Land Remediation

3.2.2 Bioassays

OPTIONAL: Bioassays provide the opportunity to demonstrate whether the most highly contaminated media (soil and/or water) are toxic to the plants, invertebrates, or aquatic life of concern, particularly in situations where vegetation or aquatic life are not currently present. Soil and/or water samples are taken into the laboratory and growth, reproduction and survival of test species are measured following standardized, peer-reviewed methods.

Bioassays can be considered in such cases where environmental concentrations are above toxicity reference values (TRVs), but organisms are still present on the site. Other factors such as toxicant bioavailability and natural selection may apply to site conditions. For example, soils with metal contamination may not be bioavailable to earthworms due to soil conditions (e.g., soil composition or pH). Therefore, earthworms may be present in sites with environmental conditions above the TRV for earthworms. In such cases, bioassay toxicity testing will establish site-specific conditions and TRVs for a particular site.

Methods developed and modified by the British Columbia Ministry of Environment and Environment Canada are recommended and listed first (Appendices H). A listing of comparable, alternative, and additional standard methods also are provided to supplement and expand bioassay and analytical capabilities. Methods developed by the American Public Health Association (APHA), American Water Works Association (AWWA), Water Environment Federation (WEF), American Society of Testing and Materials (ASTM), Organization of Economic Cooperation and Development (OECD), and the United States Environmental Protection Agency (USEPA) are included and, in many cases, are referenced in the Canadian protocols.

Bioassays may be conducted after completing the entire risk assessment, to confirm results or to understand the extent of cleanup that will be required. However, bioassays also may be done during the Effects Assessment phase as part of the development of the weight-of-evidence of environmental risk.

3.2.2.1 General procedures for laboratory bioassays:

a) Collect soil, water, or sediment from the most highly contaminated areas.

b) Refer to Appendix H for a list of suggested companies that can conduct standard bioassays and for references for bioassay protocols. Consider the use of field replicates rather than laboratory replicates.

c) Suggested species for bioassays:

 

plants:	rye grass (Lolium perenne)
earthworms:	red worms (Eisenia foetida)
fish: (freshwater)       (marine)     aquatic invertebrates: (water) (sediments)	rainbow trout (Oncorhynchus mykiss) bluegill (Lepomis macrochirus) sunfish (Lepomis sp.) chinook top smelt (Atherinops affinis)   Champia parvula echinoderm fertilization inland silverside (Menidia) stickelback   ceriodaphnia, Daphnia magna amphipod test

Bioassay(s) conducted-report(s) attached

3.2.2.1.1 In situ bioassays

a) Visit site. Use an area of the site with suspected contamination based on media sampling or source input.

b) Take field measurements of dissolved oxygen, temperature, conductivity, and pH.

c) Inform and obtain approval from Regional Ministry of the Environment and Department of Fisheries and Oceans habitat staff for in situ bioassay test.

d) Suggested species for in situ bioassays:

eyed salmonid eggs: pacific salmon

rainbow trout (Oncorhynchus mykiss)

caged fish: rainbow trout (Oncorhynchus mykiss)

caged mussels: sea mussels (Mytilus edulis)

3.2.3 Toxicity Reference Values (TRVs)

To determine if a particular level of contamination at a site poses a risk to plants or animals, you need to know how much of that material the plants or animals can tolerate before toxic effects are seen. The concentration of the pollutant in the soil or water where toxicity begins to occur is called the toxicity threshold. However, for environmental receptors such as plants or animals (i.e., not humans), the goal is not to protect each individual from any toxic effect, but rather to protect enough individuals so that a viable population and community of organisms can be maintained (provided other habitat factors are suitable). Therefore, a TRV is chosen from the concentration-response curve that provides reasonable protection for a specified percentage of the organisms. For terrestrial organisms on industrial sites, this is the EC₅₀, or the concentration that affects 50% of the organisms exposed. For aquatic organisms at industrial sites, this is the EC₂₀.

To find the EC_x for plants and animals at your site for pollutants of concern, do any (or all) of the following. Be sure to specify whether this value is dry weight (dw) or wet weight (ww).

a) Use the BCE standard/criteria or information from its supporting documentation.

BCE standard/criteria used? yes no

b) Refer to Appendix I for a list of database and other reference sources that contain information about toxic responses of plants, animals, and aquatic organisms.

List databases searched:

_________________________________________________________________________

_________________________________________________________________________

_________________________________________________________________________

c) Search the scientific literature.

