Study On Pollution Characteristics And Risk Assessment Of Heavy Metals In Soils Around Highway In Jiangsu Province

In recent years,with the rapid development of China's transportation,highways and the motor vehicles have increased rapidly.Highway traffic has become a major source of heavy metal pollution in the soils around highways.The highway is prone to cause more serious pollution due to its large traffic flow,large mobility and wide range distribution.It has been widely concerned by scholars internationally and domestically.The addition of traffic pollution sources to the soils around the highway makes the characteristics of heavy metal pollution and its spatial and temporal distribution rules more complicated and diversified.According to the "National Survey Report on Soil Pollution Status" issued by the Chinese government in 2014,the overall soil pollution in China is relatively serious.Among total sampling sites,there were 20.3%sites of soils around the highways has exceeded the risk screening values for soil contamination of agricultural land,mainly by the heavy metals,such as Cd,Cr,Pb,Cu and Zn.The current studies indicated that some soils and crops along the highways in Jiangsu Province have been polluted by heavy metals such as Pb?Cd?Cr?Zn?Cu,but the pollution characteristics,distribution and influencing factors were not fully elucidated.There is no overall systematic study on the characteristics and risk status of heavy metals pollution around major highways in Jiangsu Province.This study selected four highways(Shanghai-Nanjing Highway,Beijing-Shanghai Highway,Nanjing-Nantong Highway and Lianyungang-Huoerguosi Highway Jiangsu Section)that run through the east,west,south and north of Jiangsu Province as the case study areas.By analyzing the heavy metals in soils,crops,atmospheric particulate matters and road dusts around the typical highway sections,the heavy metal pollution status around the highways were determines.The geo-statistical analysis and multivariate statistic were applied to explore the spatial distribution of heavy metals in soils,and identify the source of pollution and its influencing factors.The enrichment coefficient method,geo-accumulation index and potential ecological risk assessment and human health risk assessment were used to evaluate the ecological risks and human health risks of heavy metals in the soils,road dusts and wheat around the different highways.Finally,the management and strategies concerning the prevention and control of heavy metal pollution in the soils around the highways in Jiangsu Province were proposed.The main findings are as follows:(1)Comparing with soil heavy metals pollution risk in agricultural land,the mean content of Cd in the soils within 150 meters of the Shanghai-Nanjing Highway exceeded the soil background value of Jiangsu Province.There were 6%sampling sites of Cd,1%sampling sites of Pb in soils exceed the risk screening values,and Cu?Zn?Cr were not exceed the risk screening values.The accumulation of heavy metals in the soils within 150 meters around the Beijing-Shanghai Highway,with the 14%of Cd,5%of Cu,1%of Pb and Zn exceeded the risk screening values.There were 21%of Cd,1%of Cu in soils around Nanjing-Nantong Highway exceeded the risk screening values.The content of each element in soils around the Jiangsu section of Lianyungang-Huoerguosi Highway exceeded the background values of Jiangsu Province.Among them,9%of Cd and 1%of Cr exceed the background values.The heavy metal content in dusts of the four highways far exceeded the soil background values of Jiangsu Province.There were 5%of Cd and 12%of Cr in wheat around the highways exceeded the national food standards,respectively.(2)The spatial distribution of heavy metals in the soils from both sides of the Danyang section of the Shanghai-Nanjing Highway was conducted.The soil Cd contents from both sides of the highways were higher within 50 meters of the highways.The Pb pollution showed a skewed distribution.The distribution of Cu and Cr contens in soils appeared decreasing with the distance.The first increase is decreasing and the increasing distribution characteristics;the total amount of Zn in the south was significantly greater than that in the north,and the content decreases with the distance.The heavy metals in wheat grains from the eastern highways were higher than that in the north areas,and the heavy metal contents in the grains increased with the inceasing of the traffic volume.(3)By analyzing the influencing of the different distances from the road shoulders,different traffic flow,different land use types and road ages to the heavy metal pollution of the surface soil around the highway,it was found that the distance caused the heavy metal content of the soil around the highway within 50 meters.The influences of the highway is less than 50 meters away from the highway.The higher the average daily traffic volume of the high-speed,the greater the soil heavy metal enrichment coefficient.The protection trees planted around the highways has a good isolation effect and can block more heavy metals accumulations.The accumulation of heavy metals Cd on both sides of the soil was consistent with road age,and other elements did not show the same pattern.The source analysis of the heavy metals in the soil of Lianhuo Highways indicated that it mainly came from traffic pollution and agricultural activities,with the contribution rates of 37%and 36%,respectively.(4)The Cd in the soils around the four highways have mild-medium pollution,while the Pb,Zn and Cu have mild-medium pollution,Cr relatively light,with Cd has moderate ecological risk.The risk of non-carcinogenic risk of heavy metals in highway dusts,atmospheric particulate matter and wheat were generally lower.(5)The management and strategies concerning the prevention and control of heavy metal pollution in the soils around the highways in Jiangsu Province were proposed,including plant the protective forests along the road,plan the land application rationally,rationally usage the fertilizers,reduce the application of fertilizers with high heavy metals content into the soils,and strengthen the risk management and control of heavy metals in soils around the highways to ensure soil quality and agricultural product safety.