Effect of Soil Organic Matter on Adsorption of Nitrification Inhibitor Nitrapyrin in Black Soil

Experiments were conducted to study the adsorption kinetics and isothermal adsorption mechanism of nitrification inhibitor nitrapyrin onto the black soil of northeastern China. The nitrapyrin adsorption kinetics of the black soil were fitted with a quasi-second-order kinetics equation before and after organic matter removal (R-2 >= 0.8320, p < .05). The adsorption isotherm was obtained by the Langmuir equation (R-2 >= 0.9400, p < .05). Isothermal adsorption requires less energy and is a spontaneous endothermic reaction with an L-type isothermal curve (n > 1), dominated by surface physical adsorption. With the decrease of organic matter content in black soil, the adsorption mechanism of nitrapyin changed from distribution mechanism to surface adsorption. The black soil's organic matter content exhibited a quadratic relation with the maximum adsorption capacity and adsorption constant (Kf) at the different temperatures, reaching significant levels (R-2 >= 0.6484, p < .05).