Temporal dynamics of urbanization-driven environmental changes explored by metal contamination in surface sediments in a restoring urban wetland park.

Spatial patterns of metal distribution along urban-rural or multi-city gradients indicate that the urbanization process directly lead to metal enrichment and contamination in the environments. However, it has not yet looked at homogenization dynamics of an urban-rural gradient pattern over time with urbanization process in an area. This study monitored anthropogenic metals (Cr, Cu, Pb, and Zn) in surface sediments from channels of a newly-opened National Wetland Park to elucidate the urbanization-driven dissolution of urban-rural gradient pattern between 2008 and 2011. Sixty-eight surface sediment samples were taken from these channels in July of both 2008 and 2011. Results showed that a spatial distribution pattern of total metal contents along the gradient of urbanization influence, evident in 2008, was homogenized in 2011 with the area development. The lead stable isotope ratio analysis identified anthropogenic Pb origins from vehicular exhausts, cements, and coal flying ashes, which elevated metal contents in the inner channels via atmospheric deposition. Specific hazard quotients of the metal contamination in surface sediment were also assessed and enhanced over time in the study wetland park. These findings suggest that emissions from traffic, construction, and energy generation contribute metal loadings in the urbanizing environment.

[The study of several aldehyde molecules by Raman spectroscopy].

The Raman spectra of formaldehyde, acetaldehyde, propionaldehyde and n-butyraladehyde (CnH2nO,n = 1, 2, 3, 4) were obtained by portable Raman spectrometer. The molecules of the four aldehydes were calculated by density functional theory (DFT). By comparing the calculated result and the experimental result, the bands of these Raman spectra were assigned. And the Raman spectra of these aldehydes molecules were analyzed and compared. These aldehydes could be real-time rapidly identified by Raman spectroscopy technology.