Environmental magnetic responses of urbanization processes: Evidence from lake sediments in East Lake, Wuhan, China

Abstract

We present a study on the environmental magnetic response to urbanization processes from nine sediment cores from East Lake in Wuhan, China. The concentration of magnetic particles, heavy metals and organic matter in the upper 2-18 cm of the sediment cores have been significantly elevated due to the input of coarse magnetite grains from industrial (e.g. power generation and steelmaking) and other anthropogenic activities (e.g. vehicle emissions). Concentration-related magnetic parameters, such as magnetic susceptibility (χ), saturation isothermal remanent magnetization and anhysteretic remanent magnetization, are significantly correlated with concentration of heavy metals and organic matter, for example, Pearson's correlation coefficients are 0.921 for χ-Cu, 0.660 for χ-Pb and 0.848 for χ-loss-on-ignition, respectively. The magnetic properties of the lake sediments document the pollution history caused by human impact on the lake catchment during urbanization. The environmental quality of the lake was fairly good before the 1960s. Magnetic, heavy metal and organic matter contents of the sediments were low and relatively constant, which indicates relatively stable natural inputs from the lake catchment. Pollution trends since the 1960s are reflected in downcore magnetic property variations of the lake sediment. The concentration of magnetic particles in the lake sediments started to increase since 1957, when the Wuhan Iron and Steel Company and the Qingshan Thermal Power Plant, which are located upwind of the lake, were built and put into production. Lake pollution was further aggravated since the acceleration of industrialization and urbanization in East Lake area in the 1980s, which is verified by the elevated concentration of heavy metals and organic matter in the sediments. The magnetic mineral concentration in the lake sediment increased continuously until it peaked in the 1990s and has remained a high level since then. These results suggest that magnetic properties respond sensitively to environmental status, and that the magnetic properties of sediments can provide an excellent record of the industrial and anthropogenic history in an urban lake catchment. © 2009 The Authors Journal compilation © 2009 RAS.