An investigation of the chemistry of ship emission plumes during ITCT 2002

Abstract

[1] A ship emission plume experiment was conducted about 100 km off the California coast during the NOAA Intercontinental Transport and Chemical Transformation (ITCT) 2K2 airborne field campaign. Measurements of chemical species were made from the NOAA WP-3D aircraft in eight consecutive transects of a ship plume around midday during 2.5 hours of flight. The measured species include NO x , HNO 3 , peroxyacetylnitrate (PAN), SO 2 , H 2 SO 4 , O 3 , CO, CO 2 , nonmethane hydrocarbons (NMHC), and particle number and size distributions. Observations demonstrate a NO x lifetime of $1.8 hours inside the ship plume compared to $6.5 hours (at noontime) in the moderately polluted background marine boundary layer of the experiment. This confirms the earlier hypothesis of highly enhanced in-plume NO x destruction. Consequently, one would expect the impact of ship emissions is much less severe than those predicted by global models that do not include rapid NO x destruction. Photochemical model calculations suggest that more than 80% of the NO x loss was due to the NO 2 + OH reaction; the remainder was by PAN formation. The model underestimated in-plume NO x loss rate by about 30%. In addition, a comparison of measured to predicted H 2 SO 4 in the plumes suggests that the photochemical model predicts OH variability reasonably well but may underestimate actual values. Predictions of in-plume O 3 production agree well with the observations, suggesting that model-predicted peroxy radical (HO 2 + RO 2 ) levels are reasonable. The model estimated ozone production efficiency ranges from 6 to 30. The largest model bias was seen in the comparison with measured HNO 3 . The model overestimated in-plume HNO 3 by about a factor of 6. This is most likely caused by underestimated HNO 3 sinks possibly involving particle scavenging. However, limited data availability precluded a conclusive test of this possible loss process.

Assessing the effect of marine isoprene and ship emissions on ozone, using modelling and measurements from the South Atlantic Ocean

“…This is in general agreement with previously reported ambient measurements of 0.5-2 ppbv NO x in ship plumes in the northern hemisphere. [32] Isoprene was emitted into the model by daylight in keeping with previous observations [3] to reach the levels measured during the cruise (see Table 1). Bloom emissions occurred for 4 consecutive days starting on 31 January at 0000 hours local time.…”

Biogenic emission measurement and inventories determination of biogenic emissions in the eastern United States and Texas and comparison with biogenic emission inventories

“…This filter was applied because of the detection limit of SO 2 on the order of a few hundred pptv. The error in the OH calculation was shown to be smaller than a factor of 2 [Chen et al, 2005]. The H 2 SO 4 steady state model calculation will be described in more detail elsewhere (A. T. Hanks et al, manuscript in preparation, 2010).…”

“…For this analysis, the value of the mass accommodation coefficient used was 0.7 as suggested by Chen et al [2005]. OH concentrations were only calculated for sulfur dioxide concentrations larger than 1 ppbv using equation (5).…”

Accounting for non-linear chemistry of ship plumes in the GEOS-Chem global chemistry transport model

“…Several studies with Lagrangian models (e.g. von Song et al, 2003;Chen et al, 2005) showed that the NO x lifetime within ship plumes is a factor 2.5-10 shorter than the lifetime of roughly 1 day estimated by the instantly diluting CTMs. These Lagrangian models account for the higher NO x concentrations in the initial dispersion stages of the plume, leading to elevated OH levels and thereby shorter NO x lifetimes.…”