XANES Determination of the Fate of Biosolids Phosphorus in Soil.

XANES Determination of the fate of Biosolids Phosphorus in Soil

Shahida Quazi, PAUL R. BLOOM, BRANDY M. TONER AND MOSHE SHENKER

 quazi001@umn.edu, prb@umn.edu, toner@umn.edu, shenker@agri.huji.ac.il

Department of Soil, Water and Climate, 1991 Upper Buford Circle, Rm 439, University of Minnesota, St Paul MN 55108, USA and Food and Environmental Quality Sciences, Hebrew University of Jerusalem, Rehovot, 76-100, Israel.

The fate of added phosphorus (P) was studied in soils with a heavy application of biosolids  using bulk and nanometer-focused P-X-ray absorption near edge structure (XANES) and x-ray florescence (XRF). Samples were obtained from the top 15 cm depth from a Typic Hapludoll with a 20-year history of biosolid amendments followed by 25 years in a corn-soybean rotation without biosolids. The treated soil had total P as high as 2400 mg kg^-1 and Bray P as high as 500 mg kg^-1. Fractionation by sequential extractions showed that most of the P added as biosolids ended up in the inorganic fractions extracted by NaOH and HCl. There was no increase in the organic P extracted with NaOH that is due to biosolids.  Scanning microprobe XRF maps showed co-location of P with Si, Al and Ca in the  <3 µm particles. Principal component analysis of XANES and linear least square fitting for both the microprobe and bulk spectra indicate that a large fraction of the P is as organic P in both the treated and control soils. The XANES results indicate the inorganic fraction was dominated by Al-P and Fe-P in the biosolids amended soils and Ca-P was only indentified in the control soils.