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The significance of amino acids and amino acid-derived molecules in plant responses and adaptation to heavy metal stress. Sheoran, V. Phytomining: a review. Role of hyperaccumulators in phytoextraction of metals from contaminated mining sites: a review. Souza, L. Use of non-hyperaccumulator plant species for the phytoextraction of heavy metals using chelating agents. Relevant facts found in the Journal of Environmental Science, , Vol 87, pages talk about lead contamination and uptake by sunflowers.
It is believed that sunflower seeds are safe to be used as oil or meal for humans since the seeds are not the main containment of the plant — leaves and stems are the primary holders of the contaminants, with roots carrying the next heaviest load and seeds holding only trace amounts.
Researchers maintain that seeds are safe. Their suggestions depend on the density of the ground contaminant, the type of pollutant usually heavy metals , the species of sunflower used Helianthus annuus, being the most common , the length of time the plants remain in the area.
As you can see, answers are not simple because the issues involved are complex and discoveries about disposal is ongoing. The laws for toxic biomass disposal vary in each country, also. The safest and most promising method is incineration at very high heat level, which involve incinerators with filters and screens to remove the toxins before gas is released.
Landfills with liners in place to prevent seepage into the ground are sometimes used. Composting is only used as a preliminary step prior to complete decontamination. Despite these problems, using sunflowers to decontaminate land and water spoiled by heavy metals or other contaminants, is beneficial overall and has been used with great success in areas like Chernobyl and Fukushima. It seems, however, that disposal of plants contaminated via phytoremediation must be accomplished through some established facility, often under the Dept.
As you can see, this is a complex issue and an excellent question by anyone. But, this is the response and it is being constantly studied, especially where radioactive soil is found. Is any plant known for this exercise? Your email address will not be published. Notify me via e-mail if anyone answers my comment. Add to Favorites By Anita B. Categories : Growing Tags : and best best-houseplants-for-clean-air for free good-soil growing hole how how-to list long make natural phytoremediation-plants plant planting plants popular soil soil-contamination soil-contamination-testing soil-removal soil-testing storage-containers that the to what what-makes-good-soil.
How to Knit Socks with 4 Needles. Countryside Machinery on the Homestead e-edition Flip Book. Hi Dan. I hope this helps. Take good care, Anita. Leave a Reply Cancel reply Your email address will not be published. Though the relation between such biomarker-based data gathered and the in-vivo risks awaits further elucidation, the application of tests based on biomarkers for soil pollution is an interesting option in dealing with combination effects on humans.
Also, estimates of risk may be derived from biomarkers which may be monitored in people exposed to soil pollution. Such biomarkers have emerged from epidemiological studies considering the combined effect of substances.
An illustration thereof is the study by Lee et al. This suggests that oxidative stress may be useful as a biomarker for combination effects. It has furthermore been proposed to evaluate effects of exposure to nitroarenes by measuring haemoglobin adducts [ 57 ], and of mixtures of volatile organochlorines by measuring glutathione conjugative metabolites [ 58 ]. Bioassays based on aryl hydrocarbon Ah receptor mediated mechanisms have been proposed which will allow a better alternative to the measurement of polyhalogenated aromatic hydrocarbons [ 41 ].
Another option is to estimate risks to human health by taking into account cumulative combination effects in line with established cause-effect relations and research into the effects of actual combinations.
It has been shown that risks of compounds with the same targets and the same modes of action may be estimated on the basis of concentration addition, while including toxicity equivalence factors for the compounds involved [ 59 ]. This has been shown to apply to receptor-mediated-and reactive mechanisms of toxicity, provided that no chemical reactions occur between the components of the mixture considered [ 60 ].
Currently this approach is applied to halogenated dioxins, benzofurans and planar polybiphenyls, though non-linear interactions are not completely absent in this category of compounds [ 61 ], and neurodevelopment effects may be underestimated, as pointed out before [ 41 ].
Extension of this approach is possible to e. Ecological risk assessment ERA is a process of collecting, organizing, and analyzing environmental data to estimate the risk or probability of undesired effects on organisms, populations, or ecosystems caused by various stressors associated with human activities.
The basic principles of ecological risk assessment are described in numerous papers [ 70 - 72 ]. All varieties of ERA are associated with uncertainties. The value or usefulness of the different ERA methodologies depends on the uncertainty, predictability, utility, and costs.
