RESUMO
Microplastics (MPs) are ubiquitously detected in the environment. The adverse impact of microplastics on marine life is well documented. Previous research has shown that MPs can adsorb heavy metals, however, this fact has not been investigated along the coast of Dubai, UAE. Elemental composition of MPs debris was determined using X-ray fluorescence spectroscopic (XRF) analysis. The analyzed MPs were extracted from 80 sediment samples collected from the wrack lines of 16 Dubai, UAE beaches. A total of 480 MPs pieces extracted from the samples were analyzed in order to detect heavy metals. The polymer composition was previously confirmed by FTIR spectroscopy, showing that polyethylene (PE) and polypropylene (PP) were the most abundant MPs. 14 heavy metals were identified in the samples: Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Pb, Ce, Pr, Nd, Pd, and Co with different concentrations. Five of them (Cr, Ni, Cu, Zn, and Pb) are priority pollutants according to EPA. Their average concentrations in oxide form were Cr2O3 (2.96 %), NiO (0.32 %), CuO (0.45 %), ZnO (0.56 %), and PbO (1.49 %).
RESUMO
Cobalt nanowires have been synthesized by electrochemical deposition using track-etched anodized aluminum oxide (AAO) templates. Nanowires with varying spacing-to-diameter ratios were prepared, and their magnetic properties were investigated. It is found that the nanowires' easy magnetization direction switches from parallel to perpendicular to the nanowire growth direction when the nanowire's spacing-to-diameter ratio is reduced below 0.7, or when the nanowires' packing density is increased above 5%. Upon further reduction in the spacing-to-diameter ratio, nanowires' magnetic properties exhibit an isotropic behavior. Apart from shape anisotropy, strong dipolar interactions among nanowires facilitate additional uniaxial anisotropy, favoring an easy magnetization direction perpendicular to their growth direction. The magnetic interactions among the nanowires were studied using the standard method of remanence curves. The demagnetization curves and Delta m (Δm) plots showed that the nanowires interact via dipolar interactions that act as an additional uniaxial anisotropy favoring an easy magnetization direction perpendicular to the nanowire growth direction. The broadening of the dipolar component of Δm plots indicate an increase in the switching field distribution with the increase in the nanowires' diameter. Our findings provide an important insight into the magnetic behavior of cobalt nanowires, meaning that it is crucial to design them according to the specific requirements for the application purposes.
RESUMO
Microplastic contamination in beach sediments along coast of Dubai is un-documented. In this study, microplastic contamination in beach sediments collected from the wrack lines of 16 beaches in Dubai was evaluated. Five samples were collected from each beach along a 100 m stretch using a 0.5 m by 0.5 m, quadrant. The number, color, and shape of microplastics were documented. The polymer types of large fibers and strings were identified through FT-IR analysis. 480 microplastics from each of the 16 beaches were selected to detect heavy metals using XRF analysis. The results showed that the average weight of microplastic is 0.33 mg per gram of dry sediment (or 953 mg·m-2) and the number of microplastic is 59.71 items per kg of dry sediment (or 165 items·m-2). Blue and fibrous microplastics were dominant. Polyethylene strings and fibers were abundantly found. 13 heavy metals were identified of which five are priority pollutants.
