Levels And Characteristics Of Phthalate Esters And Polycyclic Aromatic Hydrocarbons In The Yangtze River And Jialing River From Chongqing’s Urban Areas

Persistent organic pollutants （POPs） have become widespread pollutants in theenvironment and now represent a global contamination problem. Hazards associatedwith these pollutants are their persistence in the environment, their bioaccumulationpotential in the tissues of animals and humans through the food chain. Phthalate esters（PAEs） and Polycyclic aromatic hydrocarbons （PAHs） are typical POPs substances inthe environment, some of them listed as priority pollutants. Urban are densely populatedareas, residues level of PAEs and PAHs in water body directly affect the health of urbanresidents. So it is great significant to study PAEs and PAHs on urban water body forurban ecological environment. Taking the Yangtze River and Jialing River aroundChongqing’s Urban Areas as a research object, determination of PAEs and PAHs inwater and sediment, multi-media distribution, sources identification and ecological riskassessment have been discussed in this work. The main findings are as following:①Solid phase extraction method （SPE） for the simultaneously enrichment of5PAEsand16PAHs in water samples was optimized by the combination of single parameterdesign, Box-Behnken design and response surface analysis. Supelco-C₁₈solid phaseextraction column was used for experiment.10mL methanol was added to1Lunbuffered water samples. The column was rinsed with3.4mL eluting solvent （mixeddichloromethane, acetone and n-hexane with a volume ratio of1:1:1） with a upflowmode at5.7mL/min. The eluting rate was1.1mL/min. In addition, the sediment sampleswere firstly extracted by organic solution, and then PAEs and PAHs sediments sampleswere purified by aluminum oxide chromatography and silica gel chromatographycolumns, respectively. Both PAEs and PAHs were detected by gas chromatography-Mass Spectrometry （GC/MS）. Ultrasonic extraction conditions were optimized using anorthogonal array design. The results indicated that under the same ultrasonic power of250W, the best extraction conditions for PAEs was ultrasonicated with a frequency of45kHz for12min and for PAHs was dual-frequency （28kHz/45kHz） for60min. Goodrecoveries rates and limits of quantification of target organic matter in water andsediment were obtained.②5PAEs were discussed in water phase, pore water and sediment from theYangtze River and Jialing River around Chongqing’s Urban Areas. The total PAEsconcentration ranged from53.2to10061.3ng/L in water phase, from916.8to 15807.9ng/L in pore water and from1438.9to5045.9ng/g in sediment. PAEsconcentration in pore water was much higher than that in the water phase. In fiveanalyzed PAEs compounds, DnBP and DEHP were the main pollutants in water andsediment. Clay content in sediment was the primary factor affecting PAEs distributionwhile organic matter content had less effect in this study. Results of PAEs partitionbetween sediment solid phase and pore water phase showed that there was nocorrelation between lgK_ocand lg_Kowof PAEs. When the partitioning of DnBPconcentration between measured sediment and the surrounding pore water tended to beclose to equilibrium, DMP and DEP both had strong trends from sediment to pore waterphase and the opposite tendency was significant for DEHP. As compared to the resultsfor other studies, the PAEs concentration of the study region was in a lower-middlelevel.③16polycyclic aromatic hydrocarbons （PAHs） were determined in water phase,sediment and pore water in the study areas. Total PAHs concentration ranged from139.4to1538.6ng/L in water phase,563.5to3831.4ng/L in pore water, and642.8to4630.3ng/g in sediment. PAHs concentration had significantly positive correlation withsilt proportion of the sediment （R²=0.625-0.667，p<0.05）, which indicated that siltfraction was a main factor affecting PAHs distribution. Contamination by PAHs inwater and sediment was moderate in comparison with other areas. Sourcesapportionment by principal component analysis reflected PAHs derived fromincompleted combustion. As for dissolved PAHs, coal, oil combustion accounted for67.8%, natural gas and gasoline combustion accounted for9.4%, petroleumvolatilization and coke source accounted for7.0%. As for PAHs in surface sediments,coal, oil and natural gas combustion accounted for72.4%, petroleum volatilization andcoke source accounted for16.8%.④Sieving was performed to separate the sediments into five sizefractions（>150μm,150-96μm,96-63μm,63-47μm、47-25μm and <25μm）. Significantenrichment of PAEs was found in the four franctions of <96μm （enrichment factorswere between1.35and1.73）. PAHs were mainly enriched in the fractions of>150μm,47²5μm and150⁹6μm. PAEs and TOC content showed a linear negative correlation（R²=-0.784, p<0.05） while PAHs had positive correlation with TOC（R²=0.424）. Blackcarbon （BC） had negeligible influence on the content of PAEs and PAHs.⑤Based on the observed PAEs concentration in water samplings from the YangtzeRiver and Jialing River around Chongqing’s Urban Areas and NOEC values of aquatic organisms, two probabilistic risk approaches were applied to evaluate ecological risks of4PAEs. It was found that10%of the safety margin value was15413.16,53302.42,22.84and33.82for DMP, DEP, DnBP and DEHP respectively, which indicatednone-potential ecological risk for aquatic organism. In addition, application ofprobability distribution curves in the basic safety margin value and using HC₅（hazardous concentration for5%of species） as the endpoint of effect levels, theprobability of exceeding an exposure concentration for DnBP and DEHP were6.010^-3and1.110^-3separately. Moreover, associated with this specific probability of effects for4individual PAEs followed the order of DnBP>DEHP>DEP>DMP, which was inaccordance with the method of margin of safety. Surface sediment’s ecological risk instudy area was assessed with the methods of sediment quality guidelines （SQGs）.Results showed DEHP and DnBP compound was present in excess of the lower ERLand may exist biological effects.⑥Probability methodology were adopted to characterize ecological risk of5PAHs in water samples. Safety margin value indicated that Phenanthrene （Phe）,Fluoranthene （Flu）, Pyrene （Pyr） and Benz[a]pyrene （Bap） had potential ecological riskfor aquatic organism except for Naphthalene （Nap）. The harm probabilities of5%of thespecies affected was0.367,0.394,0.958and0.908for Phe, Flu, Pyr and Bap separately,and the risk was in sequence of Pyr>Bap>Flu>Phe>Nap. The result of ecological riskassessment indicated the concentration levels of PAHs in sediment of the study area hadnot caused the marked negative influence on organism. However, Acenaphthene（Ace）,Fluorene（Fle） and Phenanthrene compounds were present in excess of the lower ERL,and biological effects might exist. The adverse biological toxicity effect mightoccasionally happen in study areas.