Biomarkers of oxidative stress and antioxidant defences as indicators of different disinfectants exposure in the heart of rainbow trout (Oncorhynchus Mykiss Walbaum)

The aim of this study was to evaluate the impacts of different disinfectants' treatment using in aquaculture on the oxidative stress biomarkers such as thiobarbituric acid reactive substrates (TBARS) and carbonyl derivatives of protein oxidative modification, as well as antioxidant defences [superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione peroxidase (GPx) activity] and total antioxidant capacity (TAC) in the heart tissue of rainbow trout (Oncorhynchus mykiss). In the disinfectants exposure, fish were treated to chloramine‐T (final concentration 10 g m^?3), chloride dioxide (5 g m^?3), formalin (200 mL m^?3) and CIP disinfectant based on peracetic acid and hydrogen peroxide (16 mL m^?3) for 20 min and repeated three times every 3 days. Both chlorine dioxide and formalin treatment was indicated by a significant increase in the level of heart TBARS levels and carbonyl derivatives content and decreased SOD activity. Tissue oxidative stress biomarkers were unchanged upon chloramine‐T or CIP disinfectant exposure. Increased oxidative stress could modify antioxidant defences, principally causing increased CAT activity in the heart tissue of formalin‐ or ClO₂^?‐exposed fish. The correlation between oxidative stress biomarkers and GPx activity indicates that enzymes related to glutathione metabolism were responsible to formalin or ClO₂^?‐induced oxidative stress. Hence, TBARS, carbonyl derivatives and antioxidant defences could be used as biomarkers in evaluating the toxicity of formalin and chlorine dioxide using as disinfectants to trout.     

Formation of Bromate in UV/Cl2, UV/NH2Cl and UV/ClO2 Combining Processes

The effect of UV irradiation on bromate (BrO3-) formation is investigated in H2O-Br--Cl2/NH2Cl/ClO2 systems. It is found that partial bromide ion was oxidized to BrO3- by Cl2/UVC. NH3 can inhibit the forming of bromate effectively, and no production of bromate is observed by NH2Cl/UVC. The bromate formation capability of ClO2/UV system is weaker than that of the Cl2/UV. Furthermore, the amount of bromate produced in ClO2/UVC is larger than that in ClO2/UVA. Both the formation of bromate and the decomposition of chlorine dioxide are improved in acidic conditions, whereas alkaline conditions lead to reverse effects.