Subsurface Liming and Metal Movement in Soils Amended with Lime-Stabilized Biosolids
- Sally Brown *,
- Rufus Chaney and
- J. S. Angle
Samples to a depth of 1 m were taken from two long-term biosolids field studies, to examine metal and alkalinity movement. The studies, located at the University of Maryland research facility in Beltsville, MD, had received biosolids in 1976 to 1978. One study, on a Christiana fine sandy loam (clayey, kaolinitic, mesic Typic Paleuduit) had used a variety of biosolids incuding Nu-Earth (a high-metals biosolids) applied at 50 and 100 Mg ha−1 and limed-undigested, limed-digested, and limed-compost applied at 224 Mg ha−1. The digested biosolids were also applied at 336 and 448 Mg ha−1. The other study, on a Galestown sand (sandy, siliceous, mesic Psammentic Hapleudult), used limed-digested biosolids from the same treatment plant applied at 224 and 448 Mg ha−1. For both rates of biosolid application, soil pH was raised to >7.0 throughout the examined depth for the Galestown plots, pH increases were most pronounced for the limed-Sundigested biosolids (224 Mg ha−1) on the Christiana plots, with soil pH significantly higher than for the calcareous control to 80 to 90 cm. Soil pH for this biosolids treatment remained >5 to the 80 to 90 cm depth, while soil pH fell below 5 at the 40 to 50 cm depth for the calcareous control treatment. Movement of Pb, Zn, and Cu was detected in the high pH Nu-Earth treatments, with a distinct increase being observed for all three metals below 80 cm. Copper movement from the lime-undigested biosolids was detected below 80 cm, and Zn movement also occurred for soils amended with the lime-undigested and lime-compost biosolids. For the Galestown plots, distinct movement of Zn, Pb, and Mn was detected to below 60 cm for the 448 Mg ha−1 biosolids treatment. The observed movement of metal(s) and alkalinity may be linked to the formation of fulvic acid-metal complexes that become increasingly more soluble at elevated pH. Although statistically significant, movement of metals was limited and occurred only after high rates of biosolids had been applied. There is no indication that metal movement would occur in fields receiving agronomic rates of biosolids.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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