Theoretical insights into the degradation mechanisms, kinetics and eco-toxicity of oxcarbazepine initiated by OH radicals in aqueous environments

As an anticonvulsant,oxcarbazepine(OXC)has attracted considerable attention for its potential threat to aquatic organisms.Density functional theory has been used to study the mechanisms and kinetics of OXC degradation initiated by OH radicals in aqueous environment.A total of fourteen OH-addition pathways were investigated,and the addition to the C8 position of the right benzene ringwas themost vulnerable pathway,resulting in the intermediate IM8.The H-abstraction reactions initiated by OH radicalswere also explored,where the extraction site of the methylene group(C14)on the seven-member carbon heterocyclic ring was found to be the optimal path.The calculations show that the total rate constant of OXC with OH radicals is 9.47×10^(9)(mol/L)^(−1)sec^(−1),and the half-life time is 7.32 s at 298 K with the[·OH]of 10^(−11) mol/L.Moreover,the branch ratio values revealed that OH-addition(89.58%)shows more advantageous than H-abstraction(10.42%).To further understand the potential eco-toxicity of OXC and its transformation products to aquatic organisms,acute toxicity and chronic toxicity were evaluated using ECOSAR software.The toxicity assessment revealed that most degradation products such as OXC-2OH,OXC-4OH,OXC-1O-1OOH,and OXC-1OH’are innoxious to fish and daphnia.Conversely,green algae are more sensitive to these compounds.This study can provide an extensive investigation into the degradation of OXC by OH radicals and enrich the understanding of the aquatic oxidation processes of pharmaceuticals and personal care products(PPCPs).

Specific biotests to assess eco-toxicity of biodegradable polymer materials in soil

Eco-toxicity investigation of polymer materials was considered extremely necessary for their potential menace,which was widely use as mulching materials in agricultural.In this study,polyethylene(PE),polystyrene(PS)and synthetic biomaterials-Ecoflex and cellulose were applying into soil cultivated with two potential indicator plants species:oat(A v ena sati v a)and red radish(Raphanus sativum).Variety of chemical,biochemical parameters and enzyme activity in soil were proved as effective approach to evaluate polymers phytotoxicity in plant-soil mesocosm.The F-value of biomass,pH,heavy metal and electoral conductivity of Raphanus behaved significant different from T0.Significant analysis results indicated biodegradation was fast in PE than PS,besides,heavy metals were dramatically decrease in the end implied the plant absorption may help decrease heavy metal toxicity.The increase value at T2 of Dehydrogenase activity(0.84 higher than average value for Avena&0.91 higher for Raphanus),Metabolic Index(3.12 higher than average value for Avena&3.81 higher for Raphanus)means during soil enzyme activity was promoted by biodegradation for its heterotrophic organisms’energy transportation was stimulated.Statistics analysis was carried on Biplot PC1(24.2%of the total variance),PC2(23.2%of the total variance),versus PC3(22.8%of the total variance),which indicated phosphatase activity and metabolic index was significant correlated,and high correlation of ammonium and protease activity.Furthermore,the effects were more evident in Raphanus treatments than in Avena,suggesting the higher sensitivity of Raphanus to polymers treatment,which indicate biodegradation of polymers in Raphanus treatment has produced intermediate phytotoxic compounds.

Investigation on the eco-toxicity of lake sediments with the addition of drinking water treatment residuals

Drinking water treatment residuals（WTRs） have a potential to realize eutrophication control objectives by reducing the internal phosphorus（P） load of lake sediments. Information regarding the ecological risk of dewatered WTR reuse in aquatic environments is generally lacking, however. In this study, we analyzed the eco-toxicity of leachates from sediments with or without dewatered WTRs toward algae Chlorella vulgaris via algal growth inhibition testing with algal cell density, chlorophyll content, malondialdehyde content, antioxidant enzyme superoxide dismutase activity, and subcellular structure indices. The results suggested that leachates from sediments unanimously inhibited algal growth, with or without the addition of different WTR doses（10% or 50% of the sediment in dry weight） at different p H values（8–9）, as well as from sediments treated for different durations（10 or 180 days）. The inhibition was primarily the result of P deficiency in the leachates owing to WTR P adsorption, however, our results suggest that the dewatered WTRs were considered as a favorable potential material for internal P loading control in lake restoration projects, as it shows acceptably low risk toward aquatic plants.