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Evaluation of Fluoride‐Induced Metal Mobilization in Soil Columns
Author(s) -
Totsche Kai Uwe,
Wilcke Wolfgang,
Körber Markus,
Kobza Jozef,
Zech Wolfgang
Publication year - 2000
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2000.00472425002900020013x
Subject(s) - leaching (pedology) , chemistry , metal , soil water , fluoride , dissolved organic carbon , solubility , analytical chemistry (journal) , aqueous solution , environmental chemistry , inorganic chemistry , soil science , geology , organic chemistry
Fluoride in soil solution may cause substantially increased leaching of dissolved organic carbon (DOC), Al, and heavy metals from soils. Our objective was to examine whether increased metal solubility is attributable to formation of fluoro‐ or organo‐complexes. The A horizon of a Slovak soil contaminated with heavy metals and F by Al smelter emissions was used to conduct two column experiments under saturated and steady‐state water flow conditions. The columns were leached with 5 m M Na 2 SO 4 , 1 m M NaCl, and 9 m M NaF solutions at pH 5.5 and an electrical conductivity of 1000 µS cm −1 . Samples were collected in 70‐min intervals for approximately 7 d. Two experiments were performed. In the first experiment ( single F pulse ), a fluoride (F) pulse was applied for 36 pore volumes (PVs), while in the second experiment ( dual F pulse ), two consecutive F pulses (each for 2.8 PVs) were applied. For both experiments, Cl breakthrough curves (BTCs) revealed a convection‐dominated transport regime. The breakthrough of Cd, Cr, Fe, Ni, and Pb paralleled DOC breakthrough in both experiments indicating metal leaching as organo‐complex. In the dual F pulse experiment, peak separation of the DOC and the complexed F (F bound ) breakthrough was achieved. The highest F bound concentration occurred 3.8 PVs later than that of DOC. The Al BTC paralleled that of Fb bound but showed tailing with a turning point simultaneous to the highest DOC concentration. Thus, the increase in Al solubility was mainly caused by fluoro‐complexation and only to a lesser extent by organo‐complexation.