List databases searched:

_________________________________________________________________________

_________________________________________________________________________

_________________________________________________________________________

Use the following rules to select the appropriate EC_x:

a) Give preference to generally accepted toxicity reference values generated for that particular medium (accepted with caveats, peer reviewed, governmental, or NGO groups). For example, water quality criteria.

b) Give preference to reproductive endpoints, but use lethality studies if they are the only ones available.

c) Acceptable endpoints of a toxicity include:

• any reproductive endpoint (e.g., number of offspring, number of eggs laid, eggshell quality, fruit size and yield, presence of deformities in embryos or young).
• growth rates.
• lethality.
• tumor formation or other gross deformities in embryos or young.

Unacceptable endpoints include:

• changes in enzyme activities.
• DNA breakage.
• other subcellular responses and hematological parameters.

d) If an EC_x is not reported, generate the concentration-response curve from the data provided and calculate the EC_x. As a last resort, use the lowest observed adverse effects level rather than the EC_x and do not divide by any uncertainty factors.

e) If data are available from more than one study for an organism of concern, use the lowest EC_x.

f) Use information for the contaminant of concern from any test (e.g., bioassay, laboratory, field study) conducted with the organisms under consideration, if available.

g) If the organism of concern has not been tested, use the most closely related (phylogenetically) organism. Carefully consider the phylogenetic histories of the test species compared to the organisms of concern and consider any drawbacks to extrapolating between species.

For birds and mammals:

1. use EC₅₀.
2. give preference to those with the same feeding group.
3. give preference to feeding studies (not single dose studies, or injection studies), particularly of weeks to months in duration.
4. if you have data from similar animals (e.g., rodent data to compare with rodents or duck data to compare to other waterfowl), do not use any uncertainty factors. If your animals are not so closely related, divide the value by 10.
5. if the ONLY data available for any animal species are from injection or oral dosing studies, convert the dose to concentration in food, assuming an average body weight (bw) for the species and an average food consumption rate. Food consumption may be estimated from the following equations:

   F = 0.621 (bw)^0.564 (rodents)

   F = 0.577 (bw)^0.727 (mammalian herbivores)

   F = 0.235 (bw)^0.822 (other mammals)

   F = 0.398 (bw)^0.850 (song birds)

   F = 0.648 (bw)^0.651 (other birds)

For plants:

1. use EC₅₀.
2. if extrapolating within the same Family, do not use any uncertainty factors.
3. if extrapolating to another Family, divide by 2.
4. if extrapolating to another Order, divide by 20.
5. if extrapolating to another Class, divide by 500.

For soil invertebrates:

1. use EC₅₀.
2. use whatever data are available without adjustments.

For aquatic organisms (algae, invertebrates, and fish):

1. use EC₂₀.
2. use species from same class, teleost (ray finned fish) is typical. Agnatha (jawless fish) and Chondricithyes (sharks and rays) have very different biochemistries, especially in regards to PCBs and other estrogenic compounds.
3. that arepelagic invertebrates, use species similar to organism of concern, although most of the data will be on daphnia.
4. use test species with similar routes of exposure as the organism of concern. Sediment tests conducted to estimate the toxicity of a burrowing worm should use burrowing organisms as the test organism. Filter-feeding mollusks should be the organism of choice when estimating muscle or oyster sensitivity.
5. aquatic phytoplankton are represented by single species algal toxicity tests and many kinds of test organisms are available.
6. aquatic macrophytes are represented by Lemma (duckweed), although a number of new methods are under development.
7. give preference to tests conducted during a significant portion, or the most sensitive portion, of the test organism's lifespan.

Attach a list of the selected EC_x with the appropriate references. Structure the list in the following format:

Organism of Concern	Test Organism	Measurement (reproduction, mortality, etc.)	Endpoint (LOAEL ECx)	Uncertainty Factor	Value	Dry weight or wet weight	Ref.

 

Purpose: To determine the concentration in media (food, water, soil, etc.) of pollutants of concern to which the plants and animals of concern are actually exposed and to demonstrate how the plants and animals came in contact with the contaminated media.

For plants and animals to be at risk from pollutants, the compounds must exist in the environment at concentrations above the toxicity reference values and the plants or animals must come in contact with the contaminated media. This section describes appropriate sampling of the site to understand the magnitude and spatial extent of any contamination. The answers to the series of questions that follows will help determine pertinent life-history patterns of plants and animals on the site to determine if, when, and for how long they may come in contact with the contaminated environment.