There are typically two major types of ERA. The first is predictive and is often associated with the authorization and handling of hazardous substances such as pesticides or new and existing chemicals in the European Union. This kind of ERA is ideally done before environmental release.
The second type of ERA could be described as an impact assessment rather than a risk assessment, as it is the assessment of changes in populations or ecosystems in sites or areas already polluted. The predictive method is based on more or less generic extrapolations from laboratory or controlled and manipulated semi field studies to real-world situations. The descriptive method is more site specific as it tries to monitor ecosystem changes in historically contaminated soils such as old dumpsites or gas facilities or in field plots after amendment with pesticides or sewage sludge, for example.
Often ERA is performed in phases or tiers, which may include predictive as well as descriptive methods. The successive tiers require, as a rule of thumb, more time, effort, and money.
The paradigm or schemes for ERA may vary considerable from country to country, but often consist of an initial problem formulation based on a preliminary site characterization, and a screening assessment, a characterization of exposure, a characterization of effects, and a risk characterization followed by risk management. Although exposure assessment is often just as or even more important, this chapter primarily considers effect assessment. National research or remediation programs have led to the development of a large variety of guideline values.
Although hard to categorize, most fall into two categories: generic or site specific. While the site-specific guidelines require a characterization of pH, organic matter, etc. Three major classes of tools for assessing ecological effects may be identified: standardized ecotoxicity experiments with single species exposed under controlled conditions to single chemicals spiked to soil; ex situ bioassays, here defined as simple laboratory assays where single species are exposed to historically contaminated soils collected in the field; and finally monitoring, analyzing, and mapping of population or community structures in the field.
Furthermore, mesocosm, lysometer, or terrestrial model ecosystems TME may be useful; these may be considered as large multispecies bioassays or ecotoxicity tests [ 76 - 79 ]. TMEs have the advantage that they operate with the relatively undisturbed intrinsic soil populations that make up a small food web.
TME hence allow the assessment of effects of toxicants that are mediated through changes in food supply or competition and predation. One of the keystones in deriving environmental quality criteria is the use of standardized terrestrial test procedures. The emphasis of these prognostic tests is on reproducibility, standardization, international acceptance, and site independence. However, other tests have shown promising results and are likely to be prepared for standardization in the future [ 80 ].
However, the major problem in using simple laboratory tests to extrapolate to contaminated land may not be the limitations of test species and the natural variation in species sensitivity. The problems associated with extrapolating from one or a few species, exposed under controlled and typically optimal conditions, to the complex interaction of species and chemicals found in most contaminated ecosystems should also cause concern.
Although single-species laboratory tests with spiked materials have their obvious benefits, e. Bioassays, as defined in this context are one of the more frequently used higher-tier alternatives. Basically the same test species may be used in bioassays for assessing the risk of a specific contaminated soil as in standard laboratory tests. However, bioassays have the advantage, compared to the use of spiked soil samples, that the exact toxicity of a specific soil may be accessed directly: this includes the combined and site-specific toxicological effect of the mixture of contaminants and their metabolites.
Furthermore, the in situ bioavailability of that specific soil is at least almost maintained in the laboratory during the exposure period. Bioassays are therefore often considered a more realistic tool than generic soil screening levels based on spiked laboratory soils. However, a number of uncertainties or problems may be associated with the use of bioassays and the interpretation of their results. First, the test species are still exposed to the contaminants in a relatively short period compared to the permanent exposure condition found at contaminated sites.
Furthermore, they are exposed under more or less optimal conditions, in that stressors such as predation inter- and interspecies competition, drought, frost, and food depletion are eliminated during exposure. Finally, typically only a few species are tested individually.
To compensate for some of the limitations just described, contaminated soil may be assessed using multispecies mesocosms, lysometers, or TME. In these, species interactions may be evaluated by manually introducing several species to the systems or monitoring the intrinsic populations of the soil.
Natural climatic conditions may be included if the test system is kept outdoors. However, if we want to get a more realistic and large-scale picture of the impact caused by, for example, pesticide use or sewage sludge application, or to assess the environmental health at waste sites, industrial areas, or gas works, it is often necessary to conduct some kind of field observations.
Several case studies exist in which field studies have successfully elucidated the ecological risk of specific activities or the ecological impact at specific sites [ 85 - 87 ]. The small single-species bioassay, large multispecies TME, and field surveys have some drawbacks in common. First of all, it may be difficult to actually link the observed effect to a specific toxic component in the soil. Which of the many substances is actually causing the majority of the observed effects, or is it perhaps a combination of effects?
