Nutrient Accumulation And The Ecological Stoichiometry For The Plants In The Constructed Wetland

The constructed wetland has been widely applied in purifying kinds of wastewater. The new technology, comparing to the traditional wastewater treatment, the most significant point is its application of plants. They absorb nutrient in wastewater on one hand, and on the other hand, since the wastewater was lightly polluted, nutrient concentration may not sufficient for plant growth. In this paper, the research about 8 nutrient elements that plants need was conducted mainly on their concentration in biomass, accumulation and the Ecological Stoichiometry.By studying the nutrient concentration in 50 aboveground samples refered to 22 species, we found that the nutrient concentration from almost all samples are above the minimum value that the naturally growing plants contained in their biomass. That is to say, plants growing in the constructed wetland for mild eutrophic water were not in the situation of absolutely nutrient deficiency.But in the fact, even if all the nutrient was in normal range, plants may still deficiency some nutrient comparatively, according to the correlativity analysis. We studied on the ecological Ecological Stoichiometry about N: K, K: P, Ca: Mg and N: P ratio. It shows that N: P =12.9, N: K =0.72 in constructed wetland vegetation, suggesting plants were in light N deficiency. Also it shows that K: P =21.14 in constructed wetland vegetation, suggesting plants were in P deficiency, but no K deficiency.We studied the nutrient accumulation of plants in constructed wetland for mild eutrophic water. As the result shows, that the top five accumulated species almost collected the total accumulation of plants in constructed wetland for mild eutrophic water, with the ratio of 85.92 %, 70.70 %, 68.76 %, 81.20 %, 74.63 %, 71.38 %, 69.21 % and 66.78 % to K, N, Ca, Mg, P, Na> Fe and Zn, respectively. Four species (Lolium perenne, Coix lacryma-jobi, Canna indica, Miscanthus floridulus) played the main role in nutrient accumulation. As for the nutrient accumulated in aboveground and underground biomass, Na, Fe was accumulated much more in the underground biomass, with the ratio of 1.51 and 2.46, while K, N, Ca, Mg, P and Zn accumulated much more in the aboveground biomass, with the ratio of 3.48, 2.76, 3.25, 2.05, 3.65 and 1.47, respectively.We also made research on the nutrient flow in constructed wetland for mild eutrophic water and the Jade fish-seeing pond, and analysed the nutrient removal efficiency of plant purifying the mild water. The constructed wetland removed 33.31 %, 19.57 %, 58.42 %, 11.93 %, 84.18 % and 61.18 % of K, N, Ca, Mg, P, Na, Fe and Zn, respectively, and 23.84 %, 6.03%, 9.92%, 0.34%, 1.30 % and 18.11 % was accumulated in aboveground biomass. Havesting Lolium perenne, Coix lacryma-jobi, Canna indica, Miscanthus floridulus selectively and hold most other species in constructed wetland would remove nutrient accumulation with ratio 25.73 %, 5.51%, 8.96%. 0.59 %, 2.91% and 19.74% for K, N, Ca, Mg, P, Na, Fe and Zn, respectively.According to the basic characteristic of plants such as the growing season, height, life history, we divided the plant into different function groups. And as has been studied, nutrient concentration in herbs was higher than that in grasses; nutrient concentration in plants growing in winter-spring was higher than that in plants growing in summer-autumn; nutrient concentration in perennial plants...