The Stable Carbon And Hydrogen Isotope Compositions Of Hydrocarbons Associated With Atmospheric Particulates

The rapid expansion of modern industry and traffic has induced a heavy load on the hydrocarbons in atmosphere, and the human health was threatened seriously. Among the hydrocarbons, n-alkanes owns the nature of induced skin cancer, and the polycyclic aromatic hydrocarbons （PAHs） own three features of carcinogenic, teratogenicity and mutagenicity, so both have been concerned by numerous researchers. It is necessary to control the atmospheric organic pollutants by evulating the source and behavior. The atmospheric particulates with aerodynamical diameter ≤＝10μm (PM₁₀) during heating and non-heating periods in Taiyuan City and typical emission sources samples including coal soot and vehicle exhausts were all collected, the hydrogen isotope compositions （δD） of n-alkanes and the carbon isotope compositions （δ13C） of PAHs associated with PM₁₀ and emission sources were measured using GC-IRMS, and the source and behavior of n-alkanes were discussed on the basis of the effects of volatilization and ultraviolet on the δD values of n-alkanes. The primary conclusions derived from this research have been followed:The effect of volatilization on δD values of n-C15-n-C19 was remarkable with a fractionation extent of -22.5‰～-8.0‰, and such fractionation followed to the Rayleigh model with the fractionation factors （except n-C115） of 1.0042, 1.0070,1.0112 and 1.0100 respectively. Conversely, there was hardly any hydrogen isotope fractionation for n-C20-n-C32 during volatilization. Likewise, the ultraviolet has no effect on the δD values of w-alkanes.The δD variation tendency for n-alkanes associated with coal soot from power plants and civilian furnaces was nearly consistent, and the δD values ranged from -219.6‰ to -95.3‰and from-188.6‰to-128.1‰respectively. The n-C15～n-C18 alkanes were gradually enriched in D with increasing carbon number, and the δD distributions of n-C19～n-C24 alkanes in this two coal soot were both in the shape of zigzag with the even carbon n-alkanes enrichment in D. In addition, the δ13C values of PAHs associated with coking plant and civilian furnace were in the ranges of -25.1‰～-23.3‰and -26.9‰o～-24.6‰ respectively, and the PAHs in coal soot from coking plant were more enriched in 13C than that in civilian furnace. Consequently, the δ13C value of PAHs in coal soot was in relation with the coal conversion.The n-alkanes from gasoline vehicle exhaust were more enriched in D than that from diesel vehicle exhausts, with the δD values of w-alkanes in the ranges of-159.7‰～-118.2‰ and-177.2%o--133.7%o respectively. The n-C16～n-C22 alkanes from diesel vehicle exhaust became enrichment in D with increasing carbon number, and such n-alkanes from gasoline vehicle exhaust became depleted in D with increasing carbon number. This opposite tendency can be used as a criterion to distinguish sources. The δD values of n-C23～n-C29 alkanes from two vehicle exhaust samples were nearly consistent. The δ13C values of PAHs from gasoline and diesel vehicle exhausts were in the ranges of-24.6‰～-22.9‰ and -24.5‰～-22.2‰ respectively, and became enriched in 13C with increasing ring size, and were irrelevant to the fuel type.During heating period, the δD values of n-C16～n-C31 alkanes associated with atmospheric particulates ranged from -235.9‰ to-119.8%o. The δD distribution characterizations between the non-centralized heating district and commerce district were almost coincident, and so do the resident district and industry district, but the δfluctuation of n-alkanes in the control district was relaxative. The δ13C values of PAHs on atmospheric PM₁₀ ranged from -23.6%o to -26.6‰, and became more negative with increasing ring size. During non-heating period, the δD values of n-alkanes from atmospheric PMio ranged from -231.3‰ to-129.2‰. The n-C16-n-C20 alkanes became depleted in D with increasing carbon number. The δD distributions of n-C21～n-C31 alkanes between the non-centralized heating district and resident district were consistent, and that among other districts were distinct difference. The δ13C values of PAHs were in the range of -28.7‰～-24.3‰.Specifically, the PAHs in the industry district became depleted in C with increasing ring size, and the δ13C values of PAHs in the commerce district and the resident district ranged from-27.0‰ to-25.9‰, which was more depleted in 13C than that in industry district.During heating period, coal soot was the primary pollutant source, and its contributions to n-alkanes in resident district, industry district and control district were in the ranges of 40.1%-88.1%,51.1%-96.6% and 49.3%-95.2% respectively. During non-heating period, the contributions of coal soot and vehicle exhaust to n-alkanes in the non-centralized heating district were 56.2%～163.0% and 37.0%～43.8% respectively, with a ration of 3:2, indicated that the pollution from vehicle exhaust should not be ignored. In addition, the contributions of coal soot and vehicle exhaust to n-alkanes in resident district were in the ranges of 70.0%～84.9% and 15.1%～30.0%. The volatilization extent of n-C16～n-C19 alkanes ranged from 68.0% to 94.6% during heating period and from 78.8% to 96.6% during non-heating period, which indicated that the effect of volatilization on experimental result should be avoided during sample collection and analysis processes.