Elemental maps. Elemental maps of (a) carbon and (b) calcium for RA-QD02-0120-afterTEM (RA-afterTEM) that identify calcium spot within the carbonaceous particle. (c) The coordinated carbon K edge- and calcium L2,3 edge-XANES spectra of RA-afterTEM support the presence of calcium carbonate. A peak at 290.5 eV is assigned to the 1 s-π* transition of carbonate (CO3). Two peaks around 349.2 (B) and 352.5 eV (D) are assigned to the L3 and L2 edges of Ca, respectively. Two other smaller peaks (A and C) at 347.9 and 351.2 eV are the coordination peaks of peaks A and B. (d) Comparison of nn enlarged spectrum of Ca-XANES for RA-afterTEM with those for hydroxyapatite, aragonite, vaterite, and calcite. §Ca-XANES spectra of carbonate standards (hydroxyapatite, aragonite, vaterite, and calcite) are derived from Benzerara et al. ().