[Effect of LAS on physico-chemical properties and microorganism activity in soil environment]

Using a well drained paddy soil and the derived soil under vegetables in the Taihu Lake region, China, experiments of soil capillary rise, colloid dispersion and adsorption of toxic organics and heavy metals by soil under various degrees of LAS addition were conducted. Also incubation experiments of microorganism activity in soil with added LAS in different concentrations were carried out in laboratory. LAS addition resulted in lower capillary rise of soil solution, higher dispersion of soil colloids and lower capacity of soil for organic pollutants but no significant influence on adsorption of heavy metal cations. The nitrification and amonification in soil were very sensitive to LAS stress while denitrification turned to be stimulated. LAS addition gave stronger growth of soil bacteria while decreased growth of fungus. Meanwhile, soil respiration was stimulated in the first week of incubation and compressed afterwards by LAS at concentration over 5 mg/kg. It seemed that some species of microorganisms were tolerant of LAS in the studied soils.