Risk Assessment Of Polycyclic Aromatic Hydrocarbons In Soil And Maize Along Roadside

Traffic was one of the main sources of polycyclic aromatic hydrocarbons(PAHs)pollution in environment.The pollution caused by traffic had been widely concerned by scholars at home and abroad.A large amount of pollutants would be discharged by vehicles,which could accumulate in the soil through road runoff and atmospheric diffusion,then accumulate in the agricultural products through the soil-plants system,thus affecting the quality of agricultural products and becoming a potential threat to human health.Research on PAHs pollution in farmland along roadside,analysis of the distribution characteristics and the influencing factors of PAHs can provide a theoretical basis for the rational utilization and protection of farmland along roadside,which is of great significance for the prevention and control of PAHs pollution.In this paper,PAHs in farmland soil and maize along 7 main roadside around Changchun and PAHs in farmland soil,maize and maize leaves along main roadsides in Dehui were studied.The concentration of PAHs in farmland soil,maize and maize leaves in our study area was determined,the distribution characteristics of PAHs were analyzed,the sources of PAHs were analyzed,and the comprehensive risk assessment was carried out and the countermeasures of PAHs pollution control in farmland along roadside were put forward.The main conclusions of our study were as follows:The total concentration of PAHs in farmland soil along 7 main roadsides around Changchun city ranged from 1340.69 ng/g to 5230.30 ng/g,with an average value of 2954.93 ng/g and a median value of 2746.90 ng/g.The total PAHs concentration in the farmland soil along the main roadside in Dehui ranged from 197.65 to 5544.10 ng/g,with an average value of 1529.48 ng/g.The distribution of PAHs in the soil on both sides of the Beijing-Harbin expressway generally decreased,then increased and then decreased,the soil background values of each section were basically smaller than the values of the sampling points within the range of 150 m of the corresponding section.The total concentration of PAHs in maize along the 7 main roadside around Changchun city ranged from 202.70 to 716.00 ng/g,with an average value of 362.01 ng/g.The total PAHs concentration in maize along the main roadsides of Dehui ranged from 25.53 ng/g to 70.12 ng/g,with an average value of 47.45 ng/g.The total PAHs concentration in maize leaves ranged from 163.39 to 2254.7 ng/g,with an average value of 1279.43 ng/g.The concentration of PAHs in maize and maize leaves on both sides of the Beijing-Harbin expressway did not decrease with the increase of the distance from the roadbed.The source of PAHs in samples were analyzed,and the results showed that the main sources of PAHs in farmland soil along main roadsides around Changchun city were coal and biomass combustion,with transportation and petroleum sources,the source of PAHs in maize was the same as that in soil.The main sources of PAHs in farmland soil along the main roadsides in Dehui were coal and biomass as well as petroleum combustion and transportation sources,with the oil source,it was similar to the source of PAHs in farmland soil around Changchun city.The main sources of PAHs in maize and maize leaves were coal and biomass combustion,which were basically the same as PAHs in soil.Correlation analysis of PAHs in farmland soil and soil physical and chemical properties shows that,the pH value of farmland soil along main roadsides around Changchun city and the farmland soil along the main roadsides in Dehui had no correlation with PAHs in the soil,but had a correlation with organic carbon.The correlation between PAHs and chlorophyll in maize leaves along main roadsides in Dehui was analyzed,and the results showed that there was no correlation between chlorophyll and PAHs.Four different evaluation methods were used to evaluate the ecological risk of farmland soil in our study area.According to PAHs pollution level standards which proposed by Maliszewska-Kordybach,the concentration of PAHs in the soil of all sampling sites along the main roadsides around Changchun city were at the level of serious pollution;in the farmland soil samples along the main roadsides in Dehui,the samples with medium pollution or above account for 79.00% of the total samples.The evaluation results of the Nemero comprehensive pollution index method show that,among the farmland soil samples along the main roadsides around Changchun city,91.43% of the samples were above medium pollution,in the farmland soil samples along the main roadsides in Dehui,the samples with medium pollution or above account for 76.00%.The results of the toxicity equivalent factor(TEF)method showed that,there was a slight risk of PAHs pollution in the farmland soil around Changchun urban area.The farmland soil along the main highway in Dehui city didn't exceed the standard.The results of biotoxicity evaluation showed that,some of the PAHs in the farmland soil samples along the main highways around Changchun city exceeded the maximum critical safety value,causing slightly frequent biological toxicity.PAHs in farmland soil samples along major highways in Dehui also exceeded the maximum critical safety level,which also resulted in slightly frequent biological toxicity.The health risk of soil and maize in the study area was evaluated.The results showed that,the concentration of nine non-carcinogenic PAHs in farmland soil and maize samples along main roadsides around Changchun city were all within the acceptable range.Carcinogenic PAHs in soil and maize may be associated with risk and should be paid attention.PAHs in the soil and maize samples along the main roadsides in Dehui were within the acceptable range.