Microplastic pollution is concerning because it is widespread in aquatic environments and there is growing evidence of negative biological effects. Here, we present one of the first studies to examine microplastic pollution (plastic particles <1 mm) in urban wetlands and investigate relationships between contamination and urban land use. Sediment samples were collected from twenty independent urban wetlands, each with different types of urban land use within their catchments. Microplastics were observed at all wetlands, with an average abundance of around 46 items/kg of dry sediment. Plastic fragments were the most common type of microplastic, accounting for 68.5% of all microplastics found. Consistent with other studies, microplastic abundance was positively correlated with increased catchment urbanisation. On closer examination, plastic fragments and beads correlated with catchment urbanisation. Fragment abundance also increased in wetlands with catchments that had a higher proportion of industrial land use and decreased in catchments with higher residential densities. This study demonstrates the susceptibility of urban wetlands to microplastic pollution, further highlighting the ubiquitous nature of microplastic pollution. The prevalence of microplastic fragments indicates that plastic litter degradation is a significant source of microplastics in urban environments, especially in industrial areas.
Stormwater has been identified as a pathway for microplastics
(MPs),
including tire wear particles (TWPs), into aquatic habitats. Our knowledge
of the abundance of MPs in urban stormwater and potential strategies
to control MPs in stormwater is still limited. In this study, stormwater
samples were collected from microlitter capture devices (inlet and
outlet) during rain events. Sediment samples were collected from the
material captured in the device and from the inlet and outlet of a
constructed stormwater wetland. MP (>25 μm) concentration
in
stormwater varied across different locations ranging from 3.8 to 59
MPs/L in raw and 1.8 to 32 MPs/L in treated stormwater, demonstrating
a decrease after passage through the device (35–88% removal).
TWPs comprised ∼95% of all particles, followed by polypropylene
(PP) and poly(ethylene terephthalate) (PET). The concentration of
TWPs ranged from 2.5 to 58 TWPs/L and 1450 to 4740 TWPs/kg in stormwater
and sediment, respectively. A higher abundance of MPs was found in
the sediment at the inlet of the constructed wetland compared to the
outlet, indicating a potential role of wetlands in removing MPs from
stormwater. These findings suggest that both constructed wetlands
and microlitter capture devices can mitigate the transport of MPs
from stormwater to the receiving waterways.
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