Aquatic Chemistry Concepts

There’s a lot to like about a book on water chemistry that lays it out simply. Einstein said that everything should be as simple as it can be, but not simpler. Wise advice. And that is what James F. Pankow has accomplished in the second edition of his textbook, Aquatic Chemistry Concepts. It covers the “waterfront” of essential inorganic chemistry topics, and it supplies enough examples to lead the student toward problem solving. Pankow appropriately begins in the Introduction (Part I) with definitions and the theoretical basis for solving chemical equilibrium problems—thermodynamics. Part II of the book on Acid/Base Chemistry is a tour de force, from mass balances to the chemistry of dissolved carbon dioxide. Pankow’s Aunt Fatima injects humor along the way, and flashbacks from his college chemistry instructors are especially pertinent. Acid/base examples from household vinegar to ammonia illuminate the path, while “Geek Optional” boxes lend additional insight. I especially enjoyed Chapter 9, which includes problems on acid rain, acidification of lakes, and “the most worrisome” example of all, ocean acidification. When Professor Pankow published the first edition of Aquatic Chemistry Concepts in 1991, the global atmospheric concentration of carbon dioxide, a weak acid, stood at 354 parts per million (ppm). Today it is 415 ppm, a 17% increase in concentration in less than 30 years. Likewise, the pH of the surface of the ocean off Hawaii has declined from 8.12 to 8.05 – meaning a similar 17% increase in H+ concentration (see Example 9.13). Imagine … we have increased [H+] in the ocean, the base of the food chain for all aquatic life, by 17% in one generation. Aquatic chemistry concepts don’t lie. We have known since 1862 and John Tyndall’s famous experiments that CO2 absorbs back radiation and heats the atmosphere. Our real-life planetary experiment verifies the physics every year, and the average global temperature is now 0.5 °C (0.9 °F) warmer than when the first edition was published. If we fail to rein in our fossil fuel emissions of CO2 and other greenhouse gases, the signal will continue to grow ever hotter in coming decades. This textbook teaches an urgent lesson. Today, all the “master variables” that control aquatic chemistry are changing—pH, temperature, salinity, and oxidation-reduction potential. Part III explains Metal/Ligand Chemistry, and Part IV discusses the topic of Mineral Solubility. Changing ocean salinity, temperature, and pH render all these reactions in a state of planetary flux. Even the quality of our drinking water is subject to change as the master variables change. Fortunately, foundational concepts in Pankow’s book allow us to make the relevant calculations. Part V on Redox Chemistry and Part VI on Effects of Electrical Charges on Solution Chemistry further elucidate systems that are strong functions of the changing state variables of pe and pH. Although some of the most difficult chemical concepts are contained in these final chapters, Pankow lays them bare—as simple as possible, but not simpler. In the Preface to Aquatic Chemical Concepts, 1st Edition, Pankow warned, “The scope of local, regional, and global environmental problems seems to grow with each passing day. We are in a race which we do not wish to lose.” That was certainly true in 1991, and it is even more cogent today. Our list of environmental nightmares is enduring and growing—climate change, toxic chemicals, eutrophication, harmful algal blooms, and unsafe drinking water. This book, the 2nd Edition, is an advance in stating the problems simply so we can analyze them quantitatively. Only then can we effect change. -Jerald L. Schnoor, Foreword to the Second Edition