The title Environmental and Low‐Temperature Geochemistry seeks to encompass the scope of this text, from topics commonly covered in traditional geology‐based geochemistry texts as well as those in environmental chemistry and aqueous geochemistry texts. The “low‐temperature” part indicates a focus on Earth surface systems (< 50 °C for most topics covered) rather than metamorphic or igneous environments, although information from these higher‐temperature systems is also considered in some sections. The target audience is upper‐level undergraduates and graduate students, as well as professionals in geology and environmental science. The goal is to explain basic concepts from biogeochemistry and geology as they apply to understanding and predicting behavior of natural and anthropogenic constituents in systems at and near the surface of the Earth. The importance of the geological record of environmental change informs our understanding of the natural environment and improves our ability to predict system behavior, so sediment (and glacier) records of paleoclimate and environmental change are presented and examined. Increasing knowledge of the role of organisms – from microbes to macroscale plants – in inorganic and organic geochemistry is reflected in examples of biomineralization, microbial mediation of reactions, influence of root exudates, and more.

The scope ranges from the atmosphere and oceans to streams, lakes, groundwater, soils, sediments, and shallow crust. It also spans global and regional‐scale systems to pore spaces and nanoparticles. Understanding complex environmental systems requires factual, conceptual, and quantitative skills, so this book attempts to provide the background needed to objectively assess problems and questions through the lens of geochemistry. Inspiration for different sections comes from many excellent geochemistry and environmental chemistry texts, particularly those of Berner and Berner, Drever, Eby, Faure, Langmuir, Moore and Reynolds, Spiro and Stigliani, and Walther. The well‐worn copies on my bookshelf attest to their influence on my understanding of geochemistry and how to write a university‐level textbook that also can serve as a reference for earth and environmental scientists.

Chapter 1 presents basic principles of inorganic chemistry and geochemistry, including introductory kinetics and thermodynamics concepts meant to serve as a foundation for subsequent chapters. For most readers, parts of this chapter will serve as a review, but at the same time are useful for reinforcing concepts that are most applicable to environmental geochemistry. Minerals are the most abundant constituents of soils, sediments, and rocks, so Chapter 2 gives the reader foundational concepts in mineralogy and examples of minerals and mineral‐influenced processes. Harmful amounts of organic compounds like pesticides, solvents, fuels, and pharmaceuticals are a common source of contamination in soils, water, and air, so Chapter 3 contains an introductory presentation of relevant principles from organic chemistry then focuses on structure, composition, environmental behavior, consequences, and remediation of organic contaminants.

Chapter 4 focuses on aqueous systems and the biogeochemical factors that influence the composition of natural and impacted waters, presenting many topics that form the focus of aqueous geochemistry texts. So too do Chapters 5 (carbonates and the C cycle) and 6 (N, P, and S cycles), with a systems approach that conceptually and quantitatively examines reservoirs, fluxes, and processes, from inorganic to microbially affected.

Chapter 7 examines the atmosphere at a global scale, including geological and ice core records of air composition (and climate) over time, structure and composition of the current atmosphere, infrared and ultraviolet radiation, and human‐caused climate change, with up‐to‐date data on greenhouse gas sources and sinks. Urban and regional air pollution are the focus of Chapter 8, including oxygen chemistry and the role of free radicals, reactions involved in the formation and destruction of pollutants, the photochemical smog cycle, and origin and deposition of acid rain.

Chapter 9 focuses on the composition of soils, first considering processes and rates by which primary minerals transform to secondary minerals like clays, hydroxides, and carbonates. From there, Chapter 9 explores various topics, including: quantifying element mobility and how to apply it to paleoclimate analysis; thermodynamics and construction of mineral stability diagrams (and the utility of them); the geochemistry of the soil forming factors, soil profiles, and soil orders; how soils influence ecosystem response to acid rain; plant nutrients; toxic metals and metalloids; saline soils; and organic contaminants in soils.

Chapters 10 and 11 consider ways in which isotopes facilitate understanding of environmental systems as tracers, and in the case of radioactive isotopes, as environmental contaminants. Both chapters begin with fundamental concepts of isotope geochemistry. Stable isotopes are the focus of Chapter 10, with much attention paid to classic stable isotope pairs (e.g. ¹H–²H, ¹²C–¹³C, ¹⁴N–¹⁵N, ¹⁶O–¹⁸O, ³²S–³⁴S) and how they serve as useful tracers of processes – natural and anthropogenically influenced – in the atmosphere, biosphere, hydrosphere, and lithosphere. Recent advances and new applications in the areas of metal stable isotopes (e.g. Cu, Fe, Hg) and clumped isotopes (e.g. ¹³C–¹⁸O) are also highlighted. Radioactive and radiogenic isotopes are useful in dating reservoirs (e.g. layers of sediment) and tracing environmental processes, so these topics – along with radionuclides as contaminants – are the focal areas of Chapter 11.

Throughout the second edition of Environmental and Low‐Temperature Geochemistry are focus boxes that highlight certain topics in the form of brief case studies, quantitative approaches, definitions, and examples. This is a response to student input indicating that varied modes of text and text‐within‐text would be easier to digest than the format of the first edition. Another feature of the second edition is a new detailed case study (Appendix II) of groundwater contamination by the industrial chemical PFOA (perfluorooctanoic acid), an emerging contaminant of which relatively little is known about, at least in terms of how it will behave in soils, groundwater, and surface water. The second edition contains some new end‐of‐chapter problems and updated knowledge on systems undergoing change, most prominently the atmosphere and oceans relative to carbon emissions (a worsening problem), and air quality relative to urban and regional air pollutants (with some notable improvements). Reader input contributed significantly to this improved second edition, and comments on this edition are very welcome.

This text would not be what it is if not for encouragement and insights from Margaret Crowley Ryan, especially logistical, motivational, and contractual. I wrote this second edition in Granada, Spain, with support, collegiality, and friendship of F. Javier Huertas of the CSIC Instituto Andaluz de Ciencias de la Tierra. So many other colleagues enrich my understanding and appreciation of geological and environmental systems; two in particular are Jon Kim of the Vermont Geological Survey and Chris Klyza of Middlebury College. I have a great cohort of colleagues at Middlebury College in the Geology Department and in the Environmental Studies Program. Many generations of students in GEOL 323 (Environmental Geochemistry) have provided inspiration, corrections, and recommendations – too many to name them all – but a few that stick out include Bayu Imaduddin Zulkifli Ahmad, Katharine Fortin, Andrew Hollyday, Josh Johnson, Emmet Norris, and Kate Porterfield. Seongnam An, a PhD candidate at Korea University and Korea Institute of Science and Technology (KIST) in Seoul, provided much excellent feedback, for which I am grateful. Editorial handling by Antony Sami, Vimali Joseph, Andrew Harrison and others at Wiley is also much appreciated.