Migration and Transformation of Phosphorus Forms in Field Ditch Sediments

ABSTRACT

A broad attention has been paid to the field ditches as the sewage interception channel for the agricultural nonpoint source pollution, however, rare studies have involved in the phosphorus migration and transformation between the ditch sediments and overlaying water, especially, from the ditch sediments to the water. The present paper aims to explore with XPS binding energy data how pH, dissolved oxygen, sunlight affect the process of phosphorus migration and transformation in ditch sediments to the water by methods of changing pH, aerating nitrogen and oxygen in water and changing the sunlight; and hopes to provide a guidance on how to give full play to the ditch’s sewage interception capacity and avoid ditch becoming pollution source reversely. The experimental results with XPS binding energy data show that no electron transfer occurs insignificantly at different pH values in sediments, i.e. no electron transfer reaction occurs on surface. This reveals that the phosphorus absorption form HPO₄^2- in sediment substitutes OH^- state on the sediment surface. The amount of phosphorus migration and transformation is the minimum under the neutral condition, and the maximum under the alkaline condition. Under aerobic atmosphere, the data of XPS binding energy shows the surface charge of iron after oxygen aeration reduces, the surface charge of oxygen increases, i.e. Fe²⁺ is oxidized into Fe³⁺, the phosphorus is absorbed increasingly; the experimental results with XPS binding energy data disclose there exists electron transfer reaction significantly, that is the illumination affects the process of phosphorus migration and transformation through dissolved oxygen (DO) and the pH impacted on the biological processes under the presence of sunlight in sediments, indirectly. The influence of illumination on the sediment phosphorus migration and transformation is regular insignificantly. Conclusively, the amount of migration and transformation in sunlight-free group is greater than the sunlight group.

Keywords:

Dissolved oxygen, ditch sediments, light intensity, migration and transformation, pH, phosphorus fraction, XPS.