| Red soil sampled from lion mountain woods Wuhan, Hubei province was dividedinto eight types of soil particles:＜2μm organic clay,＜2μm inorganic clay, 2-20μmorganic silt, 2-20μm inorganic silt, 20-200μm organic fine sand, 20-200μm inorganicfine sand, 200-2000μm organic coarse sand, 200-2000μm inorganic coarse sand. Theadsorption of Gram-negative Pseudomonas Putida and Gram-positive Bacillusthuringiensis onto the surfaces of soil particle were investigated in this study, as afunction of time, soil suspension concentration, ionic strength, pH, temperature,bacteria incubation time, and bacteria activity. The main results are as follows:(1) The adsorption process may be divided into the following phases: fast sorptionphase, slow phase and equilibrium phase. The adsorption of bacteria on soil particleincreased with the increase of adsorption time. No remarkable increase in adsorptionwas observed after 60min.(2) Soil suspension concentration of most proper adsorption to Pseudomonas Putidawas 1.5mg.mL-1, 1.5mg.mL-1, 40mg.mL-1 and 50mg.mL-1 for the clay, silt, fine sand andthe coarse sand fractions respectively. To B.thuringiensis, soil suspension concentrationsof most proper adsorption were 0.75 mg.mL-1, 0.6 mg.mL-1 and 60 mg.mL-1 for the clay,silt and sand.(3) The adsorption isotherms followed Langmuir equation with a high correlationcoefficient. For all soil particles, Adsorption increased with an increase in cell concentration. The amounts of P.putida adsorbed increased with decreasing soil particlesize. Particle size fractions of the H2O2-treated the red soil adsorbed less P.putida thanthe natural soil fraction even though it had the highest residual organic matter aftertreatment with hydrogen peroxide. Adsorption amounts of bacteria cells followed thetrend: organic clay＞inorganic clay＞organic silt＞inorganic silt＞fine organic sand＞fineinorganic sand＞coarse organic sand＞coarse inorganic sand.(4) Adsorptions of bacteria by soil particle were greatly influenced by theenvironmental conditions. In the range of pH from 4 to 9, the Bacteria adsorbeddecreased with increasing pH. The amounts of bacteria adsorbed on soil particleincreased with increasing concentrations of MgCl2 and NaCl, Finally reaching a plateau.Temperature also significantly affects soil particle adsorption, It was disadvantage tosoil particle adsorption at extreme temperature, with optimum temperature between 20℃and 30℃.(5) The soil particle also has adsorptive capacity for dead bacteria. Sometimes,Absorbability of dead bacteria is greater than that of live bacteria to the soil particle.The effect of age of bacteria on adsorption soil particles, indicating that bacterium andsoil particle had a different effect on soil adsorption.(6) The K value of B.thuringiensis was bigger than P.putida, Affinity indicating thatB.thuringiensis was adsorbed more tightly than P.putida on soil particles.
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