Note: All environmental sampling should be conducted in cooperation with the human health effects assessment to reduce the need to sample the same area twice. Coordination between the two processes should take place at this time.

3.3.1 Exposure patterns of plants and animals

Plants and animals must come in contact with a contaminant to be considered at risk. This section helps determine the potential for organisms on the site to come in contact with contaminated media. Note that it is assume that only plants may be directly affected by contaminated groundwater. Other organisms are potentially at risk only if the groundwater contaminates surface water or is used for irrigation.

3.3.1.1 Plants

All plants on the site are assumed to be exposed to contaminated soil, as their roots have the potential to take up materials out of the soil. Deep-rooted plants also may contact contaminated groundwater. Rooted aquatic plants (also called macrophytes) such as cattails, rushes, or salt grass take up contaminants from the water column (through their leaves) as well as by their roots from sediment. Non-rooted aquatic plants (e.g., duckweed, waterlilies) also take up contaminants from the water column through their leaves. Therefore, exposure to plants should be assumed, unless the contamination is present only during the dormant period of the year (winter, for most plants, if the ground freezes).

3.3.1.2 Soil invertebrates

All soil invertebrates (such as earthworms, centipedes, and beetles) are considered exposed through ingestion of soil or movement of contaminant across their skin. Therefore, exposure to soil invertebrates should be assumed, unless the contamination is present only during the dormant period of the year (e.g., when the ground is frozen).

3.3.1.3 Birds

Birds are exposed only if they eat soil invertebrates or plants (leaves or seeds) on the terrestrial portion of the site, or if they eat aquatic invertebrates or fish from a contaminated water source. In addition, it is assumed that most birds consume some soil or sediment along with the actual foodstuff and may get additional contamination from this route.

Birds may not feed on the site for their entire life. Many birds leave the area during the winter and so have the potential to be exposed only during the late spring, summer, and early fall. In addition, if the site is small or the only vegetation present is along the edge of the site, then birds are likely to get some of their diet off-site.

Therefore, the following habits of the birds using the site must be known:

a) proportion of the year the bird resides in the area.

b) proportion of total foraging area provided by the site.

c) composition of diet (seeds, leaves, invertebrates and/or soil).

3.3.1.3.1 Residency

For each of the birds on the site-specific checklist (see Section 3.1.1.2.2) indicate whether the bird is a year-round resident (YR), summer resident (SR), or winter resident (WR).

Bird list annotated

3.3.1.3.2 Foraging area

See Appendix J for a list of references containing information about bird foraging areas. For each bird that may use the site, indicate on the site-specific checklist whether its foraging area is greater (G) or smaller (S) than the size of the site. If foraging area information is not available, use information about territory size. If no information is available, assume the foraging area is equal (E) in size to the site.

Bird list annotated

3.3.1.3.3 Diet

Refer to Appendix J for a list of references on dietary preferences of birds.

For each species present on the site, list the dietary composition in a table such as the following:

Feeding Group	% seeds	% other plant material	% soil invertebrates	% aquatic invertebrates	% fish	% other (specify)	% soil (assume 2%)	TOTAL (100%)
							2	100
							2	100

3.3.1.4 Mammals

Mammals are exposed only if they eat soil invertebrates or plants (leaves or seeds) on the terrestrial portion of the site or if they eat fish from a contaminated water source. In addition, it is assumed that most mammals consume some soil or sediment along with the actual foodstuff and may get additional contamination from this route.

Some mammals hibernate during the winter and are exposed only during the spring, summer, or fall. If the site is small or the only vegetation present is along the edge of the site, then mammals are likely to get some or all of their diet off-site.

Therefore, the following habits of the mammals using the site must be known:

a) whether the animal hibernates,

b) proportion of total foraging area provided by the site, and

c) composition of its diet (seeds, leaves, invertebrates and/or soil).

3.3.1.4.1 Residency

For each mammal on the site-specific checklist (see Section 3.1.2.2.3), indicate whether or not it hibernates (H)

Mammal list annotated

3.3.1.4.2 Foraging area

See Appendix K for a list of references containing information about mammal foraging areas. For each mammal that may use your site, indicate on the site-specific checklist whether its foraging area is greater (G) or smaller (S) than the size of the site. If foraging area information is not available, use information about territory size. If no information is available, assume that the foraging area is equal (E) in size to the site.

