Table 2.

Chemical extraction results, calculated contributions of uraninite and monomeric U(IV) and linear combination fitting (LCF) results. All results are presented as % uraninite / % monomeric U(IV). Calculated ratios for Bio2 – Bio4 assume a linear relationship between the end-members. Uncertainty ranges for bicarbonate extraction data result from combined instrumental and replicate errors. Uncertainty for EXAFS LCF data are from scan-by-scan error analysis of XAS data, however the LCF technique is only semi-quantitative and is generally assumed to be accurate to within 10% (33). Calculated values (last column) are obtained from extraction resutls. For example, Bio2 consists of 75% Bio1 and 25% Bio5, hence it is expected to include a contribution of 34 % monomeric U(IV) from Bio1 and 23% monomeric U(IV) from Bio5, for a total of 57%.

Category	System	Bicarbonate Extraction Result	EXAFS LCF Result	Calculated from Bio1/Bio5 extractions
Biologically reduced systems	Bio1	54±3 / 46±3	55±2 / 45±2	N/A
	Bio2	46±3 / 54±3	-	43 / 57
	Bio3	35±3 / 65±3	36±4 / 69±4	31 / 69
	Bio4	23±3 / 77±3	-	20 / 80
	Bio5	8±5 / 92±5	N/A	N/A
Biogenic Fe minerals	Vivianite	1±3 / 99±3	N/A	N/A
	Magnetite	93±3 / 7±3	96±2 / 4±2	N/A
Sediment	RABS	2±3 / 98±3	N/A	N/A