Phosphates in Soil

Book review by Rowena Fletcher-Wood
Science Oxford
rowena.fletcher-wood@scienceoxford.com
ECG Bulletin January 2019

A well-written, clearly laid out book covering the latest advances in phosphate chemistry in soils, including pathways, policy and remediation strategies, health effects, costs, and potential environmental hazards.

Key facts in the book are clearly identified and highlighted, indicating a strong editorial hand. There is a natural progression through the chapters, suggesting it was intended for reading in its entirety; the first three chapters, for example, serve as an extended introduction to phosphate science. Internal references and repeated introductions also make piecewise reading possible.

It is not easy to identify the intended audience for this book. Some concepts (e.g. equilibrium constants, normally covered in the chemistry A level syllabus) start at a basic level, for a reader without prior knowledge. Key terms such as heavy metal(loid) are defined from the outset, but elsewhere in the book, in-depth geological and technical knowledge is assumed. Analytical and experimental techniques of some complexity are introduced without explanation and sometimes without accompanying results. An overview of these techniques, their strengths and limitations, would ultimately underpin the discussion. More graphs would also help to visualise the concepts described.

An impressive array of mineral phases are recognised, but the assumed understanding of them varies from chapter to chapter, with chemical formulae and shorthand names provided in some cases but not in others, and no mention of their crystallography or morphology, despite the contribution of sites to selective metal sorption. Notably, the short name HA is introduced for hydroxyapatite, where HAP, another common abbreviation in the literature, is not. Through robust referencing throughout, the book very much leaves it up to its reader to do much of the footwork to fully understand the concepts conveyed. Despite this, the book’s scrutiny of mathematical models and experimental methodologies is thorough; assumptions, strengths and limitations are researched and assessed even where methodologies are infrequently reported in the literature. In particular, field versus pot studies are compared.

Despite its title, the focus of this book lies on trace metal dynamics in soils, their bioavailability, and the effect of changing phosphorus concentrations on their mobilisation. The book mainly addresses phosphorus-mediated remediation of radiological and heavy metal soil contamination and mobilisation of micronutrients, while more space could certainly be given to the comparison between phosphorus-free mechanisms and phosphorus-inclusive ones.

Summary
This book makes a brave attempt to collate findings relating to phosphate and trace elements in the hugely complex and messy system of soil solutions. Whilst affinity sequences can be established, intricate factors such as co-contamination, speciation, daughter species, phosphorus release rates, site competition, varying exposure times the mutual effects of pH on phosphorus and phosphorus on pH make quantification complex.

The book seems best aimed at a seasoned researcher with expertise pertaining only to one chapter, who wishes to broaden their understanding of their field and has time available to read and trace sources.

References
H. Magdi Selim (ed.), Phosphate in Soils: Interaction with Micronutrients, Radionuclides and Heavy Metals, CRC Press, Boca Raton, FL, 2017, ISBN 978-1-138-80318-3 (pbk), xv + 365 pp