Stage 3 - 2016: Designing the laboratory decontamination facility

Summary

All targets proposed for 2016 were fully accoplished and many more activities exceeded (e.g. scientific papers published or presented at conferences). The main objective of this reporting period was to study the opportunities for decontamination of the forest areas contaminated by metal mining waste from closed mines. Our research indicated that the sterile dumps continue to pollute the forest environment: the rainwater dissolve heavy metal ions (Cu, Ni, Pb, Ba and even Fe) as well as arsenic and carry through the flowing waters. Moreover, the wind may traslocate heavy metals- containing dust ȋn neighboring forest areas. Hence, the decontamination of such heavily polluted areas must prevent the dispersal of the contaminant material waste dumps. Laboratory decontamination facility requires the extraction of metal ions with distilled water under the action of ultrasound, followed by the neutralization with an alkaline solution to precipitate them in the form of the insoluble oxides or hydroxides, centrifuging and measuring the residual metal concentration in the supernatant. The heavy metal-containing precipitate is redissolved using a nitric acid solution and used for metal recovery. Periodically, the concentration of heavy metals and arsenic was determined by ICP-OES to ascertain the contamination of studied area. Besides, heavy metal concentrations of various extracts and supernatants were measured by AAS. The research results were presented orally at international scientific meetings and partially published ȋn impact factor journals. Thus, our team have published a total of five (5) works with impact factor, with an Impact Factor total of 4.217 points, other works being completed, sent to journals and taken ȋn considered for publication (PlosOne, Current Organic Chemistry, Revista de Chimie). Some other results were also presented at three international conferences (7 papers of which 3 were published in full ȋn proceeding of the ISI-indexed conference) and four papers were presented at national conferences. Technical feasibility studies for experimental development have shown that high concentrations of heavy metals in the dumps should be first reduced, followed then by proper decontamination of the contaminated soil in an area of ​​several dozen hectares. Therefore, our research has shown that the problem of heavy metal contamination from closed mines can not be simply solved. It deserves the joint action involving political and administrative factors, and the decontamination must involve some specialized companies able to apply the results of our research or others.

Introduction
Mining activities are associated with the most polluting sources for human communities or natural ecosystems (Kossoff et al., 2012; Hudson-Edwards et al., 2003). The pollution manifests as natural land degradation, air and water pollution, negative impact on terrestrial and aquatic ecosystems, human health and socio-economical field (da Silva et al, 2009; De Sherbinin et al., 2007). The soil heavy metal pollution around the barite closed mine of Tarnita continues to  represent high risk to the public health (Chicos et al., 2016; Ciornea et al., 2015; Stumbea, 2013; Voica et al., 2012; Flocea et al., 2013; Lucaciu et al., 2004). The sterile dumps around the closed barite mine of Tarnita-Suceava, Romania, contain increased amounts of poisonous arsenic and heavy metals such as copper, iron, lead and zinc (Chicos et al., 2016; Ciornea et al., 2015; Tutu et al., 2012; Stumbea, 2013; Stumbea & Chicos 2012). The topography, soil, vegetation, hydrology, fauna, microclimate and landscape are altered or even destroyed. The mining abandon may lead to the natural reconstruction of the ecosystem in long term; however, in the case of open cast mining, returning to the previous state is very difficult or even impossible (Voica et al., 2012). The soils have severe chemical, physical and biological limitations (Florea, 2011; Harikumar, 2016; Lucaciu et al., 2004). Many studies were performed in order to characterize the soils from Tarnita region and to estimate the level of heavy metals and acidic drainage capability. Total heavy metal, exchangeable metals, acidity and carbon and nitrogen content were estimated.
Tarnita barite mine belonged to S.C. MINBUCOVINA S.A. Vatra Dornei, which was processing non-ferrous minerals from Lesu Ursului and barite from Ostra and Alunis quarries. Lesu Ursului deposits are composed of multi-layered pyrite ore accumulations and polymetallic sulphides. The rocks from this area can be classified in: i) compact, gray, siliceous porphyrogene rocks; ii) marcastic and sericito-chlorite schists; iii) chlorite schists with sulphydes – pyrite, chalcopyrite, blend and galena; and iv) graphite schists. The minerals found in Lesu Ursului deposits are divided into four areas: first area – impregnation of copper-ferrous ores; second area – compact polymetallic and impregnation of copper-ferrous ores at 180 m from the first area; second/third area – compact polymetallic and impregnation of copper-ferrous ores at 400 m from the second area; and fourth area – compact polymetallic and impregnation of copper-ferrous ores at 800 m from the second area. Barite ores from Ostra and Alunis are present in high quantities in gneisses of Rarau as lenses, nests and impregnations. The thickness of the ore from the surface of terrestrial crust ranges between 10 and 45 m.
There were several torrential rains in 2002 several that caused ravines on main slope of tailing pond. Consequently, an exfiltration on slope pond has occurred that have a high concentration in heavy metals (data from the Environmental Protection Agency Suceava, November 2002). Thus the concentration in heavy metals exceeded the maximum permissible concentration values (iron, 0.3 mg/L; zinc, 0.1 mg/L; copper, 0.03 mg/L;  manganese, 0.05 mg/L). Thus, iron reached a concentration of 204.17 mg/L, zinc was 22.97 m/L, cooper 0.039 mg/L; and manganese, 14.27 mg/L (Ioncea, 2009a & b).
The research results obtained on investigating dumps, soils and waters from Tarnita area involved equally all partners, which worked together to implement the activities of the project in 2016. Thus, there were three visits for sampling on Tarnita polluted area and to study the effects on vegetation, soil, and waters and to take photos which evidence vegetation changes. The mobilities toward the contaminated area in 2016 took part the project researchers as well as researchers not included in the personal list of the project at (Prof. Dr. Andriana Surleva of the University of Chemical Technology and Metallurgy in Sofia and PhD. chem. Radu Necula which is studying composition flavonoid changes of plants affected by pollution).

