Isotopic Signatures and Outputs of Lead from Coal Fly Ash Disposal in China, India, and the United States.

Despite extensive research and technology to reduce the atmospheric emission of Pb from burning coal for power generation, minimal attention has been paid to Pb associated with coal ash disposal in the environment. This study investigates the isotopic signatures and output rates of Pb in fly ash disposal in China, India, and the United States. Pairwise comparison between feed coal and fly ash samples collected from coal-fired power plants from each country shows that the Pb isotope composition of fly ash largely resembles that of feed coal, and its isotopic distinction allows for tracing the release of Pb from coal fly ash into the environment. Between 2000 and 2020, approx. 236, 56, and 46 Gg Pb from fly ash have been disposed in China, India, and the U.S., respectively, posing a significant environmental burden. A Bayesian Pb isotope mixing model shows that during the past 40 to 70 years, coal fly ash has contributed significantly higher Pb (∼26%) than leaded gasoline (∼7%) to Pb accumulation in the sediments of five freshwater lakes in North Carolina, U.S.A. This implies that the release of disposed coal fly ash Pb at local and regional scales can outweigh that of other anthropogenic Pb sources.

Atmospheric Mercury Isotope Shifts in Response to Mercury Emissions from Underground Coal Fires.

Pollutant emissions from coal fires have caused serious concerns in major coal-producing countries. Great efforts have been devoted to suppressing them in China, notably at the notorious Wuda Coalfield in Inner Mongolia. Recent surveys revealed that while fires in this coalfield have been nearly extinguished near the surface, they persist underground. However, the impacts of Hg volatilized from underground coal fires remain unclear. Here, we measured concentrations and isotope compositions of atmospheric Hg in both gaseous and particulate phases at an urban site near the Wuda Coalfield. The atmospheric Hg displayed strong seasonality in terms of both Hg concentrations (5-7-fold higher in fall than in winter) and isotope compositions. Combining characteristic isotope compositions of potential Hg sources and air mass trajectories, we conclude that underground coal fires were still emitting large amounts of Hg into the atmosphere that have been transported to the adjacent urban area in the prevailing downwind direction. The other local anthropogenic Hg emissions were only evident in the urban atmosphere when the arriving air masses did not pass directly through the coalfield. Our study demonstrates that atmospheric Hg isotope measurement is a useful tool for detecting concealed underground coal fires.

Toward the Threshold of Radiation Hazards of U in Chinese Coal through the CART Algorithm.

The high volume of coal used for combustion usually leads to a large amount of coal combustion residues (CCRs), which contain the naturally occurring radioactive materials (NORMs) decayed from U and Th in coals. The high radioactivity of NORMs can cause potential harm to humans if the CCRs are used as building materials. The activities of CCRs not only depend on the concentrations of radionuclides but also largely depend on the variations of ash yields of coal. On the other hand, ash yields significantly vary in coal from less than 1-50%. This indicates that similar concentrations of radionuclides in coal with different ash yields generally do not result in similar activities in CCRs. Therefore, it is significant to build a threshold of U in coals with different ash yield levels. In this research, based on the data of 945 coal samples from China and the selected optimal model using the classification and regression tree algorithm, the threshold of U for the radiation hazard is determined to be 7.98 mg/kg for coals with ash yields higher than 20%, while the threshold of U for the radiation hazard is 5.28 mg/kg for coals with ash yields lower than 20%.

Soils and spoils: mineralogy and geochemistry of mining and processing wastes from lead and zinc mining at the Gratz Mine, Owen County, Kentucky.

