Wc. Keene et al., Composite global emissions of reactive chlorine from anthropogenic and natural sources: Reactive Chlorine Emissions Inventory, J GEO RES-A, 104(D7), 1999, pp. 8429-8440
Emission inventories for major reactive tropospheric Cl species (particulat
e Cl, HCl, ClNO2, CH3Cl, CHCl3, CH3CCl3, C2Cl4, C2HCl3, CH2Cl2 and CHClF2)
were integrated across source types (terrestrial biogenic and oceanic emiss
ions, sea-salt production and dechlorination, biomass burning, industrial e
missions, fossil-fuel combustion, and incineration). Composite emissions we
re compared with known sinks to assess budget closure; relative contributio
ns of natural and anthropogenic sources were differentiated. Model calculat
ions suggest that conventional acid-displacement reactions involving S-(IV)
+O-3, S-(IV)+ H2O2, and H2SO4 and HNO3 scavenging account for minor fractio
ns of sea-salt dechlorination globally. Other important chemical pathways i
nvolving sea-salt aerosol apparently produce most volatile chlorine in the
troposphere. The combined emissions of CH3Cl from known sources account for
about half of the modeled sink, suggesting fluxes from known sources were
underestimated, the OH sink was overestimated, or significant unidentified
sources exist. Anthropogenic activities (primarily biomass burning) contrib
ute about half the net CH3Cl emitted from known sources. Anthropogenic emis
sions account for only about 10% of the modeled CHCl3 sink. Although poorly
constrained, significant fractions of tropospheric CH2Cl2 (25%), C2HCl3 (1
0%), and C2Cl4 (5%) are emitted from the surface ocean; the combined contri
butions of C2Cl4 and C2HCl3 from all natural sources may be substantially h
igher than the estimated oceanic flux.