Heavy Metals in Urban Dust

Urban dust is contaminated by pollutants from various diffused sources and is often difficult to be controlled. It elevates the background heavy metal exposure level to humans and ecosystems in and around urban area and may give an apparent or hidden impact. In this chapter, the recent studies on heavy metals in the urban dust are summarized. First, the heavy metal pollution of the dust in the atmosphere and on the road surface is described. Then, the process of road runoff and subsequent infiltration to the soil is discussed from the viewpoint of heavy metal mobility. Finally, the ecotoxicity of road dust is shown, and the causal pollutants in the dust are discussed

Thermodynamic Study on Fusion, in Crystalline Polymer and Its Mixture with Diluent, based on Folded Chain Crystalline Model

In accordance with the regular folded chain crystallite model, an expression for the melting point depression of crystalline polymer in diluent was derived by extending the treatment given by Flory. The equation obtained is which reduces for very large x and considerably large ζ to where Tm⁰ is the melting point of the pure polymer of infinite fold length and chain length, Tm⁰(l) is tne melting point of the pure polymer of fold length l, Tm(l) is the melting point for the polymer of fold length l in the presence of diluent, ΔHᵤ is the heat of fusion per mole of repeating unit, Vᵤ and V₁ are the molar volumes of the polymer repeating unit and the diluent, respectively, x is the degree of polymerization, v₁ and v₂ are the volume fractions of the diluent and the polymer, respectively, ζ is the fold length in number of repeating units, σₑ is the end surface free energy per unit volume, Δhf is the heat of fusion per unit volume, and X₁ is the diluent-polymer interaction parameter. The model used here was discussed in relation to the fringed micelle model

Characterization of Polystyrene in Methyl Ethyl Ketone by Small-Angle X-Ray Scattering

Molecular and thermodynamic properties of polystyrene in methyl ethyl ketone were studied by a small-angle X-ray scattering with a Kratky camera. The molecular weight, radius of gyration, second virial coefficient, mass per unit length, hydrodynamic length, radius of gyration of cross section, persistence length, and radius of cross section were estimated. Some of these values were compared with the values determined by other methods. Both values agreed well each other

Determination of 3,5,6-trichloro-2-pyridinol levels in the urine of termite control workers using chlorpyrifos.

Chlorpyrifos, an organophosphorus insecticide, has been used to control termites since regulatory measures against the use of chlordanes were taken in September, 1986. We developed an improved gas chromatographic (GC) method for the assay of 3,5,6-trichloro-2-pyridinol (TCP) in the urine to use in the biological monitoring of exposure to chlorpyrifos. Urinary TCP was separated and determined accurately (C.V., 4%) with high sensitivity (detection limit, 10 ng/ml) and recovery (recovery greater than 90%) using a wide bore capillary column (WBC column). The accuracy and precision of the present GC method are satisfactory. The time course of urinary excretion of TCP was followed in workers. The urinary TCP level was low in the off-season and high in the busy season. Variation in the urinary TCP level corresponded to the termite control season and the length of the working period. The urinary TCP level showed a change reciprocal to the variations in the plasma cholinesterase activity. From these results, it is surmised that the urinary TCP level represents the extent of exposure to chlorpyrifos. The decrease in the level of cholinesterase activity is suggested to be due to exposure to chlorpyrifos. Determination of the urinary TCP level by GC using a WBC column is useful in the biological monitoring of chlorpyrifos in termite control workers and potentially has practical application to health care.</p