Study On Response Time Resolution Of Pinus Tabulaeformis Leaves For Pahs In Air During Day

With the development of industry,more and more incomplete combustion of fossil fuels and biomass will inevitably increase the concentration of polycyclic aromatic hydrocarbons(PAHs)in the atmosphere.Because PAHs have carcinogenic,teratogenic,and mutagenic "triple effects",bioaccumulation,and long-range migration characteristics,they pose great risks to environmental safety and human health.Therefore,it is particularly important to detect and monitor PAHs in the atmosphere.When detecting PAHs in the atmosphere,the choice of sampler is related to the accuracy of the detection results.The existing samplers include an active sampler and a passive sampler.Plant leaves are widely used as biological indicators to detect PAHs in the atmosphere due to their advantages of wide distribution,rich waxy layer,and low cost.Among them,Pinus tabulaeformis leaves are especially widely used due to their advantages such as evergreen and waxy layer.Previous studies have shown that pinus tabulaeformis leaves can reflect the PAHs concentration and its constituents in the atmosphere,and that there is a good correlation between periodic changes in PAHs concentrations in pinus tabulaeformis leaves and the atmosphere.But this is only limited to long-term(year and month cycle)research,and its short-term distribution mechanism remains to be explored.Therefore,in order to ensure the accuracy of plant leaves as passive samplers to detect PAHs concentration in the atmosphere,it is necessary to explore the response time and short-term distribution mechanism of the enrichment plant leaves for PAHs.However,the dynamic change of PAHs in the atmosphere within a few hours is at a trace level and the size of laboratory simulation experiment is small.The sensitivity of existing detection methods is too low,and real-time detection cannot be achieved.In response to the above problems,this paper established a highly sensitive real-time detection method for PAHs in air,which can monitor the enrichment capacity and response time of pinus tabulaeformis leaves in real time during day,and calculate the distribution coefficient of PAHs in pinus tabulaeformis leaves and air.Provide a theoretical basis and accurate guarantee for future environmental monitoring.The main contents and results of the research are as follows:1.Established an air-flow quantitative concentration injection technology,which can quantitatively concentrate the sample solution and then directly inject the sample.Targeting naphthalene,acenaphthylene,acenaphthene,fluorine,phenanthrene,anthracene.Two parameters,flow velocity and experimental temperature,were optimized respectively.Under the optimal conditions of airflow velocity of 5 mL/min and experimental temperature of 35℃,the standard recovery rate of the method reached the analytical standard,and the range was 67-108%.And good reproducibility(RSD range of 2.7-11.4%);Compared with the unconcentrated control sample,the concentration ratio of this method is 500 times.2.The correlation between PAHs concentrations in pinus tabulaeformis leaves and in the atmosphere was investigated during day.The concentration of PAHs in the atmosphere was detected within seven days by soxhlet extraction combined gas chromatography-mass spectrometry(GC-MS).The concentration of PAHs in pinus tabulaeformis leaves in 7 days was detected by the gas-liquid microextraction(GLME)independently developed in the laboratory combined with GC-MS.SPSS correlation analysis results showed that the P value was less than 0.01,indicating that there was a significant correlation between the PAHs concentration in pinus tabulaeformis leaves and in the atmosphere during day.3.A real-time detection device is established,which includes four parts:gas path system,plant system,volatile system and enrichment system.By simulating the actual environment,the air velocity and temperature of the system are regulated respectively,and the gas tightness,volatilization mode,enrichment mode and condensation mode of the device are optimized and improved.D8-NAP was selected as the target,and the exposure experiment of pinus tabulaefolia leaf was carried out during day according to the concentration of PAHs in the atmosphere in winter in heavily polluted areas in northern China.By analyzing the real-time detection results,the response time of pinus tabulaeformis leaves to the air d8-NAP was determined to be 40 min,indicating that pinus tabulaeformis leaves could be used as a passive sampler to monitor the PAHs concentration in the air within hours.Moreover,the distribution coefficient of d8-NAP in pinus tabulae leaves and air during the equilibrium period is calculated to be 0.1-0.2,which proves that the short-term allocation rate is at the same level as the long-term allocation rate.