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Finding solutions that are adapted to integrate pedoclimatic variations and specific challenges of coal mining regions.

So far, the most popular method of soil remediation has been the ex situ method, which consists in extracting contaminated soil and transporting it to a waste landfill or to a soil remediation installation. Unfortunately, there are a lot of disadvantages to this method, especially in the context of environmental protection and economics.

More and more often, when choosing a method for remediation of contaminated soil, attention is paid to biological methods. These methods consist in accelerating and optimizing natural processes of microbial decomposition occurring in the environment. For bioremediation, microorganisms that have the ability to metabolically break down hazardous substances into less toxic or non-toxic compounds are used. In order to reduce the amount of contaminants in the soil more effectively, a combined treatment system is often applied, consisting of several methods (biological, physical and chemical), enabling the optimization of the remediation process.

Physical methods have long been used on a large scale, which results in the possibility of removing or neutralizing a wide range of pollutants, including heavy metals. Physical methods range from simple engineering methods for the extraction and disposal of contaminated soil as well as more complex process methods that use semi-permeable and impermeable barrier isolation techniques. Another remediation method is the chemical method, which consists in the degradation of pollutants accumulated in the treated soil or changing their physicochemical properties in order to reduce environmental hazards. Chemical methods are characterized by a wide range of applications, both in terms of the type and extent of contamination, and are also relatively effective. However, they are also very expensive and generate large amounts of waste, and at the same time make it difficult to conduct and control processes in situ.

The last method of soil treatment is bioremediation. This method is based on accelerating and optimizing the natural processes of microbial decomposition in the environment. Microorganisms capable of using pollutants as a carbon and energy source play a fundamental role in bioremediation processes. Also, this method has its drawbacks, such as the costs of performing such an operation.

The new technology that will be developed in REECOL, consisting in non-contact soil remediation, operating in three stages of soil restoration, will not have to face these disadvantages. The first stage of remediation will stabilize the area, the second stage will enrich the soil and supply necessary nutrients, and the third stage will maintain an optimal level of growth of the planted flora. The application of individual stages of soil reclamation will depend on the effects of image analysis obtained by drone flights equipped with a multispectral camera. On the basis of the images recorded by the multispectral camera, the level of planting will be estimated and the condition of the plants based on the evaluation of the plant vegetation index.

This indicator allows to determine the state of development and the condition of vegetation by providing information on the intensity of photosynthesis in plants. On the basis of this indicator, it will be possible to modify and adjust the composition of nutrients sprayed on the reclaimed area or to dedicate a given medium to a given group of plants or to change it depending on the seasons. This will allow to achieve much better soil reclamation effects compared to known solutions. One of the aims of the project is to develop and test a new device for non-contact soil remediation technology designed to stabilize, fertilize the soil and maintain it in optimal parameters necessary for the growth of the plants This technology will use multiphase aerosol spraying over long distances, using special nozzles. The developed solution at the stage of soil stabilization will use material from cellulose waste together with seeds of selected plants. At the stage of plant growth, the developed solution will be responsible for enriching the soil by providing the necessary nutrients from bio-waste.

The last stage of the technology’s operation will be to maintain appropriate soil moisture by spraying water. The technology operation will be supervised by a system responsible for collecting information (on topography, plant development level, soil moisture and the NDVI standardized vegetation index) from sensors located on the surface and on UAVs. As part of the task, a prototype of a device for multiphase aerosol spraying will be developed, which will be subjected to bench tests to determine its parameters for individual phases of operation. Information from the site tests will be used to develop a methodology for reclamation of post-mining areas taking into account planning (identification of initial conditions, selection of vegetation), implementations and long and short-term methods of assessing the effectiveness of the applied approach. One of the tools used to carry out this task will be drone equipped with a multispectral camera. Drone surveys and recording will be carried out at the beginning of the project prior to the commencement of the reclamation work and then at set times several times during the project and in subsequent reclamation phases. On the basis of the images recorded by the multis spectral camera, the level of vegetation cover in the surveyed area before the start of the project will be estimated, followed by changes in the degree of vegetation cover in the surveyed area with the implementation of subsequent phases of the project.

