24 CHINESE JOURNAL OF GEOCHEMISTR Vol. 25 (Suppl.

) 2006

concluded that mining at the Taojiang Mn ore deposit might have caused the heavy metal contamination of both surrounding soils
and surface water.

Key words environment impact; heavy metal; soil; surface water; Taojiang Mn ore deposit

Physical-chemical modeling of oxidizing processes in high-sulfide mine tailings, and

Olga L. Gaskova, Svetlana B. Bortnikova, Ivan V. Gaskov

Background: One of the most common forms of contamination around sulfide mining sites is the release of acidic oxidation products
to surface water, soils and groundwater. Geochemical modeling techniques can provide valuable assistance in the interpretation of
field and laboratory data, thus helping to assess the risk of high pollutant loads. The Berikul gold mine is situated in the Kemerovo
region, western Siberia. The high-sulfide and low-carbonate tailings of ore cyanidation have been deposited as the pile. Over many
years of storage in the pile, the supergene alteration led to a characteristic layering: the uppermost horizon is jarosite with quartz and
gypsum, underlying is the melanterite zone, containing jarosite, pyrite and Fe-sulfoarsenates, next is a version of hardpan layer,
lithified by gypsum. The lowermost one is slightly altered tailing. Methods: The Gibbs energy of formation of bukovskyite
Fe2'3+(AsOa)(SO4)(OH) is estimated: -3480• kJ 9 moll. To visualize the chemical relationships of the secondary phases, the Eh-pH
diagram was developed. The "HCh" modeling computer code (Shvarov, 1999) has been used for equilibrium modeling by the
step-flow-through reactors. Results: Geochemical modeling indicates that extensive oxidation in the uppermost horizon has resulted
in extremely low pH 1.0 and high concentrations of dissolved SO4 and metals. Surface seeps develop higher contaminant loadings in
the underlying zone. It results in secondary melanterite, bukovskyite with gypsum formation at pH=2. The high concentrations of
dissolved SO4, Fe and As are observed up to hardpan formation. The acid released from sulfide oxidation has been extensive enough
to deplete Al-silicate minerals partly up to a hardpan horizon and carbonate minerals up to the lowermost horizon. So, these
associations are acid producing and present a potential source of acid rock drainage. The abundance of sulfide minerals and the lack
of neutralizing minerals in the tailings suggest that, without the implementation of an effective remedial program, sulfide oxidation in
the vadose zone will continue for many centuries. Consequently, such tailings have to be always mixed with the excess of carbonates
before deposition. Conclusions: Geochemical modeling has established that the recent complex mineral zonation of the tailing pile
corresponds only to the earlier stage of weathering. Financial support from the RFBR (projects 04-05-6407 and 06-05-64528) is
gratefully appreciated.

Key words mine tailings; acid drainage; thermodynamic model; environment

Environmental aspects of selected trace metals in soils and waters surrounding Singaran Nala,
Raniganj Coalfield

Supriyo Das
Department of Geology and Geochemistry, Stockholm University, Stockholm 10691, Sweden

The Raniganj Coalfield is the oldest coalfield in India that has been continuously and extensively mined since the late eighteenth
century. The present study reports a geochemical investigation and environmental quality assessment using soil and water in the area
surrounding a stream, locally known as Singaran Nala (Nala means storm water drains in Bengali), in the Raniganj Coalfield. Soil
(top soil, mud, silty clay and laterite) and rock samples (sandstone and shale) were collected from the study area and were analyzed
for trace metals (Cr, Cu, Fe, Mn, Ni and Zn). Surface waters from the stream and the Damodar River as well as ground waters from
hand pumps and underground mine pits were collected. Water samples were analyzed for major ions (Na§ Ca2+, Mg 2§ CI-, HNO3-
and SO42-) and trace metals (Cu, Fe, Mn, Ni, and Zn). Trace metal concentrations in soil samples are found higher than the average
world soil composition. Nevertheless, trace metal (Cr, Cu, Ni and Zn) concentrations in soils exceed or reach the maximum allowable
concentrations (MAC) proposed by the European Commission for agricultural soils. In particular, Ni concentrations exceed the
typical value for cultivated soils. Chromium, Cu and Ni concentrations in laterite and Cr concentration in topsoil exceed the
ecotoxicological limit. High background (sandstone and shale) trace metal concentration and probable dispersion of metals due to
Vol. 25 (Suppl.) 2006 CHINESE JOURNAL GEOCHEMISTRY 25

