20/02/2019 1:00 PM GMT+7 TP HCM
Plastic everywhere! This is what Émilie Strady found when she arrived in Ho Chi Minh City, Vietnam, in 2013. “The level of plastic pollution in the Saigon River is impressive”, exclaims the IRD researcher from the Institut des Géosciences de l’Environnement (IGE or Institute of Environmental Geosciences), whose research has been published recently. However, the researcher was not there to study this type of pollution, only metal pollution. Undeterred by this finding, she decided to expand her research theme and therefore look into aquatic contamination by micro-plastics - smaller than 5 mm - and macro-plastics – larger than 5 mm. While this is a popular topic in the ocean environment, it remains largely unstudied in fresh water, least of all in a developing country.
In conjunction with Parisian researchers from Laboratoire Eau Environnement et Systèmes Urbains (LEESU or Water, Environment and Urban Systems Laboratory), who work on the pollution of the Seine River, Émilie Strady adapted the methodology used to collect plastic contaminants to the Vietnamese situation. “For micro-plastics, plankton nets are generally used, as their mesh size is 300 micrometres, she points out. However, the concentration in the river is such that they fill far too quickly during the usual immersion time”. This time was therefore reduced from 30 minutes to 1 minute! For macro-plastics, samples are supplied by Ho Chi Minh City’s waste management services. “They collect waste floating in the canals every day. Only that captured by nets with a 2 cm mesh size is taken into account”, stresses the researcher.
The content of each filter is then analysed at the Asian Water Research Centre (CARE) where Émilie Strady is posted, and the results are unequivocal in terms of the water quality of the Saigon River: the concentration in macro-plastics is 700 times higher than that of a river running through a major city in a developed country, such as the Seine, while that of micro-plastics is 1,000 times higher. In micro-plastics, Émilie Strady and her partner Kieu-Le Thuy Chung have identified fragments, fibres such as gore-tex or nylon from fishing nets, granules used by plastic industries, polystyrene from food packaging which breaks down rapidly, etc. Macro-plastics consist primarily of fragments of plastic bags and bottles.
The results highlight the mismanagement of waste, with 350 to 7,270 g per inhabitant per year of land-based plastic waste entering the river. In addition, 92% of the fibres are of synthetic origin, which is consistent with the strong presence of the textile industry in the watershed of the Saigon River. “Industrial companies treat their wastewater discharge but the treatments are not suitable for fibres”, Émilie Strady laments.
These results are of interest to local authorities as they strive to improve water management. Efforts are being made to study the life cycle of plastic, by defining the spatial and temporal dynamics of this pollution in the water of estuaries, sediment, seafood, etc.
- via lemag.ild.fr
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