Seawater-induced mobilization of trace metals from mackinawite-rich estuarine sediments

Vanessa N L Wong, Scott G. Johnston, Edward D. Burton, Richard T. Bush, Leigh A. Sullivan, Peter G. Slavich

Research output: Contribution to journalArticle

12 Citations (Scopus)

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 μmol 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 ∑exchangeable + 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 ≈ 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.

Original languageEnglish
Pages (from-to)821-832
Number of pages12
JournalWater Research
Volume47
Issue number2
DOIs
Publication statusPublished - 2013
Externally publishedYes

Fingerprint

mackinawite
estuarine sediment
Seawater
trace metal
mobilization
Sediments
seawater
sediment
metal
drain
Metals
Acids
Ionic strength
acid
Desorption
desorption
Anoxic sediments
sulfide
Trace metals
acid sulfate soil

Cite this

Wong, Vanessa N L ; Johnston, Scott G. ; Burton, Edward D. ; Bush, Richard T. ; Sullivan, Leigh A. ; Slavich, Peter G. / Seawater-induced mobilization of trace metals from mackinawite-rich estuarine sediments. In: Water Research. 2013 ; Vol. 47, No. 2. pp. 821-832.
@article{9dddedb3a00d45b085baaa962d10a73b,
title = "Seawater-induced mobilization of trace metals from mackinawite-rich estuarine sediments",
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 μmol 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 ∑exchangeable + 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 ≈ 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 = "Anoxic sediments, AVS, Mobilization, Sea-level rise, Trace metals",
author = "Wong, {Vanessa N L} and Johnston, {Scott G.} and Burton, {Edward D.} and Bush, {Richard T.} and Sullivan, {Leigh A.} and Slavich, {Peter G.}",
year = "2013",
doi = "10.1016/j.watres.2012.11.009",
language = "English",
volume = "47",
pages = "821--832",
journal = "Water Research",
issn = "0043-1354",
publisher = "Elsevier Limited",
number = "2",

}

Seawater-induced mobilization of trace metals from mackinawite-rich estuarine sediments. / Wong, Vanessa N L; Johnston, Scott G.; Burton, Edward D.; Bush, Richard T.; Sullivan, Leigh A.; Slavich, Peter G.

In: Water Research, Vol. 47, No. 2, 2013, p. 821-832.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Seawater-induced mobilization of trace metals from mackinawite-rich estuarine sediments

AU - Wong, Vanessa N L

AU - Johnston, Scott G.

AU - Burton, Edward D.

AU - Bush, Richard T.

AU - Sullivan, Leigh A.

AU - Slavich, Peter G.

PY - 2013

Y1 - 2013

N2 - 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 μmol 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 ∑exchangeable + 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 ≈ 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.

AB - 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 μmol 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 ∑exchangeable + 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 ≈ 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.

KW - Anoxic sediments

KW - AVS

KW - Mobilization

KW - Sea-level rise

KW - Trace metals

UR - http://www.scopus.com/inward/record.url?scp=84871520939&partnerID=8YFLogxK

U2 - 10.1016/j.watres.2012.11.009

DO - 10.1016/j.watres.2012.11.009

M3 - Article

VL - 47

SP - 821

EP - 832

JO - Water Research

JF - Water Research

SN - 0043-1354

IS - 2

ER -