Study on purification of nitrogen and phosphorous in Deyeuxia angustifolia simulated experiment in Sanjiang Plain,China

It is important to better understand the nutrient distribution and circulation of the Deyeuxia angustifolia wetland in Sanjiang Plain, as this ecosystem plays a unique role in the ecological service functions of the region. However, little attention has been paid to the purification function of the wetlands in the Sanjiang Plain. Due to the agricultural exploitation since 1950's, over-fertilization has resulted severe in non-point pollution in the region. A potted plant experiment was conducted in Sanjiang Plain in 2004 to investigate the process and regulation of N and P purification of Deyeuxia angustifolia. Six levels of N and P input concentrations were set up, each for three repetitions. The water, soil, and plants were re-sampled, and TN and TP concentration in them were determined and analyzed.Results showed that the removal rate of N and P presents negative exponential increasing with time in a simulated ecosystem of Deyeuxia angustifolia. The highest removal rate of N and P was 93.26% and 98.98% in the early period of experiment, respectively. One reason is that Deyeuxia angustifolia grows quickly, and absorbs significant N and P. The other reason is that N and P content in soil is originally lower, and significant N and P can be absorbed through some routes. During the purification process, the purification role of N was promoted, while the purification decay extent was decreased through input of P. However, the purification role of P was not affected by input of N. Based on the distribution and circulation of N and P in the simulated ecosystem of Deyeuxia angustifolia, the vegetable sub-system was vital to the purification role of N, while soil sub-system played an important role in the purification of P. The purification effect of N and P was made apparent across the whole simulated ecosystem, where the purifying rate was 53.11% and 58.95%, respectively. This study can provide the scientific basis for understanding the purification function in the wetlands of the Northeastern region and in planning for the effective control of the non-point pollution.