Fan Xinghua, Brook Jeffrey R, Mabury Scott A
Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
Environ Sci Technol. 2003 Jul 15;37(14):3145-51. doi: 10.1021/es026471y.
Measurement of particle-bound organic carbon (OC) may be complicated by sampling artifacts such as adsorption of gas-phase species onto particles or filters or evaporation of semivolatile compounds off the particles. A denuder-based integrated organic gas and particle sampler (IOGAPS), specifically designed to minimize sampling artifacts, has been developed to sample atmospheric carbonaceous aerosols. IOGAPS is designed to first remove gas-phase chemicals via sorption to the XAD-coated denuder, and subsequently particles are trapped on a quartz filter. A backup sorbent system consisting of sorbent- (XAD-4 resin) impregnated filters (SIFs) was used to capture the semivolatile OC that evaporates from the particles accumulated on the upstream quartz filter. A traditional filter pack (FP) air sampler, which uses a single quartz filter to collect the particles, was employed for comparison in this study. Elemental and organic carbon were determined from filter punches by a thermal optical transmittance aerosol carbon analyzer. Field measurements show that there was no significant difference between the elemental carbon concentrations determined by the FP and IOGAPS, indicating that particle loss during the transit through the denuder tube was negligible. Compared with the OC determined by FP (3.9-12.6 microg of C/m3), the lower OC observed on the quartz filter in the IOGAPS (2.2-6.0 microg of C/m3) was expected because of the removal of gas-phase organics by the denuder. Higher semivolatile organic carbon (SVOC) on the backup SIFs during the night (1.24-8.43 microg of C/m3) suggests that more SVOC, emitted from primary sources or formed as secondary organic compounds, partitions onto the particles during the night because of the decreased ambient temperature. These data illustrate the utility of an IOGAPS system to more accurately determine the particle-bound OC in comparison to FP-based systems.
颗粒结合有机碳（OC）的测量可能会因采样假象而变得复杂，例如气相物质吸附到颗粒或滤膜上，或者半挥发性化合物从颗粒上蒸发。一种专门设计用于尽量减少采样假象的基于 denuder 的集成有机气体和颗粒采样器（IOGAPS）已被开发出来，用于采集大气中的碳质气溶胶。IOGAPS 的设计目的是首先通过吸附到涂有 XAD 的 denuder 上去除气相化学物质，随后颗粒被捕获在石英滤膜上。一个由吸附剂（XAD - 4 树脂）浸渍滤膜（SIFs）组成的备用吸附剂系统被用于捕获从上游石英滤膜上积累的颗粒中蒸发出来的半挥发性 OC。在本研究中，采用了一种传统的滤膜组（FP）空气采样器，它使用单个石英滤膜来收集颗粒。通过热光透过率气溶胶碳分析仪从滤膜碎片中测定元素碳和有机碳。现场测量表明，FP 和 IOGAPS 测定的元素碳浓度之间没有显著差异，这表明在通过 denuder 管的过程中颗粒损失可以忽略不计。与 FP 测定的 OC（3.9 - 12.6 μg C/m³）相比，IOGAPS 中石英滤膜上观察到的较低 OC（2.2 - 6.0 μg C/m³）是预期的，因为 denuder 去除了气相有机物。夜间备用 SIFs 上较高的半挥发性有机碳（SVOC）（1.24 - 8.43 μg C/m³）表明，由于环境温度降低，更多从一次源排放或作为二次有机化合物形成的 SVOC 在夜间分配到颗粒上。这些数据说明了与基于 FP 的系统相比，IOGAPS 系统在更准确地测定颗粒结合 OC 方面的实用性。
