Adil Bakir, Steven J. Rowland, Richard C. Thompson, Transport of
persistent organic pollutants by microplastics in estuarine conditions,
Estuarine, Coastal and Shelf Science, Volume 140, 1 March 2014, Pages
14-21, ISSN 0272-7714, http://dx.doi.org/10.1016/j.ecss.2014.01.004.
(http://www.sciencedirect.com/science/article/pii/S0272771414000110)
Abstract: Microplastics represent an increasing source of anthropogenic
contamination in aquatic environments, where they may also act as
scavengers and transporters of persistent organic pollutants. As
estuaries are amongst the most productive aquatic systems, it is
important to understand sorption behaviour and transport of persistent
organic pollutants (POPs) by microplastics along estuarine gradients.
The effects of salinity sorption equilibrium kinetics on the
distribution coefficients (Kd) of phenanthrene (Phe) and 4,4′-DDT, onto
polyvinyl chloride (PVC) and onto polyethylene (PE) were therefore
investigated. A salinity gradient representing freshwater, estuarine and
marine conditions, with salinities corresponding to 0 (MilliQ water, 690
μS/cm), 8.8, 17.5, 26.3 and 35 was used. Salinity had no significant
effect on the time required to reach equilibrium onto PVC or PE and
neither did it affect desorption rates of contaminants from plastics.
Although salinity had no effect on sorption capacity of Phe onto
plastics, a slight decrease in sorption capacity was observed for DDT
with salinity. Salinity had little effect on sorption behaviour and
POP/plastic combination was shown to be a more important factor.
Transport of Phe and DDT from riverine to brackish and marine waters by
plastic is therefore likely to be much more dependent on the aqueous POP
concentration than on salinity. The physical characteristics of the
polymer and local environmental conditions (e.g. plastic density,
particle residence time in estuaries) will affect the physical transport
of contaminated plastics. A transport model of POPs by microplastics
under estuarine conditions is proposed. Transport of Phe and DDT by PVC
and PE from fresh and brackish water toward fully marine conditions was
the most likely net direction for contaminant transport and followed the
order: Phe-PE >> DDT-PVC = DDT-PE >> Phe-PVC.
Keywords: Marine Strategy Framework Directive; sorption; hydrophobic
organic compounds; brackish waters; plastic particles