Effects of sampling artifacts and operating parameters on the performance of a semicontinuous particulate elemental carbon/organic carbon monitor
Effects of sampling artifacts and operating parameters on the performance of a semicontinuous particulate elemental carbon/organic carbon monitor
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DOI：
10.1021/es0510313
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发表时间：
2006-02-01
影响因子：
11.4
通讯作者：
Sioutas, C
中科院分区：
文献类型：
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作者：
Arhami, M;Kuhn, T;Sioutas, C
就观察到的 PM 的不利健康影响而言，大气颗粒物 (PM) 的碳质成分被认为非常重要。传统上，颗粒有机碳和元素碳是在过滤器上每天进行时间积分颗粒收集后离线测量的。然而，元素碳 (EC) 和有机碳 (OC) 的次日或每小时变化有助于评估来源、环境水平和人类暴露的变化。在本研究中，在代表典型城市污染的洛杉矶地区评估了 Sunset Laboratory Inc. 半连续 EC/OC 监测仪的性能。监视器间比较显示出高精度（热 OC 和 EC 的 R-2 分别为 0.98 和 0.97）。通过改变其中一台监测仪的入口配置（添加遮光器、聚四氟乙烯过滤器或两者），研究了正负采样伪影的影响。发现阳性伪影相对较大（平均 7.59 μg/m(3)），超过测量的 OC 的 50%，但实际上用 denuder 就消除了。负伪影要小得多（小于正伪影的 20%），在大多数情况下可以忽略不计。不同温度曲线的比较，包括使用光学 EC 校正的快速 4 分钟分析，表明方法之间具有良好的一致性。最后，采用尺寸选择性入口冲击器去除直径大于 250 nm 的颗粒的新颖配置允许半连续尺寸分级 EC/OC 测量。热分析不同温度下 OC 的演变表明，较大颗粒中 OC 的挥发性较高。
The carbonaceous component of atmospheric particulate matter (PM) is considered very important with respect to the observed adverse health effects of PM. Particulate organic and elemental carbon have traditionally been measured off-line after daily, time-integrated particle collection on filters. However, the subdaily or hourly variability of elemental carbon (EC) and organic carbon (OC) can help to assess the variability of sources, ambient levels, and human exposure. In this study, the performance of the Sunset Laboratory Inc. semicontinuous EC/OC monitor was assessed in a Los Angeles location representing typical urban pollution. An intermonitor comparison showed high precision (R-2 of 0.98 and 0.97 for thermal OC and EC, respectively). By changing the inlet configurations of one of the monitors (adding a denuder, a Teflon filter, or both), the influences of positive and negative sampling artifacts were investigated. The positive artifact was found to be relatively large (7.59 mu g/m(3) on average), more than 50% of measured OC, but it was practically eliminated with a denuder. The negative artifact was much smaller (less than 20% of the positive artifact) and may be neglected in most cases. A comparison of different temperature profiles, including a fast 4-min analysis using optical EC correction, showed good agreement among methods. Finally, a novel configuration using a size selective inlet impactor removing particles greater than 250 nm in diameter allowed for semicontinuous size-fractionated EC/OC measurements. Evolution of OC at different temperatures of the thermal analysis showed higher volatility OC in larger particles.