Measuring OVOCs and VOCs by PTR-MS in an urban roadside microenvironment of Hong Kong: relative humidity and temperature dependence, and field intercomparisons
Long Cui1,Zhou Zhang2,Yu Huang3,4,Shun Cheng Lee1,Donald Ray Blake5,Kin Fai Ho6,Bei Wang7,Yuan Gao1,8,Xin Ming Wang2,and Peter Kwok Keung Louie9Long Cui et al.Long Cui1,Zhou Zhang2,Yu Huang3,4,Shun Cheng Lee1,Donald Ray Blake5,Kin Fai Ho6,Bei Wang7,Yuan Gao1,8,Xin Ming Wang2,and Peter Kwok Keung Louie9
Received: 14 Apr 2016 – Discussion started: 01 Jun 2016 – Revised: 26 Oct 2016 – Accepted: 15 Nov 2016 – Published: 01 Dec 2016
Abstract. Volatile organic compound (VOC) control is an important issue of air quality management in Hong Kong because ozone formation is generally VOC limited. Several oxygenated volatile organic compound (OVOC) and VOC measurement techniques – namely, (1) offline 2,4-dinitrophenylhydrazine (DNPH) cartridge sampling followed by high-performance liquid chromatography (HPLC) analysis; (2) online gas chromatography (GC) with flame ionization detection (FID); and (3) offline canister sampling followed by GC with mass spectrometer detection (MSD), FID, and electron capture detection (ECD) – were applied during this study. For the first time, the proton transfer reaction–mass spectrometry (PTR-MS) technique was also introduced to measured OVOCs and VOCs in an urban roadside area of Hong Kong. The integrated effect of ambient relative humidity (RH) and temperature (T) on formaldehyde measurements by PTR-MS was explored in this study. A Poly 2-D regression was found to be the best nonlinear surface simulation (r = 0.97) of the experimental reaction rate coefficient ratio, ambient RH, and T for formaldehyde measurement. This correction method was found to be better than correcting formaldehyde concentrations directly via the absolute humidity of inlet sample, based on a 2-year field sampling campaign at Mong Kok (MK) in Hong Kong. For OVOC species, formaldehyde, acetaldehyde, acetone, and MEK showed good agreements between PTR-MS and DNPH-HPLC with slopes of 1.00, 1.10, 0.76, and 0.88, respectively, and correlation coefficients of 0.79, 0.75, 0.60, and 0.93, respectively. Overall, fair agreements were found between PTR-MS and online GC-FID for benzene (slope = 1.23, r = 0.95), toluene (slope = 1.01, r = 0.96) and C2-benzenes (slope = 1.02, r = 0.96) after correcting benzene and C2-benzenes levels which could be affected by fragments formed from ethylbenzene. For the intercomparisons between PTR-MS and offline canister measurements by GC-MSD/FID/ECD, benzene showed good agreement, with a slope of 1.05 (r = 0.62), though PTR-MS had lower values for toluene and C2-benzenes with slopes of 0.78 (r = 0.96) and 0.67 (r = 0.92), respectively. All in all, the PTR-MS instrument is suitable for OVOC and VOC measurements in urban roadside areas.
In this manuscript, the effect of ambient RH and T on HCHO measurements by PTR-MS was investigated, and the Poly 2-D regression was found to be a good nonlinear surface simulation of R (RH, T) for correcting measured HCHO concentration. Intercomparisons between PTR-MS and other OVOC and VOC measuring techniques were conducted through a field study in urban roadside areas of Hong Kong primarily, and good agreements were found between these different techniques.
In this manuscript, the effect of ambient RH and T on HCHO measurements by PTR-MS was...
