remediation and restoration of metal-contaminated sites: concepts and applications to mining areas
TRANSCRIPT
Vol. 25 (Suppl.) 2006 CHINESE JOURNAL GEOCHEMISTRY
flows are put forward. Key words exploitation of mineral resources; environmental pollution; benefication process; tailing disposal process
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The environmental effect of cadmium-rich Pb-Zn deposit, as exemplified by Niujiaotang Cd-rich Zn deposit, Guizhou, China
Lin YE 1~, Ziping PAN 1,3, Chaoyang LI 2, Tiegeng LIU 1 1 National Key Lab. of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China
2 Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry & South China Sea Institute of Oceanology, Chinese
Academy of Sciences, Guangzhou 510640, China
3 Graduate School of ChineseAcademy of Sciences Beijing 100049, China
Heavy metal toxic elements were usually released to circumferential environment during the activities of exploitation, ore cleaning mine and smelting in mine, especially for Pb-Zn mine. The content level of cadmium is abnormally high in the Niujiaotang cadmium-rich zinc deposit, Duyun, Guizhou Province, China, generally ranging from 2248x 10 "6 to 9850x 10 "6, with the maximum up to 13400x10 6 (average 5366x106), 5•215 6 orders of magnitude higher than the Clarke value (0.2• By investigating water, soil and plants in the ore area, it was discovered that the contents of Cd range from 0.08•215 -9 in the Fanjiahe stream, which is the only stream flowing across the ore area, 31x106--210• 6 (average 94.15x10 "6) in ore-area soils, 0.18x10 6 - 0.60• .6 (average 0.32• sweet potato, which greatly higher than the Chinese standard, showing that circumferential environment in the ore area has been polluted by Cd. The research results show the pH value of stream water is alkaline (pH=7.83-- 8.66), in which the content of Cd of ion type is not high, Cd is transported by suspended matter. It was indicated that exploitation, ore cleaning mine and smelting of mine are the main ways of releasing heavy metal toxic element Cd, and supergene weathering of ore and mine tailings are reduced by the alkaline condition in carbonatite area, which will be hazard to the mine area when the alkaline condition was destroyed. Though there are not evident poisoning symptoms in human, this is probably the result that time of mining is too short and thus accumulation of heavy metals is less in human body. However, the mine environment is a long-time problem. Even though mine had been closed for several hundred years, even thousand years, there still exist solutions which come from tail ore weathering-leaching and impact the environment. Therefore, in the process of mining development, importance should be attached to the synthetic utilization of elements and environmental protection in order to early prevent pollution, especially for those toxic elements-rich metal deposits.
Key words cadmium; Cd-rich zinc mine; environmental hazard
Remediation and restoration of metal-contaminated sites: Concepts and applications to mining areas
Domy C. AdfianC, Hyo T. Chon 2, SaUy L. Brown 3, Rosanna Ginocchio 4 1 The University of Georgia, Savannah River Ecology Lab, Aiken, SC 29802 USA
2 School of Civil, Urban and Geosystem Engineering, Seoul National University, Seou1151-744, Korea
College of Forest Resources, University of Washington, Seattle, WA 98195 USA
4 Centro de lnvestigacion Minera y Metalurgica, CIMM, Santiago, Chile
Metals, including heavy metals and metalloids, are a common group of environmental contaminants. Their sources in the environment are geogenic or anthropogenic. The growing trend in global industrialization ensures that more metals could be dispersed even in pristine ecosystems. To fuel industrialization, more metal ore mines have to be discovered and explored. These explorations often result in landscape disturbance, soil degradation and environmental contamination by unwanted mining constituents. Mine tailings brought up to the ground surface often serve as the main source of contaminants when these pyrite-rich materials oxidize. The oxidation of mine tailings results in proton generation, coupled with the dissolution of metals and other cations. Unwanted anionic constituents are also produced. The so-called "acid mine drainage" may affect the productivity of farmlands and stability of receiving streams and other bodies of water-acidifying the waters and enriching the ecosystem with metals, i.e., high total dissolved solids. The acidified overburden materials become inhospitable to plant and microbial life as they are typically low in organic matter content and infertile. This exposes the landscape to runoff and erosion. Presently, mining operators are required to
46 CHINESE JOURNAL OF GEOCHEMISTR Vol. 25 (Suppl.) 2006
restore the landscape but this is not always observed. This paper deals with the concepts on bioavailability of metals and other unwanted constituents from mining wastes, including the biogeochemical processes involved. Such processes include dissolution/precipitation, sorption/desorption, complexation, etc. The factors that influence these processes are discussed. The extent of bioavailability then would be used as a basis for exposure and risk assessment and for remediating and/or restoring the soils and landscape. Applications of the concepts include mining/smelting sites in South Korea, the USA and Chile. Two mining sites in eastern Korea, the Bunker HiI1 Superfund site in Idaho, and the E1 Teniente mine site in Chile will be discussed as "Case studies" to demonstrate environmental consequences of mining/smelting. This includes contamination of ground and surface waters, soils, farmlands and metal transfer in the food chain, phyto- and microbial toxicity, etc. Exposure and risk assessment from ingestion of crops and drinking water, and ecological risk assessment will be discussed.
