Emergent conservation in atmospheric chemical mechanisms

Abstract

Conservation laws are time-invariant properties that constrain many physical systems. For systems of chemical reactions, conservation of mass constrains how atoms flow between chemical species. Here, we demonstrate that chemical reaction networks can display emergent conserved quantities not explained by mass conservation that arise instead from coupled kinetics. While some of these kinetic relationships can be immediately recognizable in simple chemical systems, more complex mechanisms have hidden nontrivial relationships between species. We identify these emergent relationships as a broader class of invariant behavior in atmospheric chemical mechanisms, which we call kinetic invariants. Kinetic invariants emerge when branching reactions with proportional rates cause species concentrations to evolve in lockstep, and can be found across atmospheric chemical mechanisms spanning orders of magnitude in complexity. Identifying kinetic invariants can provide theoretical bounds for exact mechanism reduction and reveal underlying relationships in the atmospheric chemical system.

15 pages, 3 figures (main text) 17 pages, 4 figures (supporting info), excluding citations