Enhancing Copper-Contaminated Soil Remediation Using Walnut and Sunflower Residues

• Published in: Al-Qadisiyah Journal For Agriculture Sciences
• Main Author: Tara Hassan
• Format: Article
• Language: Arabic
• Published: University of Al-Qadisiya 2025-06-01
• Subjects: cu contaminated soil; biochar; walnut and sun flower residue
• Online Access: https://jouagr.qu.edu.iq/article_187568_7e39c7e2536c8cad7c41084f16a1fecf.pdf

Soil contamination with heavy metals, particularly copper (Cu), poses a significant challenge to environmental health and agricultural. This study evaluates the potential of organic amendments, including walnut shell biochar (produced at 700°C), sunflower husk biochar (produced at 500°C) and nutshell flour, to reduce Cu availability in contaminated soils. The amendments were applied at two concentrations (2.5% and 5%) to soils spiked with 2,000 mg/kg Cu. The untreated control soil exhibited the highest mean Cu availability (342.7 mg/kg), highlighting the severity of contamination. Upon treatment with 2.5% walnut shell biochar, Cu availability decreased significantly to 231.6 mg/kg, while 2.5% sunflower husk biochar, further reduced Cu availability significantly to 222.2 mg/kg. A more substantial reduction was achieved with 2.5% nutshell flour, which lowered Cu availability significantly to 181.4 mg/kg. At the higher application rate (5%), the amendments showed enhanced efficacy. Walnut shell biochar and sunflower husk biochar reduced Cu availability to 223.2 mg/kg and 190.7 mg/kg, respectively. Notably, 5% nutshell flour exhibited the highest immobilization potential, decreasing Cu availability significantly to 142.9 mg/kg. While in other hand study also investigates the effects of walnut shell biochar, sunflower husk biochar, and nutshell flour on the pH of Cu-contaminated soil (2,000 mg/kg Cu), The untreated control soil had a neutral pH of 7.52, while Cu contamination significantly reduced pH to 6.47, reflecting increased acidity. Application of 2.5% and 5% walnut shell biochar and 2.5% sunflower husk biochar significantly elevated the pH to 8.0, 8.21 and 7.96, respectively, achieving near-neutral or slightly alkaline conditions. Conversely, 2.5% nutshell flour resulted in a marginal pH increase to 6.59, indicating limited neutralizing potential.