Contamination Of Polycyclic Aromatic Hydrocarbons In Urban Soils In Beijing

The systemic investigations for organic pollutants in urban soils in Beijing ranged in about 1100 square kilometers have been performed in this work. The pollutant PAHs kinds, concentration, spatial distribution, possible sources were analyzed, or discussed. The soil environmental quality was evaluated, and the potential ecological risks were assessed.Soil samples were collected from campuses of universities, schools and kindergartens, public squares, fallow land and roadsides, and were analyzed for 16 PAHs by GC-MS. There was a high variability in the total PAHs (ZPAHs) concentrations, ranging from less than 366 to 27825 ng g-1. The highest EPAHs concentrations were found at street sides and industrial areas. Soil organic carbon (SOC) is one of the important factors that can influence the concentrations of PAHs in soils. It was found concentrations of ZPAHs were significantly correlated with organic carbon of soils. To trace the sources of PAHs, the ratios of phenanthrene to anthracene and fluoranthene to pyrene were used to identify pyrogenic and petrogenic sources, respectively. In most cases, PAHs in soil were pyrogenic. These sources included motor vehicle exhausts, industrial activities and coal burning.The sorption interaction of hydrophobic organic contaminants (HOCs) with natural particles (or natural geosorbents) and the subsequent slow release significantly impact the transport and ultimate fate of HOCs in environment, and simultaneously challenge the establishment of environmental quality criteria and the effectiveness of organic contaminant remediation. However, the mechanisms controlling the sorption and desorption behaviors are not well understood. In this investigation, the sorption behavior was systematacially studied for one polycyclic aromatic hydrocarbons, i.e., phenanthrene, from four different area soils. The objective is to identify sorbent and sorbate characteristics that play a predominant role in the sorption process and toestablish a conceptual sorption framework of natural geosorbents for HOCs. The sorption of phenanthrene to soil is also related to the properties of organic compound. The sorption isotherm of phenanthrene is linear, which is the result of phenanlhrene partition into soils.The intake routes and hazards of organic pollutants to human were well recognized, therefore the intake amount of organic matters through foodchain was effectively cut down. In many cases, oral ingested soil could be an important source of PAHs in human. The traditional approach for estimating the bioavailability of PAHs in oral ingested soil, is animal (in vivo) test. Compared to animal test, in vitro test possesses several advantages including satisfactory replicability, time and cost effectiveness. Also, in vitro tests are found to be well correlated to in vivo tests. Physiologically based In Vitro test developed during the last 10 years was used to estimate PAHs bioaccessibility of inadvertently ingested soil in human. The maximum PAHs absorption by human was assessed in an artificial system of human gastro-intestinal environment. Results showed that the bioavailability of intestinal is more than gastric's. In vitro test could be used not only to estimate the bioavailability of PAHs in soil in order to provide information for establishment of soil quality or clean criteria with regard to human health, but also to evaluate the effectiveness of soil remediation technologies. Therefore, in vitro test has been employed in many developed countries due to its abovementioned advantages. The use of in vitro test for screening of contaminated soil and evaluating of effectiveness of remediation technology is believed to be promising.