Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul Baseline Contamination status and temporal trends of persistent toxic substances in sediment cores from coastal areas of central Vietnam Trinh Thi Tham a , Hoang Quoc Anh b,c, ⁎ , Bui Thi Phuong a , Le Thi Trinh a , Nguyen Thi Thu Thuy d , Nguyen Thi Hong Yen e , Tran Manh Tri b , Tu Binh Minh b, ⁎⁎ a Faculty of Environment, Hanoi University of Natural Resources and Environment, Cau Dien, Tu Liem, Hanoi, Viet Nam b Faculty of Chemistry, University of Science, Vietnam National University, Hanoi, 19 Le Thanh Tong, Hoan Kiem, Hanoi, Viet Nam c Center of Advanced Technology for the Environment, Graduate School of Agriculture, Ehime University, 3-5-7 Tarumi, Matsuyama 790-8566, Japan d Faculty of Chemistry, TNU University of Science, Thai Nguyen University, Tan Thinh Ward, Thai Nguyen City, Viet Nam e National Institute of Hygiene and Epidemiology, Hai Ba Trung, Hanoi, Viet Nam ARTICLEINFO Keywords: OCPs PCBs PBDEs Sediment cores Vietnamese coastal areas ABSTRACT Residue concentrations of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and poly- brominated diphenyl ethers (PBDEs) were measured in sediment core samples from two estuary areas of central Vietnam to elucidate recent status and temporal trends of pollution based on the depth profles. Concentrations of PCBs, PBDEs, and endosulfan compounds were generally higher than those of the remaining OCPs. Peak concentrations of OCPs were found in the sediment layers corresponding to the late 1950s to the early 1980s, implying the intensive application of these insecticides in Vietnam during such periods. Although the highest PCB concentrations were measured in sediment layers dated in the 1970s, increasing PCB residues observed in the shallower layers may be related to the strong industrialization and urbanization in Vietnam. BDE-209 ex- hibited increasing concentrations and proportions to total PBDEs towards shallower depths, suggesting sub- stantial use and on-going releases of deca-BDE products in recent years. Persistent toxic substances (PTS) such as organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated di- phenyl ethers (PBDEs) are of concern due to their features of environ- mental persistence, bioaccumulation, and toxicity, and were listed in the Stockholm Convention as banned or restricted chemicals (UNEP, 2018). Global contamination and deleterious efects of these pollutants have been widely documented, and available data suggest that the East Asian region have recently received considerable attention with high degree of contamination due to the rapid urbanization and in- dustrialization processes (Tanabe and Minh, 2010; Tri et al., 2016; Minhetal.,2016).Vietnamhasastrategicpositionlocatedatthecenter of the Southeast Asian region with>3000 km of coastal areas and two major agricultural production areas: the Red River and the Mekong River Delta. In recent years, open landfll dumping sites for municipal wastes and informal waste processing areas in the two Vietnamese river deltas have become hotspots of environmental pollution and human exposure to OCPs, PCBs, and brominated fame retardants like PBDEs (Eguchi et al., 2013; Tue et al., 2013; Matsukami et al., 2015, 2017; Minhetal.,2016; Wangetal.,2016; Anhetal.,2017,2019a,2020).On theotherhand,studiesontheoccurrenceofPTSinmarineenvironment of Vietnam are still limited. Some earlier studies have reported residue concentrations of PCBs and PBDEs in surface sediment samples col- lected along coastal line of central Vietnam and highlighted the role of anthropogenic activities in the emission of these substances (Giuliani et al., 2011; Romano et al., 2013). Our recent investigation provided the most current data for the spatial distribution of OCPs, PCBs, and PBDEs from various estuarine locations in central coast of Vietnam (Tham et al., 2019). A majority of PTS investigations in Vietnam has focused on surface sediments, and little is known about the depth profles of PTS in sedi- ment cores from marine environment. Giuliani et al. (2011) analyzed PCBs in several sediment core samples collected from coastal lagoons of central Vietnam and found constant temporal trends or increasing le- vels near surface layers. A similar picture of such vertical profles was also observed for polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) anddioxin-likePCBsinsomesedimentcorestakenfromofshore waters of central Vietnam (Tri et al., 2016). To our knowledge, no compre- hensive data about multiple classes of PTS such as OCPs, PCBs, and https://doi.org/10.1016/j.marpolbul.2020.111222 Received 24 March 2020; Received in revised form 17 April 2020; Accepted 23 April 2020 ⁎ Correspondence to: H. Q. Anh, Center of Advanced Technology for the Environment, Graduate School of Agriculture, Ehime University, Japan. ⁎⁎ Correspondence to: T. B. Minh, Faculty of Chemistry, University of Science, Vietnam National University, Hanoi, Viet Nam. E-mail addresses: hoangquocanh1990@gmail.com (H.Q. Anh), tubinhminh@gmail.com (T.B. Minh). Marine Pollution Bulletin 156 (2020) 111222 Available online 03 May 2020 0025-326X/ © 2020 Elsevier Ltd. All rights reserved. T