Purpose: Mineralogical and geochemical features of mining and processing wastes collected in Owen County, part of the Central Kentucky Lead-Zinc district, were investigated. The Gratz mine, abandoned in the 1940s, is on a dairy farm. Aside from discerning the nature of mining refuse at the site, the investigation was part of the University of Kentucky College of Pharmacy's mission to explore unusual environments in the search for unique microbiological communities. Materials and methods: Four samples of a soil-plus-spoils mix were collected from spoil piles and two samples, the sluice and coarse samples, were closely associated with the site of the ore processing. Optical petrology (polarized reflected-light, oil-immersion optics at a final magnification of 500 ×), X-ray diffraction, X-ray fluorescence, inductively coupled plasma mass spectrometry, field emission scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscope (HR-TEM) with selected area electron diffraction (SAED) and/or microbeam diffraction (MBD), scanning transmission electron microscopy (STEM), and energy-dispersive X-ray spectrometer (EDS) analyses were employed to characterize the samples. Results and discussion: Calcite is the main mineral in most samples, followed by near equal amounts of quartz and dolomite. Sphalerite and galena are the principal sulfides and barite is the dominant sulfate. Geochemistry of major elements reflected the mineralogy, whereas trace elements showed different groupings between the minerals. Scandium, Cu, Ga, Ge, Cd, and Sb were found predominantly associated with Zn and Pb and sulfide minerals; Bi, Hf, In, Sn, and Zr with heavy mineral fraction; while the remaining trace elements, including the rare earths, were mostly distributed among other present phases, i.e., oxyhalides, oxides, silicates, and carbonaceous material. The data were used to illustrate the processes and conditions that control the sulfide-mineral oxidation and its potential for the environmental release of associated reaction products. Conclusions: The wastes represent a potential source of environmentally disruptive concentrations of Zn, Pb, and other sulfide-associated elements. The high share of carbonates suggests near-neutral conditions in deposited wastes, restricting sulfide weathering and further limiting the oxidant activity of Fe. The low-Fe content and its predominant presence in highly resistant hematite also constrain sulfide weathering. Consequently, the spoils have a low potential for generation of acidity and release of heavy metal(loid)s in the surrounding environment.

Fast Screening of Coal Fly Ash with Potential for Rare Earth Element Recovery by Electron Paramagnetic Resonance Spectroscopy.

Rare earth elements (REYs) are in increasing global demand, but their mining is costly and environmentally destructive. Coal fly ash (CFA) is a promising alternative source of REYs, but it is necessary to identify CFA with sufficiently high REY concentrations. This study proposes the use of electron paramagnetic resonance (EPR) spectroscopy as part of a simple method to identify CFAs with adequate REY concentrations. The EPR spectra of CFA samples taken from 186 Chinese commercial coal-fired power plants were analyzed. The results suggest that CFAs without evident 6-fold resonances are worth recycling (REY concentrations of 416 ± 108 mg/kg), while those with conspicuous 6-fold resonances are not worth recycling (REY concentrations of 55 ± 26 mg/kg). This is probably due to isomorphic substitution of Ca(II) for Mn(II) and REY(III), resulting in low concentrations of Mn(II) and REY(III) in Ca-rich CFAs. This EPR evaluation method does not require specialized sample preparation, professional skills, or secondary data analysis and has potential global significance in the fast screening of CFAs with REY-recycling potential.

Naturally Occurring Radioactive Materials in Uranium-Rich Coals and Associated Coal Combustion Residues from China.

Most coals in China have uranium concentrations up to 3 ppm, yet several coal deposits are known to be enriched in uranium. Naturally occurring radioactive materials (NORM) in these U-rich coals and associated coal combustion residues (CCRs) have not been well characterized. Here we measure NORM (Th, U, 228Ra, 226Ra, and 210Pb) in coals from eight U-rich coal deposits in China and the associated CCRs from one of these deposits. We compared NORM in these U-rich coals and associated CCRs to CCRs collected from the Beijing area and natural loess sediments from northeastern China. We found elevated U concentrations (up to 476 ppm) that correspond to low 232Th/238U and 228Ra/226Ra activity ratios (≪1) in the coal samples. 226Ra and 228Ra activities correlate with 238U and 232Th activities, respectively, and 226Ra activities correlate well with 210Pb activities across all coal samples. We used measured NORM activities and ash yields in coals to model the activities of CCRs from all U-rich coals analyzed in this study. The activities of measured and modeled CCRs derived from U-rich coals exceed the standards for radiation in building materials, particularly for CCRs originating from coals with U > 10 ppm. Since beneficial use of high-U Chinese CCRs in building materials is not a suitable option, careful consideration needs to be taken to limit potential air and water contamination upon disposal of U- and Ra-rich CCRs.

Combustion conditions and feed coals regulating the Fe- and Ti-containing nanoparticles in various coal fly ash.

