The Effect of Sampling Duration and Filter Extraction Fraction on the Measurement of Atmospheric Particulate-bound Polycyclic Aromatic Hydrocarbons and Their Nitro-derivatives

Abstract

Multiple particulate matter (PM) metrics can be analyzed using the same filter samples. Splitting samples for archival and multidisciplinary purposes is essential for a more health-relevant metric analysis. However, there is little information on minimum masses to determine aerosols, or how sampling duration and the fraction of filter used influence the concentrations of polycyclic aromatic hydrocarbons (PAHs) and their nitro-derivatives (NPAHs). This study evaluated the influence of sampling duration (24 h, 5 d, 7 d) and filter extraction fraction (1/2, 1/4, 1/8 of the filter area) on PAH and NPAH quantification in fine and coarse particulates collected using a high-volume air sampler in Auckland, New Zealand. Samples were analyzed for 14 PAHs and 9 NPAHs using high-performance liquid chromatography. Concentrations normalized to sampled air volume (pg m¯³) were consistently highest in 24 h samples and decreased substantially during multi-day sampling. Filter area fraction bias increased with sampling duration and decreased with extraction area, with 1/8 fractions showing the largest deviations from the half-filter references, particularly at extended durations, while quarter fractions remained closer to the half-filter reference. Stacked-fraction analysis indicated that small punches may not adequately represent full-filter composition during extended sampling periods. Both low- and high-molecular-weight compounds exhibited sensitivity to sampling duration. Diagnostic ratios and principal component analysis indicated compositional shifts and potential secondary formation of NPAHs during multi-day sampling. The amount of particulates collected during 24 h sampling was sufficient for analyzing PAHs and NPAHs, but required a larger sampling area (at least half of the whole filter) to reflect the entire filter. Extended sampling and small filter punches introduced greater heterogeneity and analytical bias. Shorter collection periods did not come at the cost of concentrations and may enable several consecutive monitoring samples. These findings provide practical guidance for optimizing filter-based monitoring of PAHs and NPAHs in atmospheric PM.