2.3.2. The Rice Plant Collection

During harvest, three whole rice plants were randomly collected from each plot by gently pulling the entire plant out of the ground. The samples were washed with tap water and deionized water to remove soil, and then separated into roots, shoots, and grain. The plant samples were dried at 105 ◦C for 30 min and then at 60 ◦C until dry, then crushed with a pulverizer and stored in air-tight polyethylene bags. A 0.50 g plant sample was placed in a 100 mL beaker and predigested overnight in a 10 mL solution of concentrated HNO3 and HClO4 (4:1, *v:v*) at room temperature. The following day, the beakers were placed on an electric heating plate with the temperature raised from 100 to 200 ◦C over 30 min, then the temperature was increased to 250 ◦C until the solution changed colorless, at ~2 mL of solution remaining. The solutions were then removed, cooled, brought to a 25-mL final volume, and filtered through a 0.45-μm membrane filter. The Cd and Pb concentration in the digestate were determined with GFAAS.
