Study On High Resolution Deposition Records Of PAHs And BC In Dajiuhu Peatland Shennongjia

Polycyclic aromatic hydrocarbons?PAHs?are neutral nonpolar persistent organic pollutants which widely existe in the environment.PAHs has the long-term persistent biological volatile and highly toxic chemicals and a long half time,which can undertake long distance migration between different media environment,and harm to human health and ecological environment.Most of them are volatile and can undergo evaporation and precipitation at normal ambient temperature.In tropical and subtropical region,high temperature lead them have the trend evaporation from the earth surface.In high latitudes,low temperature cause POPs to settle down from the atmosphere to the soil and water.In the chill of the ecological system,they tend to condense,settlement down and enrichment.In the remote region,which has less human activitiy impact on the ecosystem is the ideal region to study the past environmental changes.Remote sediment is widely distributed,has high resolution which indiated large amount of informationof the past environmental changes.To analyze the PAHs sedimentary characteristics in the Dajiuhu peat wetland,Hubei province,a 100cm peat core was collected and silenced into 1 cm intervals in October,2016 in Dajiuhu,Shengnongjia.16 USEPA priority PAHs?Nap?Acy?Ace?Flu?Phe?Ant?Fla?Pyr?BaA?Chr?BbF?BkF?BaP?Icd P?DBA?BghiP?were determined as well as the activities of ²¹⁰Pb isotope to study the high resolution sedimentary history and socioeconomic activities.The main findings of this thesis are listed as follow.The total PAHs concentration(?₁₆PAHs)in surface layer of peat ranged from 237.34ng/g to 1608.62 ng/g,with a mean value of 699.03 ng/g,LMW-PAHs?2³ ring?proportion between 58.95%and 58.95%,the average accounts for 71.74%of the total PAHs,Nap and Phe occupies the dominant position,Nap accounts for 37.07%of the total PAHs,followed by Phe accounts for 25.95%of the total PAHs.The variation range of TOC content is 342.67⁷45.31g/kg,the mean is 467.61g/kg,and the content of BC is between 1.20³64.78g/kg,and the mean value is 127.82g/kg,which is far higher than other research areas in China.The dating result obtained from the ²¹⁰Pb indicated that the 100 cm peat core can tracke the past 140 years'history?1875²015?.The total PAHs concentration??16PAHs?in peat core ranged from 212.67 ng/g to 830.10 ng/g,with a mean of 518.65 ng/g,Phe and Nap occupies the dominant position,Phe accounts for 38.64%±4.42%of the total PAHs,followed by Nap accounts for 23.22%±4.06%of the total PAHs.According to the concentration level and composition of characteristics of PAHs in sediment core,characteristics of PAHs history can be divided into four stages,each stage of the PAHs concentration and trends can be a good response of the intensity of human activities.The extensive logging in central China and the reclamation of farmland in the great lakes region have greatly affected the PAHs deposition.Especially since the founding of the people,the concentration of PAHs in sediment column and human activities strength index has good correlation:the content of PAHs and GDP?r²=0.302,p<0.302?,and motor vehicle ownership?r²=0.363,p<0.05?between a significant positive correlation.In addition,there is a significant positive correlation between the high molecular weight PAHs:4 rings,5 ring PAHs,and 6 cycles with GDP and energy consumption.From bottom to top the BC content showed a trend of increasing,1950s began to BC content increased,the content of nearly 10 years and gradually reduce the BC/TOC ratio shows the source of the BC in peat column in the past 20 years great changes have taken place in the BC content and oil?r²=0.741,P<0.741?,the coal consumption?r²=0.706,P<0.706?,motor vehicle ownership?r²=0.429,P<0.429?GDP?r²=0.513,P<0.01?and the population?r²=0.841,P<0.01?of all show significant positive correlation between,especially with the extremely significant correlation between population oil and coal consumption Energy structure change of human activities and the larger influence on BC contentDuring warm event,PAHs concentration decreased significantly,and accompanied by a rise in the temperature increase amplitude decrease concentration of PAHs.However,the concentration of PAHs in the cold event was increased,while the content of BC was increased,and the BC was significantly positively correlated with the temperature?r²=0.421,P<0.01?.PAHs and heavy rain s BC have small cut,PAHs and BC content after the heavy rain will be increased,especially in 1983,1994,2000,shennongjia region suffered rainstorms s PAHs and BC for precipitation response is more obvious;However,the content of PAHs and BC decreased in the dry age with less precipitation.