Pollution And Comprehensive Health Risk Assessment Of Polycyclic Aromatic Hydrocarbons In Roadside Multiple Medias

Due to the rapid development of its economy,China has the second-largest cars in the world.It is noted that heavy metals and polycyclic aromatic hydrocarbons(PAHs)which are derived from cars have led to serious environmental problems.According to the reports of the World Health Organization,the number of deaths and shorter life persons related to air pollution has increased rapidly.It is well known that the pollutants released by the vehicles almost cover all kinds of air pollution factors,so the transportation pollution has become the main source of environmental pollution.Vehicles derived PAHs can enter the roadside soil-crop systems through various ways(road dust,atmospheric dry and wet deposition),and pose a great threat to human health because of their accumulation in foods.Therefore,it is crucial to study the environmental media of PAHs in order to protect human health and road-domain environment security.The study is based on the chain of "source-transfer-contamination-influence",and takes the 310 National Highway and 30 Highway as examples.First,we used the universal kriging to predict the spatial distribution of PAHs,and evaluate the pollution situation by the single contamination index,Nemero pollution index and toxic equivalent concentration.Then,the adjusted health exposure parameters were performed to assess health risk.The main conclusions were as follows:(1)The spatial distribution of?PAHs in roadside soil showed that the concentration in soils varied with the distance from the highway,especially in the northern part of BQ transects.The space distribution patterns of PAHs was significantly different.HMW PAHs had the same spatial pattern with?PAHs,but was different from LMW PAHs.(2)Traffic-source PAHs had an effect on roadside soil.The average contents of?PAHs in the roadside soils of the four section(BQ,ZF,WG,BD)were 74.63?g·kg-1,70.10?g·kg-1,61.80?g·kg-1,and 106.37?g·kg-1,respectively.The Nemerow composite index(P)were used to assess the environmental pollution and the integrative environmental quality of soil.Compared with the environmental standards of the Canada,the Nemerow composite indexes of the 9 PAHs range from 0.07 to 0.33,which indicates that all sections are safe.It is also noted that several sites adjacent to road had been slightly polluted.The 310 national highway which had longer operating time,larger traffic flow and heavier vehicle than the 30 highway released more PAHs to roadside soils.The single factor index,P,?PAHs and?TEQ all show the same spatial patterns:the values significantly decrease within the range of 20 m from the roadbed,show wave trend ranging from 20 to 150 m,and keep stable in the range of 150 to 1000 m.According to Maliszewska-Kordybach,the roadside soils within 20 m was slightly polluted,and the roadside soils within 20?1000 m had not been polluted.The PAHs in the south of roadside soil was higher than those in the north.The PAHs in cultivated soil was significantly higher than that in forest soil.(3)The methods of triangular chart,diagnostic ratios,correlation analysis,principal component analysis(PCA)and multiple linear regression analysis(MLR)were used to identify the source of PAHs.The results showed that the PAHs in roadside soil come from the same source.PCA and MLR analysis revealed that vehicle emission,combustion and non-combusted related petroleum were the main sources of PAHs in roadside soil.The contribution rate was 58.86%(BD section)and 64.43%(BQ section),Vehicle emission was the main pollution sources.(4)Traffic-source PAHs had an effect on roadside total suspended particulate matter(TSP).The 4-ring and 5-ring PAHs were the dominant species.Total PAHs concentrations in TSP in south of road ranged from 4.81 to 10.25 ng·m-3 with a mean of 7.01 ng·m-3,and the?PAHs content in north of road ranged from 1.75 to 6.84 ng·m-3 with a mean of 4.03 ng·m-3.The average mean of PAHs on the south side of the highway was higher than that on the north side.The?TEQ of PAHs in TSP was lower than the standard of WHO and Ambient air quality standard(GB3095-2012).The content of TSP,?PAHs of TSP and?TEQ on the south side of highway had the similar spatial distribution:the values increase with the distance,then decrease,but the values decrease with the distance to the subgrade increased on the north side of highway.The migration and deposition of atmospheric particulate matter was an important source of PAHs in the roadside soils.(5)Traffic-source PAHs had an effect on roadside precipitation.The detection rate of PAHs in roadside rain was low.The 2-ring,3-ring and 4-ring PAHs were the dominant species.The?PAHs concentrations of the precipitation on the south side of highway ranged from 0.41 to 15.03?g·L-1 with a mean of 1.74?g·L-1.And the?PAHs content in north of road ranged from 0.35 to 1.44?g·L-1 with a mean of 0.71 ng·m-3.and The average mean of PAHs of rainfall in south of road was higher than that in north.Overall,The PAHs content of rainfall was lower than other research results.The average?TEQ in rainfall on the south side of highway was ten times longer than the limit about BaP of "environmental quality standard of surface water"(GB3828-2002),and had higher pollution risk,But there was no pollution about PAHs in north rainfall.The content of?PAHs of rainfall on the south side of highway exhibited bimodal distributions.While The content of?PAHs of rainfall on the north side of highway exhibited decreasing distribution.Atmospheric wet deposition was the main source of soil PAHs in the road area.(6)Traffic-source PAHs had an effect on roadside wheat.The detection rate of PAHs in roadside wheat in BQ was low.The 2-ring,3-ring and 4-ring PAHs were the dominant species.The?PAHs concentrations of wheat on the south side of highway ranged from 2.51 to 44.84?g·kg-1 with a mean of 14.41?g·kg-1.And the?PAHs content on the north side of highway ranged from 0.96 to 29.57?g·kg-1 with a mean of 12.73?g·kg-1.and The average mean of PAHs in wheat on the south side of highway was higher than on the north.The average?TEQ of roadside wheat was lower than the limit about BaP of Standard for limits of contaminants in foods(GB2672-2012).The change trend of NaP in wheat showed decreasing distribution with the roadbed distance increasing.,but the tendency towards Phe and?PAHs was not obvious.The wheat's ability to adsorb to 2-and 3-rings PAHs was strong.The PAHs in roadside wheat and soils showed weakly correlation.(7)The values of HQ and HI are less than 1 for all 9 PAHs in four research sections(BQ,ZF,WG,BD),meaning that there was no non-cancerigenic health risk.The CR for seven PAHs was lower than 10-6,meaning that there was no cancerigenic health risk.The evaluation results of health risk about wheat and TSP were consistent with that in soil.The MHI of PAHs exposure to multiple mediums on BQ section was less than 1,which illustrates that there was no non-cancerigenic health risk.The mean value of MHI in the south was higher than that in the north.The consequence of contribution rate for different mediums to MHI was wheat grain>soil>airbone particulate matter.The values of MHI are skewed distribution.The value of MCR was lower than 10-6,revealing that there was no cancerigenic health risk.The main exposure medium for PAHs health risk was soil.The change trend of MCR showed the distribution of exponential decline.