Abstract: Rhizosphere soil samples were collected from plants Nerium indicum, which grew well in a pot experiment with lead and zinc slag as substrates. The bacterial strains resistant to lead and zinc were isolated and identified, and the factors influencing lead and zinc adsorption and the adsorption mechanism were discussed. The results showed that: (1) Three bacterial strains (B1, B4, B14) could grow on the beef extract peptone medium that concentrated Pb²⁺ and Zn²⁺ (600 mg·L^-1). Based on morphology and molecular biology, B1, B4, and B14 were identified as Bacillus cereus or B. anthracis, Aneurinibacillus aneurinilyticus and Micrococcus luteus. (2) Three factors including pH, adsorption time and the initial bacterial amount which may influence the Pb²⁺ and Zn²⁺ biosorption ability were analyzed. Under the conditions of pH 5.0, adsorption time 50 min, and initial bacterial amount 0.06 g, the rates of removing Pb²⁺ and Zn²⁺ by the strain B1 reached 84.22% and 70.66%, respectively. Under the conditions of pH 6.0, adsorption time 50 min, and initial bacterial amount 0.18 g, the rates of removing Pb²⁺ and Zn²⁺ by the strain B4 reached 72.63% and 54.17%, respectively. Under the conditions of pH 4.0, adsorption time 60 min, and initial bacterial amount 0.10 g, the rates of removing Pb²⁺ and Zn²⁺ by the strain B14 reached 77.56% and 50.63%, respectively. (3) The results of scanning electron microscope (SEM) and Fourier transform infrared (FT-IR) spectroscopy revealed that the biosorption process mainly happened on the cell surface and internal biosorption also existed. The main active groups that adsorb, complexate and chelate metal ions or atoms were the hydroxyl, amino, alkyl and amide groups. The combination reaction between heavy metals and active groups on the surface of the bacteria was the main mechanism of Pb²⁺ and Zn²⁺ adsorption.

Key words: trade-off., cavitation resistance, ring-porous wood, hydraulic conductance, diffuse-porous wood