Photosynthesis of alfalfa (Medicago sativa) in response to landfill leachate contamination.

Thousands of unlined landfills and open dumpsites have put great threat on the security of soil and ground water due to leachate leakage. Alfalfa is believed potential as a phytoremediation plant for leachate contamination based on strong root system and the excellent capacity of removing various kinds of pollutants. A lab-scale investigation was conducted to figure out the sensitiveness of alfalfa photosynthesis in response to leachate contamination. The results demonstrated that both of the maximum photosynthetic efficiency (Fv/Fm) and net photosynthetic rate (Pn) were slightly inhibited in the high-dosage group. Based on statistical analysis, higher sensitivity of Pn to leaching parameters than Fv/Fm was observed. There were significant correlations between most of leaching parameters (pH, ammonium and COD) and Pn with correlation coefficients of 0.530, -0.580 and -0.578 (p < 0.01), respectively. Therefore, Pn is potential for acting as an effective indicator for staple leaching characteristics of leachate contaminated soils.