Uptake and accumulation of phenanthrene and pyrene in spiked soils by Ryegrass(Lolium perenne L.)

Phytoremediation has long been recognized as a cost-effective method for the removal of polycyclic aromatic hydrocarbons （PAHs） from soil. A study was conducted to investigate the uptake and accumulation of PAHs in root and shoot of Lolium perenne L. Pot experiments were conducted with series of concentrations of 3.31-378.37 mg/kg for phenanthrene and those of 4.22-365.38 mg/kg for pyrene in a greenhouse. The results showed that both ryegrass roots and shoots did take up PAHs from spiked soils, and generally increased with increasing concentrations of PAH in soil. Bioconcentration factors（BCFs） of phenanthrene by shoots and roots were 0.24- 4.25 and 0.17-2.12 for the same treatment. BCFs of pyrene by shoots were 0.20-1.5, except for 4.06 in 4.32 mg/kg treatment, much lower than BCFs of pyrene by roots （0.58-2.28）. BCFs of phenanthrene and pyrene tended to decrease with increasing concentrations of phenanthrene and pyrene in soil. Direct uptake and accumulation of these compounds by Lolium perenne L. was very low compared with the other loss pathways, which meant that plant-promoted microbial biodegradation might be the main contribution to plant-enhanced removal of phenanthrene and pyrene in soil. However, the presence of Lolium perenne L. significantly enhanced the removal of phenanthrene and pyrene in spiked soil. At the end of 60 d experiment, the extractable concentrations of phenanthrene and pyrene were lower in planted soil than in non-planted soil, about 83.24%-91.98% of phenanthrene and 68.53%-84.10% of pyrene were removed from soils, respectively. The results indicated that the removal of PAHs in contaminated soils was a feasible approach by using Lolium perenne L.

隧道衬砌裂缝对结构受力的影响规律研究

以深圳某区间隧道为研究背景,采用结构-荷载模型,研究了裂缝位置、裂缝深度及裂缝宽度对衬砌结构受力的影响。研究结果表明:隧道衬砌裂缝的产生使结构出现了应力重新分布的现象。当裂缝发生在拱顶位置时,隧道衬砌弯矩、剪力分别呈对称和反对称分布;当裂缝发生在拱肩、中墙或墙脚位置时,随着裂缝深度的增加,衬砌结构弯矩由近似对称向不对称变化,最大弯矩值由仰拱向拱顶部位扩散,左墙脚处出现最大负剪力值,右拱脚或左拱肩处出现最大正剪力值。随着裂缝宽度的增加,衬砌典型位置处弯矩和剪力均减小,当裂缝宽度由5 mm扩大到10 mm时,对单元受力结构影响最明显。随着裂缝深度和宽度的变化,隧道衬砌最危险截面的位置也发生了变化,需要对隧道不同部位加强监测,判断裂缝的发展状况,以保证人员、设备的安全,可为实际工程安全施工和健康运营提供指导。

新生儿梅毒血清学转阴与母婴阻断时期的关系

目的探讨梅毒螺旋体明胶颗粒凝集实验(TPPA)阳性新生儿的梅毒血清学检测结果与转阴规律及其与母婴阻断干预时期的关联。方法收集2016年1月至2018年6月广东省妇幼保健院TPPA检测结果阳性新生儿出生时的梅毒血清学检测结果,跟踪其出生后至12个月期间抗体转归情况并追踪其母亲的梅毒母婴阻断治疗方案,分析总结规律。结果共收集104例TPPA阳性新生儿病例,其中确诊先天梅毒3例,有63例(60.6%)甲苯胺红不加热血清试验(TRUST)阴性,TRUST滴度<1∶8阳性共35例(33.7%),TRUST滴度≥1∶8阳性共6例(5.8%)。有68例新生儿如期随访,TRUST阳性病例均在12个月内转阴,且91.7%的病例在3个月内转阴;除1例先天梅毒病例TPPA未能转阴外,其余均能在12个月内转阴,其中54.4%的病例在3~<6个月转阴。94.2%梅毒母亲得到有效的干预,其所生的婴幼儿TPPA转阴时间与干预时间差异无统计学意义(P>0.05)。结论出生时TPPA阳性新生儿,除确诊为先天梅毒患儿外,其梅毒血清学均能在12个月内转阴,转阴时间较集中但与母亲梅毒干预时期无关。