Spatial distribution of legacy pesticides in river sediment from the Republic of Moldova

Historical use of organochlorine pesticides (OCPs) in the Republic of Moldova could pose a potential risk for the aquatic environment due to the persistence, bioaccumulation and toxic properties of these environmental pollutants. However, knowledge on environmental concentrations of legacy OCPs in Moldova is limited. In this study, surface sediment from the two main rivers; Dniester (8 sites, n = 15) and Prut (6 sites, n = 12), and two tributary rivers; Bic (11 sites, n = 11) and Raut (6 sites, n = 6), were collected during 2017-2018 and analyzed for hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs) and their transformation products (DDDs and DDEs) using gas chromatography coupled to mass spectrometry (GC-MS/MS). Sediment concentrations of Sigma 6DDX (1.9-140 ng g(-1) dry weight (dw)) and Sigma(4)HCHs (n.d-2.5 ng g(-1) dw) were found. In the big rivers, the average Sigma 6DDX concentration (18 ng g(-1) dw) were 35 times higher than Sigma(4)HCHs (0.51 ng g(-1) dw). Whereas, in the small rivers the average Sigma 6DDX concentration (32 ng g(-1) dw) was approximately 41 times higher than Sigma(4)HCHs (0.77 ng g(-1) dw). Compared to previous studies from Eastern Europe, the sediment levels were generally similar as found in Moldova's neighboring countries (Romania and Ukraine). Overall, the contamination profile indicates long-term ageing of OCPs used in the past in the agricultural sector. Less than half of the sites (45%) had levels that pose a potential risk for benthic organisms. Hence, further work is needed to determine the bioaccumulation of OCPs in the aquatic food web in this region and the associated risks to ecosystems and human health.