The Effect Of Sewage Purification Of Sonneratia Apetala And Phragmites Communis Wetland

In this study, growth, physiological performance and nutrient uptake were investigated on the basis of observation data from Nanshan mangroves as well as simutilation experimental data in greenhouse in order to illustrate the effects of Sonneratia apetala and Phragmites communis on purifying wastewater.Though measuring some corresponding indexes in NanSha wetland park and simulation experiment in greenhouse, the results were as follows:(1) Less rainfall makes serious water pollution in autumn and winter in Nansha wetland park. Seasonal changes of pH were from 7.35 to 8.15 and the most serious season of water pollution were autumn and winter. The best purification effects of BOD, N, Cr, and Ni occurred in winter except P and COD. The average purifying rates of Sonneratia apetala were 27.4%, 77.8%, 82.4% and 58.5% respectively, while the purifying rates of Phragmites communis were 21.3%, 75.3%, 77.5% and 51.6%, indicating that Sonneratia apetala had a better water purification effect than Phragmites communis. The best purification effects of P and COD appeared in spring. The average purifying rates of Sonneratia apetala were 24.2% and 41.2%, and there were no significant difference of the rate in winter.(2) Field results showed that N and P content of soil of three sites in winter were both lower than summer. The N:P ratios in root of Sonneratia apetala and Phragmites communis didn't change with season and were 16% and 23% in winter and 21% and 25% in summer, while the N:P ratios in stem or leaf changed with season. According to the investigation results of two parts, leaf was the main N and P absorption part of two species (ranging between 42.1% and 65% in field and 52.9% and 74.4% in greenhouse). The average N absorption of winter and summer of Phragmite was higher than Sonneratia apetala (46.02g/kg and 42.60 g/kg) , while the average P absorption of winter and summer of Phragmite was lower than Sonneratia apetala (5.11 g/kg and 3.73 g/kg).(3) The soil Cr content in winter was less than summer under the condition of serious Cr pollution, indicating the Cr absorption amount of two species in winter was far more than summer and 12.7 times by Phragmite and 5 times by Sonneratia apetala. The purification effect of plants to Cr was best in some heavy metals. Cr was mainly absorbed by root, and the absorption rate of Phragmite in summer was 85.2%, greater than 62.9% in winer. This rate reached 88.3% in the greenhouse. The absorption rate of Sonneratia apetala in winter and summer were respectively 64.7% and 57.9%. This rate reached 79% in the greenhouse.(4)The Ni and Mn absorption amounts of Sonneratia apetala were both higher than Phragmite. The Ni absorption amounts of Sonneratia apetala in summer was higher than winter, and that of Phragmit was opposite. The Mn absorption amounts of Sonneratia apetala in summer was lower than winter, opposite to Phragmi as well. The Ni distribution rate of Phragmite ranked in root, leaf and stem, which accounted for 43.6% in winter, but 58% in summer. The Mn distribution rate of Phragmite ranked in leaf, root and stem, and was up to 90.6% in winter and 94.3% in summer. The Mn distribution rate of Phragmite ranked in root, leaf and stem in greenhouse, in which the ratio in root was 59% and the ratio in root and stem were reached 94.3%. The Ni absorption ratio of Sonneratia apetala was more than Phragmite, and 50% in winter, higher than 40.2% in summer. Mn were mainly absorbed by leaf, stem and old branch of Sonneratia apetala. The absorption rates were 89.4% in winter and 85.8% in summer in field, and 79% in winter and 81.5% in summer in greenhouse. A simulation experiment was set up in greenhouse with four wastewater irrigation levels (0, 1, 10, 15 times to normal and 0 times as control) for 2 months. Phyological index and nutrient status were determined once a month, while growth performance was measured every half a month, the results were as follows:The optimum concentration of irrigating with wastewater was 10 times to nomal and no obvious influences were revealed because of higher antioxidant activity to minimize the damage of membrane lipid peroxidation. The chlorophyll content and nitrate reductase activity reached maximum under 10 times of irrigation wastewater, which promoted the growth of Sonneratia apetala on the aspects of height, root collar diameter and biomass. With the increase of wastewater irrigated concentration, the biomass of Phragmites communis increased, especially for the root mass, but for root collar diameter.In a word, both of two species had strong ability of decontamination, but the purification effect and tolerance to heavy metals of Sonneratia apetala was better than Phragmites communis, which indicated that Sonneratia apetala was better on the aspect of purifying wastewater.