An approach to quantifying spatial components of exposure for ecological risk assessment

Clifford, Philip A.; Ludwig, David F.; Barchers, Daniel E.; Klingensmith, J S; Graham, Richard V.; Sielken, Robert L.; Banton, Marcy I.

doi:10.1002/etc.5620140523

Cited by 44 publications

(21 citation statements)

References 8 publications

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“…Both toxicants and the physical-chemical parameters that control exposure exist in a contagious fashion with temporal variability. Clifford et al [11] clearly mapped the distribution of surficial concentration of dieldrin and demonstrated the clumped and irregular distribution of the toxicant. Using derived bioaccumulation factors and toxicological benchmarks, the risk of direct effects to a variety of organisms was also mapped and found to be clumped.…”

Section: Distribution Of Organisms and Toxicantsmentioning

confidence: 99%

Metapopulation Dynamics: Indirect Effects and Multiple Distinct Outcomes in Ecological Risk Assessment

Spromberg¹,

John²,

Landis³

1998

Environ Toxicol Chem

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A toxicant-dosed metapopulation model was used to explore the range of possible dynamics of populations in contaminated field sites. A single species metapopulation model was developed that is discrete, deterministic, and incorporates doseresponse curves and biotic growth rates to describe the effects of contamination on a metapopulation. The distribution of the chemical contamination is assumed limited to one patch and contagious within that patch. Both persistent and degradable toxicants were modeled. Five principal conclusions resulted from our simulation studies. (1) Mortality in one subpopulation has ecologically significant effects on nondosed subpopulations. This hypothesis we term ''action at a distance'' because no direct contact with a toxicant has occurred except in the dosed patch. (2) Because uncontaminated sites connected to the contaminated site by migration of the biota are affected, these uncontaminated sites cannot be reference sites. (3) The arrangement of the patches is critical to the dynamics of the system and the overall impact of a toxicant. (4) Due to the contagious distribution of the toxicant and the stochastic function describing exposure effect, multiple discrete outcomes often are possible from the same initial conditions. These outcomes can range from extinction to the reaching of the carrying capacity for a patch. (5) If sufficient cleanup is not possible, it may be necessary to isolate the contaminated patch, allowing the formerly connected patches to regain more typical population dynamics.

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Section: Distribution Of Organisms and Toxicantsmentioning

confidence: 99%

Metapopulation Dynamics: Indirect Effects and Multiple Distinct Outcomes in Ecological Risk Assessment

Spromberg¹,

John²,

Landis³

1998

Environ Toxicol Chem

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“…Chemical contamination occurs in heterogeneous environments, and the distribution has been found to be patchy [13]. Using a template from Wu et al [11] and Wu and Vankat [14], we have developed a computer model of a generic animal metapopulation that has contaminated patches [12].…”

Section: Importance Of Spatial Contextmentioning

confidence: 99%

Design Criteria and Derivation of Indicators for Ecological Position, Direction, and Risk

Landis¹,

McLaughlin²

2000

Environ Toxicol Chem

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The baseline specifications for indicators for ecological risk assessment and management are presented. These indicators may be related to the assessment space as determined by cultural values and laws. This assessment space is a multivariate expression of the assessment endpoints. The three types of indicators include current position, the probability of leaving the assessment space, and the probability of reentering the assessment space. The formulation of indicators must recognize that ecological systems are dynamically complex and composed of both deterministic and stochastic components. As has been demonstrated in laboratory ecological systems and field experiments, the best impact indicators change over time, eliminating the possibility of a single variable being an accurate measure of position and change. We set six specific requirements for developing a useful set of indicators, as follows. The indicators must be placed in the context of the assessment space. Because projections cause the loss of information, a variety of methods with different assumptions about the nature of the system should be used. The best attributes to measure alteration of the system change over time; to use just one set may result in missing the dynamic complexity of the system and subsequent impacts. Ecological systems are both deterministic and stochastic, and representation of each is important. The stochastic component can have a tremendous impact, changing the overall dynamics. Spatial context is critical in making accurate predictions and must be known.

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“…Risk is calculated as the probability of exceeding a specified quotient or as the probability of a certain magnitude of effect, such as for levels 4 and 5 in the U.S. EPA report on terrestrial risk assessment. (17) Approaches to include spatial characteristics in risk assessment were suggested long ago (18) and have been emphasized in the past few years. (19) The heterogeneity in the spatial distribution of soil characteristics and contaminant concentrations and the need to quantify the uncertainties and minimize the cost of site investigations suggests the use of spatially explicit risk estimations, as in level 6 of the ECOFRAM report, (17) and application of geostatistical methods.…”

Section: Introductionmentioning

confidence: 99%

A Spatial Approach to Environmental Risk Assessment of PAH Contamination

Bengtsson

Törneman

2008

Risk Analysis

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The extent of remediation of contaminated industrial sites depends on spatial heterogeneity of contaminant concentration and spatially explicit risk characterization. We used sequential Gaussian simulation (SGS) and indicator kriging (IK) to describe the spatial distribution of polycyclic aromatic hydrocarbons (PAHs), pH, electric conductivity, particle aggregate distribution, water holding capacity, and total organic carbon, and quantitative relations among them, in a creosote polluted soil in southern Sweden. The geostatistical analyses were combined with risk analyses, in which the total toxic equivalent concentration of the PAH mixture was calculated from the soil concentrations of individual PAHs and compared with ecotoxicological effect concentrations and regulatory threshold values in block sizes of 1.8 x 1.8 m. Most PAHs were spatially autocorrelated and appeared in several hot spots. The risk calculated by SGS was more confined to specific hot spot areas than the risk calculated by IK, and 40-50% of the site had PAH concentrations exceeding the threshold values with a probability of 80% and higher. The toxic equivalent concentration of the PAH mixture was dependent on the spatial distribution of organic carbon, showing the importance of assessing risk by a combination of measurements of PAH and organic carbon concentrations. Essentially, the same risk distribution pattern was maintained when Monte Carlo simulations were used for implementation of risk in larger (5 x 5 m), economically more feasible remediation blocks, but a smaller area became of great concern for remediation when the simulations included PAH partitioning to two separate sources, creosote and natural, of organic matter, rather than one general.

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An approach to quantifying spatial components of exposure for ecological risk assessment

Cited by 44 publications

References 8 publications

Metapopulation Dynamics: Indirect Effects and Multiple Distinct Outcomes in Ecological Risk Assessment

Metapopulation Dynamics: Indirect Effects and Multiple Distinct Outcomes in Ecological Risk Assessment

Design Criteria and Derivation of Indicators for Ecological Position, Direction, and Risk

A Spatial Approach to Environmental Risk Assessment of PAH Contamination

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