Pollution and potential mobility of Cd, Ni and Pb in the sediments of a wastewater-receiving river in Hanoi, Vietnam

Abstract

Large quantities of untreated industrial and domestic wastewater are discharged from the city of Hanoi into urban rivers. Sediment samples from three sites in the To Lich River in Hanoi were assessed with respect to the concentrations and potential mobility of cadmium (Cd), nickel (Ni) and lead (Pb). Due to very high Cd concentrations up to 700 mg kg(-1) at one site, the sediment was considered highly unsuitable for any types of land use if dredged and disposed of on land. Chemical sequential extractions of wet and anoxic sediment samples showed that Cd and Pb were largely associated with the redox-sensitive fractions and could thus be mobilised following measures such as resuspension or dredging. To assess the potential mobilisation of heavy metals from the anoxic sediment due to oxidation, the samples were exposed to different oxidants (i.e. atmospheric air and hydrogen peroxide) and afterwards submitted to a leaching test. These experiments showed that although oxidation may increase the equilibrium pore water concentrations of heavy metals in the sediments, other sediment mineral fractions seem to effectively immobilise heavy metals potentially released from the oxidisable fraction.

Microbial contamination along the main open wastewater and storm water channel of Hanoi, Vietnam, and potential health risks for urban farmers

“…For example, as shown by Pham-Duc (2012), the estimated risk of diarrhoeal diseases due to the exposure to wastewater reused for rural agriculture across communities in Hanam was 100-fold greater than the acceptable risks (Pham-Duc, 2012). Other hazards and pollutants such as antibiotic-resistant bacteria, heavy metals and toxic chemicals were observed by other studies in the wastewater and sediment of Hanoi city (Ingvertsen et al, 2013;Pham et al, 2015). These findings point to a challenge when aiming at the safe use of wastewater and sediments for any kind of land application.…”

“…This is already practiced in To Lich River and has proven feasible (World Bank, 2013). Of note, the sludge from river and drainage systems is not recommended for use because of likely contamination with heavy metals and potentially other contaminates (Ingvertsen et al, 2013). With regard to non-technical control measures, a multi-barrier approach is recommend (Ilic et al, 2010).…”

“…Several studies have reported high levels of microbial and chemical pollution in river sediments, irrigation water, splashing water used on markets and wastewater-fed foodstuff in Hanoi (Ingvertsen et al, 2013;Nguyen and Dalsgaard, 2014;Kuroda et al, 2015). Adverse health outcomes, such as diarrhoeal diseases, helminth infections and dermatitis, due to exposure to wastewater are well documented Do et al, 2007a;Hien et al, 2007;Pham-Duc et al, 2013).…”

Geographic distribution of cadmium and its interaction with the microbial community in the Longjiang River: risk evaluation after a shocking pollution accident

“…All fractions (except the residual fraction) can become available to biota under changing environmental conditions 8 . Cd also exists in different fractions in different environments, e.g., a significant proportion of the Cd was bound to the exchangeable and carbonate fractions in a slag disposal area 9 , the acid-soluble fraction (carbonates) and Fe oxide bound in a former mining area 10 , the carbonate (Na2EDTA) fraction in sewage sludge-amended soils 11 , the redox-sensitive fractions in wet and anoxic sediment 12 , and the residual fraction in agricultural soils 13 and sediments of a Mexican reservoir 14 . The stability of Cd in different environments differed with its existence form.…”

Evaluation of the quality of drainage sludge in To Lich River basin and the proposal of suitable management solutions

“…These concentrations exceeded acceptable values for sediment and were considered toxic for aquatic life in the river [10][11][12]. TLR sediment was also considered to be unsuitable for land use purposes in agriculture, forestry, industry, commerce and service, or for crop fertilizers [13]. Heavy metals in TLR sediment were mostly generated from anthropogenic activities, such as the discharge of untreated domestic and industrial wastewater from residence and industrial clusters upstream [9,11].…”