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Contamination of the environment by heavy metals is a phenomenon of global importance today. When present in high concentrations in the environment, heavy metals may enter the food chain from soils and result in health hazards. Accumulation in street dust is one major way through which heavy metals may find their way into soils and subsequently living tissues of plants, animals and human beings. In this paper, the magnitude and sources of some heavy metals (Cu, Mn, Fe, Cd, Pb and Zn) in street dust samples in and around Gwagwalada, Nigeria, were assessed.

Street dust samples were collected from 12 sites with and without varying levels of human activities (blacksmithing, motor repair works, metal working and fabrication, vehicular traffic and residential development) in the area and analysed by atomic absorption spectrophotometry to determine the magnitude and sources of accumulation of the above heavy metals in street dust in the study area.

The mean concentrations were found to be 210, 79, 97, 3.9, 120 and 96 μg g⁻¹ respectively, for Pb, Zn, Cu, Cd, Fe and Mn across the various sampling sites. Samples collected from sites with human activities were found to contain concentrations of the metals that are generally higher than those in background areas (without human activities). However, metal working and fabrication, and motor repair works were found to have a stronger influence on the accumulation of the metals in the dust samples than vehicular traffic.

The results indicate that, contrary to what is expected, based on the observations made in several areas by many researchers elsewhere, metal working and fabrication, and motor repair works have a stronger influence on the accumulation of the metals in the dust samples than vehicular traffic in the study area.

Provides information on heavy metal contamination of the environment in an area of Nigeria.

Describes a study carried out to evaluate the accumulation of heavy metals by two different vascular aquatic plants in the artificial wetlands which were constructed for the treatment of municipal wastewater in Berlin, Germany. The studied plants were Pharagmites australis and Schoenoplectus lacustris. The investigated metals were: Zn, Cr, Cu, Fe, Cd, Ni and Pb. The translocation of such metals in the plant roots, stems and leaves was also determined. The level of metals in the influent and effluent of the wastewater, as well as the sludge, was investigated. The concentration factor of each metal by plants and sludge was further studied. Results revealed that P. australis has a higher tendency for the accumulation of metals than S. Lacustris. The level of metals was higher in roots, followed by leaves, then stems. Metals were more concentrated in the sludge than in the plants. Further study showed that the levels of metals in plants grown in the artificial wetlands were higher than in those grown in a “controlled” area. Concludes that vascular plants can act as scavengers of metals from the municipal wastewater while still maintaining a healthy status.

Introduction Clad metals are composites of two or more metals which are joined in a continuous manner by a metallurgical bond. The composite provides the specific advantages of both metals, usually the good corrosion resistance of the cladding metal and the strength and economy of the backing metal.

Every metal has a range of environmental conditions against which it is resistant or sufficiently resistant as to make the metal economically feasible. Unfortunately it is almost a rule of thumb that the more expensive the metal the smaller the range. In most cases the resistance of the metal is a function of the metal thickness, but the function is such that relatively thin metals can produce very long lives.

The main purpose of this study is to investigate the bioaccumulation pattern and fate of heavy metals in duckweed‐based wastewater treatment ponds with different depth.

Three replicates of four reactors were used in this experiment. The reactors were randomly distributed on the bench and filled with 50 percent diluted sewage for the control reactors whereas diluted sewage mixed with 5 mg Pb/l and 5 mg Zn/l was used for the treatment reactors. The reactors were stocked with Lemna gibba at 1,000 g fresh weight per each square meter. The culture tanks were exposed to temperature range of 21‐25°C and light regime of 16 hours light using halogen lamps and 8 hours dark. The light intensity was maintained around 200 μ E m⁻² S⁻¹. The experiment extended for 30 days. Regular monitoring of the growth performance of duckweed was carried out with subsequent analysis of dry matter, heavy metals, phosphorous and nitrogen content. Composite samples from the water phase were subjected to the analysis of ammonia, nitrite, nitrate, orthophosphate and sulfate concentration. The analysis of sediment and biofilm were carried out at the end of the experiment. Interpretation of results was carried out using one‐way analysis of variance.

Statistical analysis showed a significant reduction in the growth rate of duckweed within the first five days exposure time. After five days exposure, the growth rate in the treatments returned to the normal growth till day 15 after which the growth became significantly lower in the small and medium scale ponds. The results revealed that zinc is more bio‐available than lead and both metals are mostly precipitated in the sediment probably as sulfides.

The results help in enhancement of heavy metals removal in a small anaerobic pretreatment unit before entering to the pond system by sulfate addition.

The results of the study confirm the positive effect of pond depth in reducing the heavy metal toxicity to the duckweed‐based wastewater treatment ponds.

The purpose of this study is to suppress the temperature rise of high voltage wall bushing metal plate.

First, the authors built a model of a traditional metal plate and got the magnetic field intensity distribution by FEA tools. Optimized according to the magnetic field intensity distribution, the authors slot the traditional metal plate and embed permanent magnets in the slot. Finally, the authors got the temperature distribution diagrams of the above three cases at different current levels by FEA tools.

Slotted metal plate is beneficial to suppress magnetic induction intensity, but the improvement of the magnetic induction intensity uniformity is not obvious. The method of embedding a permanent magnet in a slotted metal plate can optimize the magnitude and uniformity of the magnetic induction intensity in the metal plate. The larger the current passing through the metal plate, the better the temperature suppression effect of the slotted metal plate and the slotted metal plate embedded in the permanent magnet.

The effect of structural factors, slotting plate and setting permanent magnets on slots on the temperature of supporting plate is studied. The paper proposes two methods, slotting metal panels and embedding permanent magnet metal panels, to solve the problems of eddy current loss and high calorific value of the panel, which is of great significance to the safety of the grid equipment.