Contamination levels compared

Basic oxides of metals such as Co, Mn, Fe, and Cu catalyze the decomposition of chlorate by lowering the decomposition temperature. Consequendy, less fuel is needed and the reaction continues at a lower temperature. Cobalt metal, which forms the basic oxide in situ, lowers the decomposition of pure sodium chlorate from 478 to 280°C while serving as fuel (6,7). Composition of a cobalt-fueled system, compared with an iron-fueled system, is 90 wt % NaClO, 4 wt % Co, and 6 wt % glass fiber vs 86% NaClO, 4% Fe, 6% glass fiber, and 4% BaO. Initiation of the former is at 270°C, compared to 370°C for the iron-fueled candle. Cobalt hydroxide produces a more pronounced lowering of the decomposition temperature than the metal alone, although the water produced by decomposition of the hydroxide to form the oxide is thought to increase chlorine contaminate levels. Alkaline earths and transition-metal ferrates also have catalytic activity and improve chlorine retention (8). 

Most industrial companies would like to set air quality requirements regarding health hazard at a lower concentration level compared to values found in regulations. For example, when a TWA concentration is given as x kg per nC of air for a certain contaminant, the required concentration level for design of general ventilation in an industrial enclosure could be chosen as one-third of that value. This value can be considered the target value for the first design. 

Indoor air quality The actual quality of air within a space compared with a given sample or standard, related to temperature, moisture, biological content, and contaminant levels. 

One measure of lire significance of coniaininants in soil or solid waste samples may be determined by comparing the levels with reported naturally occurring concentrations. Provided levels are within the range that may occur naturally, one might conelude that the sample contaminant levels are of little consequence. 

Comparing the six sampling points monitored in this study (Fig. 4), HEIMD followed by HDAD were the most polluted ones, showing concentration levels of total pesticides above 5 pg/L in 39% and 22% of the samples analyzed, respectively. As expected, the sampling points located in the two bays (HEM and HDM) were the less polluted, due to the dilution effect of the marine water. This dilution effect may explain also the higher contamination level observed in the northern bay as compared to the southern bay, which is comparatively larger in size and depth. 

Robertson A., B.W. Gottholm, D.D. Turgeon, D.A. Wolfe. 1991. A comparative study of contaminant levels in Long Island Sound. Estuaries 14 290-298. 

Hydrocarbon adsorption experiments show significant differences between the nickel contaminated zeolitic and non-zeolitic particles at metals levels comparable to those of the catalytic experiments. Neither hexane nor 1-hexene showed any interaction with nickel on the low surface area, non-zeolitic particles (the unpromoted material of Table I) at temperatures up to 425 C. Additionally, no interaction between hexene and the nickel on the zeolitic particles was observed over the temperature range studied. However, the nickel on the zeolitic component did cause significant retention of hexane at temperatures as low as 200 C with generation of what appeared to be higher molecular weight products. No cracking products were observed. With the uncontaminated zeolitic particles, hexane retention only occurred at temperatures above 300°C. Thus, the lower temperature retention for the contaminated particles appears to be due to the presence of nickel. 

FIGURE 2.10 Comparing MAB catalyst with a standard residual catalyst at extreme metal contaminant levels with atmospheric residue in the ACE unit. (O) LZM resid catalyst, ( ) MAB. 

The biotransformation enzyme GST showed significant and unambiguous decreased responses compared to references but it did not correlate with contamination levels for PCBs and PAHs. Since it appeared to be influenced by salinity differences it would seem to have little value as an estuarine biomarker. 

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