Ozone and nitrogen deposition from Colorado’s Craig powerstation

NOx from Craig

• The Craig powerstation is the largest uncontrolled NOx source in the state (~18k tons/yr)

• NPS is lobbying EPA for stricter controls (i.e., SCR on all three boilers)

• What is the impact in terms of

• Ozone• Nitrogen dep• PM nitrate

Approach

• Reduce NO and NO2 emissions from Craig w.r.t. three proposed scenarios• NPS option is most stringent with full SCR

• Reduce NOx from ~18k tons/yr to ~3k tons/yr• Run CAMx for a year (2005) with 12km 4CAQTF

inputs

Regional N dep from Craig

ROMO N dep from Craig

Peak ozone impacts from Craig

Ozone from Craig at Flat Tops WA

VOC vs. NOx from OMI

HCHO

NO2

HCHO/NO2

HCHO and NO2 can be detected from the OMI satellite, and provide

‘indicator species’ to help assess whether a region is

VOC or NOx limited.

HCHO/NO2 > 1Suggests NOx limited

(Duncan et al., 2010)

Craig

ROMO nitrate from Craig

Summary

• Given VOC/NOx ratios in northwestern CO, NOx controls should be effective for reducing ozone, N dep, and haze

• NOx emissions from O&G development in the region (Uintah, Piceance, and SW Wyo) are also a concern• Emissions at the surface: shorter transport?• This sector is growing, and NOx controls may be

harder to apply

Summary (cont’d)

• The benefits from full SCR at Craig could be significant:• Ozone:

• 2 – 6 ppb (8 hr avrg) ozone reduction at Flat Tops WA

• 1 – 2 ppb at ROMO• N dep:

• 0.2 kg N/ha/yr reduction at Mt Zirkel• 0.14 kg N/ha/yr reduction at ROMO

• PM nitrate:• 0.6 ug/m3 reduction at ROMO

Summary (cont’d)

• Nitrate behavior seems a little strange• N dep at ROMO was ~linear w.r.t. to reductions • Next time should use plume-in-grid to better capture

high NOx chemistry