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Chlorine dioxide (ClO2) degradation of the organophosphorus pesticides azamethiphos (AZA) and dimethoate (DM) (10 mg/L) in deionized water and in Sava River water was investigated for the first time. Pesticide degradation was studied in terms of ClO2 level (5 and 10 mg/L), degradation duration (0.5, 1, 2, 3, 6, and 24 h), pH (3.00, 7.00, and 9.00), and under light/dark conditions in deionized water. Degradation was monitored using high-performance liquid chromatography. Gas chromatography coupled with triple quadrupole mass detector was used to identify degradation products of pesticides. Total organic carbon was measured to determine the extent of mineralization after pesticide degradation. Real river water was used under recommended conditions to study the influence of organic matter on pesticide degradation. High degradation efficiency (88–100% for AZA and 85–98% for DM) was achieved in deionized water under various conditions, proving the flexibility of ClO2 degradation for the examined organophosphorus pesticides. In Sava River water, however, extended treatment duration achieved lower degradation efficiency, so ClO2 oxidized both the pesticides and dissolved organic matter in parallel. After degradation, AZA produced four identified products (6- chlorooxazolo[4,5-b]pyridin-2(3H)-one; O,O,S-trimethyl phosphorothioate; 6-chloro-3-(hydroxymethyl)oxazolo[4,5- b]pyridin-2(3H)-one; O,O-dimethyl S-hydrogen phosphorothioate) and DM produced three (O,O-dimethyl S-(2-(methylamino)-2-oxoethyl) phosphorothioate; e.g., omethoate; S-(2-(methylamino)-2-oxoethyl) O,O-dihydrogen phosphorothioate; O,O,S-trimethyl phosphorodithioate). Simple pesticide degradation mechanisms were deduced. Daphnia magna toxicity tests showed degradation products were less toxic than parent compounds. These results contribute to our understanding of the multiple influences that organophosphorus pesticides and their degradation products have on environmental ecosystems and to improving pesticide rem

The study monitored the contamination of fish muscle tissue by elements Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn at 17 sampling sites, in order to assess the pollution status of the main rivers in Serbia. Of the six commercially important fish species included in the study (pikeperch Sander lucioperca, catfish Silurus glanis, bream Abramis brama, barbel Barbus barbus, chub Squalius cephalus, nase Chondrostoma nasus), the bioconcentration factor (BCF) indicated that benthivore bream and barbel and predatory catfish have the highest tendency toward the accumulation of elements. This study achieved its primary objective and produced a contamination map of Serbia as a basis for further research. The estimated metal pollution index (MPI) showed the Tisa River to be unaffected by direct pollution (with an MPI value of 0.31) and the West Morava and Pek rivers to be affected (with MPI values of 1.92 and 0.73 for the WM1 and WM2 sampling sites and 0.65 for the Pek sampling site). Over the past two decades, Serbia has not expanded its industrial activity, which has resulted in the barely noticeable anthropogenic input of heavy metals in the rivers close to industry, and the main rivers are mostly unaffected and slightly affected. We assumed that pollution by heavy metals in the 1990s was trapped in the sediment, thus showing an increased concentration of elements in the species that live and feed on the bottom. Hg concentrations exceeded the maximum permitted concentrations (MPCs) only in catfish samples (0.62 mg kg(-1)) from the Danube (D-3 sampling site) and barbel (0.78 mg kg(-1)) from the West Morava (WM1 sampling site), while Cd concentrations exceeded the MPC in catfish samples (0.09 mg kg(-1)) from the Danube (D-1 sampling site) and chub samples (0.1 mg kg(-1)) from the South Morava (SM2 sampling site). The average concentrations of Pb exceeded the MPC in chub and barbel samples (0.32 and 0.82 mg kg(-1), respectively) from the West Morava (WM1 sampling site)