Guidelines for Developing National Strategies to Use Monitoring of Local and Diffuse Soil Contamination as Environmental

1. Guidelines for Developing National Strategies to Use Monitoring of Local and Diffuse Soil Contamination as Environmental Policy Tools Professor Mark Kibblewhite (mark@mksoilscience.eu)

2. INTRODUCTION • Local soil contaminationfrom historic and present misuse, disposal and spillage of materials may present an unacceptable risk of harm to especially humans and water resources. • Diffuse soil contamination occurs over wide areas, generally at lower levels than local soil contamination; it may present risk of chronic harm to the soil system itself, humans, water resources and biodiversity. Monitoring of local and diffuse soil contamination requires different approaches and these are considered separately.

3. LOCAL SOIL CONTAMINATION

4. Strategy for local soil contamination • Defineunacceptable risk from local soil contamination • Prioritize resources to sites presenting most risk to humans, surface and ground waters and ecosystems • Implement and monitor effectiveness of policy actions with targets to assess and drive progress

5. How much contamination is acceptable? • It is better to adopt a risk and not hazard-based approach. In this case: • the mere presence of a hazardous contaminant at any level does not in itself indicate unacceptable contamination • acceptability should be assessed in relation to risk of harm to specific receptors (e.g. humans, natural waters, ecosystems). • A risk-based approach allows site-specific decision-making and avoids land being designated as having unacceptable local soil contamination, when there is no unacceptable risk arising under its current or planned use.

6. Possible Source-Pathway-Receptor linkages Ingesting soil Inhaling vapour Ingesting dust Inhaling vapour Rising vapour Soil transfer From garden To house Wind blown dust Rising vapour Eating contaminated vegetables and ingesting soil Skin contact with dust Skin contact with soil Plant uptake Illustration of human exposure from contaminated garden soil

7. Defining unacceptable risk from local soil contamination Unacceptable risk of harm requires the definition of both unacceptable harm and an unacceptable probability of exceeding this harm This is achieved in a four steps. • Identification of the subject that is at risk of harm (the receptor) • Identification of the type of harm that may be caused by exposure of the receptor • Definition of a quantitative measure of risk of this harm • Definition of the unacceptable level of risk of harm. EXAMPLE • The risk of harm to human health from a contaminant X could be assessed in relation to risk of harm to a 6 year old female child • The type of harm that may result from exposure to contaminant X could be disease Y • The measure of risk of harm could be the lifetime chance of such a child contracting Y, relative to that for the wider population of non-exposed children • A policy decision might be made that any increase in the incidence of the disease with a probability of more than 1 in 100,000 is unacceptable.

8. Managing local soil contamination Sequential steps (at individual sites) • preliminary studies • preliminary investigation • main investigation • options appraisal • implementation of remediation strategy Targets should refer to the number / percentage of sites at which these steps are completed

9. Metrics for monitoring local soil contamination

10. Monitoring local soil contamination • Designate a single coordinating institution • Implement data collection exercises at intervals of no less than five years using an unchanging questionnaire • Establish a central inventory of data on sites of local soil contamination

12. DIFFUSE SOIL CONTAMINATION • Diffuse soil contamination is widespread and results from the transfer of contamination from other environmental compartments, such as air and water, as well as the use of chemicals on land and the spreading of organic and other wastes. • A precautionary policy position is that diffuse soil contamination should be minimized where feasible and economics allow.

13. Purpose of monitoring diffuse soil contamination • Is diffuse soil contamination an actual or potential risk (e.g. to food production and / or water quality)?

14. Strategy for diffuse soil contamination • Define prioritycontaminants • Inform decisions by assessing the spatial distribution and temporal trends in contamination • Integrate decisionswith wider environmental policy to assess where to focus control

15. Operational steps for monitoring • Designate a single coordinating institution • Definequantitative performance requirements • Confirm that the chosen design is fit for purpose • Adoptformal procedures and protocols • Maintain a central database and sample archive

16. Technical approach to monitoring diffuse soil contamination • Sampling soil over large areas followed by testing of samples for priority contaminants

17. Measurement performance specification • Absolute detection limit i.e. the minimum level of the contaminant that can be detected (mg kg-1); • Dynamic range over which measurement of levels of the contaminant are required (mg kg-1); • Maximum error allowable e.g. specified as the standard deviation of measurements of level of contaminant at 80% of the dynamic range (mg kg-1); • Detection limit for a change in level of contaminant at e.g. 50% of the dynamic range, over a specified period (mg kg-1y-1).

18. Design of sampling network • Invest in a thorough investigation of the expected measurement performance of options using statistical modeling. • Amodel approach locates sampling sites e.g. at the nodes of a regular grid. A classical approach selects sites randomly from within strata (categories of possible sampling sites) representative of e.g. different land use / cover, geology, etc. • On balance, it is recommended that countries establish systems based on regular grids as these are more flexible to meet future needs. A European-wide project aiming to develop a continental scale soil monitoring system (ENVASSO) recommended a minimum sampling density of 1 site per 300 km2.

19. Sampling and testing • Large variations in levels of diffuse contamination of soils are observed at field scales (1-10m) and it is essential to sub-sample an adequate area at each location. • Archive samples so that they can be re-tested or tested for additional contaminants at a later date • Standard ISO testing methods should be used. • Laboratories should meet international performance standards by having auditable traceability of measurements, quality control systems incorporating standard reference materials, and participation in inter-laboratory comparability exercises.

20. At what level does diffuse soil contamination present unacceptable risk? • If the contaminant does not occur naturally then its level should be as ‘low as practicable’ • If the contaminant occurs naturally then account has to be taken of background “contamination” . For example, a ‘level of concern’ could be set at two times the 90th percentile of the non-urban background level. Background “contamination”

21. Concluding reflections Soil monitoring systems are an essential part of integrated environmental management The specification of soil monitoring systems should be carefully developed and design options fully evaluated before implementation Establishing a permanent central secretariat is critical to the efficiency and enduring good performance of soil monitoring systems