For a hazard classification of soils or a ranking of soils this may not be so important. However, to evaluate potential risk-reduction measures or risk management procedures it may be important to identify the most problematic substances. A comparison of soil screening values with measured concentrations for each chemical present at a site may be helpful to identify the most likely group of substances causing the observed effect.
Other possible tools may include a toxicity identification evaluation TIE approach [ 88 ]. The TIE approach is a relatively new method, which aims to identify groups of toxicants in soils with mixed pollution.
Potentially toxic components present in the soil are fractionated and determined, and the toxicity of each individual fraction is determined by a Lux bacteria-based bioassay or the Microtox bioassay. Although perhaps promising, TIE is a time-consuming and hence costly procedure not yet used routinely. Another crucial issue when analyzing the result of bioassays, TME, and field studies is the presence or absence of a proper reference site or soil.
The control soil should in principle resemble the contaminated soil in all relevant parameters, e. The lack of adequate control or reference sites may, however, be conquered at least partially by the use of multivariate techniques [ 89 ], which relate the species composition and abundance to gradients of pollutants.
It is not the intention of this chapter to present a review of statistical tools for ecological risk assessment, and hence a detailed discussion about the use of these is not given. However, it is obvious that increased computer power and the presence of new easy-to-use software tools have increased the possibility to move away from more conventional univariate statistics such as analysis of variance ANOVA to more powerful multivariate statistics that use all collected data to evaluate effects at a higher level of organization.
Statistical methods such as the power analysis may also be very useful in planning and designing large-scale ecotoxicity studies such as mesocosms,TME, or field surveys.
As all sites are considered unique this should always be done in a site-specific manner. Essential for all steps are a negotiation and agreement of the need for further action between the risk assessor, the risk manager and other stakeholders, the so-called scientific-management decision points SMDP.
SMDP made at the end of the screening-level assessment will not set an initial cleanup goal. Instead, hazard quotients, derived in this step, are used to help determine potential risk.
Thus, requiring a cleanup based solely on those values would not be very likely, although it is technically feasible. There are three possible decisions at the SMDP:. There is enough information to conclude that ecological risks are very low or non-existent, and therefore there is no need to clean up the site on the basis of ecological risk.
The information is not adequate to make a decision at this point, and the ecological risk assessment process will proceed. The information indicates a potential for adverse ecological effects, and a more thorough study is necessary.
In the Netherlands contaminated sites are first determined using a set of soil screening levels called target and intervention values, which take both human and ecological risks into account. At seriously contaminated sites remediation or other soil management decisions are required if the risks cannot be neglected based on a site-specific ecological and human risk assessment, and the chance for dispersion of the contaminants.
Until now, the ecological risk assessment has been based on chemical analysis, including a Decision Table harbouring critical dimensions of the impacted area.
The United Kingdom and Canada have also developed framework for ecological risk assessment of contamination land. A cornerstone in the UK framework of ERA is the connection to the statutory regime for identification and control of land potentially affected by contamination. The UK framework is based on schemes found in e. USA, Canada and the Netherlands. Like these it is a based on a tiered approach where the initial Tier 0 aims to determine whether a site falls under the Part IIA of the legislation.
It involves the development of a Conceptual Site Model CSM , which described what is already historically known about the site, e. The conceptual site model is followed by an initial screening phase Tier 1 and an actual site-specific characterisation Tier 2.
Tier 1 is a simple deterministic comparison of chemical residue data and the soil quality guideline values supplemented with simple soil-specific toxicity testing. The final step Tier 3 involves more detailed in-situ studies and for example ecological modelling based on a more advanced ecological theory. Tier 3 is not likely to be conducted at many sites. Ecological Risk Assessment is often a complex process with many variables to take into account.
ERA involves many stakeholders and all have to be dealt with in a clear and consistent way. A stepwise or tiered approach is therefore useful to overcome the complexity of an ERA. Each tier will lead to a decision to proceed or to stop. A number of decisions supporting systems or frameworks have already been developed in other countries, e. However, in the present DSS measures of bioavailability and the use of the Triad approach may be built into the system more systematically.
This chapter introduces the overall framework of a novel DSS including the Triad approach and the challenge to weight and scale results used in that process. Rutgers et al. Each of these four tiers is based on a weight of evidence WoE approach combining three lines of evidence Chemistry, eco Toxicology and Ecology.
