Partitioning of polycyclic aromatic hydrocarbons in the polyethylene/watersystem

The suitability of polyethylene sheets as passive samplers of lipophilic co ntaminants in water bodies was tested. High-density polyethylene (HDPE) and low-density polyethylene (LDPE) sheets were contaminated with PAH. Unconta minated and pre-contaminated sheets were deployed simultaneously and collec ted at intervals over 32 days. The exposed sheets and water samples were an alyzed for PAR The initial PAH concentrations in the contaminated and uncon taminated sheets differed by two to three orders of magnitude, but approach ed a common equilibrium concentration during exposure. The two- to four-rin g PAH achieved quasi-equilibrium within the 32-day exposure period, whereas the five- and six-ring PAH did not. The estimated PE/water partition coeff icients were approximately three times higher for HDPE than for LDPE, and t hey were similar in magnitude to the K-OW values (the partition coefficient s between n-octanol and water). The uptake rate constants were approximatel y four times higher for HDPE than LDPE, which was attributed to the four ti mes higher specific surface area. The uptake and elimination in HDPE follow ed linear first-order kinetics, whereas for LDPE very slow elimination rate s were observed that could not be explained. The results show that PE is a simple, effective, and inexpensive material for sampling trace organic cont aminants in water.