Historical variation of black carbon and PAHs over the last ~200 years in central North China: Evidence from lake sediment records.

As the largest coal-producing province in China, the coal production of Shanxi Province accounts for one third of the country's total. Thus it is of great importance to study the pollution history of typical pollutants in Shanxi Province and their links with energy usage in North China. Sediment cores from two relatively remote lakes in central North China were retrieved to investigate historical evolutions of black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs) in the last ~200 years. The two records show several-fold increases in both concentrations and depositional fluxes of BC, char, soot, and PAHs in recent five decades, which were associated with the influence of anthropogenic activities resulting from socio-economic development in Shanxi Province. However, after ~2000 their fluxes decreased sharply due to China's effort on environmental protection. These changes indicate that atmospheric BC and PAHs loads in the region were affected significantly by recent anthropogenic activities and environmental policies. Ratios of individual PAHs and char/soot indicate pyrogenic sources of these increased pollutants in recent decades, with coking industry and coal combustion as the two major sources. Significant positive correlations between BC and PAHs were observed in both cores of Lake Gonghai and Lake Mayinghai, indicating that they were likely co-transported by BC particles from similar sources. This study provides new and important understanding of the atmospheric pollution history of BC and PAHs in North China.