Transport and sorption of organic contaminants during infiltration from Cihe River to groundwater

During the transport of organic contaminants from river to groundwater, there is natural attenuation of contaminants resulting from volatilization, biodegradation, dilution, and sorption of organic contaminants to soils. In this study, the distribution and natural attenuation of organic contaminants in the sites along Cihe River, in the piedmont plain of Taihang Mountains, was investigated. The results of collected samples of soil, river water, and groundwater indicated that the main organic contaminant groups showed in different media are quite similar. The main organic contaminants detected in different media include hydrocarbons, chlorinated hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), and pesticides. The experimental results of toluene and trichloroethylene (TCE) indicated that sorption of organic contaminants is a main natural attenuation process. The soils taken near ground surface showed a higher sorption capacity for toluene and TCE than that of the deep soils. In the experimental concentration range, sorption of organic contaminants to minerals, especially TCE, plays an important role in the overall sorption. Sorption of toluene to soils showed high nonlinearity, but linear sorption of TCE to soils was observed. There was a closer relationship between sorption affinity and soil organic carbon content for toluene than that for TCE. This indicated that sorption process was also significantly influenced by the properties (e.g., molecular structure, hydrophobicity).