Another task using the recorded material will be to assess the vegetation index and compare its level and changes in its level with subsequent phases of the project. This indicator will determine the state of development and condition of the vegetation by providing information on the intensity of photosynthesis in the plants. On the basis of this indicator, the composition of the nutrients sprayed on the reclaimed area or the dedication of a particular nutrient solution for a particular group of plants or its change according to the seasons can be modified further on in the project. Another task for which the drone and integrated camera will be used is related to the recording and analysis of the topography of the area. On the basis of the surveys, photogrammetric techniques will be used to estimate differences in the volume of the heap and changes in the topography of the reclaimed area, which can be compared with a control area within the same heap or at another analogous site. On the basis of the studies carried out, it will be possible to analyse the effectiveness of the spraying carried out under the project.

The design of the technology will be carried out in a suitable engineering environment min. Autodesk Inventor, Autodesk Autocad, etc. on the basis of which it will be possible to verify the completeness of the developed design and then to develop the technical documentation of the research model of the system. On the basis of the technical documentation, a research model of the solution will be produced, within which the integration of all system components will be realised. This will be followed by laboratory tests of the individual components of the system, in particular the spray system and the control system. Prior to the laboratory tests, a test methodology will be developed to outline the objectives and scope of the tests. The laboratory tests will include, among other things, an evaluation of the spray system’s operating range, depending on the pressure of the medium supplied to the spray system, and determination of the system’s performance. The operation of the control system using data from soil sensors and image analysis data obtained from drone flights will be subject to laboratory testing.

The testing phase will allow errors to be eliminated and solution parameters to be optimised. After the laboratory testing phase, possible improvements to the developed technology will be made, which will also be included in the technical documentation of the solution. After the laboratory tests, the research model of the non-contact reclamation technology will be subjected to site tests under field conditions, where, on the basis of the developed methodology, the effects of the solution will be assessed in comparison to sites where the technology will not be used. Within REECOL it is also foreseen to develop a method of high-quality compost mixture preparation. This is the mentioned above bioremediation method of soil treatment, however in contrast to existing solutions it is planned to be more efficient and more economically justified. The composition of the compost mixture will include among others brown coal, and solid organic wastes, e.g. feathers. During the composting process, the coal will be decomposed by biosolubilization, which is a clean technology that enables the decomposition of low-value carbon into agriculturally valuable humic substances. The complex structure of carbon prevents the plant from accessing valuable substances.

The composting process follows spontaneous natural mechanisms in which compost heaps provide a suitable environment for indigenous soil microorganisms to evolve, develop and proliferate. In the case of hardly degradable waste such as feathers or coal, it is necessary to use a more efficient technique of preparing an inoculum grown under controlled conditions in biofermenters. Inoculum will be prepared in bioreactors fed with waste media from the food industry, e.g. whey, wheat germ, distillery broth, beet pulp, potato peelings and others.

Physicochemical, microbiological and biochemical methods will be used to assess the progress of the composting process, which will indicate the level of changes taking place in the compost. The compost product developed in this way will be a carrier of minerals and other nutrients, as well as microorganisms that are essential in soil-forming processes. The final stage of the methodology evaluation will be field experiments in selected post-mining areas with the use of selected plants and the obtained compost mixture in order to determine the characteristics of soil additive behaviour, fertility testing and optimization of composting technology. The addition of the compost mixture to the soil will be an activator. for the soil, increasing its fertility. Evaluation of the effectiveness of the compost mix will be assessed using biochemical, physical and microbiological methods before and after the administration of the compost.

The evaluation of the heavy metal biosorption process will be similarly investigated in two stages using EDXRF X-ray fluorescence. It is also planned to conduct laboratory simulations directly on porous structures of ground-based on anthropogenic soil to check in what conditions it is possible to conduct a steered succession of low-growing plant species. The herbs and grass species with the ability to compete with invasive plants and trees will be selected for the germination tests. The low cost methods that improve the development of desired vegetation will be tested. In the next step, field plots will be identified and the approach developed at a laboratory scale will be tested in real conditions. On a small scale, results of these activities will reach circular economy objectives by using mine tailings in restoration processes. On a larger scale, the restoration techniques developed will enable to increase reuse of degraded areas for industrial proposes. To protect redevelopment potential of such areas, effective methods to decrease the risk of invasive vegetation spreading which hamper tree growth and forest succession are needed.

