  We characterize adjoint ideal sheaves via ultraproducts and, utilizing this
characterization, study their behavior under pure morphisms. In particular,
given a pure morphism $f:Y \to X$ between normal quasi-projective complex
varieties, a reduced divisor $D$ and an effective $\mathbb{Q}$-Weil divisor
$\Gamma$ on $X$ without common components, we have the following result: if the
cycle-theoretic pullback $E:=f^{\natural}D$ is reduced and $(Y, E+f^*\Gamma)$
is of plt type along $E$, then $(X, D+\Gamma)$ is of plt type along $D$. This
provides an affirmative answer to a question posed by Z. Zhuang.
