De Silva et al. 2023 — Industrial waste land application: soil quality, biota, and human health
A systematic review of the scientific literature on land application of industrial wastes to agricultural soils, covering fly ash, tannery waste, foundry sand, pulp sludge, red mud, sugar beet lime, wood ash, and other industrial byproducts. The review documents heavy metal contamination pathways (As, Cd, Cr, Pb, Ni, Cu, Zn) associated with specific waste types: tannery waste carries high chromium, copper, zinc, lead, strontium, and vanadium; fly ash may leach Se and As; foundry sand may contain metal contaminants; potable water treatment residuals may carry As and radioactive isotopes. The review identifies soil-to-plant-to-human food chain contamination as a key risk pathway, assesses existing regulatory frameworks, and identifies research gaps including lack of long-term mass-balance experiments and variable waste composition as barriers to establishing safe land application guidelines.
Key numbers
Review does not report primary measured concentrations; it synthesises published findings across waste types and soil contexts. Key contamination flags from the waste composition summary table:
Tannery waste: high Cr (variable); also Cu, Zn, Pb, Sr, V; high salt content. Highly relevant as a source of soil Cr contamination in leather-tanning agricultural regions.
Fly ash (Classes C and F): may leach Se and As; may contain PCBs and PAHs; variable composition. Relevant to soil As contamination near coal-burning power stations.
Foundry sand: may contain metal contaminants; variable composition.
Potable water treatment residuals: may contain As and radioactive isotopes.
Red mud (bauxite residue): high Mn; listed as soil pH modifier and sorbent.
The review concludes that the principal challenge for industrial waste land application is managing contaminants to within acceptable limits, and that long-term experiments and mass balance assessments are lacking.
Methods (brief)
Narrative/systematic literature review; no primary data collection. Sources drawn from international peer-reviewed literature including EPA Victoria, British Standards Institute, USEPA, and academic journals. Scope excluded biosolid (sewage sludge) applications as covered by prior reviews. Assessed waste types: foundry/smelter wastes, coal combustion products, tannery waste, dairy effluents, pulp sludge, sugar beet lime, wood ash, red mud, potable water treatment residuals.
Implications
Certification: Provides supply-chain framing for HMT&C’s sourcing risk assessments. Agricultural soils receiving tannery waste, fly ash, or foundry sand may carry elevated Cr, As, Pb, Cd burdens that are invisible without soil testing and that create ingredient-level contamination risk for crops grown on amended land. Relevant to supplier questionnaire design for HMT&C.
Courses: Useful background review for the “Why do agricultural soils contain heavy metals?” module; covers industrial waste as an anthropogenic contamination pathway distinct from natural geochemistry or fertiliser inputs.
Supply-chain: Establishes the regulatory and scientific context for land-application contamination as a source of heavy metal input to agricultural soils. Supports HMT&C’s general principle that supply-chain auditing should include soil-amendment history in high-risk geographies.