Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 25, 2007
Publication Date: October 7, 2007
Citation: Siebielec, G., Chaney, R.L., Kukier, U. 2007. Liming to Remediate Ni Contaminated Soils with Diverse Properties and a Wide Range of Ni Concentration. Plant and Soil. 299:117-130.
Interpretive Summary: Metal smelters which operated before about 1980 generally caused widespread soil contamination, and in some locations the metals killed all vegetation. The city of Port Colborne, Ontario, Canada, became contaminated by emissions of a Ni smelter from 1910 to 1970; but toxicity to crops occurred only on a few farms with strong acidic soils. In earlier studies we identified soil and plant Ni levels which caused Ni phytotoxicity in muck and mineral soils of Port Colborne, and showed that additions of limestone to make soils calcareous could prevent Ni phytotoxicity. In addition, liming the soils to prevent Ni phytotoxicity (interveinal chlorosis and banded chlorosis) could induce Mn deficiency (interveinal chlorosis) in susceptible crop species, which confused researchers about whether liming remediated Ni phytotoxicity potential of contaminated soils. The symptoms of Mn deficiency are somewhat like Fe deficiency and metal-induced Fe deficiency, but distinctly different from Ni phytotoxicity. The present study was conducted to test whether the combination of limestone to make the soil calcareous plus Mn fertilizer could achieve remediation of ten representative Port Colborne area soils. Each soil was adjusted to up to 4 pH levels and oat was grown; yield and shoot analysis showed whether the soil Ni reduced oat yield, and whether leaf Mn was adequate or leaf Ni indicated Ni-phytotoxicity. In addition, a soil extraction method using 0.01 M Sr-nitrate was used to compare soluble Ni in soils and plant response. In the case where soils were Ni phytotoxic at the pH at which they were collected from the field, liming gave healthy growth of oat on all soils except a woodland muck with 1.1% Ni. In addition, Ni extracted by the Sr-nitrate extraction method was correlated with leaf Ni (and thus with potential for Ni phytotoxicity) across all soils and soil pH levels, indicating that such “neutral salt” extraction methods offer great promise in predicting whether soils will cause Ni phytotoxicity. These findings have assisted in selection of cost-effective and persistent soil remediation decisions for Port Colborne regional soils.
Historic emissions from a Ni refinery at Port Colborne, Ontario, caused Ni contamination of regional soils and raised concerns about potential Ni phytotoxicity. Previous tests revealed that if these soils were made calcareous and fertilized with Mn and other common nutrients as needed to maintain fertility of such calcareous soils, full remediation (prevention of Ni phytotoxicity) would be obtained. This experiment was conducted to test this method of remediation on diverse soils from Port Colborne, and to evaluate chemical extraction tests which would be predictive of plant uptake and potential for Ni-phytotoxicity in Ni contaminated soils. Ten soils with varied levels of Ni contamination and varied soil properties were amended with limestone or nitric acid to raise or lower pH so that a wide pH range could be examined for the soils. Oat and redbeet were grown for 40 days. For lower Ni organic and mineral soils near the Ontario remediation limit (200 mg/kg), neither crop suffered Ni phytotoxicity at any pH tested. Only when more highly contaminated soils were strongly acidic did Ni phytotoxicity occur. Phytotoxic soils were fully remediated by making soils calcareous even for these Ni-sensitive crop species. Only the most contaminated organic soil remained slightly toxic — but this soil was remarkably contaminated (over 1.1 % of Ni). The Sr-nitrate extraction method was much more effective in predicting plant Ni concentrations than DTPA method. This test would provide an inexpensive soil extraction result highly predictive of potential for phytotoxicity across soils.