Sediment records of global and regional Hg emissions to the atmosphere in North China over the last three centuries

Abstract

Reconstructing the long-term Hg history in major emission countries is important for understanding the global Hg cycle and controlling Hg pollution. In this study, the atmospheric Hg history was reconstructed over the last three centuries based on three lacustrine sediment records from southeastern Inner Mongolia in North China, and its relationship with global and regional Hg emissions was revealed. These records show little Hg pollution in the 18th and 19th centuries. This implies a limited influence of Hg emitted from Europe and North America in this region, which is confirmed by their different Hg trends during the two World Wars and the post-1970s. Atmospheric Hg in the region had increased gradually since the 1900s, primarily contributed by emissions from the former Soviet Union in Lake Dalihu (DLH) and Lake Zhagesitai (ZGST) and from the Beijing-Tianjin-Hebei region in Lake Kulunnao (KLN). In the last century, two decreases in Hg fluxes occurred in the KLN core due to the economic recession in the 1960s–1970s and reduced energy consumption and industrial production in the 1990s. In the DLH and ZGST cores, only one decrease occurred, corresponded with the dissolution of the Soviet Union in the 1990s. Although atmospheric Hg emissions in China had stabilized or even decreased in the last decade, atmospheric Hg continued to increase, particularly in KLN, because of emissions from small cities in the region. This study can help understand Hg sources and control Hg pollution in North China and supplement the understanding of the global Hg cycling.