Distribution,source,risk Evaluation And Adsorption Of Polycyclic Aromatic Hydrocarbons (PAHs) In Weihe River

Polycyclic aromatic hydrocarbons(PAHs)are a group of persistent organic pollutants(POPs)which have carcinogenic,teratogenic and mutagenic,and it widely exists in water,soil and atmosphere.PAHs in aqueous phase can enter the human body through food chain,which can cause great harm to the human.Weihe River is one of the most important rivers in GuanZhong region in Shaanxi Province,China,and suffered serious organic pollution.As a kind of typical hydrophobic organic pollutants,PAHs are readily introduced into the solid particles from the aqueous phase.During the adsorption processs,Dissolved Organic Matter(DOM)can significantly affect the adsorption between solid and liquid phases,but the mechanism is not clear.Therefore,it is high time to known the concentrations,temporal and spatial distribution,source and environmental ecological risk and adsorption behavior of PAHs.Simultaneously,it is significant that organic pollution control of river in arid areas and water security in GuanZhong region.In this study,there were 37 sampling spots in Weihe River,and the contents of 16 PAHs in water and sediments were determined.The distribution,source and environmental ecological risk of PAHs were analyzed.With phenanthrene and pyrene as the target contaminant,from the presence or absence of DOM angle by batch equilibrium method systematically studied the Weihe river suspended particles of these two target contaminant adsorption kinetics and thermodynamics of the characters of the targets deposited in the Weihe river adsorption mode and mechanism on the matter.This research has acquired following conclusions:1.The temporal distribution of PAHs concentrations were as the following sequence: 2014 > 2015 > 2016,it shows that the ∑PAHs concentrations decreased with years.In 2015 and 2016,the spatial distribution of ∑PAHs concentration in water dissolved phase as the following sequence: upper > middle > lower.For sediments samples,the spatial distribution of ∑PAHs concentration in 2015 as the following sequence: middle > lower > upper,in 2016: upper > lower.> middle.Compared with other polluted rivers in the world,the concentrations of PAHs in the Weihe River were at a moderate level.2.The analysis results of the diagnostic ratios showed that the PAHs in Weihe River originated from both pyrolytic and petrogenic sources.Principal component analysis showed that the main source of PAHs was the coal combustion,followed by the diesel or gasoline combustion or petroleum leakage.The ecological risk assessment with BaP toxicity equivalent method showed that PAHs in the water dissolved phase had serious ecological risk.The results of the ERL/ERM and TEL/PEL and Mean sediment quality guideline(mSQG-Q)showed that the ecological risk of PAHs in sediments is relatively low.3.According to adsorption kinetic experiments,phenanthrene and pyrene adsorption equilibrium was reached in 8 h and 4 h basically,and the adsorption process was in line with the pseudo-second-order kinetic model.The isothermal adsorption process in which suspended particles adsorbed phenanthrene and pyrene was well fitted by Freundlich model and linear model,elevated temperatures will inhibit the adsorption process,reduced adsorption capacity of suspended particles and caused isothermal adsorption process more tend to non-linear.Inaddtion,the process was a spontaneous exothermic reaction which was mainly physical adsorption.4.The time of adsorption equilibrium of phenanthrene and pyrene essentially unchanged.Adsorption kinetic and thermodynamic adsorption process showed that the presence of amino acids adsorption process was similar to absence of amino acids adsorption.The presence of amino acids can decrease adsorption capacity of phenanthrene and pyrene,lead isothermal adsorption process more tend to non-linear,inhibit the adsorption process.