Comparative analysis of bias in the collection of airborne pollutants:Tests on major aromatic VOC using three types of sorbent-based methods

摘要

This study was undertaken to establish one of the most reliable sampling methods and to precisely evaluate the bias involved in the collection of airborne pollutant samples.For the purpose of our study,we investigated the performance of three different types of sampling techniques by measuring major aromatic volatile organic compounds (VOC) in outdoor airthe target analytes specifically include benzene,toluene,ethylbenzene,and xylene (commonly called BTEX).As the first step of our approach,we designed and developed a multi-channel sampling system consisting of a six-port mass flow controller (SJU-MFC) system.Because this system allowed the collection of up to six replicate samples,our measurement results were analyzed and screened statistically for the derivation of high-quality BTEX data.The feasibility of this sampling system was further tested through a comparison with concurrent measurement data sets obtained by two additional,but independent,sampling techniques:(1) automatic continuous sampler (ACS) and (2) on-line GC (O-GC) system.Based on the data sets collected concurrently by three different sampling methods,we attempted to evaluate the compatibility of sampling techniques.Although the results obtained by SJU-MFC system were not statistically different from those of the O-GC system,they were moderately distinguishable from those of ACS.Such patterns were seen consistently,when examined by correlation analysis.The overall results of our study thus generally point out that the compatibility of data sets,when the proper caution is taken,improve significantly among different sampling methodologies.