We monitored the water quality and hydrological conditions of a horizontal subsurface constructed wetland (HSSF-CW) in Beijing, China, for two years. We simulated the area-based constant and the temperature coefficient with the first-order kinetic model. We examined the relationships between the nitrogen (N) removal rate, N load, seasonal variations in the N removal rate, and environmental factors—such as the area-based constant, temperature, and dissolved oxygen (DO). The effluent ammonia (NH 4 + -N) and nitrate (NO 3 ? -N) concentrations were significantly lower than the influent concentrations ( p < 0.01, n = 38). The NO 3 ? -N load was significantly correlated with the removal rate ( R 2 = 0.96, p < 0.01), but the NH 4 + -N load was not correlated with the removal rate ( R 2 = 0.02, p > 0.01). The area-based constants of NO 3 ? -N and NH 4 + -N at 20 °C were 27 ± 26 (mean ± SD) and 14 ± 10 m?year ?1 , respectively. The temperature coefficients for NO 3 ? -N and NH 4 + -N were estimated at 1.004 and 0.960, respectively. The area-based constants for NO 3 ? -N and NH 4 + -N were not correlated with temperature ( p > 0.01). The NO 3 ? -N area-based constant was correlated with the corresponding load ( R 2 = 0.96, p < 0.01). The NH 4 + -N area rate was correlated with DO ( R 2 = 0.69, p < 0.01), suggesting that the factors that influenced the N removal rate in this wetland met Liebig’s law of the minimum.
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