Search

Disentangling fire and its controls over thousands of years ago is a major challenge in the study of paleofires. In this paper, we synthesize sedimentary charcoal and black carbon from the coastal plain of Laizhou Bay, China to improve our ability to reconstruct fire history in the past 5000 years, and to assess the controls of fire using principal component analysis and multiple regression approach. The results show that there were three distinct fire episodes at the intervals of 5300–5100 yr BP., 1190–1060 yr BP., and 300–0 yr BP., based on the Changyi (CY) profile. A large-scale fire episode was synchronous with a rapid climate variability that occurred 5300 yr BP., which had frequent drought and cold epoch. High fluxes of black carbon and charcoal were closely related to mass migration and the use of fire for land reclamation from 1190 to 1060 yr BP. Subsequently, anthropogenic biomass burning for cereal cultivation has reached a higher level over the past 300 years. However, between 4600 and 4000 yr BP. the shifts in the frequency of high-magnitude floods and climate aridity consequently resulted in the decline of fire-episode frequency and the abandonment of the late Neolithic settlements in the study region. Therefore, climate is still a prerequisite factor for fire occurrence on the southern coast of Laizhou Bay in the past 5000 years. A rapid climate variability was not only responsible for various fire patterns, but also could affect human settlements and the mode of production during middle-late Holocene. In the past 1000 years, human land use has been a more important control of fire. However, temperature has become one of the evidently identified controls of fire across the study area in recent decades. To synthesize the methods of Principal Component Analysis and Multiple Regression Analysis with multi-proxy evidence is necessary for us to better understand fire and its controls on coastal plain of Laizhou Bay at the region. • Charcoal and BC have recorded fire mid-Holocene at the Laizhou Bay of China. • Climate was still a prerequisite control of fire at the Laizhou Bay mid-Holocene. • In the past 1000 years, human land use has been an important control of fire. • Temperature has become one of the identified controls of fire across the study area. • Principal component analysis will contribute to disentangling fire and its controls. [ABSTRACT FROM AUTHOR]

Abstract: The aggressive traffic interventions and emission control measures implemented to improve air quality during the 2008 Beijing Olympic Games created a valuable case study to evaluate the effectiveness of these measures on mitigating air pollution and protecting public health. In this paper, we report the results from our field campaign in summer 2008 on the on-road emission factors of carbon monoxide, black carbon (BC) and ultrafine particles (UFP) as well as the ambient BC concentrations. The fleet average emission factors for light-duty gasoline vehicles (LDGV) showed considerable reduction in the Olympic year (2008) compared to the pre-Olympic year (2007). Our measurement of Black Carbon (BC), a primary pollutant, at different elevations at the ambient site suggests consistent decrease in BC concentrations as the height increased near the ground level, which indicates that the nearby ground level sources, probably dominated by traffic, contributed to a large portion of BC concentrations in the lower atmospheric layer in Beijing during summertime. These observations indicate that people living in near ground levels experience higher exposures than those living in higher floors in Beijing. The BC diurnal patterns on days when traffic control were in place during the Olympic Games were compared to those on non-traffic-control days in both 2007 and in 2008. These patterns strongly suggest that diesel trucks are a major source of summertime BC in Beijing. The median BC concentration on Olympic days was 3.7 μg m−3, which was dramatically lower than the value on non-traffic-control days, indicating the effectiveness of traffic control regulations in BC reduction in Beijing. [Copyright &y& Elsevier]