Depending on the desired new use of a site, ecological rehabilitation using nature based solutions (NBS) will aim to reach the expected ecological services (i.e provisional, regulating or cultural). These services are based on “support services” or ecosystem functions which are all the natural processes inherent in an ecosystem, such as organic matter mineralization, water cycling, nutrient provision to plants. Each of the functions of an ecosystem can be characterised by one or more chemical, physical or biological processes, which can generate ecosystem services. In rehabilitation, soils play a first order role.

Nine ecological functions have been identified that are inherent to soils (Blanchart et al., 2019; EFESE). Processes inherent to soil functions are the result of interactions between abiotic and biotic components of soil. Their evaluation can be obtained by measuring physico-chemical and biological parameters (ex: nitrogen, carbon, water holding capacity, microbial biomass, carbon mineralization, etc.). Some of these parameters are direct indicators while others, such as soil texture, are components that will influence these processes. More and more work is also moving towards the evaluation of functions by evaluating groups of parameters (Blanchart et al., 2019). Many physico-chemical parameters are known to reflect soil quality from an agronomic point of view (Bastida et al., 2008) and the review by Bünemann et al. (2018) showed their prevalence in function measurement studies, although biological indicators can also provide significant information on soil functioning. Indeed, biological indicators are more sensitive to shortterm disturbances (Bastida et al. 2008).

Various recent or ongoing studies have identified known indicators, biotic and abiotic, of soil functions (Baptist et al., 2018). Currently, soil monitoring at European level is based on physico-chemical data such as the RMQS (Soil Quality Measurement Network) (Morvan et al., 2008). In recent years, however, several projects have focused on the identification of sensitive biological indicators and recently discussions have been reopened for a Soil Framework Directive. Soils contain a great abundance and diversity of microorganisms which are key players in many ecosystem functions and services, and therefore in soil quality (Brackin et al., 2017). Information on soil biodiversity as well as on the biological activity of its micro-organisms would provide a more precise view of the state of soil functions and services because they influence important processes specific to this ecosystem (Vincent et al., 2018; Brackin et al., 2017). Remote sensing is the process of measuring reflected radiation at a distance (typically from satellite or aircraft).

Remote sensing technology allows for detecting and monitoring the physical characteristics of large areas. The remote sensing data are used for soils, forestry, agriculture, urban and water research (Pandey at al 2020) (Pierzchała 2020.) In the term of reclamation of degraded areas remote technologies are used mostly for identification of spatio-temporal changes in land cover forms. Second area of using remote sensing data is monitoring of vegetation condition on reclaimed and developed lands. The health state of vegetation was assessed base on NDVI, NDMI, EVI and RVI indicators that had been delivered by U.S. Geological Survey (Landsat 5 and 8 satellite images) (Buczyńska 2020). Based on existing knowledge and experimental on site experimentations and monitoring, REECOL aims to define a toolbox of methods and (bio)indicators to measure key ecological functions and processes that reflect the degree and nature of ecosystem degradation and that are tailored to monitor the rehabilitation scenarios and thus provide input data for proposing a certification methodology for post mining ecological rehabilitation.

The aim of REECOL project is testing the data delivered by the European Space Agency (Sentinel 2 satellite images). The advantages and limitations of these data sources for long term monitoring will be analysed and the possibilities of its application will be assessed. Where short term monitoring provides data on the immediate success of an ecological rehabilitation scheme, long term monitoring solutions are essential to measure sustainability. The satellite and unmanned aerial vehicle (UAV) data will be used for monitoring results of reclamation activities and observe undesired processes on terrains with high redevelopment potential (spread of invasive species and succession of
woody vegetation).

