Published on the Web 5/29/2009.
Soil acidification as a confounding factor on metal phytotoxicity in soils spiked with copper-rich mine wastes†
Article first published online: 6 JAN 2010
Copyright © 2009 SETAC
Environmental Toxicology and Chemistry
Volume 28, Issue 10, pages 2069–2081, October 2009
How to Cite
Ginocchio, R., de la Fuente, L. M., Sánchez, P., Bustamante, E., Silva, Y., Urrestarazu, P. and Rodríguez, P. H. (2009), Soil acidification as a confounding factor on metal phytotoxicity in soils spiked with copper-rich mine wastes. Environmental Toxicology and Chemistry, 28: 2069–2081. doi: 10.1897/08-617.1
- Issue published online: 6 JAN 2010
- Article first published online: 6 JAN 2010
- Manuscript Accepted: 24 APR 2009
- Manuscript Received: 2 DEC 2008
- Soil acidification;
- Smelter dust;
- Copper toxicity;
Pollution of soil with mine wastes results in both Cu enrichment and soil acidification. This confounding effect may be very important in terms of phytotoxicity, because pH is a key parameter influencing Cu solubility in soil solution. Laboratory toxicity tests were used to assess the effect of acidification by acidic mine wastes on Cu solubility and on root elongation of barley (Hordeum vulgare L.). Three contrasting substrates (two soils and a commercial sand) and two acidic, Cu-rich mine wastes (oxidized tailings [OxT] and smelter dust [SmD]) were selected as experimental materials. Substrates were spiked with a fixed amount of either SmD or OxT, and the pH of experimental mixtures was then modified in the range of 4.0 to 6.0 and 7.0 using PIPES (piperazine-1,4-bis(2-ethanesulfonic acid)), MES (2-(N-morpholino)ethanesulfonic acid), and MOPS (3-(N-Morpholino)-propanesulfonic acid) buffers. Chemical (pore-water Cu and pH) and toxicological (root length of barley plants) parameters were determined for experimental mixtures. Addition of SmD and OxT to substrates resulted in acidification (0.11–1.16 pH units) and high levels of soluble Cu and Zn. Neutralization of experimental mixtures with MES (pH 6.0) and MOPS (pH 7.0) buffers resulted in a marked decrease in soluble Cu and Zn, but the intensity of the effect was substrate-dependent. Adjustment of soil pH above the range normally considered to be toxic to plants (pH in water extract, >5.5) significantly reduced metal toxicity in barley, but phytotoxicity was not completely eliminated. The present results stress the importance of considering confounding effects on derivation of toxicity thresholds to plants when using laboratory phytotoxicity tests.