Environmental processes are occurring in a complex and interrelated web of processes, and can be compared to self-regulating and self-sustaining systems, with abundant feedbacks, emergent properties, and tipping points. Cells are examples of autopoietic (generating its own boundaries), while ecological systems are sympoietic (boundary-less) systems. Aquatic and environmental chemistry rely on a description of coupled equilibrium thermodynamic equations, as well as a kinetic description of geochemical processes. Energetic considerations of both chemical and biological processes often rely on a well-known suite of enzymatic reactions that can accelerate otherwise sluggish reactions. The overall reaction of several pathways is fastest, when coupled in parallel, and slowest, when coupled serially. While in this open access book, classical equilibrium thermodynamic concepts are presented, along with kinetic descriptions, they are over-simplifications of complex, self-regulating environmental systems. Classical and complex systems approaches need to be considered for understanding how natural systems respond and attenuate pollutant effects. Case studies accompany some of the chapters to further illustrate this point.

Dr. Peter H. Santschi is a distinguished professor in the Department of Marine and Coastal Environmental Sciences at Texas A&M University, Galveston, TX, USA. He received his training in Geochemistry and Oceanography during his post-graduate work at L-DEO at Columbia University, N.Y., after graduating from the University of Bern, Switzerland, with a Ph.D. in Chemistry in 1975. Dr Santschi’s research interests include Marine and Environmental Chemistry, and Environmental Radiochemistry and Biogeochemistry. He is the author and co-author of more than 400 journal articles and book chapters, many of them related to the role of natural organic matter, in particular, exopolymeric substances, play in the self-cleansing capacity of aquatic systems.

Dr. Antonietta Quigg is a Regents Professor in the Department of Marine Biology at Texas A&M University, Galveston, TX, USA. She received her training in Chemistry and Biochemistry as an undergraduate at La Trobe University and Ecology and Evolutionary Biology at Monash University as a graduate student, both in Melbourne, Australia. Dr Quigg then completed a postdoc at Rutgers Universities Institute for Marine and Coastal Sciences where she studied the evolution of phytoplankton. Dr. Quigg’s research interests are diverse and include marine and environmental chemistry, pollutant and emergent contaminant effects of the microbial communities which occupy estuarine, coastal and open ocean environments. She is the author and co-author of more than 190 journal articles and book chapters.