Deep-Sea Plastic Accumulations by Turbidity Currents: NW South China
Boulder, Colo., USA: Benthic plastic litter is a main source of pollutants
in oceans, but how it disperses is largely unknown. This study by Guangfa
Zhong and Xiaotong Peng, published today in Geology, presents
novel findings on the distribution patterns and dispersion mechanisms of
deep-sea plastic waste in a submarined canyon located in the northwestern
South China Sea.
Evidence collected from a series of manned submersible dives indicate that
the plastic litter items transported and deposited in the canyon are most
likely controlled by turbidity currents. Here the plastic litter items are
highly heterogeneously distributed: Up to 89% of them occur in a few scours
of the canyon.
The plastic items are mostly accumulated in longitudinal litter piles of
2–61 m long, 0.5–8 m wide, and 0.1–1.2 m high on average (Figures 1 and 2).
Plastic particles and fragments generally occurred on the upstream-facing
sides of large boulders and other topographic obstacles, indicating
obstruction during down-valley transportation (Figure 1). Furthermore, the
litter piles were mostly distributed in the up-valley dipping slopes
downstream of the scour centers (Figure 3), which is tentatively linked to
the deceleration of turbidity currents after shedding down the steep
upstream slopes of the scours and undergoing a hydraulic jump at the scour
centers. This interpretation is supported by the sedimentological evidence
from grain-size analysis of associated seabed sediment.
The results of this study lend support to the hypothesis of
turbidity-current–controlled dispersion of plastic litter and bear
implications on deep-sea environmental protection and surveillance. The
focused and patterned distribution of benthic plastics in the canyon that
can be reasonably explained by morphodynamic interactions sheds light on
monitoring or even removal of deep-sea macro-plastic pollutants.
Transport and accumulation of plastic litter in submarine canyons—The role of gravity flows
Guangfa Zhong; Xiaotong Peng
Contact: Guangfa Zhong, firstname.lastname@example.org, State Key Laboratory of Marine Geology, Tongji
University, School of Ocean and Earth Science, Shanghai
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