Mammal list annotated

3.3.1.4.3 Diet

Refer to Appendix K for a list of references on dietary preferences of mammals.

For each species present on the site list the dietary composition in a table such as the following:

Feeding Group	% seeds	% other plant material	% soil invertebrates	% fish	% other (specify)	% soil (assume 2%)	TOTAL (100%)
						2	100
						2	100

3.3.1.5 Aquatic invertebrates

Use the following rules to determine exposure:

a) Planktonic invertebrates are exposed to toxicants primarily by absorption from the water column, although ingestion is an additional route.

b) Aquatic insects can be exposed through the water column, sediment, or ingestion of plant material or other insects.

c) Clams and other shellfish are exposed through the water column and this will be the primary route for water-soluble materials. Ingestion is the main exposure pathway for materials bound to particulates or that bioconcentrate in plankton.

3.3.1.6 Fish

Fish have 100% exposure to the water column. However, lifestyle determines exposure to the sediment. Flatfish or other bottom dwellers and borrowers are exposed to the interstitial water concentration of the sediment so that should be used as an exposure pathway instead of water concentration. Higher trophic level fish (such as some of the salmonids) also are exposed by eating smaller fish with contaminants in their tissues.

3.3.2 Environmental concentrations

The following sections describe how to collect various media for determining the concentration of the contaminants of concern and provide guidance on how to select appropriate analytical chemistry methods.

3.3.2.1 Selection of media

To determine which media to sample, refer to the Conceptual Site Model diagrams and to the dietary composition tables for birds and mammals (sections 3.3.1.3.3 and 3.3.1.4.3) to help answer the following questions. The goal is to sample food eaten by birds, mammals, and fish as well as the contaminated soil and/or water. In addition, if groundwater contamination is of concern (either due to drainage to surface waters or because of uptake by plant roots), groundwater should be sampled to describe the direction, extent, and concentration of the plume. Answers to the following questions will help determine which media to sample.

a) Are there terrestrial plants or animal receptors of concern?

No. Skip to question b)

Yes. Take the following samples:

soil (Section 3.3.2.2)

plants (Section 3.3.2.5)

soil invertebrates (Section 3.3.2.6)

b) Are there aquatic plants or animal receptors of concern (fish, shellfish, birds, mammals)

No. Skip this question

Yes. Take the following samples:

groundwater (Section 3.3.2.7)

surface water (Section 3.3.2.8)

sediment (Section 3.3.2.8)

aquatic invertebrates (Section 3.3.2.9)

fish (Section 3.3.2.9)

aquatic plants (Section 3.3.2.10)

3.3.2.2 Sampling design

The number of samples taken should be sufficient to characterize all different parts of the site. This will vary depending on site size. More detail is provided in each media sampling section. Note that the goal is to provide sufficient data to use the techniques in Risk Quotient Calculation (Section 8.1.1.3). These techniques require a spatially explicit approach to chemical concentration. Refer to the following text for more detailed discussion of environmental sampling designs:

Gilbert, R.O. 1987. Statistical Methods for Environmental Pollution Monitoring. Van Norstrand Reinhold, New York, New York.

3.3.2.3Analytical chemistry

All environmental media samples should be submitted for chemical analysis as soon as possible. Keep samples cool (<10° C) between time of collection and analysis. Be sure to specify whether the results should be reported as dry weight (dw) or wet weight (ww) concentrations. The measurement units of these results should be comparable to the measurement units of the toxicity reference values selected in Section 3.2.3. Asking the laboratory to report percent moisture will provide flexibility for converting between wet weight and dry weight at any time. Soil and water pH, soil organic carbon, and water hardness should also be requested from the testing laboratory ate the time of sample submission. See Appendix L for a list of analytical chemistry laboratories in British Columbia.

3.3.2.3.1 Methods

A variety of methods exist for sample analysis. The method chosen depends on the matrix being analyzed (soil, water, biota), the required precision and accuracy, and the required level of detection.

See Appendix M for a list of methods available Consult with your analytical laboratory on their preferred method. List the method(s) used in the following table:

Media	Chemical	Method	Detection limit (dw or ww)	No. of site samples	No. of QA/ QC samples
soil
water
etc.

 

3.3.2.3.2 Detection limits

Detection limits should be set at 0.1 times the lowest toxicity reference value for organisms exposed to each media, unless current methodology precludes doing so. Include the detection limits in the above table.

