Element Flows Associated with Marine Shore Mine Tailings Deposits

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• 作者：Bernhard Dold
• 刊名：Environmental Science & Technology
• 出版年：2006
• 出版时间：February 1, 2006
• 年：2006
• 卷：40
• 期：3
• 页码：752 - 758
• 全文大小：256K
• 年卷期：v.40,no.3(February 1, 2006)
• ISSN：1520-5851

文摘

From 1938 until 1975, flotation tailings from the Potrerillos-ElSalvador mining district (porphyry copper deposits)were discharged into the El Salado valley and transportedin suspension to the sea at Chañaral Bay, AtacamaDesert, northern Chile. Over 220 Mt of tailings, averaging0.8 ± 0.25 wt % of pyrite, were deposited into the bay, resultingin over a 1 kilometer seaward displacement of theshoreline and an estimated 10-15 m thick tailings accumulation covering a ~4 km² surface area. The Chañaral casewas classified by the United Nations EnvironmentalProgramme (UNEP) in 1983 as one of the most seriouscases of marine contamination in the Pacific area. Since1975, the tailings have been exposed to oxidation, resultingin a 70-188 cm thick low-pH (2.6-4) oxidation zone atthe top with liberation of divalent metal cations, such asCu²⁺, Ni²⁺, and Zn²⁺ (up to 2265 mg/L, 18.1 mg/L, and 20.3 mg/L, respectively). Evaporation-induced transport capillarityled to metal enrichment at the tailings surface (e.g. up to 2.4%Cu) in the form of secondary chlorides and/or sulfates(dominated by eriochalcite [CuCl₂·H₂O] and halite). These,mainly water-soluble, secondary minerals were exposedto eolian transport in the direction of the Village of Chañaralby the predominant W-SW winds. Two element-flowdirections (toward the tailings surface, via capillarity, andtoward the sea) and two element groups with differentgeochemical behaviors (cations such as Cu, Zn, Ni, andoxyanions such as As and Mo) could be distinguished. It canbe postulated, that the sea is mainly affected by thefollowing: As, Mo, Cu, and Zn contamination, which wereliberated from the oxidation zone from the tailings andmobilized through the tidal cycle, and by Cu and Zn fromthe subsurface waters flowing in the El Salado valley (up to19 mg/L and 12 mg/L Zn, respectively), transported aschloro complexes at neutral pH.