Quantitative characteristics and sizes of nanoparticles (NPs) in coal fly ash (CFA) produced in coal-fired power plants as a function of coal type and plant design will help reveal the NP emission likelihood and their environmental implications. However, little is known about how combustion conditions and types of coal regulate the NP abundance in CFAs. In this study, based on single particle (SP)-ICP-MS technology, particle number concentrations (PNCs) and sizes of Fe- and Ti-containing NPs in CFAs were determined for samples collected from power plants of different designs and burning different types of coal. The PNCs of Fe- and Ti-containing NPs in all CFAs measured were in the range of 1.3 × 107 - 3.4 × 108 and 6.8 × 106 - 2.2 × 108 particles/mg, with the average particle sizes of 111 nm and 87 nm, respectively. The highest Fe-NP PNCs likely relate to the highest contents of Fe and pyrite in the feed coal. In addition, high TOC in CFAs are associated with metal-containing NPs, resulting in elevated abundances of these NPs with relatively large sizes. Moreover, elevated PNCs of NPs were found in CFAs produced by coal-fired power plants burning low-rank coals and with small installed capacity (especially those under 100-MW units). Compared to cyclone filters, ESPs and FFs with higher removal efficiency typically retain more Fe-/Ti- containing NPs with smaller sizes. Based on a structural equation (SE) model, raw coal properties (coal rank and Fe/Ti content), boiler types, and efficiency of particulate emission control devices likely indirectly affect PNCs of Fe- and Ti-containing NPs by influencing TOC contents and their corresponding metal concentrations of CFAs. This study provides the first analytic and comprehensive information concerning the direct and indirect regulating factors on NPs in various CFAs.

Average Linkage Hierarchical Clustering Algorithm for Determining the Relationships between Elements in Coal.

The modes of occurrence of elements in coal are important not only because they can provide insights into the sources of mineral matter in coal but also because they are vital in determining the behavior of their environmental and human health impacts. Besides a number of physical and chemical analyses for determining the modes of occurrence in coal, some statistical methods have been commonly adopted to investigate elements in coal. Among many statistical methods, the hierarchy clustering algorithm is the most common method for deducing modes of occurrence of elements in coal. However, different hierarchical clustering algorithms with a number of similarity measures sometimes result in different modes of occurrence of elements in coal, and subsequently in some cases, such results could be confusing. Therefore, which algorithm is more effective in determining the modes of occurrence in coal deserves to be investigated. In this paper, the data sets of coals from the Adaohai coal mine in Inner Mongolia, China, are used for this performance evaluation. From the analytical results with the average linkage hierarchical clustering algorithm on Adaohai coal samples, many instructive and surprising insights can be concluded. For example, selenium, Be, and Tl do not appear to be in agreement with geochemical principles, that is, substituting for P, associated with rare earth elements, and occurring in Fe-sulfides, respectively. In conclusion, the average linkage hierarchical clustering algorithm with correlation similarity is much better in the analysis of the geological processes than the previous statistical method used in Adaohai coal samples, that is, centroid linkage hierarchical clustering algorithm with Pearson correlation similarity.

A two-stage desalination process for zero liquid discharge of flue gas desulfurization wastewater by chloride precipitation.

A two-stage desalination process was developed to achieve zero liquid discharge (ZLD) of flue gas desulfurization (FGD) wastewater by precipitating chloride as Friedel's salt. Influential factors for Friedel's salt precipitation, including dosage, reaction time, concentration of sulfate, were investigate by batch tests. Batch results showed that at calcium to aluminum molar ratio of 3.0, the optimal chloride removal and the highest crystallinity of Friedel's salt were obtained. Sulfate impeded Friedel's salt precipitation by competitive inhibition mechanism, and thus calcium sulfate removal was designed in advance of chloride removal. Batch results and long-term results of bench-scale experiments showed that magnesium and part of sulfate were effectively removed by lime addition in Stage I of the proposed process, and then the remaining sulfate and 48.1 % of chloride were precipitated as ettringite and Friedel's salt in Stage II. The effluent of the two-stage process was alkaline with low turbidity, and had considerable desulfurization capacity. Techno-economic evaluation showed that the two-stage process is technically feasible, economically viable and environmentally friendly technology for ZLD of FGD wastewater.

Nanoquartz in Late Permian C1 coal and the high incidence of female lung cancer in the Pearl River Origin area: a retrospective cohort study.