The DSS in this chapter is not a full and comprehensive document for managing risk of contaminated land. It focuses strongly on supporting decisions made when considering risk to the terrestrial environment. Therefore it addresses only indirectly the risk to ground water and associated connected fresh water systems.
Nevertheless information about e. Furthermore, it is important to realise that the management of a contaminated site is more than assessing ecological risk. Issues like for example risk for humans, availability and cost of remediation solutions, development plans for the vicinity or the region are equally important.
Basic flowchart for ecological risk assessment [ 90 ]. It aims at involving as many stakeholders as possible in order to describe site characteristics and to review all available information from the site, e. The spatial borders of the site should be defined and the current and the future landuse have to be defined. Consultation between administrators, planners and experts therefore has to take place as early as possible in the process.
An inquiry among all stakeholders should be conducted as one of the first initiatives. The aim should be to collect as much information about soil characteristics as possible. One of the first actions to be taken among all stakeholders is to decide which landuse is required for the site, as this will determine the required data collection and testing.
Many land-uses may be defined, but generally the four following overall categories of land-use classes are used:. Most often a site specific ERA will be initiated only when soil concentrations exceed soil screening levels. However, this may not in itself be a sufficient criterion to go through the entire ERA procedure. Some boundary conditions, based on the present and future type of land-use, the level of contamination and various ecological considerations have to be met in order to rationalize an ERA.
The experts and the rest of the stakeholders should answer a number of simple questions in order to conclude whether the required boundary conditions are fulfilled. At stage II, site-specific ecological features and receptors relating to the land-use defined in Stage I need to be outlined. This includes aspects like key species and life support functions.
The potential ecological receptors should be identified in order to determine whether potential source-pathway-receptor linkages can be established. This includes not only ecological receptors directly linked to the site but also those linked indirectly e. In Table 9 some examples are given of land-use and related ecological aspects.
This table can be used as a starting point for the selection of ecological aspect. Experts from ecotoxicology and ecology should be involved in the selection of ecological aspects. If after finalising Stage I and Stage II it is still considered that there is a need for a site specific evaluation of ecological risk the process continues to Stage III using the weight of evidence approach described below. In order to deal with conceptual uncertainties in a pragmatic way, it has been proposed to use weight of evidence WoE approaches for ERA [ 90 - 93 ].
The rationale is, like in justice, that many independent ways to arrive at one conclusion will provide a stronger evidence for ecological effects, making ERA less uncertain. In the sediment research area the application of WoE started at an early stage and was called the Sediment Quality Triad. For terrestrial ecosystems WoE approaches and the Triad are still in a developing stage. The Triad approach is based on the simultaneous and integrated deployment of site-specific chemical, toxicological and ecological information in the risk assessment as given in Figure 6.
The major assumption is that WoE in three independent disciplines will lead to a more precise answer than an approach, which is solely based on, for example, the concentrations of pollutants at the site.
A multidisciplinary approach will help to minimise the number of false positive and false negative conclusions in ERA. It also gives acknowledgement to the fact that ecosystems are too complex to analyse in one-factorial approaches. Schematic presentation of the integration of three fields of research according to a Triad [ 92 ].
Chemistry: The concentration of contaminants in the environment totals, bioavailable , accumulated in biota, or modelled via food-chains is used for calculation of risks on the basis of toxicity data from the literature. Toxicology: Bioassays with species across genera are carried out in order to measure the actual toxicity present in environmental samples from the site.
Ecology: Field ecological observations at the contaminated site are compared to the reference site. Deviations from the reference site, which can be plausibly attributed to the contamination levels, are funnelled into the Triad. Triad is a powerful weight of evidence approach originally developed in order to evaluate sediment quality.
In the terrestrial compartment less experience is available on the practical use of the Triad. This chapter describes the use of Triad in more detail and gives an insight into some of the important decisions risk assessors have to make when conducting the Triad in practise, e. The Triad approach includes a tiered system in which each consecutive tier is increasingly fine-tuned to the site-specific situation. In the first tier the research is simple, broad and generic. In later tiers more specific and complex tests and analyses may be used.
For each of the LoE in the Triad there are a variety of analyses or tests that can be chosen. Some examples are:. Chemistry: Measurement of total concentrations, bioavailable concentrations, bioaccumulation, etc. Ecology: Field observations of vegetation, soil fauna, micro-organisms, etc. In Chapter 6, a number of tests or tools that are for suitable for use in each tier are presented for the chemistry, toxicology and ecology LoE.
