I keep getting line breaks in the middle of the chemical formula NH415NO3. If NH415NO3 comes at the end of a line, sometimes NH4 and 15NO3 are split onto different lines, and the 15 is place before the 4.
Here's my full premble and some text:
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author={Eric Ireland},
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\title{Methods used in \textsuperscript{15}N tracer experiments for measuring DNRA in soils}
\author{Eric Ireland}
%\date{\today}
\begin{document}
\isodate
\newcommand{\fan}{{\ch{^{15}NH4NO3}}\xspace} % \fan = 15NH4NO3 in mbox
\newcommand{\afn}{{\ch{NH4^{15}NO3}}\xspace} % \afn = NH415NO3 in mbox
\newcommand{\an}{{\ch{NH4NO3}}\xspace} % \an = NH4No3 in mbox
\newcommand{\fnto}{{\ch{^{15}N2O}}\xspace} % \fnto = 15N2O in mbox
\maketitle
\begin{abstract}
%abstract goes here
\end{abstract}
For the \ch{^{15}N} field experiment, \SI{100}{\g} oven dried equivalent of fresh, homogenised, sieved soil (\SI{2}{\mm}) was placed in cylindrical vials with sealed bottoms. The bulk density was kept the same as the surround soil at each site. Soils were pre-incubated for \SI{24}{\hour} at the ambient temperature at the site, before \ch{^{15}N} tracer was added. Treatments were \fan or \afn with \ch{^{15}N} at \SI{99.2}{atom\percent} excess. They were added at a rate of \SI{2}{\ug\of{\ch{NO3^{-}-N}}\per\g\of{soil}} or \SI{2}{\ug\of{\ch{NH4^{+}-N}}\per\g\of{soil}} using the 5-needle injection technique, also used by \citet{wang_soil_2016}. Soils were incubated in the field for \SI{139}{\hour}. Soil water varied from \SIrange{50}{55}{\percent} WHC during the incubation. Triplicate samples were collected randomly from each treatment at \SIlist{0.5;40;88;139}{\hour} after \ch{^{15}N} labelling to determine the concentrations and isotopic compositions of \ch{NH4+} and \ch{NO3-}.
For the \ch{^{15}N} laboratory incubations, either \fan or \afn with \ch{^{15}N} at \SI{20}{atom\percent} excess was added. Each treatment had three replicates. \SI{30}{\g} of fresh, sieved soil was incubated in \SI{250}{\ml} conical flasks, and \SI{2}{\ml} of \fan or \afn solution was added to each flask at a rate of \SI{7.14}{\micro\mole\of{\ch{^{15}N}}\per\gram\of{soil}}, i.e. \SI{50}{\ug\of{\ch{NH4^{+}-N}}\per\g\of{soil}} and \SI{50}{\ug\of{\ch{NO3^{-}-N}}\per\g\of{soil}}. Soils were adjusted to \SI{60}{\percent} WHC (does not say whether water was added subsequently to keep them at \SI{60}{\percent} as they dried out). Conical flasks were sealed with rubber stoppers and aired every \SI{48}{\hour} for \SI{1}{\hour}. They were incubated at \SI{25}{\celsius}. Soils were extracted at \SIlist{0.5;24;72;144}{\hour} after \ch{^{15}N} labelling to determine the concentrations and isotopic compositions of \ch{NH4+} and \ch{NO3-}.
\end{document}