BACKGROUND: The Pearl River Origin area, Qujing District of Yunnan Province, has one of the highest female lung cancer mortality rates in China. Smoking was excluded as a cause of the lung cancer excess because almost all women were non-smokers. Crystalline silica embedded in the soot emissions from coal combustion was found to be associated with the lung cancer risk in a geographical correlation study. Lung cancer rates tend to be higher in places where the Late Permian C1 coal is produced. Therefore, we have hypothesized the two processes: C1 coal combustion --> nanoquartz in ambient air --> lung cancer excess in non-smoking women. METHODS/DESIGN: We propose to conduct a retrospective cohort study to test the hypothesis above. We will search historical records and compile an inventory of the coal mines in operation during 1930-2009. To estimate the study subjects' retrospective exposure, we will reconstruct the historical exposure scenario by burning the coal samples, collected from operating or deserted coal mines by coal geologists, in a traditional firepit of an old house. Indoor air particulate samples will be collected for nanoquartz and polycyclic aromatic hydrocarbons (PAHs) analyses. Bulk quartz content will be quantified by X-ray diffraction analysis. Size distribution of quartz will be examined by electron microscopes and by centrifugation techniques. Lifetime cumulative exposure to nanoquartz will be estimated for each subject. Using the epidemiology data, we will examine whether the use of C1 coal and the cumulative exposure to nanoquartz are associated with an elevated risk of lung cancer. DISCUSSION: The high incidence rate of lung cancer in Xuan Wei, one of the counties in the current study area, was once attributed to high indoor air concentrations of PAHs. The research results have been cited for qualitative and quantitative cancer risk assessment of PAHs by the World Health Organization and other agencies. If nanoquartz is found to be the main underlying cause of the lung cancer epidemic in the study area, cancer potency estimates for PAHs by the international agencies based on the lung cancer data in this study setting should then be updated.

Determination of Chemical Speciation of Arsenic and Selenium in High-As Coal Combustion Ash by X-ray Photoelectron Spectroscopy: Examples from a Kentucky Stoker Ash.

Knowledge of the chemical speciation of arsenic and selenium in coal fly ash is essential in the evaluation of the environmental behavior of fly ash disposed in a landfill in a natural environment. In this study, a series of high-As coal fly ash from stoker boilers were collected to determine the chemical forms of arsenic and selenium. The ash surface chemical characteristics and the speciation of arsenic and selenium were characterized by X-ray photoelectron spectroscopy and X-ray-induced Auger electron spectroscopy. The results indicate that the surface enrichment ratio for selenium (63.3-309.5) is higher than that of arsenic (1.2-21.2). The Wagner chemical-state plot of arsenic indicates that As is mainly present as As(V) bonded to oxygen ligands, that is, the [AsO4]3- anion; Se is found predominantly as elemental Se (62.0-83.3%), followed by selenite (16.7-38%). The extreme enrichment of both arsenic and selenium arsenic is controlled by iron oxides in the coal fly ash.

[SIMULTANEOUS TREATMENT OF OSTEOARTHRITIS OF MEDIAL COMPARTMENT WITH POSTERIOR CRUCIATE LIGAMENT INJURY].

OBJECTIVE: To study the results of high tibia osteotomy (HTO) combined with- posterior cruciate ligament (PCL) reconstruction for osteoarthritis (OA) of the medial compartment wit PCL injury. METHODS: Between March 2008 and June 2014, 11 patients with OA of the medial compartment and PCL injury underwent HTO combined with PCL reconstruction. There were 5 males and 6 females, aged 43-55 years (mean, 50.3 years). All patients had a trauma history, and the duration of injury was 3-5 years (mean, 3.7 years). At preoperation, Hospital for special surgery (HSS) score was 54.73 ± 8.60, Lyshoim score was 56.91 ± 4.51, KT-1000 test was (5.71 ± 1.13) mm, and knee range of motion (ROM) was (125.21 ± 4.77)degrees. The preoperative femoral tibia angle (FTA) and posterior slope angle (PSA) of the tibia plateau were (184.82 ± 2.40)degrees and (7.18± 1.17)degrees on the X-ray film. RESULTS: Incisional fat liquefaction occurred in 1 case, and wound healed after dressing change; primary healing of wound was obtained in the other cases. All 11 cases were followed up 12-28 months (mean, 17 months). Bone union was observed at osteotomy site within 6 months, without delayed union or nonunion. After operation, genu varus deformity was corrected with different degrees; the stability of knees was improved in all patients; and the pain of medial knee was released significantly. At 12 months after operation, the FTA was significantly reduced to (176.64 ± 1.96)degrees; at last follow-up, the HSS score was significantly increased to 88.27 ± 4.76, KT-1000 test was significantly reduced to (3.18 ± 0.87) mm, and Lyholm score was significantly increased to 86.45 ± 2.34, all showing significant differences when compared with preoperative ones (P < 0.05). At last follow-up, the knee ROM was (124.63 ± 2.98)degrees and the PSA was (7.91 ± 1.30)degrees, showing no significant difference when compared with preoperative ones (P > 0.05). CONCLUSION: The PSA will not be changed when a combination of HTO and PCL reconstruction is used to treat OA of the medial compartment with PCL injury if the right osteotomy site and reasonable bone graft are selected. The short-term effectiveness is good because of good recovery of the lower extremity force line and knee stability, but the long-term effectiveness remains to be further followed up.

