Maryam Ahmadvand - Department of Irrigation Engineering, Abouraihan Campus, University of Tehran, Iran
Jaber Soltani - Department of Irrigation Engineering, Abouraihan Campus, University of Tehran, Iran
Seyyed Ebrahim Hashemi Garmdareh - Department of Irrigation Engineering, Abouraihan Campus, University of Tehran, Iran
Maryam Varavipour - Department of Irrigation Engineering, Abouraihan Campus, University of Tehran, Iran

Nitrogen leaching from agricultural lands is a major threat to groundwater and surfacewaters. This study investigated the relationship between the characteristics of wheat-straw biocharproduced at different temperatures and its impact on the uptake of NO3--N.Methods: Three types of biochar were produced from wheat straw at three different pyrolysistemperatures of 300, 400 and 500°C, and sampling was done 3 times for each biochar. Physical andchemical characteristics of biochar were determined using a variety of methods including specific surfacewith methylene blue adsorption method, and elemental content with elemental analyzer, and watersolubility with standard ASTM (D5029-28) method. Statistical analysis was performed using Freundlichand Langmuir models. Nitrate concentration was measured using a UV-V spectrophotometer with awavelength of 500 nm.Results: It was indicated that with an increase in biochar pyrolysis temperature from 300 to 500°C, thehydrogen, oxygen and nitrogen in the biochar were significantly decreased (P < 0.05) while the carboncontent, surface area, density and water solubility in biochar (P < 0.05) were increased. The results alsoshowed that the maximum nitrate adsorptive capacity of the three types of biochar occurred at pH=6and contact time of 120 minutes. With increasing the temperature of biochar preparation, the efficiencyof biochar nitrate adsorption increased significantly.Conclusion: The present study shows that pyrolysis temperature greatly influences the biocharchemical and physical characteristics, and subsequently nitrate adsorption ability of the biochars. Thewheat straw biochar, which is produced at a pyrolysis temperature of 500°C, has the highest adsorptioncapacity for nitrate.

Biochar, Nitrates, Adsorption