Effect of Potamogeton Crispus on Calcium and Phosphorus Cycle in Lake Sediments and Overlying Water of Middle Yangtze River
|School||Huazhong Agricultural University|
|Keywords||Sediments Crispus Overlying water Fractionation Calcium classification CacO3-P coprecipitation|
\Submerged plants as this region an important part of the ecosystem of the \Meanwhile, the water CaCO3-P is an important co-precipitation purification mechanism, \In order to study this topic crispus on lake sediment and overlying water between calcium and phosphorus cycle impacts in two elements: test \Cycle of \under conditions of simulated lake ecosystem pot experiment. Test set sediment calcium, phosphorus, and the overlying water plus various treatment crispus grown in crispus growth 50 d. (Seedling) and 166 d. (Reproductive stage) were measured when the sediments overlying water, pore water and crispus calcium, phosphorus changes, while the overlying water pH, sediment Eh, overlying water content of chlorophyll a and other indicators for monitoring; trial \is on this basis, the Yangtze River calcium activity of several different shallow lake sediments for the study, the test results further demonstrate to study recovery crispus sediment and overlying water on intercellular calcium, phosphorus cycle effects. The main conclusions are as follows: (a) in P. crispus growth 50 d., The planting crispus calcium can increase sediment and sediment TP concentrations, and in the overlying water crispus high phosphorus levels that sediment TP content increased more obvious; crispus grown in 166 d., in addition to the blank treatment, other treatment sediment TP concentrations have declined. This may be due to the different growth period crispus rhizosphere secretion by affecting the role of oxygen makes up sediment thereby changing the redox potential of the metal ions in sediment conditions, as well as affect the sediment adsorption and desorption of phosphorus, which is crispus maintain low nutrient levels of water an important mechanism. Crispus underground part of total phosphorus in the growth of P. crispus 166 d. Than when grown 50 d. When there is a substantial increase, which is decreased sediment TP one of the reasons. (2) Planting crispus can reduce sediment Ca2-P and Al-P content, indicating that the growth of P. crispus can effectively absorb sediments Ca2-P and Al-P, in which crispus seedling growth, deposition Calcium can effectively promote physical crispus plants were Ca2-P absorption. With time, the sediments Fe-P and Al-P content is reduced, Fe-OP and Al-OP content increased. (3) sediment exchangeable Ca content and Ca2-P was significantly negatively correlated, CaCO3-Ca, Ca5 (PO4) 3OH-Ca and CaSO4-Ca are associated with Org-P, Fe-P, Al-OP, Fe -OP and other insoluble phosphate was significantly positively correlated with the four forms of calcium Ca10-P no correlation, indicating that as the sediment exchangeable Ca content increased, reactive phosphorus content decreases and increases of insoluble calcium insoluble phosphate showed an increasing trend, but in a short time insoluble Ca10-P less susceptible to calcium deposits form changes. (4) Planting crispus can effectively remove the overlying water TP, explained not only by the root absorption crispus phosphorus in sediments, and its stems and leaves of phosphorus absorption capacity is also very strong. Crispus overlying water biological phosphorus removal effect on the whole, with the relative balance of phosphorus in overlying water related to the overlying water soluble phosphorus concentration in the presence of P. crispus relatively stable, generally removed from the particulate phosphorus phosphorus transformation, ultimately manifested as TP removal overlying water, and in the strongest seedling plant growth, but with the gradual decline of the plant, its ecological benefits phosphorus also decreased. Calcium sediments overlying water on TP removal of a significant effect, planting crispus calcium deposits together with the most obvious effect of phosphorus. As balance between interstitial water TP direct impact on the overlying water soluble phosphorus. (5) under the conditions in the sediment calcium can increase the growth of P. crispus overlying water Ca2 concentration, but not calcium deposits under the conditions crispus growth, but lower concentrations of Ca2 overlying water, which may be due crispus itself absorption of the overlying water Ca2, only calcium concentration in sediments reached a certain range, crispus can be transported to the stems and leaves of Ca2 release overlying water. Ca2 concentration in the overlying water is also affected by the concentration of interstitial water Ca2 influence Ca2 higher the concentration of interstitial water, overlying water Ca2 concentration decreased less. Meanwhile, the overlying water Ca2 concentration with the overlying water TP, TSP and interstitial water TP showed a significant positive correlation. (6) planting crispus can increase total calcium content of the sediments, and with the growth of P. crispus extension of time in increments become more pronounced. Tests show that in the presence of P. crispus, overlying water with CaCO3-P co-precipitation occurs, which is due to planting crispus can increase the pH of the overlying water and thus contribute to the co-precipitation phenomenon. Calcium sediments overlying water to make corresponding increase in Ca2 concentration, increasing the starting Ca / P, thus speeding up the process of crystallization. Planting crispus and the joint action of calcium deposits increased by co-precipitation of CaCO3-P rate, thereby reducing the concentration of phosphorus in overlying water. (7) crispus planting can reduce calcium or sediment overlying water content of chlorophyll a, but with the planting time, the role of this algal weakened, while the calcium in the sediment under the conditions of P. crispus algal role but remained significant over time. Crispus chlorophyll a removal is mainly through the removal of phosphorus crispus to achieve, and the role of calcium sediments and overlying water is occurring CaCO3-P co-precipitation, thereby reducing the phosphorus concentration in overlying water, sediment and inhibit The release of phosphorus to the overlying water.