3.3.2.3.3 Quality Assurance/Quality Control (QA/QC)

A trip blank, a spike, and a split sample must be included with at least every 20 site samples. Include the number of QA/QC samples in the above table.

See the British Columbia Field Sampling Manual, 1996 edition for a more complete discussion of QA/QC. Data quality objectives (DQOs) are formal data quality specifications, which must be tabulated within a quality assurance manual. These DQOs establish the maximum amount of error allowed for the data to meet its specified use. The DQOs should be established before sample collection to avoid situations where resources are spent collecting samples which do not fit the DQOs. Once DQOs are established and sampling has begun, regular performance checks are performed to verify that the DQOs are satisfied. Corrective action must be taken when DQOs are not met. Out-of-control events and actions must be recorded.

It is highly recommended that before implementing any environmental samples, all monitoring/sampling plans be approved by BCE. Remember to coordinate with the human health effects risk assessment sample collections.

3.3.2.4 Soil sampling

When collecting samples, observations on the appearance and abundance of soil organisms can be recorded as additional information. This information can serve as anecdotal evidence in Tier 1 or 2 EcoRAs.

3.3.2.4.1 Number and spatial distribution

At least three sample points should be taken in each different area of the site (e.g., grass-covered, bare ground, under vegetation). If there are suspected point source(s) of contamination, a greater number of samples should be taken near the source with diminishing numbers forming concentric rings outward. Additional samples should be taken in any down-gradient area (downwind or downslope).

It may be necessary to take samples off-site to completely characterize the extent of a gradient. One option is to characterize the site first and return for additional off-site sampling if a gradient is not completely defined.

Number of samples: ______________________________________________________________

Show sample locations on the site map

Map attached

3.3.2.4.2 Depth

Composite samples should be taken at 0 to 15 cm depth for characterization of plant exposure. However, for sandy soil (e.g., Fraser River sand), take a soil sample at 0 to 50 or 70 cm depth.

Optional: Deeper core samples of various soil strata can be taken to characterize current and potential migration of contaminants.

Number of samples taken at 0 to 15 cm depth: ________________

Number of samples taken at deeper depth:

Depth: _____________ cm

Number: ______________

Label all sample locations on the site map with sampling depth.

Map labeled

3.3.2.4.3 Methods

Samples may be collected using either a soil corer or a trowel for surface samples and with appropriate coring devices for deeper samples.

If contaminants of concern are metals or metalloids, use only plastic trowels and corers. Samples should be packaged in plastic bags and stored under cool conditions until analyzed. Decontaminate sampling device between each sample.

contaminants are metals/metalloids-use plastic devices

If contaminants of concern are organic compounds, use only metal sampling devices. Store samples in glass containers and keep cool until analyzed. Decontaminate sampling device between each sample.

contaminants are organic compoundsuse metal and glass devices

See Appendix N for references for specific soil collection methods. List which methods were used.

List of methods attached

 

3.3.2.5 Terrestrial plant sampling

3.3.2.5.1 Number and spatial distribution

At each soil sample location, collect a vegetation sample (if vegetation is present).

Collect grass, shrubs, and tree leaves separately at each location. Collect at least 50 grams of each.

Number of plant samples taken:

Grass: _________________

Shrubs: ________________

Tree leaves: _____________

Label all sample locations on the site map with the depth of sampling. Note which types of vegetation samples were collected at each sample point.

Map labeled

 

3.3.2.5.2 Methods

Samples are collected using either metal or plastic scissors.

If contaminants of concern are metals or metalloids, use plastic scissors. Samples should be packaged in plastic bags and stored under cool conditions until analyzed. Decontaminate scissors between each sample.

contaminants are metals/metalloids-use plastic devices

If contaminants of concern are organic compounds, use only metal sampling devices. Store samples in glass containers and keep cool until analyzed. Decontaminate sampling device between each sample.

contaminants are organic compounds-use metal and glass devices

See Appendix G for reference for specific plant collection methods

3.3.2.6 Soil invertebrates

When collecting soil samples, remove to a separate sampling container any invertebrates (e.g., earthworms, centipedes, beetles) found in the soil. These may be taken from the same sample that will be analyzed for soil chemistry or may be taken from a separate sample collected adjacent to the core collection site.

Invertebrates are separated from the soil either by picking them out with a tweezers or by passing the soil through a small diameter sieve. Collect all the invertebrates in the sample or 50 grams, whichever is the least.

