Effects of light regime, temperature, and plant age on uptake of arsenic by Spartina pectinata and Carex stricta.

We report here on efforts to show that a combination of native wetland plant species might perform better than a monoculture in wetlands designed for arsenic remediation by supplementing weaknesses. Carex stricta and Spartina pectinata were used in hydroponic experiments. (i) Arsenic uptake was first assessed at two ages via exposure to control or arsenic-laden solutions (0 or 1.5 mg As L(-1) as Na2HAsO4) for two weeks. Age had no significant effect on arsenic concentrations in roots, but translocation factors were greater in older plants of C. stricta and S. pectinata (0.45 and 0.07, respectively) than in younger plants (0.10 and 0.01, respectively). (ii) Seasonal effects were assessed by determining uptake kinetics for both species in conditions representative of spring temperatures (15/5 degrees C) and light regimes (1050 micromol m(-2) s(-1), 13 h day(-1)) and summer temperatures (28/17 degrees C) and light regimes (1300 micromol m(-2) s(-1), 15 h day(-1)). Both species had comparable rates of arsenic uptake into roots in summer conditions (44.0 and 46.5 mg As kg(-1) dry wt. h(-1) in C. stricta and S. pectinata, respectively), but C. stricta had a higher maximum net influx rate in spring conditions (24.5 versus 10.4 mg As kg(-1) dry wt. h(-1)).