Cupric Ion Activity in Peat Soil as a Toxicity Indicator for Maize

Copper phytotoxicity in soils is difficult to assess because Cu accumulates at and damages roots, and is not readily transferred to shoots. Soil chemical properties strongly influence Cu speciation, so that total soil Cu alone is not a broadly useful indicator of potential toxicity to plants. The pr...

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Bibliographic Details
Published in:Journal of environmental quality 2001-01, Vol.30 (1), p.78-84
Main Author: McBride, M.B.
Format: Article
Language:English
Subjects:
Agriculture
Biological and medical sciences
Copper - chemistry
Copper - toxicity
Dose-Response Relationship, Drug
Fundamental and applied biological sciences. Psychology
Ions
Non agrochemicals pollutants
Phytopathology. Animal pests. Plant and forest protection
Plant Leaves - chemistry
Plant Leaves - drug effects
Plant Roots - chemistry
Plant Roots - drug effects
Pollution effects and side effects of agrochemicals on crop plants and forest trees. Other anthropogenic factors
Pollution effects. Side effects of agrochemicals
Risk Assessment
Sewage
Toxicity Tests
Zea mays - physiology
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Summary:Copper phytotoxicity in soils is difficult to assess because Cu accumulates at and damages roots, and is not readily transferred to shoots. Soil chemical properties strongly influence Cu speciation, so that total soil Cu alone is not a broadly useful indicator of potential toxicity to plants. The present study measured free Cu2+ activity in Cu‐enriched peat soils using the ion selective electrode. The soil Cu2+ activity was related to the severity of phytotoxicity as measured by several indicators in a maize (Zea mays L.) bioassay, including leaf chlorosis, root stunting, and reduced shoot growth and Fe concentration. A soil Cu2+ activity of 10−7.0 to 10−7.5, corresponding to total Cu of about 275 mg/kg in the peat soil, caused phytotoxicity in maize seedlings. It is proposed that Cu2+ activity is more directly related to phytotoxic effects than other soil tests, such as extractions with strong acids or chelating agents, because it is the free Cu2+ in soil solution that has the most direct toxic effects on roots. There was very limited uptake of Cu into maize shoots, and even when Cu2+ activity and total soil Cu were raised into the extreme toxicity range of 10−5 and 4000 mg/kg, respectively, shoot Cu remained less than 35 mg/kg. These results indicate the inadequacy of the USEPA risk assessment of potential for Cu toxicity to crops amended with sewage sludge, which assumed a no‐effect level of maize shoot Cu of 40 mg/kg.
ISSN:0047-2425
1537-2537
DOI:10.2134/jeq2001.30178x