| Mangrove forest is aquatic or wetland woody plant community grown in tropical coastal or estuarine intertidal zone, with high productivity, high rate of return and decomposition. The unique physiological and ecological characteristics make it able to withstand high salt, water and temperature, and it can bear and purify different contents of sewage full of nitrogen, phosphorus or heavy metals. In recent years, many scholars put forward the idea of using mangrove plants to build freshwater wetland to improving the purification effect. The results of fresh water domestication experiment show that most species can survive in fresh water, especially Aegiceras corniculatum can adapt to the freshwater well, and the survival rates was the highest up to 95%, the results make it possible to use mangrove plants building freshwater wetland. But there is few report about the freshwater adapted mangrove plants’ responds to sewage and the purification effect.Aegiceras corniculatum was chosen as the experimental material, the experiment was taken in the greenhouse to reveal its responds to different concentration of sewage in the view of physiology and ecology, also the hydroponic test was taken to explore its purification effect on total organic carbon(TOC), total nitrogen(TN), total phosphorus(TP), p H and the turbidity of water, and compared with Phragmites australis the typical traditional decontamination plant. The results show that:1. Freshwater adapted A. corniculatum seedlings could survive under ten times concentration of sewage, the relative growth rate(RGR) ranked as follows: W2>W4>W1/2>WC= W5>W1/4=W1>W10, but the difference was not significant. The plants grow well in W2 and W4, and the growth of height was up to 1.117 cm, however, the plants in W10 were inhibited seriously.2. The photosynthetic physiological indexes of A. corniculatum in different treatment increased firstly and then decreased with the increase of sewage concentration, the net photosynthetic rate, transpiration rate and stomatal conductance of plants in W4 were highest, up to 12.994-14.037 μmol CO2 m-2 s-1, 7.261-8.724 mmol m-2 s-1 and 0.310-0.379 mol H2 O m-2 s-1, and there was a significant positive correlation between the three indexes. The chlorophyll content was: W4>W5>W2> W1>Wc>W1/2>W1/4>W10, and there was a significant positive correlation between the net photosynthetic rate and the content of chlorophyll, especially the chlorophyll a.3. Low concentration of sewage had no significant effects on the seedlings, but the seedlings in high concentration of wastewater were damaged seriously. The malondialdehyde(MDA) accumulation and electrolyte leakage rate of plants in W10 were highest, followed by W5, and the other groups were less than or equal to Wc. In addition, the roots were damaged more seriously than the leaves under the same treatment.4. The freshwater adapted Ac seedlings could purify TOC, TN, TP, p H and turbidity remarkably, significantly higher than the comparison group without plants, the purification effects of pollutants are: TOC>TN>TP. Prolonging the hydraulic retention time is helpful to removal TOC, TN and to improve p H and turbidity of the water.5. The purification effects on TOC, TN, TP of freshwater adapted A. corniculatum seedlings were higher than or equal to Phragmites australis. Theoretically, freshwater adapted Ac can be used in artificial wetlands construction for enhancing the purifying effects.6. According to this research, under the W4 treatment, the daily removal quantity of TOC, TN and TP were the highest, up to 69.97 mg, 11.51 mg and 1.89 mg. Hence, adjusting the concentration of sewage is suggested in order to ensure the plants grow well and make the largest purifying effects in freshwater environment at the same time. |
PDF Full Text Request