Soil Sampling Content
Contaminated land is a global environmental problem that results not only in ecological and human health risks, but can also have large financial implications in terms of remediation costs and re-development issues. Many industries contaminate soils as part of their everyday activities and the ability to evaluate the hazards that accompany soil toxicity are paramount in the oil and gas, mining, agriculture and urban development industries. Contaminant availability is measured using analytical methods on extracted samples and may provide a first indication of the potential risk. The concept that toxicity can be readily extrapolated from pollutant concentrations in a complex matrix is not accurate. Pollutant mobility, availability and uptake, and metabolism by native organisms are crucial issues neglected by basing risk assessments on analytical values alone. As a general rule, risk assessment cannot be solely based on the analytical determination of total contents of specific contaminants because information on unexpected chemicals or bioavailability is not provided and the risk can be underestimated. There is an increasing need to incorporate bioassays in risk assessments and hazard identification.
Environmental risk assessment in soils needs to be holistically conceived on the basis of the combination of chemical and toxicological approaches for the following reasons
- Toxicity, and therefore risk, largely depends on bioavailability
- Bioavailability and toxicity are influenced by the soil physicochemical properties and the chemical form of the pollutants
- Toxicity and mobility within the ecosystem largely depend on specific chemical forms and binding state.
- Changes in environmental conditions such as acidity, redox potential or levels of available organic ligands can modify metal speciation and change how these species move in the environment.
Different species may be subject to different exposure pathways and may exhibit different sensitivity to toxicants. In order to assess environmentally relevant soil toxicity, a suite of organisms from different taxonomical groups and ecological levels is recommended. EBPI has several options in this regard and can provide organisms from a multitude of groups for sample analysis. Testing soil samples with different species also permits the consideration of diverse exposure routes and toxic endpoints. By using several different organisms, samples can be profiled by their responses and this data can be combined with soil physicochemical properties, total and available concentrations of pollutants and pollutant bioaccumulation to produce a type of toxicological fingerprint. These fingerprints can be simple for pure samples but become much more complex for mixtures. However, relating the relative toxicity of these mixtures becomes much easier by comparing responses to known pure samples and determining threshold values based on this result.
EBPI offers several assays that look at soil or sediment leachates or extracts which can be correlated to bioavailable or free contaminants in the sample. These assays require some form of preparation step remove the aqueous fraction from the soil however, the extracts can be analyzed using the full range of organisms as the matrix is more compatible.
This type of analysis, while robust, ignore the percentage of contaminant bound or adsorbed to soil particulate that prefers the organic environment and is not extracted. These samples may in fact underestimate the total available contaminants to local organisms and may underestimate the degree of contamination. For these reasons EBPI also sells several direct contact tests including the BioTox™ LumoPlate™, Sedi-Tox™ test and the higher order plant tests which do not rely on aqueous extraction methods, can be done more quickly and follow exposures that mimic the natural environment. Several of these methodologies have been incorporated into high throughput assay designs to improve operator time and decrease costs.
In addition, EBPI is pleased to offer the first direct contact genotoxicity test that employs bacteria to assess soil and sediment samples directly for genotoxic effects. These assays permit rapid evaluation of DNA damaging agents in soils and do not require extra processing steps. They also present a more biologically relevant exposure situation and are quite sensitive for many organic and inorganic genotoxic contaminants.