Guidelines for Developing National Strategies to Use Monitoring of Local and Diffuse Soil...
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Transcript of Guidelines for Developing National Strategies to Use Monitoring of Local and Diffuse Soil...
Guidelines for Developing National Strategies to Use Monitoring of Local and Diffuse Soil
Contamination as Environmental Policy Tools
Professor Mark Kibblewhite([email protected])
INTRODUCTION
• Local soil contamination from 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.
LOCAL SOIL CONTAMINATION
Strategy for local soil contamination
• Define unacceptable 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
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.
Ingestingdust
Ingestingsoil
Inhalingvapour
Inhaling vapour
Eating contaminatedvegetables and
ingesting soil
Skin contactwith dust
Skin contactwith soil
Soil transferFrom gardenTo house
Rising vapour
Rising vapour
Wind blown dust
Plant uptake
Possible Source-Pathway-Receptor linkages
Illustration of human exposure from contaminated garden soil
Defining unacceptable risk from local soil contaminationUnacceptable 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.1. Identification of the subject that is at risk of
harm (the receptor)2. Identification of the type of harm that may be
caused by exposure of the receptor 3. Definition of a quantitative measure of risk of
this harm4. Definition of the unacceptable level of risk of
harm.
EXAMPLE1. 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
2. The type of harm that may result from exposure to contaminant X could be disease Y
3. 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
4. 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.
Managing local soil contamination
Sequential steps (at individual sites)
1. preliminary studies 2. preliminary investigation3. main investigation4. options appraisal5. implementation of
remediation strategyTargets should refer to the number / percentage of sites at which these steps are completed
MetricTotal number of sites undergoing risk assessment or risk management (i.e. all sites within inventories)
Number of sites with preliminary studies in progressPercentage of total number of sites with preliminary studies in progressNumber of Potentially Contaminated SitesPercentage of the total number sites currently identified as Potentially Contaminated Sites
Number of Contaminated SitesPercentage of the total number sites identified as Contaminated SitesNumber of sites where a remediation strategy is being implementedPercentage of the total number of sites where a remediation strategy is being implemented
Number of sites incurring costs within expenditure categories
Metrics for monitoring local soil contamination
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
Actors
Activities Outputs (Examples)
Central Government (responsible Ministers and their officials)
Setting an overarching policy framework
Key policies, e.g.:1. Avoid new contamination2. Risk-based approach, focusing resources on higher risk sites3. Polluter pays principle applies, but with financial and legal incentives to
encourage site assessment and management4. Local-level regulation to encourage integrated actions by land owners /
managers / developers and regulatory authorities
Legislature Designing and enacting a national legislative regime
Legislation and statutory regulations, e.g.:1. Legal definitions e.g. of “contaminated site”2. Responsibilities3. Liability
Central Agency (e.g. Environmental Protection Agency)
Developing and maintaining technical guidance; monitoring progress
1. Regulatory and technical procedures for assessing and managing sites of local soil contamination
2. Definition and publication of intervention values for contaminants3. Technical expertise for ‘difficult’ sites4. Operation of national monitoring system for local soil contamination
1. Land owners / managers / developers
2. Regional / municipality departments for development control (spatial planning) and environmental protection
3. Technical experts and specialized contractors
4. Citizens and stakeholder organizations
Identifying sites; assessing risks; defining site management plans (according to regulations defined by central agency)
1. Systematic identification of possible sites of unacceptable local soil contamination
2. Preliminary studies / preliminary investigations of candidate sites3. Main investigations of sites where required4. Designation of sites as ‘contaminated land’ (by regional / municipal
authorities)Implementing and signing-off site remediation(according to regulations defined by central agency)
1. Evaluating options for management of contaminated sites and agreeing detailed plans
2. Completing and confirming success of site plans.
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.
Purpose of monitoring diffuse soil contamination• Is diffuse soil contamination an
actual or potential risk (e.g. to food production and / or water quality)?
Strategy for diffuse soil contamination
• Define priority contaminants• Inform decisions by
assessing the spatial distribution and temporal trends in contamination• Integrate decisions with
wider environmental policy to assess where to focus control
Type of contaminant Examples (potential priority contaminants)
Heavy metals Cadmium, Chromium, Copper, Lead, Mercury Nickel, Zinc.
Metalloids Arsenic, Antimony, Selenium
Persistent Organic Pollutants
Poly-Chlorinated Biphenyls (PCBs), Poly-Aromatic Hydrocarbons (PAHs), Dioxins, Furans, banned pesticides
Operational steps for monitoring
• Designate a single coordinating institution • Define quantitative
performance requirements• Confirm that the chosen
design is fit for purpose
• Adopt formal procedures and protocols •Maintain a central
database and sample archive
Technical approach to monitoring diffuse soil contamination• Sampling soil over large areas
followed by testing of samples for priority contaminants
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).
Design of sampling network• Invest in a thorough investigation of the expected measurement
performance of options using statistical modeling.• A model 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.
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.
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.
Land cover Soil-forming material
Metal Mean +/- 2 standard deviations
Median +/- median absolute deviations
10th to 90th percentiles
Urban All Cd 0.1-2.3 0.2-2.0 0.2-1.4Pb 11-370 17-210 28-140
Agriculture Mudstone Cd 0.3-1.9 0.4-1.5 0.4-1.4Pb 14-110 17-74 23-89
Chalk till Cd 0.2-1.3 0.2-1.1 0.3-1.0Pb 9-65 11-48 13-42
Sandstone / Mudstone / Shales
Cd 0.3-2.3 0.2-1.8 0.2-1.4Pb 14-320 18-220 28-240
Background “contamination”
Concluding reflectionsSoil 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