Accumulation of trace elements in coal ash-amended agricultural soil

Author

Chakanyuka, Millicent

Title

Accumulation of trace elements in coal ash-amended agricultural soil

Abstract

Background: The addition of coal ash to agricultural soil can improve soil properties and nutrient availability, but may also introduce toxic trace elements. Coal ash is increasingly considered a viable soil amendment due to its mineral content and potential to enhance soil structure and nutrient levels. However, its use may also introduce harmful trace elements into agricultural systems, raising concerns about long-term environmental and health impacts.
Objective: The long-term accumulation of coal ash in agricultural soil was evaluated for trace element loading. This study aimed to evaluate the long-term accumulation of trace elements in agricultural soil resulting from coal ash application. The focus was on assessing how repeated amendments influence trace element concentrations and potential risks.
Methods: An experimental design was implemented in agricultural plots where soil was amended with coal ash over an extended period. Soil samples were systematically collected and analysed for key trace elements. Soil physicochemical properties were also measured to understand changes in fertility and structure.
Key findings: Coal ash amendment reduced soil pH, shifting conditions toward slightly acidic conditions from 7.049 to 6.124. Statistical analysis revealed no significant differences between treatments (p-values 0.474-0.854), indicating that coal ash amendment did not produce statistically detectable changes in soil heavy metal concentrations.
Conclusion: Coal-ash addition introduced only trace-level amounts of Cd, Cu, Cr, Ni, Pb and Zn to the soil, while Ni and Pb rose modestly, yet every metal remained well below international guideline limits. Statistical tests (p > 0.05) confirmed no significant elevation above background. Consequently, the amended soil is classified as “uncontaminated to very slightly contaminated,” demonstrating that the coal ash used is chemically benign for agronomic use under the conditions tested.

Date

May 2025

Publisher

BUSE

Keywords

Soil fertility

Soil physical properties

Supervisor

Dr A. Kanda