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United States Department of Agriculture

Agricultural Research Service

Research Project: Improving Nutrient Utilization in Western Irrigated Crop Production Systems

Location: Northwest Irrigation and Soils Research

Title: Copper and zinc speciation in a biosolids-amended, semiarid grassland soil

Authors
item Ippolito, James
item Barbarick, R -
item Brobst, R -

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 23, 2014
Publication Date: September 1, 2014
Citation: Ippolito, J.A., Barbarick, R.B., Brobst, R.B. 2014. Copper and zinc speciation in a biosolids-amended, semiarid grassland soil. Journal of Environmental Quality. 43:1576-1584.

Interpretive Summary: We utilized semi-arid grassland plots that received surface applied biosolids (no incorporation; 0, 1, 2, 5, 10, and 15 tons per acre) in 1991 (single) or again in 2002 (repeated) to help understand short- and long-term changes in soil copper and zinc chemistry. Using soil pH, soluble anion and cation concentrations, and dissolved organic carbon content, copper and zinc associated with minerals or dissolved organic phases was modeled, in addition to using scanning electron microscopy-energy dispersive x-ray analysis. Greater than 89 and 96 percent of copper and zinc, and greater than 99 percent of zinc were adsorbed to oxides in all single or repeated biosolids-applied soils, respectively; however, only 59-79 percent of copper was adsorbed to hydrous ferric oxides while 21-41 percent was associated with dissolved organic carbon in the repeated biosolids plots. Results suggested some downward copper movement with dissolved organic carbon associated with repeated biosolids application, yet long-term changes in copper and zinc soil chemistry remain stable.

Technical Abstract: Predicting trace metal solid phase speciation changes associated with long-term biosolids land application is important for understanding and improving environmental quality. Biosolids were surface-applied (no incorporation; 0, 1, 2, 5, 10, and 15 tons per acre) to a semi-arid grassland in 1991 (single) or again in 2002 (repeated). In July 2003, soils were obtained from the 0-3, 3-6, and 6-12-inch depths in all plots. Using soil pH, soluble anion and cation concentrations from 0.01 moles per liter calcium chloride extractions, and dissolved organic carbon content, copper and zinc associated with minerals, hydrous ferric oxide, or dissolved organic phases was modeled using Visual Minteq. Scanning electron microscopy and energy dispersive x-ray analysis was also utilized to identify solid phase metal associations present in single and repeated biosolids-amended soils. Based on soil solution chemistry and verified using Visual Minteq, greater than 89 and 96 percent of copper and zinc, and greater than 99 percent of zinc were adsorbed to hydrous ferric oxides in all single or repeated biosolids-applied soils, respectively. However, when detected in the repeated biosolids treatments, only 59-79 percent of copper was adsorbed to hydrous ferric oxides while 21-41 percent was associated with dissolved organic carbon; downward copper movement was associated with dissolved organic carbon. The scanning electron microscopy and energy dispersive x-ray analysis of clay-sized separates from all soil depths led to direct observation of iron-zinc, aluminum-zinc, and aluminum-copper associations. Results implied that even after surface-applying biosolids either once or twice of up to 15 tons per acre, soil solution concentrations, Visual Minteq predictions, and scanning electron microscopy and energy dispersive x-ray analysis suggested minimal shifts occur in phases controlling long-term copper and zinc solubility.

Last Modified: 12/18/2014
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