mining activity could be responsible for their elevated values in soils. Enrichment factor (Ef), geoaccumulation index (Igeo), metal
pollution index (MPI), sediment quality guideline index (SQG-I) and enrichment index (EI) are calculated to estimate the overall
contamination level and toxicity of the soils. The high Ef, Igeoand MPI values indicate high metal contamination in laterite and silty
clay. Moreover, the range of SQG-Ibackground values indicates moderate to high toxicity of the soils. However, the
SQG-Intervention values indicate low pollution level, and the EI values suggest no threat to the human health t~om the consumption
of the crops produced in the study area due to trace metal contamination in the soils. Low mobility of metals in the waters above
pH=6 probably results in low dissolved metal concentrations (below instrumental detection limit of atomic absorption spectrometry)
in water samples. High metal absorption by laterite could also cause low dissolved metal concentrations. Silicate weathering and coal
mining contribute towards the dissolved major ion composition in waters.

Key words coal mine; trace metal; soil; laterite; toxicity

Possible uses of kaolin wastes and transformed materials from the Amazon region (northern
Brazil) for environmental applications

Romulo Simoes Angelica

The most important Brazilian kaolin district is located in the Amazon region. The beneficiation of this kaolin produces great
volumes of wastes, mainly composed of coarse-grained kaolinite not suitable for the paper industry but still very fine and ideal for
several other purposes. About 1000 M ton kaolinite-rich wastes are produced annually. The sludge is disposed on artificial
sedimentary lakes that occupy extensive areas, with huge impacts on the environment due to extensive deforested areas needed
for their construction. This work is indeed to present the different studies that have been carried out in order to characterize and
find proper applications of such wastes and transformed products. Possible applications include: (1) production of high-reactivity
metakaolinite and fine-grained silica for construction materials; (2) alumina for different applications (ceramic and adsorbents).
Methods used include: drying and calcination of the kaolin-residue, Al-extraction for low-granulometry alumina and silica (here
named as sioclay) production. Start- and transformed materials were characterized by means of XRF, XRD, DTS-TG-DSC, FTIR,
SEM-EDS, BET, among others. Technological assays were also carded out for ceramic purposes. The mineralogy is dominated by
kaolinite, quartz and trace amounts of anatase, rutile, hematite and goethite. Total chemical analyses of all worked materials also
reflect the theoretical composition of kaolinite. Both metakaolinite and sioclay do not exhibit X-ray diffraction patterns and
present a very small grain size. Metakaolinite, alumina and sioclay exhibit increasingly values of specific area. For the ceramic
products, sintering increases its mechanical resistance. Adsorption tests of different metals on kaolin-transformed products were
carried out in a batch reactor. Tests will be presented for As, which is a toxic and carcinogenic metalloid. Results for As (V)
adsorption carried out in this investigation reveal the ability of sioclay>alumina>metakaolin to remove this element by sorption
from the solution. The adsorption capacity is consistent over a wide pH range. The equilibrium of adsorption is best described by
Langmuir isotherms. The combination of cheap and simple preparation procedures and high adsorption capacity can make those
materials attractive for As-removal from contaminated waters.

Key words kaolinite; waste; adsorption; arsenic; ceramic

Geochemical sampling with special reference to environmental risk assessment

Weidong YANG 1, Baojin ZHAO 1, William Pulle2

We usually conduct environmental investigation through sample study. Therefore, it is essential that samples should be representative,
at all time, and of the object be studied. However, the issues of sample representativeness and sampling errors are often neglected by
investigators. Based on modem geo-statistics and sampling theory, this paper addresses these issues in more detail and presents a
case study related to environmental risk assessment. The issue of sample representativeness can be measured in the following three
aspects: (1) whether the sample numbers are large enough to reflect the characteristics of the initial object being studied); (2) whether