Phosphorus L(2,3)-edge XANES: overview of reference compounds.

Synchrotron-based X-ray absorption near-edge structure (XANES) spectroscopy is becoming an increasingly used tool for the element speciation in complex samples. For phosphorus (P) almost all XANES measurements have been carried out at the K-edge. The small number of distinctive features at the P K-edge makes in some cases the identification of different P forms difficult or impossible. As indicated by a few previous studies, the P L(2,3)-edge spectra were richer in spectral features than those of the P K-edge. However, experimentally consistent spectra of a wide range of reference compounds have not been published so far. In this study a library of spectral features is presented for a number of mineral P, organic P and P-bearing minerals for fingerprinting identification. Furthermore, the effect of radiation damage is shown for three compounds and measures are proposed to reduce it. The spectra library provided lays a basis for the identification of individual P forms in samples of unknown composition for a variety of scientific areas.

Distribution of sulfamethazine, chlortetracycline and tylosin in manure and soil of Canadian feedlots after subtherapeutic use in cattle.

Feedlots are potential point sources for the flow of antibiotics into the environment due to common use of antibiotics such as sulfamethazine, chlortetracycline and tylosin. Hence soils and manures originating from a grassland control, an experimental and a commercial feedlot were analyzed and mass balances were calculated for these antibiotics. Up to 9990 microg kg(-1) sulfamethazine and 401microg kg(-1) chlortetracycline on a dry matter basis were determined in feedlot manure. Soil concentrations were two orders of magnitude smaller. This corresponds to 7-40% of the calculated residual amount. In the commercial feedlot chlortetracycline was found down to soil depths of -40 cm; sulfamethazine was still detectable 1 year after medication. Sulfamethazine and chlortetracycline were additionally determined in manure of a control treatment in the experimental feedlot where cattle never received antibiotics. This was attributed to runoff from upslope pens. Consequently, antibiotics partially persist within feedlots and may be dislocated into the surrounding environment by vertical transport and runoff.