The quantification and effects of system pH value on the interactions between Pb(II) and the biopolymer in activated sludge were investigated. The biopolymer had two protein-like fluorescence peaks (Ex/Em = 280 nm/326–338 nm for peak A; Ex/Em = 220–230 nm/324–338 nm for peak B). The fluorescence intensities of peak B were higher than those of peak A. The fluorophores of both peaks could be largely quenched by Pb(II), and the quencher dose for peak B was about half of that for peak A. The modified Stern-Volmer equation well depicted the fluorescence quenching titration. The quenching constant (Ka) values for both peaks decreased with rising system pH value, and then sharply decreased under alkaline conditions. It could be attributed to that the alkaline conditions caused the reduction of available Pb(II) due to the occurrence of Pb(OH)2 sediments. The Ka values of peak B were bigger than those for peak A at the same system pH values. Accordingly, the aromatic proteins (peak B) played a key role in the interactions between metal ions and the biopolymer.
An abandoned herbicide factory site was used as an example of how planning should be considered for development of the site for transportation use in Dalian, China. Exposure pathways and parameters for three types of transportation use (land for a traffic hub, land for an urban road, and land for a subway) were developed. Twenty-five sampling sites were selected and 38 soil samples were collected in March 2015. Hexachlorobenzene and benzo(a)pyrene which were extracted by Soxhlet extraction and detected by gas chromatography mass spectrometry were the most significant pollutants detected. The maximum concentration of the two pollutants in the surface layer (0–0.5 m) were 0.57 and 3.10 mg/kg, and in the bottom layer (1.0 m) were 2.57 and 3.72 mg/kg, respectively. In this study, risk assessment results based on the established exposure scenario and parameters showed that there was a significant difference in traffic hub land use under specific exposure pathway and common insensitive land use exposure pathways (direct ingestion of soil, dermal contact with soil, and inhalation of soil-derived dust). Commonly considered hexachlorobenzene and benzo(a)pyrene carcinogenic risk values exceeded the maximum acceptable level (10−6) and were found to be 23.9-fold and 189-fold higher than the carcinogenic risk values, respectively. Parameter sensitivity analysis data showed that for transportation use, the two parameters “EFOa” and “OSIRa” were the most significant factors associated with variation of the carcinogenic risk value. For traffic hub land use, urban road land use, and subway land use, the main exposure pathways were through “inhalation of soil vapors outdoors (from surface soil),” “direct ingestion of soil,” and “inhalation of soil vapors indoors (from bottom soil),” which contributed 84.75, 73.00, and 100.00% to the total risk value, respectively.