If contaminants of concern are metals or metalloids, use plastic tweezers. Invertebrates should be packaged in plastic bags or glass containers and stored frozen until analyzed.

contaminants are metals/metalloids-use plastic devices

If contaminants of concern are organic compounds, use metal tweezers. Invertebrates should be packaged in glass containers and stored frozen until analyzed.

contaminants are metals/metalloids-use plastic devices

Label all sample locations on the site map where invertebrates were found.

Map labeled

3.3.2.7 Groundwater samples

3.3.2.7.1 Number and spatial distribution

Groundwater sampling should be conducted in a manner that will illustrate the amount of chemical currently in the groundwater aquifers, both under the site and downgradient off-site. Sufficient number of samples should be taken to define the boundaries of any plume of contamination.

During all drilling, appropriate care should be taken not to penetrate any barriers that prevent the movement of surface water into deeper aquifers. Otherwise, previously uncontaminated groundwater may become contaminated solely as a result of the sampling process.

A minimum of 10 samples is required to find the general location of potential plumes of contamination. This may have been done during the initial site assessment, in which case this portion of the risk assessment can immediately focus on better defining the plume.

Once a general area of contamination is identified, a sufficient number of groundwater samples must be taken to define the boundaries of the plume, particularly its extent downgradient. The number of samples required to do this will depend on the plume size.

3.3.2.7.2 Methods

If contaminants of concern are metals or metalloids, use plastic sampling devices (with the exception of metal-tipped drills, if needed). Samples should be stored in glass or Teflon-lined jars and stored under cool conditions until analyzed.

contaminants are metals/metalloids-use plastic and glass devices

If contaminants of concern are organic compounds, use only metal sampling devices. Store samples in glass containers and keep cool until analyzed.

contaminants are organic compounds-use metal and glass devices

Refer to Appendix N for detailed methods for groundwater sampling. List which methods were used.

List of methods attached

3.3.2.8 Surface water and sediment sampling

When collecting samples, observations on the appearance and abundance of sediment organisms can be recorded as additional information. This information can serve as anecdotal evidence in Tier 1 or 2 EcoRAs.

3.3.2.8.1 Number and spatial distribution

Use a sufficient number of samples to characterize the surface water variability so that a spatially explicit model can be used in calculating risk values (see Section 8.1.1.3.2).

3.3.2.8.2 Methods

Refer to Appendix N for detailed methods for surface water and sediment sampling. List which methods were used.

List of methods attached

3.3.2.9 Fish and aquatic invertebrate sampling

3.3.2.9.1 Number and spatial distribution

The fish and aquatic invertebrate sampling should occur concurrently with the chemical sampling. Samples should be taken at the same location and at the same time as much as is possible. This approach to sampling will facilitate the calculation of risk values as delineated in section 8.1.1.3.

Permits are required for the collection of fish and other aquatic species. Proponents are advised to contact their local office of the Department of Fisheries and Oceans and BC Environment for specific permit requirements.

3.3.2.9.2 Methods

Refer to Appendix N for detailed methods for sampling of fish and aquatic invertebrates. List which methods were used.

List of methods attached

3.3.2.10 Aquatic plant sampling

3.3.2.10.1 Number and spatial distribution

Sampling strategies for aquatic plants depend on the type of plant and the planned use of the data. Aquatic plants can be divided into two main types according to whether the plants are physically attached to the sediment (i.e., rooted plants) or whether they float on the water (i.e., floating plants). Plant tissue sampling is conducted to address risks to herbivores (animals that eat the plants), but can also be conducted to address risks to the plants themselves if the appropriate effect data are available. Therefore, be sure to collect samples from each type of plant that is an important food for animals or that is desired for its own sake. Collect stems, roots and leaves, as these parts are edible for many aquatic plants..

To properly address spatial issues, the pattern of contamination in the receiving environment (sediment or water) must contain some gradient (i.e., is not homogeneous). For example, there is no benefit in sampling duckweed (a floating plant) along with water samples if no contaminant gradient exists in the water. A spatially explicit sampling program, however, should always be considered for rooted plants when addressing which areas of the aquatic portion of the site might require remediation. The number and spatial distribution of samples for a spatially explicit sampling program is driven by the scale of the contamination gradient

Methods

Sampling methods for aquatic plants are the same as those described for terrestrial plants (Section 3.3.2.5).

This completes the Analysis Phase. Go to Section 8 to put all the information together into a Risk Calculation.