| Livestock waste contains abundant phytic acid. A large amount of livestock waste goes into the environment making phytic acid be an important component of phosphorus pool in the environment. Heavy metal pollution of soil in China is getting worse, which leads to desolation of farmland and pollution of groundwater, and becomes a serious constraint to sustainable agriculture development. As an excellent chelating agent, Phytic acid plays an important role in food, chemical industry and heavy metal pollution remediation. With the rapid development of science and technology, synchrotron radiation, and isotopes, the determination of phytic acid technology has been become more mature, which is helping to study-the behavior of phytic acid in the environment as a powerful tool. Interaction between phytic acid and heavy metals in the environment has become a burning issue to research. In this research we studied distribution and occurrence form of P and phytic acid in farmland and freshwater ecosystem through field investigation. We have also carried out lab experiment to analyze adsorption and desorption characteristics of phytic acid on mineral and soil interface, and to explore speciation change of metals. To ensure phytic acid’s effects on organisms in contaminated soil, we designed wheat soil pot experiment to study plant’s response to different heavy metals when phytic acid was added in soil. Antioxidant enzymes’activity and heavy metals’distribution in plant was also determined. The obtained results are summarised as follows:Taking Liangzi Lake, a typical freshwater lake, and Yue Lake, an urban lake, as the research object, the phosphorous forms, phytic acid content and phytase activity in Liangzi Lake and Yue Lake as well as the ages of sediments in Liangzi lake were analysied. The results indicated that content of inorganic phosphorus accounted for 40% to 71% of total phosphorus, but organic phosphorus content was very low. Near the water inlet, distribution of inorganic phosphorus content was HC1-P≈NaOH-P (above 0.8 m) and HC1-P> NaOH-P (below 0.8 m), however the opposite results were gained near the water outlet. Distribution of organic phosphorus content in Yue Lake and Liangzi Lake were basically the same as MLOP>MROP>LOP. Before 2ka.BP, total phosphorus and phytic acid accumulation was increased with the age. In 2-4 ka.BP, total phosphorus and phytic acid accumulation increased first and then stabilized. Before 8.6 ka.BP (under 4.5m), phosphorus content was at low level. The experimental results showed that TP and phytic acid content in the sediment could accurately reflect phosphorus input history to some extent. In Yue Lake, TP content in surface sediment in life pollution area was higher than constructed wetlands. Distribution of IP in Yue lake in YH2 was HCl-P> NaOH-P, in YH1 was HCl-P> NaOH-P. MLOP was the most important components of OP. Among OP components, content of phosphorus form was MLOP> LOP>MROP. Phytic acid content and phytase activity in Yue Lake gradually decreased with the increase of the depth. In the soil surface (more than 1 m), phytic acid content and phytase activity in pollution area were greater than the artificial wetland. The above results showed that in the process of urban lake pollution, phosphorus mainly accumulated in the surface sediment.The speciation of P, phytic acid content and phytase activity in different types of soil was also studied. The results show that P leaching greatly in cropland and tend to accumulate in deep soil layer. The analysis of P in soil which collected from Liangzi Lake indicates P always accumulate in surface (< 0.4 m) and deep layer (> 1.4 m) of soil and paddy soil deposit much more P than rapeseed soil in deep layer. In addition, NaOH-P>HCl-P in soil obtained from Liangzi Lake while, it was different in vegetable field. Soil contains more MOLP and LOP than lacustrine deposit, but the content of MLOP was higher than LOP in soil as well as in lacustrine deposit, and the former fluctuates was more acutely as the active form of organic P in soil. And it is worth noting that, the activity of phytase in both materials maintain in the same level, even phytic acid exist less in cropland soil.Batch experiments of absorption and desorption of heavy metals was carried out to understand the interaction of mineral materials with phytic acid added at different time length, temperature and concentrations. The results showed that the optimal temperature of the 4 mineral materials (Fe-Mn ore、steel slag、goethite、montmorillonite) for the absorption of the 3 metals (Cd、As、Zn) was 25℃; the saturation adsorption time was 24 h. In addition, slag and Fe-Mn ore have better absorbing ability. Interaction among phytic acid, As and Cd which are called complexation alleviates the absorption on interface of mineral materials. The results suggest that, the change in distribution of phytic acid and heavy metals on interface was inevitable when phytic acid, heavy metal and mineral materials appear concurrently, and finally effect metals and phytic’s migration in environment.The effect of phytic acid addition on heavy metals’absorption and desorption in the interface of soil as well as their speciation were studied. The results showed that the absorption of As and Cd were decreased at different levels in phytic acid-added soils, especially the red and brown ash ones. Meanwhile, on the contrary, desorption rate was elevated. But when phytic acid interacting with Zn, Zn was absorbed incrementally with increased phytic acid concentration, and has lower desorption than Cd and As. In red soil and black soil, the concentration of As, Cd, Pb and Zn emerged in available form raised as time goes by, while it were opposite in grey alluvial soil and brown soil; as time passed, speciation of the 4 metals in soils were all changed under phytic acid treatment at varying degree. In special, Zn, Cd and Pb in reduced form as well as As in obligate (or non) absorption state and residual form. In short, phytic acid makes a tremendous impact on the distribution and availability of heavy metals in soil, and this will influence relevant pollution regulation positively through alter heavy metals transformation.A pot experiment was conducted to determine the effects of As on wheat when adding phytates. The results showed that the biomass of wheat had varying degrees of improvement after adding phytic acid; the accumulation of As in aboveground and underground parts of wheat was reduced with phytic acid addition (18.8%-98.9%); Phytate added, positively affected the antioxidant enzyme system and MDA in wheat leaves in three kinds of soils. Addition of phytate in the soil improved the mobility of As in soil medium and reduced the As stress of wheat roots. |
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