The use of bioassays for soil evaluation

Many countries have established lists with priority pollutants (Ferguson Kasamas 1999 ATSDR 2001) focusing on substances that are hazardous to human health and/or the environment. These lists refer to chemicals with known toxicity at least for particular receptors. If information on the nature of pollution is available, chemical analysis may focus on selected chemicals. In case of waste sites or if data on site history are scarce, comprehensive chemical analysis would be required to reduce the risk of disregarding substantial pollutants. This is expensive. The application of bioassays may circumvent extended routine analysis by indicating toxic samples directly. 

Detailed investigation of soil samples with comprehensive analysis is possible but expensive. In particular, if multiple pollutants are present, bioassays may be less costly (Environment Canada 1999). 

The more available fractions comprise dissolved contaminants and the part sorbed by expanded (soft and flexible) organic matter (Luthy etal. 1997). Substantial research has been accomplished over the last years and is still ongoing to quantify the available or non-available part of pollution (Cuypers etal. 2000 Loibner etal. 2000 Liste Alexander 2002). However, no routine 

Bioassays applied to contaminated soil samples provide an overall toxicity measure that accounts for numerous site-specific variations. Factors that may lead to an enhanced or reduced toxicity are no longer a matter of estimation but are measured directly with the test system. 

Bioassays are not always preferable, especially, if simple chemical analysis is sufficient (e.g. spill with known pollution) to answer questions such as what is the spatial extent of the spill. Many bioassays have an extended test duration and may only be competitive if they can substitute for comprehensive chemical analysis. Nevertheless, one should keep in mind that bioassays provide additional information not achievable with conventional chemical analysis, which could be a compensation for longer test duration. 

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