title: Effect of wheat and rice straw biochars on pyrazosulfuron-ethyl sorption and persistence in a sandy loam soil.
abstract: The objective of this research was to investigate the effect of wheat and rice biochars on pyrazosulfuron-ethyl sorption in a sandy loam soil. Pyrazosulfuron-ethyl was poorly sorbed in the soil (3.5-8.6%) but biochar amendment increased the herbicide adsorption, and the effect varied with the nature of the feedstock and pyrolysis temperature. Biochars prepared at 600°C were more effective in adsorbing pyrazosulfuron-ethyl than biochars prepared at 400°C. Rice biochars were better than wheat biochars, and higher herbicide adsorption was attributed to the biochar surface area/porosity. The Freundlich constant 1/n suggested nonlinear isotherms, and nonlinearlity increased with increase in the level of biochar amendment. Desorption results suggested sorption of pyrazosulfuron-ethyl was partially irreversible, and the irreversibility increased with increase in the level of biochar. Both sorption and desorption of pyrazosulfuron-ethyl correlated well with the content of biochars. The free energy change (ΔG) indicated that the pyrazosulfuron-ethyl sorption process was exothermic, spontaneous and physical in nature. Persistence studies indicated that biochar (0.5%) amendment did not have significant effect on herbicide degradation, and its half-life values in the control, 0.5% WBC600- and RBC600-amended rice planted soils were 7, 8.6, and 10.4 days, respectively.
authors.affiliation: a Division of Agricultural Chemicals , Indian Agricultural Research Institute , New Delhi , India.
authors.forename: Suman
authors.initials: S
authors.lastname: Manna
authors.forename: Neera
authors.initials: N
authors.lastname: Singh
mesh_terms: D000327:Adsorption; D002606:Charcoal / Q000737:chemistry*; D052918:Environmental Restoration and Remediation / Q000379:methods; D006207:Half-Life; D006540:Herbicides / Q000737:chemistry; D012275:Oryza / Q000737:chemistry; D011720:Pyrazoles / Q000737:chemistry*; D011743:Pyrimidines / Q000737:chemistry*; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry*; D013696:Temperature; D014908:Triticum / Q000737:chemistry
chemical_list: D006540:Herbicides; D011720:Pyrazoles; D011743:Pyrimidines; D012987:Soil; D012989:Soil Pollutants; C540010:biochar; D002606:Charcoal; C433343:ethyl 5-(4,6-dimethoxypyrimidin-2-ylcarbamoylsulfamoyl)-1-methylpyrazole-4-carboxylate
keywords: Pyrazosulfuron-ethyl; adsorption; desorption; persistence; wheat and rice straw biochars