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This paper presents the results of a laboratory investigation of the influence zone (IZ) of air sparging (AS) in different media at different surface tension. Different kinds of media were used in two-dimensional tank experiments, designed to determine (1) the effect of surface tension reduction on the airflow pattern during AS in different air travelling modes (channels and bubbles) in homogeneous aquifer and (2) the airflow distribution and migration characteristics in heterogeneous aquifer at different surface tension during AS. The results demonstrated that in homogeneous gravel aquifer, the IZ was almost identical with or without surfactant addition into groundwater, the air saturation, however, was increased with decreasing surface tension. In homogeneous coarse sand tank saturated with 500 mg/L sodium dodecyl benzene sulphonate (SDBS) solution, the IZ was approximately 1.3 times larger than that in the same medium saturated with distilled water. In addition, the density of airflow channels was much larger in medium saturated with SDBS solution. In heterogeneous subsurface saturated with distilled water, when the permeability ratio between two adjoining layers was 8:1, air would bypass low-permeable soils. In contrast, the air would infiltrate into low-permeable soils when SDBS concentration in groundwater was 1000 mg/L. The results indicate that surfactant-enhanced air sparging can effectively improve the volatile organic compounds removal both in homogeneous and heterogeneous media.

Objective: To investigate the clinical effects of spinal canal decompression and pedicle screw reduction and fixation, and intervertebral bone grafting fusion for the treatment of lumbar spondylolisthesis associated with nerve compression symptoms., Methods: Postlaminectomy vertebral lamina reconstruction and pedicle screw reduction and fixation were performed in 32 patients with lumbar spondylolisthesis between August 2007 and August 2008. Of them, 26 patients were followed up for more than 1 year, including 16 males and 10 females who ranged in age from 55 to 76 years (mean 62.5 years). The course of disease was 2-10 years. All patients had low back pain, numbness and pain in one or both lower extremities and intermittent claudication symptoms. Radiograms showed L3, L4 or L5 anter-olisthesis of I to III degree. There were 18 cases of regressive olisthesis and 8 cases of spondylolysis. The clinical improvement, the vertebral reduction, the lamina fusion rate and canal stenosis state were observed and assessed., Results: The wounds healed well in all 26 cases without occurrence of significant complications. Clinical improvement was assessed according to the JOA lower back pain score scale. The mean preoperative score was 5.2 +/- 1.5, and 23.1 +/- 1.9 at 3 months after operation. The result was excellent in 20 cases, good in 5 cases, and fair in 1 case. The mean score on the last followed-up was 22.9 +/- 2.4, and the result was excellent in 19 cases, good in 5 cases, and fair in 2 cases. JOA score at 3 months after operation and that at the last followed-up were significantly different from that before operation (P = 0.00), and there was no significant difference between JOA score at 3 months after operation and that at the last followed-up (P > 0.05). Complete reduction was achieved in 17 degree I case and 5 degree II cases. Two degree II cases were improved to degree I, and 2 degree III cases were improved to degree I. Vertebral fusion was achieved 3 months after operation in 20 cases, and in all cases at the last followed-up. CT examination at the last follow-up showed no stenosis of the vertebral canal, dural sac and nerve root compression. The rebuilt vertebral lamina fused well. No graft bone absorption or failing fixation occurred., Conclusion: Postlaminectomy reconstruction of the vertebral lamina and pedicle screw reduction and fixation can achieve satisfactory reduction and spine biomechanical stability in the treatment of lumbar spondylolisthesis, and can prevent latrogenic stenosis of the vertebral canal due to nerve oppression by the postoperative scar and nerve adhesion, with good early and medium-term curative effects. In addition, it provides a new way of thinking in the treatment of lumbar spondylolis-thesis.

Four simulated landfill anaerobic bioreactors were performed to investigate the influence of alkalinity on the anaerobic treatment of municipal solid waste (MSW). Leachate was recirculated in all the four reactors. One reactor was operated without alkalinization. The other three were operated under alkaline conditions. Na(2)CO(3), NaHCO(3) and NaOH were added to leachate in the second, third and fourth reactor, respectively. Experimental results showed that CO(3)(2-) and HCO(3)(-) addition had a more pronounced effect on MSW stabilization while the effect of addition of OH(-) was weak. The concentration of COD, BOD(5), total nitrogen (TN), ammonium nitrogen (NH(4)(+)-N) and nitrate nitrogen (NO(3)(-)-N), etc. in leachate significantly reduced in four reactors. The removal efficiencies were 90.56%, 92.21%, 92.74% and 90.29% for COD, 66.45%, 72.38%, 68.62% and 68.44% for NO(3)(-)-N, and 96.5%, 98.75%, 97.75% and 98% for NO(2)(-)-N in the control, Na(2)CO(3), NaHCO(3) and OH(-) added reactors, respectively. The final BOD(5)/COD was 0.262, 0.104, 0.124, and 0.143, and pH was 7.13, 7.28, 7.42, and 7.24 for control, Na(2)CO(3) added, NaHCO(3) added, and OH(-) added reactor, respectively. Therefore, alkalinity addition had positive effect on the stabilization of MSW.