Effect of channel bed sediment on the transport behaviour of
superparamagnetic silica encapsulated DNA microparticles in open channel
Recently, superparamagnetic silica encapsulated DNA microparticles
(SiDNAFe) were designed and in various experiments used as a
hydrological tracer. We investigated the effect of bed characteristics
on the transport behaviour and especially the mass loss of SiDNAFe in
open channel injection experiments. Hereto, a series of laboratory
injection experiments were conducted with four channel bed conditions
(no sediment, fine river sediment, coarse sand, and goethite-coated
coarse sand) and two water qualities (tap water and Meuse water).
Breakthrough curves (BTCs) were analysed and modelled. Mass loss of
SiDNAFe was accounted for as a first-order decay process included in a
1-D advection and dispersion model with transient storage (OTIS).
SiDNAFe BTCs could be adequately described by advection and dispersion
with or without a first-order decay process. Mass loss of SiDNAFe
increased as a function of the surface roughness of the beds. Retention
of SiDNAFe due to surface roughness was 1-2 orders of magnitude greater
than gravitational settling rates, as determined in Tang et al. (2022).
We speculate this was due to boundary layer kinetic attachment. The
dispersive behaviour of SiDNAFe generally mimicked that of NaCl tracer,
although SiDNAFe traveled faster on average due to a smaller effective
cross-sectional area. No pattern was observed between SiDNAFe mass
recovery and water qualities used. DNA concentration data uncertainty
was mostly associated with lower SiDNAFe concentrations in the BTCs.
This research highlights that riverbeds are important sinks, and the
surface roughness affects the fate and transport characteristics of
SiDNAFe when in proximity to the water-sediment interface. SiDNAFe
possess promising potential as a surrogate for multi-tracing
micro-contaminants (e.g., microplastics) in large rivers, which could be
a promising tool for enhancing understanding of hydrological processes.