Insert a figure, caption and label in a multicols environment

This doesn’t float so will appear exactly where you place it

% preamble
\usepackage[margin=10pt,font=small,labelfont=bf]{caption}   % reqd for captionof in minipage figs
\usepackage{calc}                                           % reqd to calc minipage dims

% image
\begin{minipage}{\linewidth-10pt}% -10pt to avoid hbox overflow
  \includegraphics[width=\linewidth]{img/tas}
  \captionof{figure}{Total Alkali--Silica for Martian igneous rocks \autocite{Filiberto2017}}
  \label{fig:tas}
\end{minipage}%

Referencing

WIP

Macros

These are some of the custom commands I use when producing documents. There are packages that provide similar (and probably better) solutions but these are for when I need to fall back on pandoc to convert to Word etc.

A chemical isotope or isotope ratio

% where #1 is the element and #2 (and #3) are the atmoic mass number
\newcommand\isotope[2]{\textsuperscript{#1}#2}
\newcommand\isotopeRatio[3]{\isotope{#2}#1/\isotope{#3}#1}

Or just use mhchem