Artificial Tiles Research Articles

The Radioactivity Levels and Safety Assessment of Building Materials in Nanjing, Jiangsu Province, China

In order to invetigate the natural radioactivity levels of typical building materials in Nanjing, Jiangsu Province,China, the specific activities of natural radionuclides (226Ra,232Th and40K) in samples of building materials were measured by ORTEC HPGe gamma ray spectrometer. And the radium equivalent activity, the internal and external exposure index, and relative annual effective dose equivalents were also claculated. The average concentrations of all the samples ranged from 64 to 318.79 Bq·kg-1, 11.35 to 144.83 Bq·kg-1and 92.57 to 951.68 Bq·kg-1for226Ra,232Th and40K, respectively. Their average values were in the ranges: 0.33-1.50 for the internal exposure index (Ira); 0.29-1.51 for the external exposure index (Ir); 0.34-1.74 mSv·a-1 for HEextand 0.36-1.76 mSv·a-1for HEint. The average radium equivalent activity varied from 106.49 to 541.77 Bq·kg-1. According to the standard, most samples were in a lower radioactivity level expect a few of artificial tiles. But, we must perfect detection and management system of many materials to ensure radiation safety and physical health.

Vertical profiles of current velocity and dissolved oxygen saturation in biofilms on artificial and natural substrates

We determined vertical changes in current velocity and dissolved oxygen concentration in biofilms on artificial and natural substrates using microelectrodes. We used biofilms developed on glass slides dipped in an artificial stream for 3 months, artificial clay tiles dipped in an outdoor artificial stream for 3 months, and natural pebbles. In the biofilm on a glass slide, current velocity significantly decreased from the surface of the biofilm and became 0 cm s−1 at the surface of the glass slide. Vertical profile of current velocity versus depth indicated a presence of a viscous sublayer of 0.2-mm thickness above the surface of glass slide. Dissolved oxygen (DO) concentration increased within the biofilm and attained the maximum (123%) at the surface of the glass slide, indicating active photosynthesis by sessile diatoms at the layer corresponding to the observed viscous sublayer. In the biofilm on an artificial tile, DO increased to 163% saturation at 24.849-mm depth, followed by rapid decrease (6%) at the surface of the tile. A similar result of remarkable decrease in DO saturation was also found in the biofilm on a natural pebble. These results suggest that smoothness of the substrate surface is related to the vertical profile of DO saturation. The thickness of the viscous sublayer and oxygen-depleted area (up to several hundred micrometers, μm) was sufficient for the presence of bacteria, protists, and other metazoan animals, suggesting high activity and diversity of those heterotrophs in the bottom part of biofilms.

Perlphyton as Indicators of Enrichment in Lake Pend Oreille, Idaho

ABSTRACT Periphyton in the littoral zone of Pend Oreille Lake, a large (383 km2, deep (Zmax — 380 m)) meso-oligotrophic lake in northern Idaho, were studied to compare with pelagic productivity and to identify areas of inshore degraded water quality. Periphyton growth was determined on artificial tiles and natural substrates at 0.5 and 1.5 m depths. Means for all measures of production on natural substrates were higher than means for artificial substrate. Indicators of biomass were higher on 0.5 m tiles than those at 1.5 m; exposed sites, however, showed less difference between depths than did the more sheltered sites. Because of inorganic interference, ash-free dry weight provided a better measure of periphyton biomass than dry weight. Significant differences existed between sites, indicating greater algal growths in developed and relatively confined bays. Cymbella was dominant on natural substrate, while Cymbella, Mougeotia, and Rhizoclonium were co-dominant on artificial substrate. Blue-green algae biomass comprised only a small part of the total biomass on either artificial or natural substrates. Periphyton biomass in Pend Oreille Lake was comparable to other lakes showing accelerated eutrophication. Despite Pend Oreille Lake's great depth and large profundal area, littoral productivity was similar to lakes more shallow in nature with higher overall productivity. In-shore water quality degradation was documented at a time when open-lake conditions indicated the lake was meso-oligotrophic. Given that changes in lake trophic status would first show up in littoral areas–compared to the relatively slow changes taking place in the phytoplankton of pelagic areas–periphyton monitoring should provide valuable refinement to in-depth limnological studies on open waters of lakes.