Impact Of The Loading And Removal Of Water And Suspended Sediment On The Transpot Of Polycyclic Aromatic Hydrocarbon In The Yellow River Of Henan Section

In 2014,225 samples(25 water samples,25 suspended sediment samples and 25 surface sediments per season,3 seasons as total)were collected during three sampling cruises from 25 sites(16 in the main stream and 9 in the tributaries)located in the Yellow River of Henan Province to survey residual level of polycyclicaromatichydrocarbons(PAHs)in the Yellow River.The concentrations of ?16PAHs in the surface water(dissolved phase and particle phase)and sediment of the Yellow River in Henan Province ranged from 33.6 ng L-1 to 383 ng L-1 and 5.84 to 4670 ng g-1 dw,respectively.Comparing to the residual level of ?16PAHs during 2005,the level significantly declined with the decreasing of coal consumption(from 87.2% to 77.7%)and the increasing of clean energy(natural gas,from 2.20% to 4.50% and hydropower,from 1.90% to 5.30%).In addition,the efficiency of energy conversion for electricity generation and heating by power stations increased from 34.2 % to 43.5% in Henan Province.Meanwhile,the water quality of the Yellow River basin greatly improved,which the percentage of river length up to I-III levels as the total length in Henan Province increased from 43.2% in 2005 to 59.9% in 2014.The pollution level of ?16PAHs in the surface sediment of the Yellow River in Henan Section was relatively low in comparison to the other basin in China and abroad.Both in the sediment and the surface water,the ?16PAHs concentrations in main stream were much lower than those in tributaries,declaring that the tributaries were the important source of the main stream.Especially,the concentrations of ?16PAHs in the main stream obviously rose after the Yiluo River and Qin River feeding into the Yellow River.The composition of the surface sediment were discussed,where the percentage of large rings PAHswere greater than that ofsmall rings PAHs.For the small rings PAHs,the concentrations of Nap displayed slight fluctuation,but the percentage occupying the small rings PAHs and ?16PAHs varied a lot.On the contrary,the percentage of each 9 large rings PAHs changed a little.Positive correlation between SS concentration and concentrations of ?16PAHs in the main stream elucidated that SS was a vital carrier of PAHs,and plotted a trend with decreasing firstly and then increasing.The suspending sediment in the Yellow River were scouring up by the river flow which were deposited mainly due to the hydrological changes of slower flow,from the upper stream.Most values oflgKOC-lgKeq for Nap,Ace,Flu,Phe,Ant,Fla and Pyr are larger than 0,which indicate a releasing status from the SS to the river water for these PAHs.However,the other PAHs mostly present KOC<Keq with a trend that these PAHs are sorbed on SS from water.These results were coincide with the study of PAHs release during the process of sediment resuspension.In addition,the percentage of r-PAHs was much higher than that of s-PAHs,which demonstrated that the SS in the lower reaches of the Yellow River were introduced into the river with not a long time.In the conservation of mass model for water and SS,the SS load of scouring(middle reaches,M1~M8)and deposition(lower reaches,M9~M16)are 38.4 and 42.2 Mt in Henan section of the Yellow River;7.88 Mt SS,maybe the scoured sediment,are diverted away with 50.3 Bm-3 river water from this section by the water diversion project(WDP)in 2014.In the Henan Section of the Yellow River,the loading of ?16PAHs was 6915 kg,and removal was 6161 kg in 2014,the difference of 754 kg could be lost due to air-water exchange or degradation.The loading of ?16PAHs included 3588 kg flowing from the upstream of the Yellow River,368 kg from tributaries,and 2959 kg due to scouring.The removal of ?16PAHs included 3688 kg flowing out to the next section of the Yellow River,1532 kg depositing to the bottom of the river,and 960 kg diverted under WDP program.The influence on the loading and removal of PAHs through the deposition and scouring process were significant,which could equal to the main stream flowing in or out of the Henan Province.Pyr was at the high ecological risk level with the evaluation by the method of overlapping areas of probability density curves and the margin of safety.The overlapping areas of Pyr was 0.15 and the value was less than 1(0.19)indicating that the probability of threatening 10% aquatic organisms was 16.6%.The other 7 PAHs were no ecological risk but the combined ecological risk of 8 PAHs were significantly high with the overlapping areas 0.41 and at 50.8% level threatening 10% aquatic organisms of the Yellow River in Henan Province.