Different European legislation and standard – method of certification or final sign-off of rehabilitation requires the appropriate application form to be completed and adequate information to be provided by the applicant in a rehabilitation report. This includes evidence that the rehabilitation meets the completion criteria and a risk assessment.
The completion criteria must provide a clear definition of successful rehabilitation for each domain at the mine site in the form of a set of measurable benchmarks against which the rehabilitation indicators can be compared to determine whether the objectives are being met. At least one completion criterion must be developed for each indicator. Completion criteria should specifically relate to the environmental, social and economic context of the mine site. However, it is possible that some completion criteria may be applied uniformly across a region if supported by technical evidence.

The benefits of providing high quality information include expediting the assessment by the administering authority, improving the likelihood of a positive outcome, and minimising any necessary residual risk payment. The completion criteria are an important component of the certification process and need to be agreed before the application can proceed. The other necessary component is clear and comprehensive information on the performance of the rehabilitation from when it was undertaken until when the application for certification is made. This project aims at developing a detailed framework of the certification system and to provide a method that can be applied across coal mining operations of different size and location. The challenge of the proposed approach compared to the current certification processes is at the regular Evaluation of performance of rehabilitation through Monitoring, Auditing and evaluation, and Corrective actions to fulfil the completion criteria. It is planned that within the REECOL project, the certification framework will be described providing a pathway for the definition of coal mine rehabilitation.

The Directive 2006/21/EC3 on the management of waste from the extractive industries (“the Directive” or “EWD”) provides minimum requirements, procedures and guidance to prevent or reduce as far as possible any adverse effects on the environment and any resulting risks on human health from the management of extractive waste. For the closure and after-closure phase, the EWD requires MS to ensure that the operator requests an authorisation to start the closure procedure. This request is based on the latest periodic review of the Extractive Waste Management Plan (EWMP) taking into account the actual environmental impact of the waste facility and elaborates in detail the closure tasks and programmes including expected costs. Some MS require a separate closure plan. The Commission has adopted a Decision on technical guidelines for the financial guarantee (FG) establishment in accordance with the EWD. Some Member States (MS) suggested providing additional technical guidance for the implementation of the FG provisions.

The guideline document aims to support the EWD implementation by elaborating technical guidance for – Collection and description of the Closure Best Practices by Mining Typology – FG calculation prior to the commencement of waste deposit, and FG periodic adjustment; – Elaboration of updated closure plans taking into account the environmental impact of the operations; and – Approaches for determining the cost of the respective activities to implement the closure plan. Regarding the European legislation according to mining closure, there is an environmental regulation which raises some types of environmental concerns: mining waste, nature protection, water protection, environmental liability.

The mining waste directive (Directive 2006/21/EC of the European Parliament and of the Council on the management of waste from the extractive industries) introduce obligatory permits and setting requirements for building or modifying an extractive waste facility. Besides that, a document which includes the best available techniques (BAT Reference Document, BREF) was developed, on the management of waste from ore processing and waste-rock in mining activities. It covers activities related to tailings and waste-rock management of ores that have the potential for a significant environmental impact (“Mining Waste – Environment – European Commission”, 2019). With reference to water protection, mine water is covered by the Water Framework Directive, which introduces river-basin management with a focus on ecology, and requires that “good” status must be achieved for all EU water since 2015.

It is complemented by the Groundwater Directive, which sets quality standards for underground water and introduces measures to prevent or limit the pollution of groundwater. In the case of Nature protection, the habitats and birds Directives the EU nature conservation policy has a central element of which is the Natura 2000 network of ecological sites. Mining projects in and around Natura 2000 sites are not automatically ruled out, but they must be assessed in a proper way to have a significant effect on a protected site. If such effects are expected, mining projects must either be avoided or amended. The mining industry is affected by the Environmental Liability Directive which is based on the “polluter pays” principal. Operators have a duty to avert environmental damage or take or finance restorative measures if such damage occurs due to their negligence or fault. Finally but not less important, health and safety issues have to be taken into account. Mining and quarrying has one of the highest rates of accidents at work and of work related health problems, thus the Health and Safety at Work Directive sets the general principles for prevention and protection of workers against occupational hazards.