A cleaner river: long term use of semipermeable membrane devices demonstrate that concentrations of selected organochlorines and PAHs in the Brisbane River estuary, Queensland have reduced substantially over the past decade.

We first used semipermeable membrane devices as samplers to evaluate concentrations of organochlorines and PAHs in the Brisbane River in 1998. Here we revisit this work and repeat the study a decade later in the same season (summer), also taking account of results from a similar study involving PAHs in the summer of 2001-2002. The accumulation of organochlorines and most PAHs in the samplers in the recent assessment was substantially less than in the 1998 deployment, suggesting that the ambient concentrations of these chemicals have decreased considerably over the last decade. In all cases there was high reproducibility of the mass of chemicals accumulated in the sampler. We used performance reference compounds in the later deployment, and assuming that the kinetics were similar in both deployment periods, we estimate that the concentration of dieldrin, the organochlorine found at highest concentrations, decreased from approximately 3.9 ng/L to about 1.4 ng/L. The decrease of most other analytes of interest including DDE and DDD was greater, potentially indicating that dieldrin is still entering the Brisbane River through run-off from urban areas where it was used widely for treatment of termites until 1995. DDT use in Australia ceased in the mid 1980s.

Partitioning of polycyclic aromatic hydrocarbons in the polyethylene/water system.

The suitability of polyethylene sheets as passive samplers of lipophilic contaminants in water bodies was tested. High-density polyethylene (HDPE) and low-density polyethylene (LDPE) sheets were contaminated with PAH. Uncontaminated and pre-contaminated sheets were deployed simultaneously and collected at intervals over 32 days. The exposed sheets and water samples were analyzed for PAH. The initial PAH concentrations in the contaminated and uncontaminated sheets differed by two to three orders of magnitude, but approached a common equilibrium concentration during exposure. The two- to four-ring PAH achieved quasi-equilibrium within the 32-day exposure period, whereas the five- and six-ring PAH did not. The estimated PE/water partition coefficients were approximately three times higher for HDPE than for LDPE, and they were similar in magnitude to the K(ow) values (the partition coefficients between n-octanol and water). The uptake rate constants were approximately four times higher for HDPE than LDPE, which was attributed to the four times higher specific surface area. The uptake and elimination in HDPE followed linear first-order kinetics, whereas for LDPE very slow elimination rates were observed that could not be explained. The results show that PE is a simple, effective, and inexpensive material for sampling trace organic contaminants in water.

Critical internal and aqueous lethal concentrations of chlorobenzenes with the crab Portunus pelagicus (L).

The toxicity of a series of chlorobenzenes to juvenile crabs Portunus pelagicus (L) was investigated. These compounds are lipophilic with a strong capacity to bioconcentrate. An increase in toxicity during molting was observed. There was also an increase in toxicity with increasing log Kow and molecular weight, which was best described using nonlinear regression equations relating LC50 and log Kow. Chlorobenzene residues in animals that died from the exposures were measured and the critical internal lethal concentration and volume fraction were estimated for each compound. A mean concentration value of 3.24 mumol g-1 on a wet weight basis and a mean volume fraction of 0.140 cm3 toxicant cm-3 tissue lipid were determined at time zero. However, these values decreased with increasing periods of exposure according to first-order kinetics with a constant rate of 0.0287 hr-1. This indicates that toxicity is a function of both concentration in the tissues and the period during which it has been present. The critical internal lethal concentrations measured in this study were not consistent with the constant critical internal concentration/critical volume fraction hypotheses.