In artisanal gold mining practiced in North Sulawesi Island, Indonesia, gold is separated from ore by the use of mercury, which forms an amalgam with gold. All related processes are undertaken with a low level of technical knowledge and skills, no regulation, and with disregard for the safety of human and environment health. The situation is generating serious potential health and environmental risks in the area. As part of an ongoing monitoring program, total mercury concentrations were examined in water, bottom sediment and fish samples from three main rivers in Talawaan Watershed, which receives drainage from gold mining practices. Monitoring began in May-June 2000, almost 2 years after artisanal gold mining had begun. At that time, the mercury concentration in the sediment was generally low, except in places close to the gold processing plants. In the present study, a more systematic sampling and analysis was conducted in May-June 2001. Bottom surface sediments, water, and fish samples were collected at 12 sites along the three main rivers in the watershed. In addition, one site outside the watershed was sampled to serve as a control. Sample collections were conducted in three phases in duplicate, with two-week intervals between each phase. The mercury concentration observed in this study indicated that an increase took place along the three main rivers in the watershed. Solutions to this problem must be formulated as soon as possible in order to avoid a major health, economic, and ecological disaster arising from the continuing discharge of Hg. The present study proposes that mercury dispersion occur downstream of the mining. 相似文献
Charged ultrafiltration membranes were prepared by photografting sodium styrene sulfonate onto photosensitive polyacrylonitrile membrane containing bromine atoms. The degree of the photografting was characterized by contact angles of air or n-octane in water and FTIR spectra for the negatively charged membrane. Permeations of dextran and dextransulfate through the negatively charged membranes were studied by ultrafiltration in the aqueous solutions of both solutes. With an increase of photoirradiation, the permeability of the solutes decreased. Also, an electrostatic repulsion of the solute and the membrane was confirmed by direct comparison between the permeability of the solutes, dextran, and dextransulfate, each having similar molecular size. 相似文献
We have developed a new calibration technique for multielement determination and U-Pb dating of zircon samples using laser ablation-inductively coupled plasma mass spectrometry (ICPMS) coupled with galvanometric optics. With the galvanometric optics, laser ablation of two or more sample materials could be achieved in very short time intervals (~10 ms). The resulting sample aerosols released from different ablation pits or different solid samples were mixed and homogenized within the sample cell and then transported into the ICP ion source. Multiple spot laser ablation enables spiking of analytes or internal standard elements directly into the solid samples, and therefore the standard addition calibration method can be applied for the determination of trace elements in solid samples. In this study, we have measured the rare earth element (REE) abundances of two zircon samples (Nancy 91500 and Pre?ovice) based on the standard addition technique, using a direct spiking of analytes through a multispot laser ablation of the glass standard material (NIST SRM612). The resulting REE abundance data show good agreement with previously reported values within analytical uncertainties achieved in this study (10% for most elements). Our experiments demonstrated that nonspectroscopic interferences on 14 REEs could be significantly reduced by the standard addition technique employed here. Another advantage of galvanometric devices is the accumulation of sample aerosol released from multiple spots. In this study we have measured the U-Pb age of a zircon sample (LMR) using an accumulation of sample aerosols released from 10 separate ablation pits of low diameters (~8 μm). The resulting (238)U-(206)Pb age data for the LMR zircons was 369 ± 64 Ma, which is in good agreement with previously reported age data (367.6 ± 1.5 Ma). (1) The data obtained here clearly demonstrate that the multiple spot laser ablation-ICPMS technique can become a powerful approach for elemental and isotopic ratio measurements in solid materials. 相似文献
Supramolecular liquid-crystalline polymer microparticles were fabricated by combining a simple phase reversion method with hydrogen-bonding formation between an azopyridyl polymer and a series of dicarboxylic acid compounds. Their surface morphologies and phase behaviors were studied by changing the molecular length of the diacids, and then their photoresponsive behaviors were observed upon UV irradiation. Photoinduced deformation occurred for the supramolecularly assembled microparticles showing LC phases, whereas no changes in morphologies were observed for microparticles exhibiting amorphous or crystalline. The photoinduced LC-to-isotropic phase transition were responsible for the light-responsive behaviors of the supramolecular liquid-crystalline microparticles. 相似文献
The cover image is based on the Research Article Pre‐thermal treatment in binary solvent systems promoting β crystalline phase of electrospun poly(vinylidene fluoride) nanofibers by Praewpanit Nuamcharoen et al., https://doi.org/10.1002/pi.6008 .