Key words biogeochemical process; bioavailability; mobility; remediation
HFO as the main contaminant carrier and transporting agent downstream the Zarshuran As deposit, NW Iran
Soroush ModabberP, Farid Moore 2 I Water & Soil Pollution Investigation Bureau, Department of Environment, Tehran, 1ran
2 Department of Earth Science, Shiraz University, Shiraz, 1ran
The Zarshuran arsenic deposit has been exploited for more than one thousand years. During this period of time, trace element pollutants have been transported downstream via natural agents, however this process has been exacerbated by human interferences, such as mining activities, especially in recent years. Geochemical study of metallic contaminants revealed a high concentration of elements especially of As, Sb, Hg, and T1 in ore, waste piles, water and stream sediments, so that the arsenic concentration ranges between 40-0.028 mg/L in water samples of the Zarshuran Stream. In order to investigate the mechanism of contaminant transport downstream the mine, the concentrations of arsenic and other trace elements detected in ore-waste assemblage were measured in water samples taken from 11 stations. Also, the pH and Eh values have been measured in the same waster samples. The arsenic ore mainly consists of orpiment and realgar, associated with a small amount of Sb, Hg, T1, minerals. Weathering of this assemblage gives rise to a mine water having an arsenic concentration of 22 mg/L. As concentrations are reduced to 4.272, 3.069, 0.421, 0.083, and 0.036 mg/L at distances of about 1, 1.3, 3.3, 7 and 15.2 km down the mine, respectively. The water samples have been passed through the 0:45g filters to determine the fraction of contaminants transported in dissolved phase and also in particulate phase. The geochemical study of contaminant transport indicates that contaminants are transported mainly as colloidal and particulate phases in the upstream and only 13% of arsenic is transported as the dissolved phase. The milky appearance of stream is evidence for colloidal transport. From 6 km downward the mine, particulate phase is not the significant cartier of contaminants and more than 90% of the arsenic is transported as dissolved phase. The very positive correlation between trace element concentrations and Fe, colloidal deposition evidence as an ocher-colored precipitate on stream bed sediments accompanied by a decrease in contaminant concentrations in stream water, the physicochemical (Eh and pH) conditions, near neutral pH values, considerable difference in concentration of Fe in dissolved and total phases, weathering of iron sulfides in the ore-waste assemblage, XRD analysis of precipitates, indicate strongly that HFO is the main carrier and transporting agent in this area. Scorodite which is the main agent in most areas, is omitted because of its pH dependent solubility. Hence the most possible candidates for this would be jarosite and goethite.
Key words environmental geochemistry; transporting agent; HFO; Zarshuran deposit; Iran
Investigation on the origin of Se-rich soils in Yutangba: Evidence from selenium speciation and native selenium
J ianming Z H U I , Ha ibo QIN I'2, Lei LEI ~'2, Wenl iang H A N 1'
1 State Key Lahoratrry of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China; E-mail:
: Graduate School of Chinese Academy of Sciences, Beijing 100039, China