Occurrence, partition behavior, source and ecological risk assessment of nitro-PAHs in the sediment and water of Taige Canal, China

Nitrated polycyclic aromatic hydrocarbons(NPAHs)are widespread organic pollutants that possess carcinogenic and mutagenic properties,so they may pose a risk to the environment and human health.In this study,the concentrations of 15 NPAHs and 16 polycyclic aromatic hydrocarbons(PAHs)in 30 surface water samples and 26 sediment samples were measured in 2018 from the Taige Canal,one of the main rivers flowing into Taihu Lake,China.The total NPAH concentrations in water and sediment ranged from 14.7 to 235 ng/L and 22.9 to 96.5 ng/g dw,respectively.9-nitrophenanthrene(nd–76.3 ng/L)was the dominant compound in surface water,while 2+3-nitrofluoranthene(1.73–18.1 ng/g dw)dominated in sediment.Among PAHs,concentration ranging from 1,097 to 2,981 ng/L and 1,089 to 4,489 ng/g dw in surface water and sediment,respectively.There was a strong positive correlation between the log octanol-water partition coefficient(Kow)and log sediment-water partition coefficient due to hydrophobic interaction.The fugacity fraction value increased with the decrease of log Kow,and chrysene was transferred from water into sediment.The residual NPAHs in surface water and sediment of the Taige Canal have partial correlation.Diesel engine and coal combustion emissions were probably the principal sources of NPAHs in surface water and sediment.The results of ecological risk assessment showed that some NPAHs inwater(e.g,1-nitropyrene and 6-nitrochrysene)and sediment(e.g.,2-nitrobiphenyl,5-nitroacenaphthene,9-nitrophenanthrene and 2+3-nitrofluoranthene)had moderate ecological risks,which should be of concern.

Nitrated and parent PAHs in the surface water of Lake Taihu,China:Occurrence,distribution,source,and human health risk assessment

Nitrated polycyclic aromatic hydrocarbons(NPAHs)have toxic potentials that are higher than those of their corresponding parent polycyclic aromatic hydrocarbons(PAHs)and thus have received increasing attention in recent years.In this study,the occurrence,distribution,source,and human health risk assessment of 15 NPAHs and 16 PAHs were investigated in the surface water from 20 sampling sites of Lake Taihu during the dry,normal,and flood seasons of 2018.The PAH concentrations ranged from 255 to 7298 ng/L and the NPAH concentrations ranged from not-detected(ND)to 212 ng/L.Among the target analytes,2-nitrofluorene(2-n Flu)was the predominant NPAH,with a detection frequency ranging from 85%to 90%and a maximum concentration of 56.2 ng/L.The three-ringed and four-ringed NPAHs and PAHs comprised the majority of the detected compounds.In terms of seasonal variation,the highest levels of the NPAHs and PAHs were in the dry season and flood season,respectively.Diagnostic ratio analysis indicated that the prime source of NPAHs was direct combustion,whereas in the case of PAHs the contribution was predominantly from a mixed pattern including pollution from unburned petroleum and petroleum combustion.The human health risk of NPAHs and PAHs was evaluated using a lifetime carcinogenic risk assessment model.The carcinogenic risk level of the targets ranged from 2.09×10^(-7)to 5.75×10^(-5)and some surface water samples posed a potential health risk.

Degradation of Azo dye direct black BN based on adsorption and microwave-induced catalytic reaction

The novel microwave catalyst MgFe204-SiC was synthesized via sol-gel method, to remove azo dye Direct Black BN （DB BN） through adsorption and microwave-induced catalytic reaction. Microwave- induced catalytic degradation of DB BN, including adsorption behavior and its influencing Factors of DB BN on MgFc204-SiC were investigated. According to the obtained results, il indicated thai the pseudo-second-order kinetics model was suitable fbr the adsorption of DB BN onto MgFc204-SiC. Besides, the consequence of adsorption isotherm depicted that the adsorption of DB BN was in accordance with the Langmuir isotherm, which verified that the singer layer adsorption of MgF%O4- SiC was dominant than the multi-layer one. The excellent adsorption capacities of MgFe204-SiC were kept in the range of initial pH from 3 to 7. In addition, it could be concluded that the degradation rate of DB BN decreased over ten percent after the adsorption equilibrium had been attained, and thc results from the result of comparative experiments manitbsted that the adsorption process was not conducive to the process of microwave-induced catalytic degradation. The degradation intermediates and products of DB BN were identified and determined by GC-MS and LC-MS. Furthermore, combined with the catalytic mechanism of MgFe204-SiC, the proposed degradation pathways of DB BN were the involution of microwave-induced OH and holes in this catalytic system the breakage of azo bond, hydroxyl substitution, hydroxyl addition, nitration reaction, dcamination reaction, dcsorbate reaction, dehydroxy group and ring-opening reaction.