Microwave assisted soil and waste dissolution for estimation of total phosphorus

Abstract

A study was undertaken to compare the US‐EPA 3051 (SW‐486) microwave digestion and conventional nitric/perchloric acids (HNO₃‐HClO₄)‐aluminum block methods for the dissolution of phosphorus (P) in a wide variety of soil, compost, and waste materials, including topsoil, soil amendments, river sediments, sewage sludge, river dredge, compost, and soil parent materials. Dry ashing the sample before 3051 microwave dissolution with the 3051 Method was used as an alternative method. The US‐EPA microwave assisted 3051 digestion method is a more rigorous method for determination of total P, recovering more P from soil, sediment, and compost materials than the conventional HNO₃‐HClO₄ method. Dry ashing before the 3051 microwave increased precision of total P estimation for materials high in organic matter, particularly composts. The 3051 method recovered more than 93.5% of the established or certified total P values from most soil, sediments, and composts.