Spatial and seasonal patterns and long term variability of the composition of the haze in the United States: an analysis of data from the IMPROVE network

July 1996.Principal investigators: William C. Malm, Marc L. Pitchford.Includes bibliographical references.This report describes data for the three year period, March 1992 through February 1995, of the Interagency Monitoring of Protected Visual Environments (IMPROVE) measurement program. IMPROVE is a cooperative visibility monitoring effort between the United States Environmental Protection Agency, (EPA) federal land management agencies, and state air agencies

Meteorological and Back Trajectory Modeling for the Rocky Mountain Atmospheric Nitrogen and Sulfur Study II

The Rocky Mountain Atmospheric Nitrogen and Sulfur (RoMANS II) study with field operations during November 2008 through November 2009 was designed to evaluate the composition and sources of reactive nitrogen in Rocky Mountain National Park, Colorado, USA. As part of RoMANS II, a mesoscale meteorological model was utilized to provide input for back trajectory and chemical transport models. Evaluation of the model's ability to capture important transport patterns in this region of complex terrain is discussed. Previous source-receptor studies of nitrogen in this region are also reviewed. Finally, results of several back trajectory analyses for RoMANS II are presented. The trajectory mass balance (TrMB) model, a receptor-based linear regression technique, was used to estimate mean source attributions of airborne ammonia concentrations during RoMANS II. Though ammonia concentrations are usually higher when there is transport from the east, the TrMB model estimates that, on average, areas to the west contribute a larger mean fraction of the ammonia. Possible reasons for this are discussed and include the greater frequency of westerly versus easterly winds, the possibility that ammonia is transported long distances as ammonium nitrate, and the difficulty of correctly modeling the transport winds in this area

Dataset associated with "Volatile organic compounds and ozone at four national parks in the southwestern United States"

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

Origin of Fine Particulate Carbon in the Rural United States

Carbonaceous compounds are a significant component of fine particulate matter and haze in national parks and wilderness areas where visibility is protected, i.e., class I areas (CIAs). The Regional Haze Rule set the goal of returning visibility in CIAs on the most anthropogenically impaired days to natural by 2064. To achieve this goal, we need to understand contributions of natural and anthropogenic sources to the total fine particulate carbon (TC). A Lagrangian chemical transport model was used to simulate the 2006–2008 contributions from various source types to measured TC in CIAs and other rural lands. These initial results were incorporated into a hybrid model to reduce systematic biases. During summer months, fires and vegetation-derived secondary organic carbon together often accounted for >75% of TC. Smaller contributions, <20%, from area and mobile sources also occurred. During the winter, contributions from area and mobile sources increased, with area sources accounting for half or more of the TC in many regions. The area emissions were likely primarily from residential and industrial wood combustion. Different fire seasons were evident, with the largest contributions during the summer when wildfires occur and smaller contributions during the spring and fall when prescribed and agricultural fires regularly occur