Phosphorus Dynamics in Soil-Water-Sediment Environment
Eisa Ebrahimi, Mohammad Reza Ojani
Abstract
Phosphorus, a crucial element for plant growth, is relatively scarce in the Earth’s crust. Its availability in surface soils ranges from 100 to 50 mg/kg. Plants can only absorb phosphorus in the form of orthophosphates, with H2PO4- being most absorbable at low pH levels. The average phosphorus concentration in soil solution is about 0.05 mg/L, but plant-satisfying levels range from 0.003 to 0.3 mg/L, underscoring the need for judicious phosphorus fertilization. Storage and stabilization reactions in soil, mainly facilitated by iron and aluminum oxides, play a key role. Compounds in most soils use hydroxyl exchange mechanisms for H2PO4- adsorption. Under alkaline conditions, minerals like calcium carbonate can absorb H2PO4-/ HPO42−, leading to precipitation. To ensure plant health, phosphorus fertilizers, especially calcium orthophosphates like triple superphosphate, are commonly used. These fertilizers offer essential phosphorus for plant growth and development, supporting vital processes like respiration and photosynthesis. Excess phosphorus in aquatic ecosystems, known as eutrophication, poses environmental risks, often originating from concentrated agricultural and livestock operations. Proper management of phosphorus inputs is crucial for balancing plant growth support with environmental preservation. Understanding phosphorus dynamics in soil, water, and sediments is vital for sustainable agriculture and conservation efforts. Adsorption isotherms provide insights into phosphorus absorption mechanisms in sediments, impacting water quality in surface and subsurface systems.