Chlorocarbon-Related Contamination

Chlorocarbons are a particular concern owing to their persistence in the environment and the lack of metabolic cleansing pathways in organisms and high fat solubility. Consequently, these substances bioaccumulate in the food chain, with unclear or deleterious effects on health and environmental quality. Chlorocarbons are considered separate from pesticides (see separate discussion) in this discussion and are chlorinated benzenes or phenols and chlorinated alkanes or alkenes. Volatile compounds in water were purged for determination by IMS with a corona discharge (CD) ion source. Chlorobenzene at 3 to 30 mg/L was determined in 5 min, which was considered suitable for on-site measurements at a restoration site. 

Subsurface soil-gas sampling in test wells was made using an IMS encased in a 51-mm diameter stainless steel probe along with supporting electronics. Resolving power was 38 for DtBP and 31 for tetrachloroethylene or perchloroethylene (PCE). This instrument was placed into service at a site contaminated with PCE. The presence of PCE was confirmed by GC-MS analysis of a gas sample at a laboratory certified by the Environmental Protection Agency (ERA). This demonstrated the viability of a down-well IMS-based analyzer. 

Water sampling with a spiral hollow polydimethylsiloxane (PDMS) membrane was used with IMS for in situ sampling and analysis of trace chlorinated hydrocarbons in water in a single procedure. Aqueous contaminants permeate across the membrane into a gas flow, through the membrane tube, and into a specially made 

IMS analyzer. The IMS analyzer exhibited a resolving power of R = 33 and 41, respectively, for negative- and positive-mode reactant ions, and the detection limits in negative polarity were 80 pg/L for PCE and 74 pg/L for trichloroethylene (TCE). The time-dependent response to TCE was experimentally and theoretically studied for various concentrations, membrane lengths, and flow rates. Findings supported the use of membrane extraction for the continuous monitoring of chlorinated hydrocarbons in water with an IMS analyzer. 

---