several million tons of sand that can no longer be used to make metalcasting molds and cores. A possible use for these materials is as an ingredient in manufactured soils; however, potentially harmful metals and resin binders (used to make cores) may adversely impact the soil microbial community. Stress on the microbial community can indicate a potential threat to plant, animal and human health. In this study, the microbial activity of soil amended various amounts of molding sand (clay-coated sand known as 'green sand') or core sands was determined. The green sands were obtained from iron, aluminum and brass foundries; the core sands were made with various organic polymers typically used by the foundry industry. Overall, incremental additions of these sands resulted in a decrease in the microbial activity. A brass green sand, which contained high concentrations of the heavy metals Cu, Pb and Zn, severely impacted the microbial activity. In contrast, the microbial activity in soil amended with an aluminum green sand was much higher than soil alone. In core sand-amended soil, the microbial activity generally decreased as the blending ratio was increased; however, by the end of the experiment the microbial activities were generally found to be higher than in green sand-amended soil. The microbial activity is a sensitive indicator of environmental stress caused foundry sand constituents and may be useful to assess which foundry sands are suitable for beneficial use in the environment.

Technical Abstract: Each year U.S. foundries landfill several million tons of sand that can no longer be used to make metalcasting molds and cores. A possible use for these materials is as an ingredient in manufactured soils; however, potentially harmful metals and resin binders (used to make cores) may adversely impact the soil microbial community. In this study, the dehydrogenase activity (DHA) of soil amended with molding sand (clay-coated sand known as 'green sand') or core sands at 10, 30, and 50% (dry wt.) was determined. The green sands were obtained from iron, aluminum and brass foundries; the core sands were made with phenol-formaldehyde or furfuryl alcohol based resins. Overall, incremental additions of these sands resulted in a decrease in the DHA which lasted throughout the 12 week experimental period. A brass green sand, which contained high concentrations of Cu, Pb and Zn, severely impacted the DHA. By week 12 no DHA was detected in the 30 and 50% treatments. In contrast, the DHA in soil amended with an aluminum green sand was 1.8 times higher, on average, at week 4 and similar to the control by week 12. In core sand-amended soil, the DHA generally decreased as the blending ratio was increased; however, by week 12 the DHAs were found to be higher than in green sand-amended soil. The DHA assay is a sensitive indicator of environmental stress caused foundry sand constituents and may be useful to assess which foundry sands are suitable for beneficial use in the environment.