25th International Meeting on Organic Geochemistry IMOG 2011

P-054
Hyper-accumulations of monosulfidic sediments in the Peel-
Harvey Inlet, Western Australia
Robert S Lockhart 1 , Paul Greenwood 1,2 , Richard Bush 3 , Kliti Grice 1
1 WA Organic and Isotope Geochemistry Centre, Curtin University, Bentley, WA, Australia, 2 John de Laeter
Mass Spectrometry Centre, University of Western Australia, Crawley, WA, Australia, 3 Southern Cross
GeoScience, Southern Cross University, Lismore, NSW, Australia (corresponding
author:R.Lockhart@curtin.edu.au)
Recently discovered hyper-accumulations of reactive
iron monosulfides, in association with high
concentrations of organo-sulfur compounds (OSC),
within the eutrophic environment of the Peel-Harvey
estuary in Western Australia, are the subject of
current scientific interest (Sullivan et al., 2006).
Linked to major algal bloom episodes, the deposits
manifest themselves as a viscous monosulfidic black
ooze (MBO) which, in addition to physically choking
this busy water-way, pose a series of potential
environmental hazards including rapid deoxygenation
and acidification of surface waters and release of
potentially toxic metals (Bush et al., 2004a; Ward et
al., 2010). While much published research focuses
on the role of inorganic sulfur geochemistry in such
environmental systems (Burton et al., 2006; Bush et
al., 2004b; Rickard & Luther, 2006), reactions
involving organo-sulfur compounds, which are also
likely to play a key role in biomineralisation pathways,
remain poorly understood.
In response, a range of analytical techniques were
employed to characterise the dynamic organic
geochemistry of these deposits, via detailed
examination of a series of cored sections recovered
from several key accumulations within the estuary.
Analysis of extractable lipid hydrocarbon fractions has
been complimented by chemical degradation
techniques for polar and/or refractory material which,
along with catalytic Hydropyrolysis (Hypy), allow the
selective cleavage of specific structural bonds (e.g. C-
S, S-S, C-N or C-O) within residual macromolecular
material, in order that the products are more
amenable for GC-MS and CSIA analysis. This
approach has provided the first fundamental
knowledge regarding the primary sources of
sedimentary organic carbon involved in the formation
of MBO in eutrophic estuaries. Furthermore, this
study is unique in that it examines the interaction
between organic and inorganic sulfur compounds in a
natural anoxic environment.
Investigation of extract and hydropyrolysate fractions
confirms a dominantly algal and higher plant derived
source of organic matter. Meanwhile, a range of
unique hydrocarbons have been released following
Raney nickel desulfurisation of the polar fraction,
extracted from the sediments. This indicates that
reactions between reduced sulfur-species played an
important role during the incorporation of organic
matter within the early stages of diagenesis in this
contemporary, highly sulfidic and toxic, environment.
In addition, phospholipid fatty acid analysis (PLFA)
has revealed information regarding microbial
community (aerobic and anerobic) structure within the
sediments.
References
Burton, E. D., Bush, R. T., and Sullivan, L. A., (2006)
Chemosphere, 64:1421-1428.
Bush, R. T., Fyfe, D., and Sullivan, L. A., (2004a)
Australian Journal of Soil Research, 42:609-616.
Bush, R. T., Sullivan, L. A., Fyfe, D., and Johnston,
S., (2004b) Australian Journal of Soil Research,
42:603-607.
Rickard, D. and Luther, G. W., III, (2006) Reviews in
Mineralogy and Geochemistry, 61:421-504.
Sullivan, L. A., Bush, R. T., and Burton, E. D., (2006)
Report produced for the Department of Environment,
Western Australia
Ward, N. J., Bush, R. T., Burton, E. D., Appleyard, S.,
Wong, S., Sullivan, L. A., and Cheeseman, P. J.,
(2010) Marine Pollution Bulletin, 60:2130-2136
201