1. Oil and Gas related emissions that could impair visibility increased in Bakken area, mostly since 2002. 2. Coal-fired power plant emissions decreased during the same time period 3. Most fine particle concentrations declined during this time, but at sites closest to O&G activity declined more slowly or increased. 4. Impacts from Oil & Gas are most evident in elemental carbon, fine soil & coarse mass (15-30% of visibility impairment). 5. These likely due to flaring, truck traffic (diesel engines & dust), surface disturbance and secondary growth. 6. Maybe Oil & Gas impacts on sulfates and nitrates, but these harder to discern with receptor techniques due to concurrent decline in emissions from other sources.
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