Whole air canister samples were collected at four national parks in the southwestern United States. The parks are Carlsbad Caverns National Park (CAVE) in New Mexico, Grand Canyon National Park (GRCA) in Arizona, Great Basin National Park (GRBA) in Nevada, and Joshua Tree National Park (JOTR) in California. Sampling took place at each site from 4 April 2017 to 14 September 2017. In addition to these measurements, a short intensive study was conducted in and around CAVE in September 2017. This intensive included measurements from nearby Guadalupe Mountains National Park (GUMO) and Bitter Lake National Wildlife Refuge. Whole air samples were analyzed for 56 individual volatile organic compounds using a five-channel, three-GC (gas chromatograph) analytical system, which employed three flame ionization detectors (FIDs), one electron capture detector (ECD) and one mass spectrometer.This file contains the sample information and concentrations of data collected during a study to characterize volatile organic compounds at four national parks in the southwestern US. These data are associated with the manuscript: Benedict, K.B., Prenni, A.J. El-Sayed, M.M.H., Hecobian, A., Zhou, Y., Gebhart, K.A., Sive, B.C., Schichtel, B.A., Collett Jr, J.L., submitted. Volatile organic compounds and ozone at four national parks in the southwestern United States. Atmospheric Environment. The abstract from the submitted manuscript is as follows: The National Park Service is tasked with protecting the lands it oversees, including from impacts from air pollutants. While ozone is regularly monitored in many parks across the United States, precursors to ozone formation are not routinely measured. In this work we characterize volatile organic compounds (VOCs) at four national parks in the southwestern United States: Carlsbad Caverns (CAVE), Great Basin (GRBA), Grand Canyon (GRCA), and Joshua Tree (JOTR). Whole air samples were collected for VOC analysis for five months (mid-April through mid-September) in 2017. Samples were collected from 3 PM to 5 PM local time, corresponding approximately to the time of expected peak ozone concentrations, and were analyzed using gas chromatography for a variety of compounds including alkanes, alkenes, aromatics, biogenics, and alkyl nitrates. Among the four parks, the total measured VOC mixing ratio was greatest at CAVE, mostly due to an abundance of light alkanes (on average 94% of all VOCs measured) from oil and gas sources. VOC concentrations at the other three parks were similar to each other and approximately 7-10 times lower than at CAVE. While VOC sources varied across sites, VOC-OH reactivity was dominated by biogenic compounds at all sites except CAVE, which had similar contributions from biogenics and from light alkanes. To better characterize source influences, intensive measurements were conducted in and around CAVE for one week in September 2017. These measurements showed an oil and gas influence throughout the region and indicated that the whole air samples collected over the five-month study did not capture the full range of VOC mixing ratios present at other times of the day.This work was funded by the National Park Service. The CSU portion of the work was funded by Cooperative Agreement H2370094000, Task Agreement P13AC01187
