Distribution Characteristics And Environmental Behaviour Of Polycyclic Aromatic Hydrocarbons In The Subantarctic Multimedium Environment

As persistent toxic substances?PTs?,polycyclic aromatic hydrocarbons?PAHs?are ubiquitous in the environment.PAHs come from a wide range of sources with characteristics of semi-volatile,long-range migration and biological toxicity.In addition,various derivatives of PAHs with stronger toxicity can be generated during the long-range transport process.According to the global transport theory of PTs,PAHs can be transported from middle and low latitudes to high latitudes and settled in various environment media.However,with the serious status of global warming,this process will become more complicated since the role of the polar sink may have changed.Compared with other regions around the world,the polar area is the background region of global contaminants and the barometer of global climate change for its less disturbance by human activities.Therefore,the polar area is an ideal region to track the global transportation of persistent toxic substances,such as PAHs.In order to clarify the transmission process and fate of PAHs under the influence of global climate change,this research will focus on the occurrence,distribution characteristics,medium portioning,and transformation of PAHs in polar environment.Based on the cooperation between China's 30th Antarctic scientific expedition and Peru's international voyage in 2014,atmospheric and surface seawater samples in the sub-antarctic Bransfield Strait were collected to analyze the concentration of PAHs in the atmosphere?gas phase and particle phase?and seawater?dissolved phase?.The results showed that PAHs was detected in all samples,the concentrations of PAHs in the atmosphere and seawater ranged from 3.75 to 8.53 ng/m³ and 5.42 to 34.37 ng/L,respectively.In general,the concentration of PAHs in seawater tended to decrease with the increase of latitude,and the South Shetland Islands presented a higher level of PAHs than that along the Antarctic Peninsula.The distribution characteristics of PAHs between the particulate phases and gas phases of atmospheric samples at each site were different.The atmospheric backward trajectories analysis of the HYSPLIT model showed that the PAHs in the particle phase mainly came from local source,while the gas phase is greatly affected by the exogenous PAHs.The composition characteristics of PAHs in the atmosphere and seawater was similar,with the three-ring and the four-ring PAHs as the main components,accounting for more than 50%.While the five-ring and six-ring PAHs only accountted for 2%¹4%.Among them,phenanthrene is the main compound,accounting for 30%and 47%respectively in seawater and atmosphere.The water-air exchange flux and dry deposition flux of PAHs in Bransfield Strait were calculated.The net water-air exchange flux of PAHs was 1429.77⁴115.33 ng m^-2d^-1,and the dry deposition flux was 78.11¹51.29 ng m^-2 d^-1.The direction of PAHs transmission was from the atmosphere to the seawater,indicating that although global warming aggravates the"secondary release"of PAHs,the subantarctic sea in summer was still"sink"of PAHs.In addition,molecular diagnostic ratios were used to analyze the sources of PAHs in seawater and atmosphere,and the results showed that the PAHs in the subantarctic area was coeffected by both local source?operation of research stations and polar tourism,etc.?and the long-range transmission of pollutants.The concentration of PAHs,OH-PAHs and soil total organic matter?TOM?in the soil samples of the Fildes Peninsula in the Antarctica were analyzed,in order to reveal the spatial distribution characteristics,migration and transformation rules of PAHs in the subantarctic typical terrestrial environment.The results showed that the concentration of PAHs was 21.831⁷7.114 ng/g dw,and the concentration of OH-PAHs was 0.300¹.847ng/g dw.The TOM and PAHs were analyzed to reveal their effect on the spatial distribution characteristics of OH-PAHs,and the results showed that there was no significant correlation between the spatial distribution of OH-PAHs and the occurrence of PAHs in the soil of the Fildes Peninsula in the Antarctica,while OH-PAHs had a positive correlation with TOM.