ELECTRONIC SUPPLEMENTARY MATERIAL
SEDIMENTS, SEC 1 • SEDIMENT QUALITY AND IMPACT ASSESSMENT •
RESEARCH ARTICLE
Investigating speciation and toxicity of heavy metals in anoxic marine sediments – a case
study from a mariculture bay in Southern China
Bing Xia 1, 3 • Pengran Guo 2 • Yongqian Lei 2 • Tao Zhang 1 • Rongliang Qiu 1 •
Klaus-Holger Knorr 3, 4
Received: 30 January 2015 / Accepted: 9 September 2015
© Springer-Verlag Berlin Heidelberg 2015
Responsible editor: Marc Babut
1
School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou
510275, China
2
Guangdong Provincial Public Lab of Analysis and Testing Technology, China National
Analytical Center (Guangzhou), Guangzhou 510070, China
3
Department of Hydrology, University of Bayreuth, Bayreuth, Germany
4
Present address: Institute for Landscape Ecology, Hydrology Group, University of Münster,
48149 Münster, Germany
Corresponding authors:
 Klaus-Holger Knorr
kh.knorr@uni-muenster.de
 Pengran Guo
guopengran@gmail.com
1
The purpose of XRD analysis
Sequential extraction procedures for speciation of metals, e.g. the Tessier method (Tessier
et al. 1979), the BCR method (Ure et al. 1993), and the Forstner method (Ngiam and Lim
2001), were developed for natural sediments or artificial materials (Dodd et al. 2000) to
extract defined heavy metal fractions such as acid soluble, reducible, oxidisable (including
organic bound and sulfide bound), and residual fractions. However in mariculture bays of
China, especially in mariculture bays of Guangdong province, intensive mariculture can cause
exceptionally high eutrophication, favoring reducing and anoxic conditions, thereby also
increasing sulfide contents in surface sediments (Cao et al. 2007; Wu et al. 1994). Sequential
extraction procedures for natural sediment are not fully suitable for mariculture area
sediments because the procedure of these methods (such as the extraction of organic matter
bound fraction) uses oxidizing extractants which have a strong impact on sedimentary sulfides;
therefore these methods cannot be used to evaluate the sulfidic fraction separately. On the
other hand, low contents of sulfides in other sediment samples less affected by mariculture
also limit the applicability of the AVS-SEM approach (Chapman et al. 1998; Fang et al. 2005).
Thus, we propose to use a revised protocol to assess the heavy metals speciation in
mariculture area sediments with a broad range of geochemical conditions (Guo et al. 2009;
Wang et al. 2011).
The results of sequential extraction procedures are subject to uncertainties for many
reasons, such as dissolution of nontarget mineral phases and concurrent release of metals of
interest, or redistribution between species during the extraction procedure. This remains a
common limitation in sequential extraction procedures, nevertheless they are still widely
employed due to their simplicity and the possibility to perform such investigation in less
equipped laboratories (Dodd et al. 2000). To provide support for the selectivity of our
proposed approach, X-ray diffraction analysis (XRD) was used to investigate the efficiency
and selectivity of the extraction steps on sediment minerals. More details on the method
development have been published elsewhere (Wang et al. 2011).
Materials and Methods
After freeze-drying of bulk sediments and the extracted residuals, sample powders were
2
X-rayed as thin films. The range of the diffraction angle was 5°～90°, at a scanning rate of
0.048°/step and a step time of 576 s. Diffraction data were analyzed by Jade 5.0 software
(PDF 2004 cards).
Results from XRD analysis
As depicted in the figures below, the mineralogy of the investigated sediments is diverse
and comprises several phases that should be adequately reflected in the different fractions of
our sequential extraction: calcite (d=4.70658、2.98539Å), kaolinite (d=7.10972、3.55149、3.23309、
1.53905 Å), montmorillonite (d=9.99548、4.45181 Å), iron oxide minerals (d=2.81105、2.59912、
1.94572 Å), illite (d=9.99548、4.9722、4.45181、3.33670、3.23309、1.99102 Å), chlorite (d=7.10872、
4.97722、3.55149 Å), quartz (d=3.33670、4.23980、2.45048、2.27895、2.12309、1.81561 Å), etc.
After extraction by step1-step4, reflecting the non-residual fractions, the diffraction peak
intensities of minerals such as calcite, montmorillonite, iron oxide minerals disappeared or
were reduced significantly. This indicated that the extraction of non-residual metals could
effectively dissolve these minerals. After a single extraction representing the AVS-SEM
extraction (equivalent to the single step4 of the sequential extraction) the changes of the
diffraction peaks were quite similar to changes observed after extracting the non-residual
fraction. This indicates, not surprisingly, that the AVS extraction provides a bulk extract of the
non-residual fractions, but does not provide information about the lability of the predominant
fraction. However, XRD is not suitable to directly support our statement that the residual
fraction was attacked by the AVS-SEM, due to the high contents of Si and Al (indicator
elements of this fraction). Therefore, changes in Si or Al are obscured by too high background.
We only can use XRD as an indirect support, stating that although we extracted e.g. less Ni,
similar non-residual phases were extracted. Therefore we attribute the excess Ni from
AVS-SEM to the residual fraction.
3
Fig. S1
X-ray diffraction patterns and predominant mineral phases for a sediment sample
prior to extraction
4
Fig. S2
Changes in mineralogy of the sediment sample after extraction of non-residual
fractions (step 1 ～ step 4) by the proposed sequential extraction scheme
5
Fig. S3
Changes in mineralogy after extraction of AVS from sediment samples, equivalent
to step 4 in the proposed sequential extraction scheme
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