Estimating Contributions Of Sources Of Organic Pollutants In Airborne Particles By Isotopic Tracer

Atmospheric particles as an important component of air pollution have caused immense harm to human health, environment, and climate. Particles with different sizes can access to different parts of the body, so that the harm is also different. Compared with coarse particles (aerodynamic diameter (Da), 2.5 microns≤Da≤10 microns), fine particles, PM_2.5 (Da≤2.5 microns) are more easily deposited in lung, bronchia, and alveolus. They cause more respiratory and lung disease. Most of particles existed as organic matters are carcinogenic, teratogenic, and mutagenic material, and 81.9 percent of the organic matters focus in PM_2.5. In order to protect people's health, we have to reduce and eliminate the organic pollutants in PM_2.5. For that, it is necessary to quantitatively estimate sources of the organic pollutants.The ingredients of organic pollutants are complex. The general methods such as the conventional element content analytic method, scanning proton microprobe (SPM) and simultaneous X-ray fluorescence (SXRF) are difficult to quantify the originations of the organic pollutants. In present study, an isotope technology was used in environmental science. Specific activities of ¹⁴C and carbon isotopic compositions were used to quantify the originations of organic pollutants in atmospheric particles. Organic pollutants in atmospheric particles originate from: non-fossil products (soil dust, plant burning products) and fossil products (vehicle burning and oil burning products). Carbon is a popular molecule in nature. It has a radiocarbon (¹⁴C) with a half life of 5730y and two kinds of stable carbon isotopes (12C and ¹³C). as well known, there are no ¹⁴C in fossil fuels. This has provided us a very simple and effective way to distinguish atmospheric particle sources of organic pollutants with 14 C.Carbon existed in organic pollutants is as the form of organic carbon (OC). Since ¹⁴C only exists in non-fossil materials, the ¹⁴C values of OC, indicated by percent modern carbon, reflect a distribution of non-fossil carbon to all OC. The distribution of fossil carbon can then be obtained. Every material has intrinsic carbon stable isotopic composition (δ¹³C), so that using a mass approach balance ofδ¹³C can further separate non-fossil sources as well as fossil materials sources. Based on this thought above, a method was developed to separate the sources of OC in PM_2.5 using specific activities of ¹⁴C and stable carbon isotopic composition in this paper.The current apparatus used to measure the ¹⁴C are liquid scintillation chamber (LSC) and accelerator mass spectrometry (AMS), and the required amount of carbon is 1000 mg and 1 mg, respectively. 1000 mg of carbon in atmospheric particles is hard to be obtained, so the AMS is the only way to be used for determining the ¹⁴C of particulate matter. Thus, an AMS pre-treatment system, which is used to convert different kinds of carbon into a graphite.In this study, a complete set of AMS pre-treatment system was developed. In this system, the vacuum degree reaches as high as 8 - 2.5Pa, it can handle various forms (solid, gaseous) samples, and the working efficiency reaches as high as for 10/days. In addition, the atmospheric particles of the Baoshan District of Shanghai are studied for analysis of organic pollutants. The results showed that the source of organic pollutants in the Baoshan District in winter is mainly fossil products, accounting for 64.74 percent of the total organic pollutants, The distribution of non-fossil accounting for 35.26 percent. Surface layer soil (0 - 5cm) is mainly falling dust.