This chapter is an attempt to present a decision support system, which can guide risk assessors in their assessment of site-specific ecological risk. A number of site-specific questions need to be answered before a final decision on performing an ecological risk assessment can be made.
This chapter introduces a flow chart for ecological risk assessment of contaminated sites. The flowchart is presented as decision trees as shown in Figure 8 together with a more in-depth introduction to the relevant questions that needs to be addressed and answered when performing a site-specific ecological risk assessment. The assessment of ecological risk is performed stepwise in tiers.
Higher tiers represent gradually more and more complex studies, but also more expensive and laborious studies. The full site-specific risk assessment covers four tiers, i. The main principle in going from a simple screening over a more refined screening to a detailed assessment of the contaminated site is to minimize time and effort. The actual performance of the risk assessment and use of the various tiers may be very site-specific.
After deciding in the two first stages of the ERA that ecological concern needs special consideration, the risk assessment starts typically with a simple evaluation at the screening level. This is done in order to minimize costs until new information indicates the need for further assessment and more sophisticated studies. Therefore, the tools used in the first screening need not only to be reasonably quick and easy, but also relatively cheap. On the basis of the results of instruments used in Tier 1 it is decided to either stop further assessment or continue to a higher tier.
Tier 2, still considered being at the screening level, aims at refining the measurement of exposure and at the same time to provide further insight into the toxicological and ecological properties of the contaminated soil. Tier 2 deviate from the conservatism normally associated with the use of total concentration in the risk assessment by taking rough estimations of bioavailability into consideration in the chemical LoE.
A better screening of the toxicological and ecological properties of the soil compensates for the reduced conservatism in the Chemistry LoE of the Triad. The tools for use in Tier 2 are described in more details in the toolboxes C2, T2 and E2. On the basis of the results in Tier 2 a decision should be made to either stop further assessment or continue to a higher Tier.
The tools in Tier 3 differ from the ones used in Tier 1 and Tier 2 in that they are more laborious, costly and may take longer. The stakeholders should beforehand negotiate a minimum set of tests. Is it for example necessary to consider all trophic levels in the toxicological and ecological LoE? Or does the land-use suggest otherwise? Is it necessary or possible to estimate the bioavailability of all the substances exceeding their SSL? If not, how are the non-investigated substances dealt with?
The tools described for use in Tier 3 are described in more details in the toolboxes C3, T3 and E3. Depending on the results from Tier 3 a decision should be made to either stop further assessment or continue with an even more detailed assessment in Tier 4. In Tier 4, the aim of the studies is to answer any remaining questions and to decrease existing uncertainties and this may often require more in-depth research. Tools in Tier 4 can be similar to tools of Tier 3, but more focus has to be on site-specific circumstances.
For example bioassays should be done with organisms, which normally occur at the site. Furthermore, it may be more relevant to consider ecological effects outside the contaminated area on e. This Tier requires specialised knowledge and experience with ERA, which implies that costs can be high and only a limited number of people may be able to perform the tests. Generally only on a very limited number of site evaluations will include investigations at this level.
If the results of Tier 4 still indicate risk there are basically two possible solutions. Accept the risk and leave the contamination or remove parts of the contamination. In order to facilitate the selection of appropriate tools in the right context, the tools have been compiled in subclasses or toolboxes.
Each of these is a collection of tools considered to be potentially useful in the designated tiers and LoE of the Triad, i. Furthermore, the tools are arranged according to their complexity, price and practicability or in other words depending on whether they are most useful for screening or detailed assessment, i. At the very first stage of the ERA process, total concentrations of all relevant chemicals are individually compared to soil screening levels SSL in order to evaluate whether there is a need for a site specific assessment of ecological risk.
In the current Stage III of the ERA, this first generic evaluation of risk is followed by a more site-specific screening of risk including information from all three lines of evidence in the Triad. In the Chemistry part of the Triad more site-specific information is collected by:. Refining and targeting the comparison of soil concentrations with soil related benchmarks for site-specific purposes. Incorporation of the accumulative risk of a mixture of contaminants by calculating the toxic pressure TP of a mixture and by doing so generating more site-specific insight to the potential ecological impact of a contaminated site.
Each of these steps can be done separately or in combination, e. The approach entirely depends on the strategy taken by the stakeholder group and the availability of data. The main objective of the selected toxicity tests or bioassay at Tier 1 should be to screen the soil for presence of toxic compounds.
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