Local and non-local sources of soot (black carbon) have different influences on surface concentrations and radiative forcing (change the Earth’s energy balance) in different regions of China. These sources contribute to poor air quality in many regions.
A study led by scientists at the U.S. Department of Energy’s Pacific Northwest National Laboratory revealed the influence of local and non-local soot sources and its impact on regional radiative forcing and poor air quality in many regions of China.
Researchers used simulations of the Community Earth System Model with emissions for the years 2010−2014 and a black carbon (BC) source-tagging technique to quantify the source attribution of BC and its direct radiative forcing in China. They found that in regions with high emissions (e.g., north, south, and northeast China), local emissions predominantly contributed to BC concentrations, while non-local emissions more strongly influenced near-surface BC over central and western China, which have lower emissions. The study showed that during polluted days, nonlocal sources played an important role in increasing regional BC concentrations. In the winter haze season, more than 50 percent of surface BC in China originated from emissions in north China, which contributed more than 90 percent to local BC and a substantial amount to south, southwest, and central-west China. The study showed that local emissions accounted for 65 percent of BC direct radiative forcing (i.e., atmospheric heating) in China, while outside sources contributed 35 percent. Meanwhile, emissions from China accounted for 8 percent of BC concentration and 29 percent of the total air column load of BC in the Western United States in spring. Efficiency analysis showed that a reduction in BC emissions over eastern China could have a greater benefit for the regional air quality in China, especially in the winter haze season.