| Phytic acid, which contains P28%and exists widespread in plants, is considered to be the repository of phosphorus in plants. Monogastric animals, such as pigs and chickens, lack phytase, resulting in that dietary phytate can not be utilized and get into the environment with animal manure. Therefore, heavy amout of phytic acid in sediments occupy an important position in both phosphorus nutrition of plants and the source of agricultural nonpoint source pollution. Thus, to know phytic acid in the soil environment migration, as well as the relationship of eutrophication are of great significance in soil and water environment for the potential dangers. This paper established greenhouse microcosm experimental apparatus to discuss the migration and release of phytate in agricultural nonpoint source pollution, and studied the adsorption and desorption of phytate in three typical soils. The results were summarsed as follows.1. By using microcosm experiment to simulate releasing of sediment phytate and its relationship with eutrophication, the results showed that the addition of phytic acid in sediment deteriorated the water quality, which was particularly reflected in the increasing TP by20.83%-30.77%and COD by24.87%. Addition of phytate increased water pH to a lesser extent, but had no influence on Conductivity and DO.2. The restoration of eutrophication water by two types of hydrophyte, curly pondweed (Potamogeton crispus) and cress (Oenanthe decumbens), was studied under microcosm experimental condition. The results showed that average water TP (0.021mg/1) for planting curly pondweed was lower than planting cress (average0.030mg/1). The P uptaking contribution rate for curly pondweed (62.02%-84.31%) was greater than cress (39.33%～53.34%) However, compared with curly pondweed, cress decreased COD by an average of12.15%, and pH and Cond of the water were less affected by the two hydrophytes.3. Adding phytic acid significantly increased TP and OP by14.95%and25.86%on an average respectively, and moderately labile OP by74.86%and66.28%for autumn/winter and spring/summer seasons respectively.However, adding phytate decreased labile OP by48.24%and39.14%for autumn/winter and spring/summer seasons respectively4. Planting different hydrophytes affected P fractions in sediment significantly, curly pondweed had4.33%of TP and12.13%of total IP greater than cress. However, total OP in cress was3.76%higher than crispus.5. Lower utilization of phytate occurred in autumn/winter season ranging26.7%～34.7%. Higher utilization of phytic acid was found in spring/summer season, the average about44.31%with a maximum value of64.4%. Generally, cress had for utilization of phytic acid of60%, while curly pondweed utilization of phytic acid of about40%, indicating that the cress was better than curly pondweed in utilization of phytate.6. A batch experiment was used to study the adsorption and desorption behavior of phytic acid in three types of soils. The results showed that the adsorption kinetics could be better fitted with First kinetic equation, Elovich equation and Double constant equation. The adsorption speed of phytic acid in soils ranked as Red soil> Calcareous alluvial soil> Brown soil. Desorption kinetics equation could also be fitted by the above three kinetic equation with the desorption speed ranking Brown soil> Calcareous alluvial soil> Red soil. The adsorption isotherm for three soils was well fitted with Freundlich equation and Langmuir equation. The maximum adsorption capacity of phytic acid for three soils ranked as Red soil>Calcareous alluvial soil> Brown soil. Ambient temperature on the adsorption of phytic acid showed as25℃>15℃>35℃>5℃; the effects of pH on the adsorption performance of phytic acid were Neutral> Acid> alkaline; and in addition to soil OM, Removal OM improved adsorption capacity of phytate significantly. |
