Distribution Characteristics And Ecological Risk Assessment Of Polycyclic Aromatic Hydrocarbons From The Upper Reach Of The Huaihe River

Polycyclic aromatic hydrocarbons?PAHs?are a class of toxic pollutants that are ubiquitous in the environment and mainly originate from incomplete combustion?fossil fuels,biomass and coke?.Due to their persistence,long-range transport properties,toxicity,carcinogenicity,mutagenicity and bioaccumulation,PAHs have certain risk to aquatic organisms and human health.The Huaihe River is one of the seven major rivers in China and the source of drinking water in Xinyang.Previous studies were focused on distribution and sources of PAHs in water and sediment,but there was little information about seasonal variation and pollution history of PAHs.Therefore,the surface water,suspended particulate matter?SPM?and surface sediment samples were collected from the upper reach of Huaihe River in dry period of December 2013,level period of April and flood period of August 2014,respectively.This research analyzed the concentration,component characteristics and source of PAHs in different periods in water,SPM and sediment,discussed the correlativity between PAHs and organic carbon,black carbon in sediment,evaluate the combined ecological risk of PAHs in water using the probabilistic risk assessment method.It hoped that the characteristics of PAHs revealed in this study could serve as a reference for the development of relevant remedial strategies for the management of Huaihe River.An isotopic dating method and sediment core were used to reconstruct the high-resolution atmospheric deposition record of PAHs,in order to trace the history and predict the trend of PAHs from the upper reach of Huaihe River.The results showed that:The concentrations of total PAHs ranged from 79.94 to 421.07 ng/L with the average values of 140.37 ng/L in water,and the 3-ring PAHs was predominant.The concentrations of total PAHs ranged from 268.12 to 2816.90 ng/g with the average values of 986.13 ng/g in SPM,and the 2-ring PAHs was predominant.Compared with other rivers around the word,the concentrations of PAHs in water and SPM from the upper reach of Huaihe River were in the medium pollution level.Typical seasonal variations were that the concentration of PAHs was the highest in the dry period,and the lowest in the flood period in water.In SPM,typical seasonal variations were that the concentration of PAHs was the highest in the dry period,and the lowest in the level period.The ratios of Ant/?Ant + Phe?and Fla/?Fla + Pyr?reflected PAHs in water and SPM were from the mixed of petroleum origins and wood,coal combustion.Total PAHs concentrations varied from 3.96 to 379.27 ng/g with the average values of 65.29 ng/g in surface sediment and the 4-ring PAHs was predominant.The concentrations of PAHs in sediments were at low level,compared with some other rivers around the word.Typical seasonal variations were that the concentration of PAHs was the highest in the level period,and the lowest in the dry period in surface sediment.In the dry and level period,4-ring PAHs was predominant,however,3-ring PAHs was predominant in the flood period.PCA/MLR showed that sediment samplings were mainly suffered from the burning of fossil fuel source in three periods,the contribution rate was 60.33%,57.92% and 69.71% in the dry,level and flood period.The correlation showed that TOC and BC had no effect on the concentration of PAHs in dry and flood period,but there was significant correlation between the concentration of PAHs and TOC,BC in level period.A ²¹⁰Pb and ¹³⁷Cs dated sediment core was used to reconstruct the high-resolution atmospheric deposition record of PAHs,in order to trace the history and predict the trend of PAHs in this area.From 1912 to 2014,the concentration of PAHs in sediment core ranged from 2.31 to 21.86 ng/g and average deposition rate was 0.58 cm/year.The vertical variation of PAHs was consistent with the economic development of our country.Since the 1970 s,there was a sharp increase of PAHs concentrations in the studied core.The contribution of low molecular weight gradually decreased and high molecular weight increased which reflected the inevitable transformation from an agricultural economy to an industrial economy.The concentration of PAHs was affected by TOC and BC in sediment core.PCA/MLR showed that PAHs was mainly from the burning of fossil fuels which contribution rate was 60.12%.Overlapping areas of probability density curves and margin of safety?MOS10?were used to estimate the combined ecological risk of seven PAHs to aquatic organisms.The results showed that ?PAH7 had certain risk to aquatic organisms.The risk of ?PAH7 in sediment was the highest while in water was the lowest.In different period,the risk of ?PAH7 in flood period was the highest and level period was the lowest in water.In SPM and sediment,the risk of ?PAH7 in dry period was the highest,while the level period was the lowest.Comparing the risk of PAHs in sediment in 2007,this study was lower.