Colorado Front Range Emissions Study Regional study of the impact of oil and gas operations on ambient hydrocarbon levels in the Northern Front Range based on:  wind sector analysis of long-term multi-species measurements at the NOAA Boulder Atmospheric Observatory (Weld County),  and Mobile Lab intensive campaign to characterize the chemical signature of local point and area sources of alkanes. This research seeks to better quantify emissions of ozone precursors and greenhouse gases. NOAA BAO Instrumented Tall Tower Mobile Lab: CH 4, CO 2, CO and O 3 and targeted flask sample collection Well-calibrated GHG and VOC measurements Gabrielle Petron and Gregory Frost

Air samples collected at the BAO and SGP* have a strong alkane signature. Both sites are in major oil and gas production regions. * SGP is a NOAA aircraft site in Northern Oklahoma. Samples collected below 650 meters were used for this analysis BAO: Distinct Alkane Signature NOAA Cooperative Tall Tower Measurement and Sampling Network SGP Median summer mixing ratio at 7 NOAA Towers Midday data only (June-Aug ) NWF BAO

Alkane source in NE wind sector: Denver Julesburg Basin North & East SOUth West Boulder Atmospheric Observatory: - 30-sec met data at 3 vertical levels - daily midday air sample collection from 300 meter level and analysis in NOAA ESRL labs Air samples from the North and East wind sector have the strongest alkane signature (all year round), suggesting this is where the alkane source is likely located.

Mobile Lab intensive sampling in Front Range Mobile Platform to sample close to sources High-frequency analyzers to detect plumes and target flask sampling Discrete air sampling (PFP) for multi- species chemical analyses in the NOAA lab Programmable Flask Package and Programmable Compressor Package designed by Doug Guenther, GMD Mobile Lab Map of discrete samples collected with Mobile Lab in June-July 2008 Denver Julesburg Basin, O&G wells

Same alkane signature at BAO and in Mobile Lab samples y=0.50x r 2 =0.98 y=0.48x r 2 =1 The alkanes are strongly correlated in BAO N&E wind sector samples and in Mobile Lab samples.  The alkanes come from the same source located in NE part of the Front Range. Samples collected with the Mobile Lab close to feedlots, a landfill, a waste water treatment plant have enhanced methane compared to the other samples.

Oil and Gas Operations in DJ Basin Drilling Rig Compressor Station Condensate Tank Gas Well Processing Plant Weld County 2006: wells, 877 spuds [Bar-Ilan et al., 2008]

Comparison of atmospheric molar ratios with WRAP/Environ bottom-up inventory The observed alkanes atmospheric molar ratios are in line with the distribution of emissions ratios for venting and flashing emissions from oil and gas upstream and midstream operations. The prevalent alkane signature observed in the Northern Front Range at BAO (blue) and with the Mobile Lab (red) are different from the urban air signature (black and green). Western Regional Air Partnership Phase III inventory: Emission inventories for total VOC and NOx from oil and gas exploration, production and midstream gathering and processing operations in the major fossil fuel basins throughout six states (CO, MT, NM, ND, UT, and WY). Environ was commissioned by WRAP to build the inventory.

Conclusions Oil and Gas operations in the Colorado Northern Front Range have a regional impact on air composition. This was a study of opportunity to characterize emissions of climate and air quality relevant gases. The complementary capabilities of ESRL’s research divisions and close collaboration with regional public and private entities provide high quality information which can be used by regulatory and policy agencies. In order to enhance our policy-relevant science and to develop a process-level understanding of O&G impacts on air quality and climate in the Rocky Mountain region, the following efforts should be pursued: – Intensive studies using towers, ground sites, and mobile platforms – Ongoing long-term in-situ or discrete chemical measurements at tall towers – Meteorological data from towers and wind profilers