Design of the laboratory decontamination plant

An installation was projected that can be carried out both at laboratory and pilot scale, which was used in the study of decontamination of waste material from dumps containing heavy metals and arsenic. This technology can not be applied now to decontaminate soils polluted due to relatively low concentrations of contaminants and concentrations of each metal variability ȋn part. The problem encountered at Tarniţa in the Eastern Carpathians represent the existence of high concentrations in waste dumps that continue to pollute. At present, the invention is drawn up and is going to be sent for patenting process of decontamination of areas heavily contaminated with heavy metals and arsenic around the disused mines. Laboratory decontamination facility requires the extraction of heavy metal ions with distilled water under the action of ultrasound. Then, the acidic extract is neutralized with an alkaline solution when the contaminants precipitate in the form of the insoluble oxides or hydroxides followed by centrifugation and determination of residual metal concentration in the supernatant. The precipitate is next redissolved in a low concentrated nitric acid solution, and the resulted solution used for metal recovery.
Description of the decontamination facility. The scheme of the laboratory facility, which can be extended to pilot scale or industrial micropilot is shown in Fig. 1. A quantity of 1 g -100 g (in laboratory scale) is mixed with 20 mL - 2 L of distilled water (rainwater, spring water in the industrial installations), and stirred under the action of ultrasound for 15- 30 min. Use a lab sonicator (1) with the vibrator shaft inserted in the extraction solution. We can proceed a two-stage extraction; the solid material is extracted with water using a ratio of 1 g / 10 mL by sonication, decantation and the resumption by adding another volume of 10 mL of distilled water to 1 g of the solid material which was extracted once. From the extraction basin, the decontaminated solid can be washed, chemically analyzed to calculate the concentrations of any heavy metals (in trace amounts) and tested biologically and toxicologically (most simply by measuring the germination energy of cereals (percentage of wheat seeds germinated after three days on decontaminated soil). If the solid material is non-toxic and has no concentration above acceptable limits (Tudorachi, 2016), then it can be evacuated ȋn environment: (exhaust).

Fig. 1. Scheme of the decontamination plant for tailings dumps in Tarniţa: 1 – Mechanical
ultrasound  shaker; 2 - Collector of solution containing heavy metals and arsenic ions;
3 - Filter; 4 - Pump;  5 - Centrifuge; 6 – Tank for filtration- or centrifugation-based
decontaminated solutions; 7- Ion exchange tower ; S - Solid; L - Liquid.

