| The estuary hydrodynamic environment is complex and changes strongly,and the sediment transport volume is large,the material exchange is frequent,and it is easily interfered by human activities.The ETM is the area with the highest SPM concentration in the estuary.It has a trapping effect.In order to initially reveal the effect of the ETM on the transmission process of PAHs,and to explore the changes in the particle size composition of the particulate matter and its effect on the transmission of pollutant at the river-sea interface.In the wet season and dry season,We collected continuously and filtered the water by layer in the ETM of the Jiulong River Estuary in Fujian Province.PAHs,black carbon,organic carbon in the dissolved and particulate phases were detected.The particulate phase was subjected to particle size classification filtering.The changes of the concentration of 5 sizes of particles under the tides and the variation of the PAHs were studied,and the phase distribution of PAHs was discussed based on the composition of OC/EC in the SPM.The paper obtained the following results:1.The concentration of SPM(0.17～0.64 g/L)in the ETM is significantly higher than that of the upstream and downstream,and the bottom layer is higher than the surface layer,and the concentration of SPM will change regularly with the tide.During high and low tides,the concentration of SPM in the surface and bottom increases significantly,and the SPM in the bottom are more significantly affected by the tidal effect and has greater range of variation.The SPM are divided into 5 levels according to particle size:>153 μm,153～63 μm,63～23 μm,23～10 μm,<10 μm.It is found that the concentration of SPM with different particle sizes is different in the ETM.SPM with a particle size of less than 10 μm accounted for the highest proportion in wet and dry season,reaching 43%to 74%,and has the greatest impact on the change in the total concentration of SPM.2.There are seasonal differences in the composition and content of PAHs in the ETM of the Jiulong River.The PAHs in the dissolved phase in the wet season(50.4～433.6 ng/L)>dry season(23.9～147.8 ng/L),the total concentration of the particulate phase basiclly equal(49.5～10387.5 ng/L in the wet season and 97.5～7212.9 ng/L in the dry season),but was significantly higher than the upstream(8.8～196.1 ng/L)and downstream(6.6～995.0 ng/L).The concentration of PAHs in the dissolved phase is similar in the surface and bottom layers,but the concentration of PAHs in the particulate phase in the bottom water is significantly higher than that in the surface water.The Kp of PAHs(Flu,Phe,Fluo,Py)is higher in the surface layer than in the bottom layer in the wet season,and the surface layer is lower than the bottom layer in the dry season,and the Kp value in the dry season is generally higher than that in the wet season.The trend of the Kp value is very close to the tide change,presumably due to the variation of the SPM caused by the hydrodynamic effect in the ETM tide change.3.The total concentration of PAHs in particulate phase has a positive correlation with OC/EC.There is a strong linear relationship between concentration of BaP and OC/EC in the wet season,the correlation index r2 of BaP and OC reached 0.75 and the correlation index r2 of BaP and EC reaches 0.41.It indicates that EC and OC have a significant effect on the adsorption of PAHs.Compared with the adsorption capacity of PAHs,the change of the concentration of SPM has a more significant effect on the distribution of PAHs in the two phases.4.Through the comparative analysis of the concentration of SPM with different sizes and the concentration of PAHs.the concentrations of PAHs and OC in SPM with sizes of 23～63 μm is the highest in the wet season.In the dry season,the concentrations of PAHs in SPM with sizes less than 10 μm is the highest,indicating a large specific surface area for fine particles has a great influence on the adsorption capacity of PAHs. |
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