Emission of unintentionally produced polychlorinated biphenyls (UP-PCBs) in China: Has this become the major source of PCBs in Chinese air?

There are two kinds of primary emissions of PCBs to the atmosphere; one is primary emissions due to intentionally produced PCBs (IP-PCBs), and the other is due to unintentionally produced PCBs (UP-PCBs). This paper presents UP-PCB emissions in China from 1950 to 2010. The total UP-PCB emissions in the 61 years were estimated to be 146.1 t, approximately 98.1% of which were from cement (132.5 t) and steel industries (6.3 t). The emissions from Chinese coking industry were 115 kg from 1950 to 2010, less than 0.1% of the total UP-PCB emissions in China. Both the temporal and spatial trends of these UP-PCB emissions were investigated. The UP-PCB emissions started to increase quickly at the middle of 1980s due to the fast and continuously developing cement and steel industries in China, and exceeded IP-PCB emissions possibly during the beginning of 2000s. The spatial pattern of UP-PCB emissions was in general consistent with the population distribution pattern, indicating the anthropogenic nature of the UP-PCB emissions. The gridded Chinese emission inventories for UP-PCBs from cement and steel industries on a 1/6° latitude and 1/4° longitude resolution were also compiled. The gridded UP-PCB emissions in 2005 were compared with PCB air concentrations measured by our group (IJRC-PTS) in 2005, and a significant correlation between these 2 datasets was found for the rural sites, but not for the urban sites. It is most likely that these UP-PCB emissions were a major source for PCB in Chinese rural air, and possibly responsible for the increase of PCBs in Chinese air as a whole from 2004 to 2008, reported in recent publications. To our knowledge, this is the first dataset of the Chinese UP-PCB emissions spanning 61 years from 1950 to 2010, and also the first gridded emission inventories for UP-PCBs on a national scale.