Phosphorus Transport From Agricultural Soils to Coastal Wetlands

• Main Authors: Liao,Wen-Han, 廖文翰
• Other Authors: Liu,Yu-Ting
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/40474151649995211476

碩士 === 東海大學 === 環境科學與工程學系 === 103 === The world population growth increase food needs. Modern agriculture depends on a large number of chemical fertilizers, phosphorus as fertilizer use in soil. But only about 15% to 30% of phosphorus will absorb by crops, other will fix by soil, create a critical loss in environment. Release fixed phosphorus in the soil is a possible ways to increase the efficiency of phosphorus. The phosphorus lost from soil transmitted by rivers finally back to the ocean. More than 90% of phosphorus transmitted in particle type in rivers. Wetlands as the interface between terrestrial and ocean, it have the ability to receive and store runoff. In order to enhance the ability and efficiency of phosphorus retention in wetlands, the prerequisite is to understand the transformation mechanism of phosphorus. How the spatial and temporal changes and environmental features affect conversion of phosphorus species. What species dominates the P repository, what biogeochemical factors control the P releases, and at what point the P release occurs in the terrestrial and ocean interfaces. In this study, study area is Gaomei Wetland and around agriculture field. And collect agricultural soil, sludge from irrigation ditch, and sediment in the wetland as the samples. There have two methods used to determine the phosphorus species in environment, chemical sequential extraction and X-ray absorption near edge structure (XANES). The experiment results, pH will affect the distribution of phosphorus species. Place which in low pH calcium phosphorus content were less than iron phosphate content. The place in high pH calcium phosphate content is more than iron phosphate. Iron phosphate is the main species transmission in rivers. Because water has separated air and soil or sludge, make soil or sludge into hypoxia condition. Make Fe3+in soil reduce to Fe2 +, soluble Fe2+ in water oxidation to Fe3+. Fe3+ in water combines with PO4 and become iron phosphate particles. The results of chemical sequential extraction and XANES spectroscopy, the iron phosphate and calcium phosphate have similar trend. However, the results of aluminum phosphate were different in two methods. The recovery of chemical sequential extraction is not good, and there has a lot of uncertainty in the process, so the results of the chemical sequential extraction aren’t credible, XANES spectrum is a better method.