Study the Effect of Absorption Solution for Same Composite Polymeric Material
In this paper concerns an investigation of absorption solution in materials of polymeric composite were prepared two types of the matrix material were used (PE,PVC). Also two types of fiber were used (woven and short glass fiber ).with volume fraction 20%. The sample were immersed in different solution (NaCO3-KOH –HCL , Normality 0.5 N) for equal time at constant temperature (room temperature ±20C ) . The result show that the relative mass gain increased with increasing the immersion time till they tend saturation moisture mass after that the relative mass gain decreased . The result show that sample in (KOH)solution had higher mass gain while the sample immersed in (HCL) had lower mass gain .Also the results show that the sample immersed in (NaCO3) has maximum diffusion coefficient which means minimum absorption resistance, while the sample immersed in (HCL) has minimum diffusion coefficient which means maximum absorption resistance.
Diffusivity of water in Unplasticised PVC
The current study concerns an investigation of diffusion mechanism of different kinds of water into thermoplastic material (type unplasticised PVC, (UPVC)) that is often used as pipes for healthy draining purposes and other services. After preparation of samples from this material, they were immersed in glass containers which contain (sea water, river water, rain water, distilled water, and tap water), the weights of these samples are measured at periodic time of soaking. The aim of this work is introducing an idea about the diffusion behavior and the penetration of water through the material under study, then, the values of diffusion coefficient (Dx) are evaluated for each type of water mentioned above. After comparing the obtained results from these tests, it is found that the distilled water has the higher value of (D X) into the (UPVC) material, it is followed by the sea water and then the rainwater, while each of the river and tap water record the lowest values.
Human exposure to methylmercury from crayfish (Procambarus clarkii) in China
Methylmercury (MeHg) accumulation in aquatic food raises global concerns about human exposure to MeHg. Crayfish is the world’s third largest farmed crustacean species and a favorite aquatic food in many countries. However, human health hazard due to MeHg exposure via crayfish consumption is unclear, partly because appropriate survey data are lacking. We report on mercury concentrations and speciation in edible tail muscle of crayfish collected from restaurants in 23 Chinese cities. On average, MeHg constituted 99.1 % of mercury in tail muscle, and MeHg concentrations were comparable with those reported for fish in China. Variation in MeHg concentrations was not attributable to broad geographic region (i.e., provinces) or tail length. For different populations, potential health risk (characterized by hazard quotient or HQ) of MeHg exposure through crayfish consumption depended largely on crayfish consumption rates. In particular, a health hazard (HQ > 1) was found for high-rate consumers (i.e., 95 %ile or higher) in some cities in the middle and lower reaches of the Yangtze River (MLYR), during the peak consumption season. Our results suggest that more attention should be paid to dietary MeHg intake via crayfish consumption in China, particularly for communities with high consumption in MLYR.