|Other Abstract||With the rapid development of China's industry and agriculture, the untreated or improper handled industrial waste water discharge, large-scale use of pesticides, all kinds of vehicle exhaust emissions, the burning of solid waste, large number of organic pollutants entered the water bodies through the atmosphere dry and wet deposition and surface runoff, and accumulated in the sediment, posing potential threat to water environment and human health. Among various ways of organic pollution treatment of water bodies, phytoremediation, with its low-cost, in situ, landscaping, etc. has been an accepted measure for cleaning polluted soil and water. In view of this, the organic pollution of water and surface sediment in Chaohu lake, which is a typical lake along the middle and lower reaches of the Yangtze River, were investigated, field experiment on phytoremediation of organic pollutants in the dredged sediment of Yuehu Lake, which is a small urban eutrophic lake in Wuhan, was set and phytoremediation of organic pollution by willow (Salix matsudana) and cattail (Typha angustifolia) were studied. The main results are as follows:
1) Through qualitative analysis of water and surface sediment of Chaohu Lake, it was revealed that in Chaohu Lake was polluted by organic chemicals. A total of 120 kinds of organic chemicals, mainly polycyclic aromatic hydrocarbons (PAHs) and phthalates, of which 13 species are listed in the U.S. EPA priority control chemicals has been detected. It also showed that the types of organic chemicals in sediment were much higher than those in water, and indicated that the sediment was the “sinks” of organic chemicals. By comparing the numbers of each sampling sites and analysis of the source of typical organic chemicals, it indicated that pollutants in Chaohu Lake mainly came from the northwest corner, where was the estuary of rivers heavily polluted by the pharmaceuticals, food production, plastic products, chemical industry and so on.
2) In view of the qualitative analysis, quantitative analysis of 24 kinds semi-volatile organic chemicals was carried out. The results showed that chemicals in highest concentrations were phthalates (PAEs), of which the prominent were DBP and DEHP, two most commonly used plasticizer. The extensive use of plastics has caused pollution to the environment. PAHs was also an important type of pollutants. By analysis of the molecular indices, it showed that they mainly origined from the combustion of liquid fossil, which may be due to the large number of the fishing boats and transport vessels exhaust emission and the atmospheric deposition whereafter.
3) Phytoremediation of sediment in the field experiment showed that PAHs trended to be accumulated in the rhizosphere, and the accumulation efficiency of willow was better than that of cattail, perhaps due to stronger transpiration of willow. The high lipophylic (logKow＞3) of PAHs made it difficult for plant to uptake, and it was deduced that the phytoremediation mechanisms of PAHs was mainly rhizodegradation after accumulation.
4) Willow showed efficiency on phytoremediation of two dinitrotoluene chemicals pollution, 2,4-DNT and 2,6-DNT, while cattail only acted on 2, 4-DNT in the dry area. The phytoremediation mechanisms of PAHs was mainly phytoextraction due to their lower lipophylic (log Kow:0.5-3), which was in the range for plant uptake.
5) The phytoremediation efficiencies of the two PAEs with the shortest branched-chain (DMP and DEP) by willow were similar to those of DNTs. And cattail also showed significant efficiency on these two chemicals. Meanwhile, cattail showed a good efficiency on isophorone pollution phytoremediation, making it a potential plant types to remediate isophorone contaminated soil.
In conclusion, Chaohu Lake has been polluted by organic chemicals, of which the most serious were PAEs and PAHs, and they trended to accumulate in the sediment, posing a potential threat to human health. Through a field trail of phytoremediation of dredged sediments from the Yuehu Lake, the mechanisms of phytoremediation of PAHs pollution was mainly through rhizodegradation after accumunation, and that of DNTs was mainly through phytoextraction. It was also indicated that Salix matsudana and Typha angustifolia were two potential phytoremediation plants to remediate soil polluted by 2,4-Dinitrotoluene and isophorone, respectively.|