Spatial and temporal changes of heavy metal concentrations in mosses and its indication to the environments in the past 40 years in the city of Shanghai, China

The mosses have been widely used as bioindicators to investigate pollution and changes of heavy metals in different countries and regions. For a better understanding of the environmental changes in the past 40 years in Shanghai, one of the largest cities in the world, we studied the spatial and temporal changes of five heavy metal depositions in two species of the moss genus Haplocladium. By means of the atomic absorption spectroscopy (AAS) method, the concentrations of Cd, Cr, Cu, Pb, and Zn in the plants of moss Haplocladium samples collected from 16 sites in Shanghai in 1965, 1974–1976, 1978–1982, and 2005 were determined and shown in the color Isogram maps made with the computer program Arcmap 9.0. The trends of the heavy metal concentrations in selected sites including Sheshan Mt., Jin Shan Petrochemical Plant, and the four representative sites of Shanghai were analyzed with two-factor analysis of variance and linear regression analysis, respectively. The results showed that the concentrations of the five heavy metals at all sample sites increased distinctly from 1965 to 2005, especially after the 1980s. The increasing rate was Cr>Cu>Cd>Pb>Zn. The heavy metal concentrations were distinctly associated with local emission point sources and changes in emission levels, and the major emission sources in Shanghai were industry and traffic.