Emissions from China: Implications for the Regional and Global Environment

Emissions from China: Implications for the Regional and Global Environment Yuxuan Wang Harvard University ACCESS VIII Colloquium Sep. 2-3, 2005

Uncertainty in the Bottom-up Emissions Bottom-up emissions ~ ( activity rate * emission factor)

NestedGrid Version of GEOS-CHEM 1 x1 4 x5

Aircraft and Chinese Station Data Time frame: Feb. – Apr., 2001

A priori Emissions of CO and NOx Uncertainties: 154% for CO, 27% for NOx Source: Streets et al. [2003] r

CTM Underestimates Observations of CO and NOy aircraft Surface stations

Inversion Analysis of observations Atmospheric “forward” model gives C = kE • Bayesian approach to linear inversion with Gaussian statistics a posteriori state vector a posteriori error covariance matrix Monitoring site measures concentration C Inverse model E = k-1C a “top-down” estimate Eese (fuel burned) X (emission factor) a a priori “bottom-up” estimate Ea sa

Inversion requires a large increase in a posteriori emissions

Inversion requires a large increase in a posteriori emissions Wang et al., JGR, 2004

Revising the ‘Bottom-up’ CO Emissions : Low Efficiency Industrial Processes +34% higher (73% from industrial sector) courtesy of Q. Zhang

NH2OH Low levels of O2 Aerobic denitr. N2O, NO N2O, NO Microbial Sources of N2O and NOx O2 O2 Nitrification: NH4+ NO2-  NO3- Denitrification: NO3- N2O  N2 The weight of the evidence suggests that nitrification provides the dominant source of N2O.

Survey of Field and Laboratory Studies • Yield of N2O and NO increases with decreasing levels of O2 • So does the NO / N2O ratio

N Processed through the Agriculture/Animal/Human Food Chain 226 McElroy and Wang, GBC, 2005

Top-down Budget of N2O • Sink: photolytic process in the stratosphere  lifetime 120 yr • Pre-industrial concentration: 270 ppb  natural source of 10.9 TgN/yr • Current concentration (314ppb) and annual increase rate (0.8ppb)  current source of 16.6 TgN/yr • Anthropogenic source: 5.7 TgN/yr • Fossil fuel and industrial processes: 1.3 TgN/yr • Microbial sources: 4.4 TgN/yr  2% yield for N2O

NOx/N2O = 3 or 6% yield for NOx Biomass burning sources are excluded McElroy and Wang, GBC, 2005

Trends in N Processed through the Global Food Chain Use the yield of 2% for N2O McElroy and Wang, GBC, 2005

Trends in Atmospheric N2O using a One-box Model dC / dt = S / 4.8 – C/τ McElroy and Wang, GBC, 2005

Summary • The nested grid model provides an adequate account of the meteorological features in spring time over China [Wang et al., JGR, 2004a] • The current inventory underestimated Chinese emissions of CO and NOx [Wang et al., JGR, 2004b] • Emissions of NOx and N2O from the disposal of N in organic wastes are significant for large developing countries. This source is underestimated in contemporary models of global atmospheric chemistry.[McElroy andWang, GBC, 2005] • Further studies are needed to refine our understanding of the fate of N in animal wastes

Emissions from China: Implications for the Regional and Global Environment