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The adsorption of lead on clean and sulfur-modified nickel surfaces was studied as a function of immersion time. The effect of preadsorbed sulfur and lead adsorption on nickel oxidation was also examined by open-circuit potential (OCP) measurements. Sulfur adsorbed on nickel inhibits the formation of the inner NiO layer, which results in an enhanced nickel oxidation/dissolution in aqueous solutions. The adsorption of lead is enhanced by as much as 1200% when the nickel electrode is first modified by a monolayer of adsorbed sulfur. The chemical shift in Pb(4f) binding energies indicates that lead (Pb2+) ions interact directly with the preadsorbed sulfur on nickel. Lead adsorbed on sulfur-modified nickel electrode is also found to retard the oxidation/dissolution of nickel, which is enhanced by sulfur. On sulfur-modified nickel surfaces, 70% of the lead adsorption occurs during the initial 30 s of immersion. The rate of lead adsorption approaches zero after an immersion time of 10 min. On the basis of the observations of this study, a model for the sulfur-induced lead adsorption has been formulated.

Sewer construction in Taiwan lags other developed nations, and the authorities are undertaking major sewerage system construction projects in several cities. In Kaohsiung City, sewerage networks pass through residential, commercial and industrial areas. The composition of sewage thus is highly complicated. Eight target monitoring positions are chosen to analyze the compounds and concentrations of hazardous air pollutants. Pollutant concentrations are used to evaluate the cancer risk increment based on inhalation intake for sewer workers under using exhaust ventilation and wearing personal gas filtering equipment. GC/MS analysis confirmed that concentrations of benzene and trichloromethane compounds in sewer air for all the monitoring positions exceeded the minimum risk levels (MRLs) of 0.009 ppm benzene and 0.1 ppm trichloromethane, and the maximum concentrations reached 148.4 and 327.3 ppm, respectively. The cancer risks of benzene and trichloromethane for workers without personal protection approached 2.77-3.98 × 10 -3 and 29.74-42.70 × 10 -3 , respectively. Through ventilation for 15 minutes and the wearing of gas filtering equipment, the cancer risks for benzene and trichloromethane were reduced to 0.0003-0.0004 × 10 -3 and 0.0029-0.0041 × 10 -3 , respectively. The authorities thus must order all workers to follow a strict code of practice for sewer entry before entering sewer systems. This code of practice should include a minimum time for general exhaust ventilation and the use of personal protection equipment.