摘要: In many wetland ecosystems, the major nutrient processing occurs at or beneath the surface of the sediment. Accordingly, to understand nutrient processing by a wetland ecosystem, the manner in which nutrients reach the below ground sites of processing and the manner in which products of nutrient processing may possibly be removed from the sediments and exported must be understood. Below ground processes in wastewater treatment include uptake by microbes or macrophyte roots, cation exchange, adsorption, dissimilatory reduction by microbes, biologically mediated or chemical oxidation, and a variety of other decomposition processes; in all cases, the processes occur only after the chemicals have been physically carried to the active sites. The major mechanisms of transport are two -- namely, active transport by plants and physical transport by water movement. The physical transport by water movement …