| Title: | Seawater-induced mobilization of trace metals from mackinawite-rich estuarine sediments |
| Author(s): | Wong VN; Johnston SG; Burton ED; Bush RT; Sullivan LA; Slavich PG; |
| Address: | "School of Geography and Environmental Science, Monash University, Wellington Rd, Clayton, VIC 3800, Australia. vanessa.wong@monash.edu" |
| DOI: | 10.1016/j.watres.2012.11.009 |
| ISSN/ISBN: | 1879-2448 (Electronic) 0043-1354 (Linking) |
| Abstract: | "Benthic sediments in coastal acid sulfate soil (CASS) drains can contain high concentrations (~1-5%) of acid volatile sulfide (AVS) as nano-particulate mackinawite. These sediments can sequester substantial quantities of trace metals. Because of their low elevation and the connectivity of drains to estuarine channels, these benthic sediments are vulnerable to rapid increases in ionic strength from seawater incursion by floodgate opening, floodgate failure, storm surge and seasonal migration of the estuarine salt wedge. This study examines the effect of increasing seawater concentration on trace metal mobilization from mackinawite-rich drain sediments (210-550 mumol g(-)(1) AVS) collected along an estuarine salinity gradient. Linear combination fitting of S K-edge XANES indicated mackinawite comprised 88-96% of sediment-bound S. Anoxic sediment suspensions were conducted with seawater concentrations ranging from 0% to 100%. We found that mobilization of some metals increased markedly with increasing ionic strength (Cu, Fe, Mn, Ni) whereas Al mobilization decreased. The largest proportion of metals mobilized from the labile metal pool, operationally defined as Sigmaexchangeable + acid-extractable + organically-bound metals, occurred in sediments from relatively fresh upstream sites (up to 39% mobilized) compared to sediments sourced from brackish downstream sites (0-11% mobilized). The extent of relative trace metal desorption generally followed the sequence Mn > Ni approximately Cu > Zn > Fe > Al. Trace metal mobilization from these mackinawite-rich sediments was attributed primarily to desorption of weakly-bound metals via competitive exchange with marine-derived cations and enhanced complexation with Cl(-) and dissolved organic ligands. These results have important implications for trace metal mobilization from these sediments at near-neutral pH under current predicted sea-level rise and climate change scenarios" |
| Keywords: | "Adsorption Aluminum/analysis/chemistry Binding, Competitive Climate Change Copper/analysis/chemistry Diffusion *Estuaries Ferrous Compounds/*chemistry Geologic Sediments/*chemistry Humic Substances/analysis Hydrogen-Ion Concentration Iron/analysis/chemist;" |
| Notes: | "MedlineWong, Vanessa N L Johnston, Scott G Burton, Edward D Bush, Richard T Sullivan, Leigh A Slavich, Peter G eng Research Support, Non-U.S. Gov't England 2012/12/04 Water Res. 2013 Feb 1; 47(2):821-32. doi: 10.1016/j.watres.2012.11.009. Epub 2012 Nov 14" |
