不同连通性含水层溶质运移模拟尺度提升研究

含水层溶质运移数值模拟是预测地下水污染物演化特征的重要方法。考虑到模型计算时间和精度,如何将小尺度实测获得的水文地质参数换算到模型网格尺度,即尺度提升,是数值模拟过程中的关键问题。本文针对不同连通性含水层,考虑不同尺度提升方法和网格尺度的大小等因素,探究尺度提升对溶质运移模拟精度和效率的影响。结果表明:对具有不同连通性的含水层,能够获得相对误差小于5%的升尺度模型,然而网格大小或尺度提升方法选取不当会使误差增大;简单拉普拉斯方法是较优的尺度提升方法,尤其对于中连通性含水层;网格大小是影响升尺度模型精度的主要因素,对于高连通性含水层更加明显。

Congenital fibrovascular pupillary membranes: case series with pathological correlation and surgical treatment

Dear Editor,We present three cases of congenital fibrovascular pupillary membranes(CFPM) with pathological correlation and surgical treatment. CFPM was first described by Cibis et al;as a new entity of anterior segment malformation termed “congenital pupillary-iris-lens membrane with goniodysgenesis”.

Secondary positioning of rotationally asymmetric refractive multifocal intraocular lens in a patient with glaucoma:A case report

BACKGROUND Asymmetric multifocal intraocular lenses(IOLs)are now widely used in the modern cataract surgery,providing a good level of visual performance over a range of distances and high postoperative patient satisfaction.We report a case of improved visual quality after shifting the near segment of an asymmetrical multifocal IOL to the superotemporal placement in the dominant eye of a glaucoma patient.CASE SUMMARY A 72-year-old woman with bilateral glaucoma underwent phacoemulsification in the dominant eye(left eye)with implantation of an asymmetrical multifocal IOL.Postoperative uncorrected distance visual acuity(UDVA)was 0.0 logMAR(20/20 Snellen)and uncorrected near visual acuity(UNVA)was 0.1 logMAR(20/25 Snellen).Two weeks later,the patient presented to our clinic with decreased vision due to migration of lens epithelial cells to IOL anterior surface and edema of corneal endothelial cells.Anterior capsule polishing and superotemporal placement of near segment[+3.00 diopter(D)addition(add)]of IOL were performed.As a result,UDVA at the first week and first year after reposition was 0.0 logMAR(20/20 Snellen),and compared with 0.3 logMAR(20/40 Snellen)in the first week,the UNVA was improved to 0.0 logMAR(20/20 Snellen)one year after surgery.CONCLUSION The postoperative inflammatory reaction and lens epithelial cells proliferation were obvious in this glaucoma patient.Capsule polishing and rotation of the lens were beneficial to the patient,which not only enhanced the patient's vision,but also improved the patient's satisfaction.Therefore,glaucoma patients need to be cautious of implanting multifocal IOLs.Placement of a near segment of an asymmetrical multifocal IOL in the dominant eye should be performed on an individual basis.

Fe(Ⅱ)-mediated transformation of schwertmannite associated with calcium from acid mine drainage treatment

Schwertmannite is an important Fe(Ⅲ)-oxyhydroxysulfate in acid mine drainage (AMD) polluted areas and its stability depends on surrounding environmental factors and previously bound elements.The treatment and neutralization of AMD normally involve the use of lime,which leads to the discharge of abundant Ca in the mining area.Such an environmental disturbance brings up an important and less considered problem of how the reductive transformation of schwertmannite associated with coexisting Ca occurred.Here,the Fe(Ⅱ)-mediated transformation of Ca-adsorbed schwertmannite and subsequent Ca repartitioning behaviors were investigated.Results showed that adsorbed Ca had a weak inhibitory effect on Fe(Ⅱ)-mediated schwertmannite transformation.Release of SO_(4)2-and SEM images both indicated that transformation rates of schwertmannite decreased under the influence of adsorbed Ca.XRD patterns indicated that adsorbed Ca altered schwertmannite transformation pathways and product compositions upon treatment with 0.4 mmol/L Fe(Ⅱ).The end products of Sch notably contained both goethite and lepidocrocite;however,transformation products of SchCa only contained goethite all along.Approximately 33.5%of the surface adsorbed-Ca was released into solution within 6 hr after Fe(Ⅱ) injection.Aqueous Ca behaved in a“first release and then im-mobilization”manner,which indicated dissolution and secondary mineralization drove Ca migration during the Fe(Ⅱ)-mediated transformation of SchCa.Adsorbed Ca blocked the surface sites for subsequent Fe(Ⅱ) adsorption,limited the Fe(Ⅱ)-Fe(Ⅲ) ETAE,and decreased the transformation rates.This work sheds light on the complex geochemical behavior of schwertmannite under the influences of environmental perturbations in AMD environments.

Thiocyanate-induced labilization of schwertmannite: Impacts and mechanisms

Schwertmannite is an amorphous iron(III)-oxyhydroxysulfate that forms in acid mine drainage(AMD) environments. The characteristic of high heavy metal adsorption capability makes schwertmannite a potentially useful, environmentally friendly material in wastewater treatment. Unstable schwertmannite is prone to recrystallization.Understanding the mechanisms that induce schwertmannite labilization and affect its capacity to remove heavy metals are of great environmental and geochemical significance.Thiocyanate(SCNˉ) is a hazardous pseudohalide that is also normally found in AMD.However, little is known about the impact of Fe(III)-binding ligand SCNˉ on schwertmannite stability and its subsequent capacity to bind trace elements. Here, we investigated the adsorption of SCNˉ on schwertmannite and subsequent mineral transformation to characterize this little-known process. The appearance of Fe2+indicated that the interactions between schwertmannite and SCNˉ may involve complexation and reduction reactions. Results showed that the majority of the adsorbed-SCNˉ was immobilized on schwertmannite during the 60-days transformation. The transformation rates of schwertmannite increased with increasing concentrations of SCNˉ. Goethite was detected as the dominant transformation product with or without SCNˉ. The mechanisms of SCNˉ-promoted dissolution of schwertmannite can be described as follows:(1) formation of Fe(III)–NCS complexes on the schwertmannite surface and in solution, a process which increases the reactivity of solid phase Fe(III);(2) the extraction of Fe(III) from schwertmannite by SCNˉ and subsequent schwertmannite dissolution; and(3) the formation of secondary minerals from extracted Fe(III). These findings may improve AMD treatment strategies and provide insight into the use and potential reuse of schwertmannite as a trace element sorbent.

Sodium Titanate/Carbon （Na2Ti3O7/C） Nanofibers via Electrospinning Technique as the Anode of Sodium-ion Batteries

To overcome the sluggish kinetics in sodium-ion batteries, sodium titanate/carbon （Na2Ti3O7/C） composite nanofibers as anode materials have successfully been synthesized via a simple electrospinning method. After calcination at 800 ℃ for 3 h, the obtained Na2Ti3O7 nanoparticles are randomly dispersed in the matrix of in situ pyrolized carbon nanofiber. The Na2Ti3O7/C hybrid nanofiber obtained with 2.5 wt% ofpoly （vinylpyrrolidone） additive in the precursor solution has the smallest diameter of-120 nm and the finest particle size of -40 nm, exhibiting the best rate performance of 101 mAh.g-1 at 4 C and excellent capacity retention of 82% at 1 C after 100 cycles. Furthermore, this composite nanofiber also demonstrates good cycling performance under low current density of 0.1 C, which is attributed to the formation of stable solid electrolyte interface （SEI） film induced by small volume expansion/contraction of the fine NazTi3O7 nanoparticles during the charge/discharge process.