**1. Introduction**

434 Pesticides in the Modern World - Risks and Benefits

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> Carbon tetrachloride (CCl4) has been used as a grain fumigant, pesticide, solvent for oils and fats, metal degreaser, fire extinguisher and flame retardant, and in the production of paint, ink, plastics, semi-conductors and petrol additives (Agency for Toxic Substances and Disease Registry (ATSDR), 1994). Its properties are shown in Table 1. CCl4 is classified by the International Agency for Research on Cancer (IARC) and the US Environmental Protection Agency as a Group B2 carcinogen and also listed on the CERCLA Priority List of Hazardous Substances maintained by the Agency for Toxic Substances and Disease Registry (ATSDR, 2008). CCl4 is a common contaminant in soil and groundwater. CCl4 is found in approximately 20% of the US Superfund National Priority List sites (Ferguson & Pietari, 2000). But, there are limited published case studies of CCl4 contamination in karst aquifer. Karst aquifers are distinguished by an abundance of large subsurface openings and are therefore especially vulnerable to chlorinated-solvent contamination (CCl4, TCE, PCE). The release of chlorinated solvents into karst aquifers presents a difficult challenge to environmental scientists, managers, and regulators. The importance of karst aquifers to


Table 1. Physical properties of carbon tetrachloride (Fouw, 1999)

Transport of Carbon Tetrachloride in a Karst Aquifer in a Northern City, China 437

As shown in the Fig.3, the contaminated site is a NE synclinal basin with area of approximately 200 km2. Its southeastern and northwestern boundaries are two NE mountain chains composed of Cambrian and Ordovician limestone with elevations from 100 m to 248 m above the sea level. Quaternary deposits in the central lowlying area of the basin are composed of alluvium, proluvium, sand, sandyclay and subclay. The thickness of Quaternary is from 5 to 30 m, and the elevation varies from 30m to 40m above the sea level.

Fig. 2. View of the pesticide plant and its wastewater drainage

Fig. 3. Bedrock geologic map of Qiligou water-bearing basin

**2.2 Geological and hydro-geological settings** 

water supply and their vulnerability to contamination by chlorinated solvents are reasons to seek improved understanding of how chlorinated solvents behave in karst aquifers (Wolfe et al., 1997). This chapter discusses CCl4 transport and fate in a karst aquifer in a northern city of China based on *years of continuous monitoring* of CCl4 concentrations*.*