Treatment of infection with improved pulsed lavage.

OBJECTIVE: To develop a more effective surgical lavage technique to improve the efficacy of treatment for infections after a tibia/fibula fracture. METHODS: A retrospective analysis was performed on 46 patients who received pulsed lavage with a side-hole double-valve lavage tube in the Second Hospital of Tangshan, Tangshan, China. Patients with the same injury treated with conventional lavage techniques in the same period were used as controls. The lavage success rate and the infection cure rate were analyzed to evaluate this therapy. RESULTS: All patients showed wound healing by first intention, and there was no recurrence during the follow-up period of > 12 months. Compared to the control group, the group that received pulsed lavage showed higher lavage success rates and cure rates. CONCLUSION: Pulsed lavage therapy with a side-hole double-valve lavage tube can improve the efficacy of treatment infections after tibia/fibula fractures and constitutes an effective modification to conventional lavage techniques. .

Geochemistry of ultra-fine and nano-compounds in coal gasification ashes: a synoptic view.

The nano-mineralogy, petrology, and chemistry of coal gasification products have not been studied as extensively as the products of the more widely used pulverized-coal combustion. The solid residues from the gasification of a low- to medium-sulfur, inertinite-rich, volatile A bituminous coal, and a high sulfur, vitrinite-rich, volatile C bituminous coal were investigated. Multifaceted chemical characterization by XRD, Raman spectroscopy, petrology, FE-SEM/EDS, and HR-TEM/SEAD/FFT/EDS provided an in-depth understanding of coal gasification ash-forming processes. The petrology of the residues generally reflected the rank and maceral composition of the feed coals, with the higher rank, high-inertinite coal having anisotropic carbons and inertinite in the residue, and the lower rank coal-derived residue containing isotropic carbons. The feed coal chemistry determines the mineralogy of the non-glass, non-carbon portions of the residues, with the proportions of CaCO3 versus Al2O3 determining the tendency towards the neoformation of anorthite versus mullite, respectively. Electron beam studies showed the presence of a number of potentially hazardous elements in nanoparticles. Some of the neoformed ultra-fine/nano-minerals found in the coal ashes are the same as those commonly associated with oxidation/transformation of sulfides and sulfates.

[Irrigation using side-hole double valve lavage tube for orthopaedic postoperative infection in 126 cases].

OBJECTIVE: To develope a modified surgical lavage tube to improve the efficacy of the treatment of orthopaedic postoperative infection. METHODS: A retrospective analysis was performed on 126 patients who received the pulsed lavage therapy with side-hole double valve lavage tube between March 2005 and March 2010. There were 98 males and 28 females, aged 19-63 years (mean, 35 years). The infected sites included femur in 61 cases, tibiofibula in 46 cases, humerus in 12 cases, and patella in 7 cases. The lavage tube obstruction and defluvium, secondary infection of drainage opening, and wound healing were observed during treatment. RESULTS: No lavage tube defluvium occured during the lavage in all cases. Lavage tube obstruction occurred in 68 cases, edema at the peripheral tissue was caused by obstruction in 9 cases; secondary infection at the lavage and drainage opening in 10 cases, which were cured after corresponding treatment. All cases achieved wound healing by first intention within 2 weeks. Lavage tube and drainage opening were closed within 1 month. All patients were followed up 1-5 years (mean, 18 months) with no recurrence. CONCLUSION: Pulsed lavage therapy with side-hole double valve lavage tube can obviously improve the efficacy of the treatment of orthopaedic postoperative infection, so it is an effective modification to convention lavage.

Applied investigation on the interaction of hazardous elements binding on ultrafine and nanoparticles in Chinese anthracite-derived fly ash.

