Pollution and toxicity of bauxite residues to sea urchins
Environ. Toxicol. Chem. 21, 2002
1277
ogy allowing for the assessment of a multiple set of endpoints
independently of the source of test materials, such as drugs,
or industrial pollutants or complex mixtures [14–19].
on their inorganics concentrations, and samples 5 and 150PP
had the same black color (unlike the others, which were red-
dish). It is suggested that, depending on the emission from the
factory and wind direction, the 5 and 150PP samples shared
a similar contamination, possibly including ashes and pyrolysis
products from the power plant. This hypothesis should be ver-
ified in further studies. The possible role for other neighboring
plants in causing the observed composition and toxicity of
solid waste should also be investigated (G. Oggiano, personal
communication).
Cytogenetic analysis failed to provide evidence for mor-
phologic aberrations, yet it showed a significant decrease in
metaphase:anaphase ratio, suggesting an alteration of the cy-
toskeleton. These data were in partial agreement with the cy-
togenetic effects of aluminum salts reported previously [15].
However, it should be noted that the effects of these complex
mixtures may not reflect the effects of individual components.
The observed differences between seawater release of met-
als from G20 compared to Portovesme samples are not sur-
prising in view of the established differences in the physico-
chemical properties of bauxite ores [1] that comprise a mul-
titude of mineralogic forms and are characterized by different
structures and chemical composition. As additional source of
variability, differences in ore processing and waste handling
might result in different composition and toxicity of solid res-
idues [19]. Hence, the present information on the different
behaviors of Gardanne versus Portovesme samples might rep-
resent only a first step of more complete information when
data from other bauxite manufacturing plants becomes avail-
able.
The results of the present study provided support for the
working hypothesis that bauxite solid residues, collected in
the vicinity of bauxite manufacturing plants, might exert de-
velopmental and reproductive toxicity [19], consistent with our
previous reports showing toxic effects of bauxite sludge to sea
urchin and mussel sperm and embryos [2,3]. Those data were
interpreted as due predominantly to aluminum and iron toxicity
based on the analytical approach (strong-acid extraction) uti-
lized at that time and on the massive Al and Fe levels in sludge
compared to very low levels of the other elements analyzed
for. Those previous analytical data are confirmed in the present
report by comparing the sparing concentrations of minor metal
contaminants in the Gardanne G20 dust sample collected at
the factory fence (Table 4) as compared to the substantially
different composition of Portovesme samples (Tables 6 and
7
). The present study has provided evidence that the toxic
effects from soil and dust samples from bauxite manufacturing
plants may or may not be related to Al/Fe toxicity according
to their environmental availability. In the case of Portovesme
samples, the observed effects are derived mainly from the
minor metal contaminants, especially Zn, Pb, and Mn, with a
tight correlation between their levels and sample toxicity. By
relating metal analysis to toxicity for soil and dust samples
from two bauxite manufacturing plants, we have been able to
elucidate more clearly the source(s) of toxicity in the bauxite
residues.
In the case of Gardanne, most toxic samples were found
in a sector of 120Њ east of the bauxite plant. This observation
may be suggested to be consistent with the prevailing west
winds in the region. The analytical data set presently available
includes early data (1996) on the 27 sampling sites obtained
by strong-acid digestion and recent data (1999) obtained from
the G20 sample (out of factory) by both strong-acid digestion
and seawater extraction. The present limitation in the analytical
data set does not allow us to relate seawater-extractable in-
organics levels and the toxicity data of the whole set of sam-
pling sites. Even so, the available data from the G20 sample
point to the presence of seawater-extractable Al, Fe, and Mn,
whereas Zn and Pb fail to show any detectable increase in
their seawater release. Hence, the environmental availability
of these inorganics appears to be drastically different in the
G20 sample compared to Portovesme samples.
This study confirms our previous findings [2,3] about the
developmental toxicity to sea urchins of red sludge from baux-
ite manufacturing. This holds true for the Gardanne sludge and
solid deposition, with environmental concern unrestricted to
marine organisms in the vicinity of the coastal disposal site,
but also potentially involving terrestrial biota. The character-
istic, highly toxic dust from the G20 site collected at the factory
fence outside the factory might represent a subject of envi-
ronmental concern in the town of Gardanne, deserving appro-
priate investigations.
CONCLUSIONS
This study first reports on analytical versus toxicity data of
bauxite solid residues. Inorganic contamination and environ-
mental availability of some metals were evaluated under dif-
ferent conditions, providing the following evidence: a set of
multiple contaminants including Al, Fe, Mn, Pb, and Zn; a
wide variation of sample composition within each sampling
area, with a significant association between seawater-soluble
contaminants and toxicity. The most severe toxicity of some
Portovesme samples was associated with a dramatic dose-re-
lated seawater release of Zn and, to a lesser extent, Mn and
Pb.
Seawater extraction of a dust sample (G20) from Gardanne
factory showed increasing seawater release of Al, Fe, and Mn
and affected developing sea urchin embryos and sperm (re-
flected by damage to offspring quality); the highest frequency
of toxic soil samples within a circular set of sites around Gar-
danne was included in a 120Њ angle eastward from the factory,
in agreement with the prevailing west winds in the region.
The results suggest that solid deposition from bauxite plants
may be a subject that is broadly unknown and yet of envi-
ronmental health concern. The present study suggests that the
traditional strong-acid extraction methods for analyzing in-
organic complex mixtures may provide misleading informa-
tion, that is, not reflecting the actual release of soluble com-
ponents from the complex mixtures. Realistic extraction meth-
ods not confined to strong-acid extraction would be useful in
evaluating environmental availability and effects of complex
mixtures. Differences in sample toxicity among and within
selected sites suggest a variability in geochemical and/or tech-
nological aspects of treatment of the bauxite ores.
In the case of the Portovesme factory, a significant corre-
lation was obtained when the observed toxicity was measured
against the levels of minor metals in the bauxite residues,
namely, Zn, Pb, and Mn. It is worth noting that the most toxic
samples from Portovesme were effective in inducing devel-
opmental arrest (P2); moreover, these effects were detected at
very low concentrations, ranging from 0.03 to 0.3%. It is also
noted that samples 5, 150, and 150PP are very similar based