Reflectance properties and physiological responses of bulrush in wetland parks to heavy metal contamination

Abstract

Wetland park ecosystems of Yangtze River Delta are located in highly populated areas and subject to high levels of contamination. Monitoring of wetlands to assess degrees of pollution damage requires periodic retrieval of information over large areas, which can be effectively accomplished by remote sensing technologies. The biophysical principles of remote sensing of vegetation under stress need to be understood in order to correctly interpret the information obtained at the scale of canopies. To determine the potential to remotely characterize and monitor pollution, plants of Bulrush, a major component of wetland park communities in Yangtze River Delta, were treated with two metals to study their sensitivity to pollutants and how this impacted their reflectance characteristics. Several growth and physiological parameters, as well as their reflectance were measured. Significant differences between treatments were found in at least some of the measured parameters in pollutants. Reflectance was sensitive to early stress levels only for cadmium. Pollutants that differ in their way of action also had different plant reflectance signatures. The high degree of correlation between spectral reflectance and plant stress by heavy metal contamination showed the potential of using remote sensing to assess the type and degree of pollution damage.