[北大 稳定同位素分馏]PKU-Lecture 4-Reservoir-transport effect.pdf

Lecture 4: Isotope fractionation in simple and complex systems or processes: Quantification To recap the structure of this course (textbook), we started with concepts and terminologies and followed by the underlying mechanisms of stable isotope fractionation. The two intrinsic isotope fractionation factors can be unified. Simple mixing phenomena have been introduced and explored. Now, we proceed to explore more complex processes in the real-world. 1 读万卷书 行万里路 The real-world problem is often a mixture of both equilibrium and non- equilibrium fractionation processes. They are rarely just composed of one single elemental step. Natural processes are often complex series or network of many elemental steps with or without reaching equilibrium. I will start with a group of representative cases to introduce mathematical tools that can be used to quantify isotope fractionation phenomena. The mathematic operations have mostly been worked out in disciplines related to chemical kinetics and transport. We do not need to reinvent the wheels, but we need to plug in our own terminologies such as R, δ, ∆, and α. What’s different when applying these operations to stable isotopes is that we have to work with a set (usually two or three) of parallel equations in order to express the processes in terms of R or δ notations because R or δ are obtained by dividing the two sets of equations. Later in the course when we deal with higher-dimensional cases (see next chapter) you will see that the term θ will be obtained when we divide three set of equations, e.g. 16O, 17O, 18O, or four sets when dealing with 32S, 33S, 34S, and 36S. 2 读万卷书 行万里路 In cases of thermodynamic equilibrium processes