A multifaceted instrumental approach was employed to determine the chemistry and mineralogy of pulverized-coal-combustion fly ashes from two Chinese power plants. Techniques included traditional optical microscopy, X-ray diffraction, and chemical analysis along with a variety of electron beam methods. The aim is to demonstrate and bring together the wide variety of procedures dealing with F as the key element of concern, and determining its location in the mineral nanoparticles. The Hg content of the Anwen (Songzao coalfield) fly ashes is higher than that of the Diandong (East Yunnan) fly ashes, possibly owing to the greater C and Cl in the Anwen fly ashes. Both fly ash sources contain a variety of amorphous and nano-crystalline trace-element-bearing particles, both associated with multi-walled carbon nanotubes and as particles independent of carbons.

[Effectiveness of low molecular weight heparin for prevention of deep vein thrombosis after total hip arthroplasty].

OBJECTIVE: To investigate the pathogenesis of deep vein thrombosis (DVT) after total hip arthroplasty (THA) and the preventive effectiveness of low molecular weight heparin (LMWH). METHODS: The occurrence condition of DVT in 90 cases undergoing THA treated with LMWH between February 2003 and March 2004 was retrospectively analyzed. Among 90 cases, 39 were treated with LMWH at a dose of 5000 U/day (high dose group) and 51 at a dose of 2500 U/day (low dose group). Another 90 cases undergoing THA without LMWH treating between February 2002 and February 2003 were used as control group. There was no significant difference in gender, age, illness cause, course of disease, or the type of prosthesis among 3 groups (P > 0.05). RESULTS: DVT occurred in 19 cases (21.1%) of control group, in 2 cases (5.1%) of high dose group, and in 5 cases (9.8%) of low dose group, showing significant differences between two treated groups and control group (P < 0.05), but no significant difference between two treated groups (P > 0.05). There was no significant difference in gender, age (> 65 years and < or = 65 years), pathogen (trauma and bone disease) of each group, as well as of the same type patients within 3 groups (P > 0.05). The DVT incidence rate in the patients with bone cement artificial joint was significantly higher than that in the patients with non-bone cement artificial joint (P < 0.05), but there was no significant difference in the same type patients within 3 groups (P > 0.05). The postoperative blood loss in high dose group, low dose group, and control group was (463.5 +/- 234.2), (342.4 +/- 231.6), and (288.2 +/- 141.6) mL; showing no significant difference between the high and low dose groups, between low dose and control groups (P > 0.05), while showing significant difference between high dose and control groups (P < 0.05). CONCLUSION: The DVT incidence rate in THA patients with bone cement artificial joint is high; LMWH can reduce the DVT incidence rate and has good safety.

[Treatment of lumbar spondylolisthesis with spondylolisthesis reduction system internal fixation and decompression, posterior alone interbody cage fusion and bone grafting].

OBJECTIVE: To investigate the clinical outcomes of lumbar spondylolisthesis associated with lumbar spinal stenosis through decompressive laminectomy, spondylolithesis reduction system (SRS) internal fixation, single posterolateral Vigor Spacer threaded fusion cages and intertransverse process arthrodesis bone grafting. METHODS: From June 2002 to June 2006, 58 cases of lumbar spondylolisthesis were treated with decompressive laminectomy, fixed by SRS instrumentation, posterior installed with interbody Vigor Spacer Cage and bone grafted between intertransverse process arthrodesis. There were 47 males and 11 females, aged 32-66 years old (45.8 on average). The course of disease was 3 months to 7 years, with an medium course of 25 months. According to the Meyerding standard, 38 cases were classified as degree I and 20 as degree II. Spondylolisthesis between L4 and L5 covered 21 cases and between L5 and S1 covered 37 cases. There were 44 cases of lumbar spondylolisthesis and 14 of degenerative lumbar spondylolisthesis. The intervertebral height was 1.5-10.5 mm with the average of 5.1 mm. RESULTS: All patients' incisions obtained healing by first intension after operation. The operation time was 50-90 minutes with an average of 65 minutes. The blood loss was 200-500 mL with an average of 250 mL. The patients were followed up for 10-38 months with an average of 23.6 months. According to the Macnab criteria, 54 cases were excellent, 3 good, 1 fair and the choiceness rate was 98.3%. According to the Meyerding classification, 38 cases of degree I and 19 out of 20 cases of degree II obtained complete reduction, and the rate of complete reduction was 98.3%. There were 57 (98.3%) cases which fused well 3-6 months after operation. The intervertebral height resumed to 9.6-12.5 mm with an average of 11.6 mm, and no intervertebral height loss was found. CONCLUSION: The treatment of lumbar spondylolisthesis with decompressive laminectomy, SRS internal fixation, single posterior lateral Vigor Spacer threaded fusion cage and bone grafting has excellent clinical results and stable reduction.