Zhaiqin,Chongqing University |
Yangxing,Chongqing University |
Zhouyu,Chongqing Academy of Environment Science
Advanced Materials Research | Year: 2012
The potential ecological risk index, proposed by Hakanson, was employed for evaluating the heavy metal contamination of the Yangtze River sediment in Chongqing downtown section. Basing on the analysis of last fifteen years monitored data from two national monitoring sections, the results indicated that: The potential ecological risk of the Yangtze River Chongqing downtown section was classified as moderate. The sequence of potential ecological risk was Zn < Pb(As) < As(Pb) < Cu < Cd < Hg, while the concentration of heavy metal in the sediment was Zn > Cu > Pb > As > Cd > Hg. The concentrations of Cd and Cu had significant correlation, Hg should be taken into prior consideration for pollution control and reduction due to its highest potential ecological risk. The RI in 2005 was highest, Hg contributed the most. All the heavy metal except for Pb had distinctive variance, but the variance of RI was not significant annually, It might carried the connotation of little difference on Pb emission amount. According to the location of monitoring site factor variance analysis, it implied that only the potential ecological risk of As and Cd varied significantly.
Yang C.,Chongqing Academy of Environment Science |
Lei B.,Chongqing Academy of Environment Science |
Wang Y.,Chongqing Academy of Environment Science |
Zhang S.,Chongqing Academy of Environment Science
Yingyong Jichu yu Gongcheng Kexue Xuebao/Journal of Basic Science and Engineering | Year: 2014
Understanding the spatial pattern of the urban heat island (UHI) and its influencing factors is crucial for improving the eco-environment of cities. This study aimed to investigate how land use, urban greenland and water body affect the spatial pattern of UHI using TM data in core areas of Chongqing City. The normalized difference vegetation index (NDVI) and land surface brightness temperature (thermal band, band 6)was obtained from the TM data to analyze the UHI. Then, with the combination of field survey and the land use types, the relationships between UHI and land use, urban greenland and water body were explored by GIS and corresponding mathematical statistics. The results show that the UHI is wide distributed. The spatial pattern of UHI is closely related to land use and is consistent with the trends in rapid urban expansion. In addition, different land cover types demonstrate various responses to bright temperature. The construction land is easiest to lead to UHI, while vegetation and water body effectively slow down UHI. The UHI decreases along with the increasing vegetation cover and will disappear if the fractional vegetation cover is greater than 50%. The greater the fraction of urband greenland is, the more prominent is the different temperature within the UHI, forming the cool island. The water temperature is two degree lower than urban greenland on average and thus urban water body is relatively the most direct and effective method to slow down UHI.