Development of Ecological Impact Assessment (EIA) framework for pollutants in the urban environment

Why is a framework required?

The impacts of development, both past and future, on urban and peri-urban ecosystems must be considered during the planning process. An examination the effects on habitat destruction and fragmentation and the potential loss of biodiversity is an integral part of this process.

However, the detrimental effect of the pollutants arising from some activities on ecosystems is seldom investigated, particularly where the pollutant loading on an area may already be high from an accumulation of a number of sources or an industrial legacy.

Forest Research is currently developing the EIA component of the Pollutants in the Urban Environment (PUrE) framework to enable users to quantify the influence of pollutants in the urban environment on terrestrial ecosystem health and function.

Structure of the framework

The EIA will consist of three Levels:

  • Generic
  • Simple
  • Detailed.

These align with the tiers in the proposed Environment Agency Ecological Risk Assessment Guidance for Contaminated Land.

This iterative framework means that the user can exit the process when the objectives of the assessment have been met; i.e. when enough information has been gathered. If uncertainties are unacceptable the user progresses to the next level/s which requires more data but yields a more certain risk assessment result.

Generic level

At the Generic level the user will be able to compare measured or ‘typical’ soil concentrations with Soil Screening Values, where available, or NOEC (No Observed Effect Concentration), LOEC (Lowest Observed Effect Concentration), EC (Effect Concentration) and LC (Lethal Concentration) values from the literature.

Simple level

Depending on the outcome of the above analysis and the objectives of the user, they may then progress through a tiered structure to the Simple level, using recommended ecotoxicological tests and more complex databases containing detailed information on the derivation of the EC and LC values (e.g. soil properties, species, test conditions) and simple models to predict metal uptake into vegetation.

Detailed level

Finally, in the Detailed level, the user will be able to examine the potential for food-chain transfer of pollutants from a combination of ecotoxicological tests and models.

Why ecotoxicological tests are also required

In addition to the above, the proposed Environment Agency guidance has a selection of toxicity tests that are recommended for the Ecological Risk Assessment process. These methods include assessments of soil microbial function, soil invertebrate function and vegetation germination and growth.

However, these tests have originally been developed for use in agricultural systems (e.g. during pesticide approval) and, as a result, often use species not indicative of those likely to be present in urban greenspace.

They also provide assessments of ecological function and do not consider the food-chain transfer of contaminants. In some species of vegetation the concentrations of a contaminant may be higher in the plant tissue than in the soil in which it is growing. This has serious implications for the long term assessment of the cycling of contaminants during litter fall which are not an issue when considering crop species.

Forest Research is currently developing a range of ecotoxicological tests that use both species relevant to urban scenarios and take into account food-chain transfer.