Temporal and spatial variability of trace volatile organic compounds in rainwater Katherine M. Mullaugh ⇑ , Joanna M. Hamilton, G. Brooks Avery, J. David Felix, Ralph N. Mead, Joan D. Willey, Robert J. Kieber Department of Chemistry & Biochemistry, University of North Carolina Wilmington, Wilmington, NC, USA highlights  A HS-SPME method optimized for the detection of VOCs in rainwater.  Rainwater was collected and analyzed for VOCs over a one-year period (111 samples).  Methylfuran occurred most frequently (detected in 86% of samples).  Rainwater is not an effective removal mechanism of BTEX at this location (<0.1%). article info Article history: Received 9 January 2015 Received in revised form 9 April 2015 Accepted 10 April 2015 Available online 15 May 2015 Handling Editor: I. Cousins Keywords: VOCs Rainwater BTEX HS-SPME Methylfuran Carbon tetrachloride abstract This study presents the first detailed concentration profile of trace VOCs in atmospheric waters. Analytes were detected and quantified in 111 unique rain events in Wilmington, NC, USA over a one-year period. Headspace solid phase microextraction was optimized for detection of these compounds at sub-nanomo- lar levels. Distinct seasonality in both the occurrence and concentration of compounds was observed with the lowest abundance occurring during low irradiance winter months. In contrast to other rainwater components studied at this location, VOCs did not show any correlation between rainfall amount and concentrations. There was significant spatial variation with regards to air-mass back-trajectory for methyfuran with higher concentrations observed in terrestrial events during the growing season. Air mass back trajectory also impacted CCl 4 concentrations in rainwater with evidence of a possible oceanic input. However there was no significant impact of air-mass back-trajectory on the concentration of BTEX observed in rain indicating that storm origin is not the controlling factor driving concentrations of these analytes in precipitation. Members of the BTEX family did, however, have significant correlations with each other occurring in ratios aligned closely with ratios reported in the literature for gas-phase BTEX. Using available gas-phase data from locations with similar anthropogenic sources and Henry’s Law con- stants, calculated concentrations agreed with VOC levels found in Wilmington rain. Results of this study indicate local gas-phase scavenging is the major source of VOCs in rain and wet deposition is not an effi- cient removal mechanism (<0.1%) of VOCs from the atmosphere. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction During the last three decades, extensive research has reported the concentrations and atmospheric reactions of volatile organic compounds (VOCs) in the atmosphere (Field et al., 1992; Monod et al., 2001; Williams, 2004). The concentration, variability and atmospheric fate of these compounds is of interest because they pose a direct risk to human health (Kim et al., 2013) while also indirectly impacting air quality by contributing to photochemical smog (Monod et al., 2001) and the formation of secondary organic aerosol (SOA) (Kalberer et al., 2004). Biogenic emissions of VOCs are generally considered more significant than anthro- pogenic emissions on a global scale (Williams, 2004) however anthropogenic emissions can be the major source of VOCs on a local scale, largely due to the use of fossil fuels (Field et al., 1992; Perez-Rial et al., 2009). VOCs in this study with known potential biogenic sources include carbon tetrachloride (Roy et al., 2011), toluene (Juttner and Henatsch, 1986; White et al., 2009), and methylfuran, a product of isoprene oxidation (Montzka, 1995). http://dx.doi.org/10.1016/j.chemosphere.2015.04.027 0045-6535/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Department of Chemistry & Biochemistry, College of Charleston, Charleston, SC, USA. E-mail address: mullaughkm@cofc.edu (K.M. Mullaugh). Chemosphere 134 (2015) 203–209 Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere