Where has the pollution gone? A survey of organic contaminants in Ho Chi Minh city / Saigon River (Vietnam) bed sediments

Abstract

A wide range of persistent organic chemicals, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), some insecticides, as well as polybrominated diphenyl ethers (PBDEs) and some perfluoroalkyl substances (PFASs) were analyzed in 17 bed sediments collected along the Saigon River and at adjacent canal mouths from upstream to downstream in Ho Chi Minh City (Vietnam). Concentrations were rather low for PAHs, as well as for legacy PCBs and dichloro-diphenyl-trichlorethane and metabolites (DDTs), or below detection limits for several PFASs and all PBDEs measured. Several insecticides (chlorpyrifos-ethyl, and the pyrethroids cypermethrin and λ-cyhalothrin) displayed rather high concentrations at a few sites within the city. There was no distinct upstreamdownstream trend for PAHs, (DDTs) or PCBs. Although adjacent canal sediments tended to be more contaminated than Saigon River sediments, the differences were not significant. Emissions are almost certainly substantial for PAHs, and probably also for other contaminants such as PBDEs and some PFASs. During the dry season, contaminants are presumably stored in the city, either in canals or on urban surfaces. Heavy rainfall during the monsoon period carries away contaminated particle flows into the canals and then the Saigon River. The strong tidal influence in the river channel hinders the accumulation of contaminated particles. Contaminated deposits should accordingly be investigated further downstream in depositional environments, such as the mangrove.

Nutrient budgets in the Saigon–Dongnai River basin: Past to future inputs from the developing Ho Chi Minh megacity (Vietnam)

“…As mentioned above, dredging of the urban canals can explain the high removal of P from the system, sediment being much richer in P in canals (Strady et al, 2017). This conclusion is in line with the observations made by Babut et al (2019) on the disappearance of organic pollutants in the Saigon River.…”

“…H C M C is the largest city in Vietnam and one of the most dynamic in the world (World Economic Forum News, January 2017). Because of urban sprawl and the lack of wastewaters treatments, the quality of the water is deteriorating, which endangers the resource as well as the human activities that depend on it (Babut et al, 2019;Nguyen, Le, Bui, Phan, & Visvanathan, 2011;Strady et al, 2017).…”

Phosphorus adsorption/desorption processes in the tropical Saigon River estuary (Southern Vietnam) impacted by a megacity

“…The same trend was observed with Total P in waters. This may be related to the flushing of sediment with high P content from urban canals of HCMC during the wet season; a similar hypothesis of high flushing in the beginning of the wet season was recently proposed by Babut et al (2019). It is also shown that during the dry season P was largely taken up by algae, especially between distance − 40 and − 10 km where Chl-a concentrations increased up to 150 μg L − 1 (Fig.…”

Metals geochemistry and ecological risk assessment in a tropical mangrove (Can Gio, Vietnam)

“…Mangrove river network acts as a unique gate for water outlet from Ho Chi Minh City to the South China Sea. Industrial activities, economic developments and rapid population growth are inducing high pressure on water and sediment quality of the adjacent river, the Sai Gon River (Babut et al 2019, Strady et al 2017. Strady et al (2017) stated that the main rivers and canals in the city were moderately contaminated by major metal(oid)s. Recently, Thanh-Nho et al (2018) highlighted that metals can be transferred over long distance from upstream to the mangrove forest, and that elevated inputs of metals in the estuary were the result of enhanced runoff and soil leaching during the monsoon season.…”