Pratt Gregory C, Bock Don, Stock Thomas H, Morandi Maria, Adgate John L, Ramachandran Gurumurthy, Mongin Steven J, Sexton Ken
Environmental Outcomes Division, Minnesota Pollution Control Agency, 520 Lafayette Road, St. Paul, Minnesota 55155, USA.
Environ Sci Technol. 2005 May 1;39(9):3261-8. doi: 10.1021/es0497328.
Concurrent field measurements of 10 volatile organic compounds (VOCs) were made using passive diffusion-based organic vapor monitors (OVMs) and the U.S. Federal Reference Method, which comprises active monitoring with stainless steel canisters (CANs). Measurements were obtained throughout a range of weather conditions, repeatedly over the course of three seasons, and at three different locations in the Minneapolis/St. Paul metropolitan area. Ambient concentrations of most VOCs as measured by both methods were low compared to those of other large metropolitan areas. For some VOCs a considerable fraction of measurements was below the detection limit of one or both methods. The observed differences between the two methods were similar across measurement sites, seasons, and meteorological variables. A Bayesian analysis with uniform priors on the differences was applied, with accommodation of sometimes heavy censoring (nondetection) in either device. The resulting estimates of bias and standard deviation of the OVM relative to the CAN were computed by tertile of the canister-measured concentration. In general, OVM and CAN measurements were in the best agreement for benzene and other aromatic compounds with hydrocarbon additions (ethylbenzene, toluene, and xylenes). The two methods were not in such good agreement for styrene and halogenated compounds (carbon tetrachloride, p-dichlorobenzene, methylene chloride, and trichloroethylene). OVMs slightly overestimated benzene concentrations and carbon tetrachloride at low concentrations, but in all other cases where significant differences were found, OVMs underestimated relative to canisters. Our study indicates that the two methods are in agreement for some compounds, but not all. We provide data and interpretation on the relative performance of the two VOC measurement methods, which facilitates intercomparisons among studies.
使用基于被动扩散的有机蒸汽监测仪（OVM）和美国联邦参考方法，对10种挥发性有机化合物（VOC）进行了同步现场测量，美国联邦参考方法包括使用不锈钢罐（CAN）进行主动监测。在一系列天气条件下、三个季节的过程中反复进行测量，并在明尼阿波利斯/圣保罗大都市区的三个不同地点进行测量。与其他大型都市区相比，两种方法测得的大多数VOC的环境浓度都较低。对于某些VOC，相当一部分测量值低于一种或两种方法的检测限。两种方法之间观察到的差异在测量地点、季节和气象变量方面是相似的。应用了对差异具有均匀先验的贝叶斯分析，并考虑了两种设备中有时出现的严重删失（未检测到）情况。相对于CAN，OVM的偏差和标准差的估计值是根据罐测量浓度的三分位数计算的。一般来说，对于苯和其他添加了烃类的芳香族化合物（乙苯、甲苯和二甲苯），OVM和CAN的测量结果最为一致。对于苯乙烯和卤代化合物（四氯化碳、对二氯苯、二氯甲烷和三氯乙烯），两种方法的一致性不太好。在低浓度下，OVM略微高估了苯浓度和四氯化碳浓度，但在所有其他发现显著差异的情况下，相对于罐，OVM的测量值偏低。我们的研究表明，两种方法对某些化合物一致，但并非对所有化合物都一致。我们提供了两种VOC测量方法相对性能的数据和解释，这有助于不同研究之间的相互比较。
