Release of Particulate Lead from Four Lead Corrosion Products in Drinking Water: A Laboratory Study Coupled with Microscopic Observations and Computational Fluid Dynamics.

Particulate lead resulting from the detachment of lead corrosion products (LCPs) contributes significantly to lead contamination in drinking water. Since LCPs formed under different water chemistry possesses different crystal structures, their hydrodynamic behaviors could be significantly different in flowing water. In this study, flushing experiments and microscopic observations were employed to investigate the release of cerussite (PbCO3), hydrocerussite (Pb3(CO3)2(OH)2), chloropyromorphite (Pb5(PO4)3Cl), and lead dioxide (scrutinyite α-PbO2/plattnerite ß-PbO2), the four LCPs commonly found in the drinking water distribution system. Under the same flow rate, particulate lead release showed the following trend: lead dioxide > cerussite ∼ chloropyromorphite > hydrocerussite. In the range of 1-10 L/min, a higher flow rate enhanced the release of cerussite, chloropyromorphite, and lead dioxide, while the release of hydrocerussite was not significantly affected, likely due to its platelike crystal structure that reduced the shear force exerted by the flowing water. The detachments of visible cerussite and chloropyromorphite particles were captured using a digital microscope at flow rates of 8.0 and 8.2 L/min, and the shear forces causing their detachments were determined to be 5.8 × 10-11 and 3.1 × 10-10 N, respectively, using computational fluid dynamics (CFD). Our study demonstrated that crystal structure could be an important factor affecting the detachment of LCPs and CFD could be a useful tool to characterize their hydrodynamic behaviors.

The effect of multilevel anterior cervical fusion on neck motion.

BACKGROUND: Anterior cervical decompression and fusion (ACDF) procedures are successful in treating multilevel cervical radiculopathy and cervical myelopathy. It was reported that this procedure would result in a loss of cervical range of motion. However, few studies have focused on the exact impact of multilevel (more than 3 levels) ACDF on cervical range of motion. METHODS: 29 patients underwent a 3-level or 4-level ACDF. In all the patients, preoperative active cervical ROM measurement was performed, and postoperative measurement was performed at 1-year follow-up by a CROM device. The pre- and postoperative data were compared to each other using paired t tests (α = 0.05). RESULTS: The patients had significantly less ROM after the surgery in all planes of motion. Major reduction was observed in flexion (39.5%), left and right lateral flexion (25.7 and 25.9%), with relatively minor impact on extension (18.3%), left and right rotation (14.0 and 14.4%) observed. In the three cardinal planes, major reduction was observed in the sagittal plane (28.2%) and coronal plane (25.8%), while minor impact observed in the horizontal plane (14.1%). CONCLUSIONS: The patients of cervical spondylotic myelopathy had an obvious reduction in active cervical ROM following multilevel ACDF. However, patients might not experience great difficulties in performing daily activities with regard to the loss of neck motion after fusion.