Effect of Biochar on Soil Quality Polluted by Open Dumping Leachate in Kani-Qrzhala Area Erbil Governorate

Abstract

This study indicated landfill leachate poses serious threats to soil quality beacause of high content of content soluble salts, nutrient, and heavy metals. This study investigated soils collected from Erbil city landfill at four sites and depths (0-90 cm) to assess contamination levels and evaluate biochar for remediation. Results showed soil ph values between 7.40 and 7.82, indicating neutral to slightly alkaline conditions. Electrical conductivity was more high ranging from 9.79 to 20.85 ds m^-1, reflecting severe salinity. Organic matter content was generally low, from 1.48% at site 3 to 3.21% at site 1, below the optimum for soil fertility. Macrontrients showed high variability potassium ranged from 648.13 mg.kg^-1 at site 3 to 1104.67 mg.kg^-1 at site, sodium from 86.41 mg.kg^-1 at site 3 to 158.25 mg.kg^-1 at site 4 and phosphates peaked 22.52 mg.kg^-1 at site 2. Nitrate concentrations were also elevated 36.71-55.89 mg.kg^-1, indicating nutrient enrichment from waste inputs. Heavy metals extracted by EDTA confirmed contamination risks near leachate ponds. Application of walnut shell biochar and oak wood biochar at % w/w significantly reduced heavy metal bioavailability and improved soil quality, demontrating biochars effectiveness as a remediation strategy. These results show that landfill leachate strongly degrades soil quality and soil health, while biochar serve as low cost and sustainable amendment to improve soil quality.