  The chemical composition of gas in galaxies can be measured in detail from
absorption spectroscopy. By studying gas in galaxies in this way, it is
possible to investigate the small and faint galaxies, which are the most
numerous in the universe. In particular, the chemical distribution of gas in
absorbing systems gives us insight into cycles of gas in and around galaxies.
Here we study chemical enrichment within 64 Damped Lyman-alpha Absorption (DLA)
systems between $1.7 < z < 4.2$. We use high-resolution spectra from VLT/UVES
to infer dust depletion from relative abundances of several metals. We perform
a component-by-component analysis within DLAs, and characterise variations in
their chemical enrichment. Unlike hydrogen, the metal columns can be
characterised for individual components. We use them to derive the dust
depletion ([Zn/Fe]fit), as an indicator for chemical enrichment. We find that
some DLAs are chemically diverse within themselves, with [Zn/Fe]fit ranging up
to 0.62 dex within a single system. This suggests that absorbing gas within
these galaxies is chemically diverse. Although we do not find a clear trend of
decreasing dust depletion with redshift, we do see that the most chemically
enriched systems are at lower redshifts. We also observe evidence for dust-poor
components at all redshifts, which may be due to the accretion of pristine gas
onto galaxies. We combine the chemical and kinematic properties of the
individual gas components and observe potential signatures of infalling gas,
with low depletion at velocities below $\sim$100km/s, and outflows, with high
depletion and velocities of $\sim$600km/s. We find over-abundances of
alpha-elements (an enhancement of $\sim$0.3dex) and under-abundances of Mn in
several components, which is likely a signature of core-collapse SNe
nucleosythesis in the ISM. We observe these effects mostly at lower levels of
chemical enrichment.