Determinarea periodică a concentraţiilor reziduale de metale grele

They were made several visits ȋn Tarniţa area in order to vegetation study, sampling to measure contaminants and take pictures showing modifications of vegetation under the aggressive influence of heavy metals and arsenic.
Total heavy metal, exchangeable metals, acidity and carbon and nitrogen content were estimated. The sequential extraction method was used to determine the geochemical phase distribution of heavy metals in three samples of Tarnita soil. The heavy metal content was determined in each extract by ICP-OES. The results revealed that the soils are highly contaminated with heavy metals: Cu, Pb, Zn, Ba, Cr, Mn, Cd, Ni, Ag, but also with metalloid As. The acidity of the soils samples varied between 7.5 and 2.04. The high acidity was strongly correlated with heavy metals availability and contamination of waters and surrounding soils by leaching. The total heavy metal content of the acidic sample is three times higher than the neutral pH samples: 6.24 g/kg and 2 g/kg, respectively. The most abundant heavy metals in the studied samples were Cu and Pb. Ba and Ni were found only in the neutral soil samples. The results from sequential extraction revealed that cooper is retained by amorphous and crystalline iron oxides in soil: 72%. The highest content of lead was found in amorphous iron oxide fraction: 79%. Up to 1% of copper and lead were found in the residual fraction. The highest heavy metal content was found in the fractions associated with iron oxides. Although, metals fixed on iron oxides have limited mobility, the acidic soil conditions may cause their displacement to more mobile fractions, increasing thus their availability.
We examined noxious element concentrations in sterile dump material, soil and water samples collected in the proximity of the abandoned Tarnita barite mine, and evaluated the anthropogenic contaminant effects on the environment. All the results were published in impact factor journals or presented at the international and national scientific meetings.
Our results show the existence of extremely high contamination in copper, lead, iron, arsenic, and zinc (the mean values exceed the background values many times) on the first 5 km in the water flow direction. Also Ni, Mn, Na, Al, and Ba are present in high concentrations. The high concentrations of iron in the sterile dump reduce metal concentrations downstream, but these concentrations are high enough all around the closed mine, severely affecting human and environment health. In the stressed environment, near the mining area, plants are extremely rare, which may be related to the high levels of metals. Not only heavy metals and arsenic, but also low pH of the sterile dump severely affected the environment. Therefore, we have chosen wheat as a marker for heavy metal and arsenic toxicity in Tarnita area, but also we investigated some plant species in that area.
Among the hazardous elements found in Tarnita forest area, copper, Cu, is known to affect liver, kidneys, and eyes and to induce neurological disturbances in humans, whereas lead, Pb, is poisonous to the central and peripheral nervous system, circulatory and digestive systems, as well as to the kidneys. Iron, Fe, is harmful to heart and liver and causes siderosis, nickel, Ni, provokes allergic reactions, affects lung and kidney, and is carcinogenic, zinc, Zn, induces epigastric pains, affects the central nervous system, muscles and cardiovascular system, manganese, Mn, may provoke motor and mental disorders, and is involved in Parkinson pathology, whereas, arsenic, As, cardiac dysfunction and skin cancer. Moreover, these elements also affect the plant growing: Ni is about 8 times more toxic than Zn to plants, Cu is also highly toxic to plants, Pb manifests acute toxicity to plants, animals and microorganims, As        affects the plant growth, and Zn reduces the biological activity, in general.
Although the ecological rehabilitation works at Tarnicioara tailings pond are carried in extent of approximate 90%, as the authorities claim, we consider that heavy metals should be completely removed from the environment, since they cannot be degradated as organic compounds or natural ones. The stabilization and rehabilitation measures taken on Tarnita environment did not prevent the water pollution from this area, especially Brateasa River. Simply building the dams or close the pollutants in sterile dumps or tailing ponds does not solve the challenge. Hence, we tried water extraction, as nature make by rainfalls, precipitation with alkaline media, such as sodium hydroxide or more eco-friendly lime, followed by the electrolysis of the nitric acid solubilized precipitate and recovery and reuse the metals.
Besides, samples from 12 wild populations of Thymus pulegioides located along Bistrita River (Eastern Carpathian Mountains), an aromatic and medicinal plant, were collected. Then, a phytochemical analysis for various polyphenolics by chromatographic and spectrophotometric methods was performed. Also, a comparative GC-MS analysis of essential oils from one of the samples (Madei) with their mixture (collective drug). Chemical composition of the essential oils was established by gas chromatography coupled with mass spectrometry (GC/MS). The phenolic acid and flavonoid content of the Thymus pulegioides samples was estimated by means of a reverse phase HPLC-UV method. The interpopulational variability in respect to the level of essential oil was observed. A major quantity of carvacrol was marked out in one of the wild populations (Madei) as compared to the collective drug of all the samples combined. Supplementary the analysed wild populations were characterized by a relatively low amount of thymol, thus the plant material could be used in formulae for food supplements. Currently this plant is studied ȋn regarding the accumulation of heavy metals in the Tarniţa area.

 

Stage 4 - 2017

Establishment of a decontamination facility at the laboratory level and monitoring its effectiveness

Activity 4.1. Performing the decontamination facility in the laboratory
Activity 4.2. Technical feasibility studies for experimental development - Part 2
Activity 4.3. Participation at scientific meetings in specific project areas (international and national symposia)

Deliverables: submission of a scientific manuscript for publication and final report.

I. Summary of Stage 4.
All activities foreseen in the project for 2017 were totally fulfilled and even surpassed in many activities (for example on referring to results dissemination: three papers published, one accepted, and more others in evaluation).

Consideration has been given to find new possibilities of decontamination of forest areas with mining metallic waste from closed barite mines. In the previous year, a device for decontamination was carried out and used during this reporting period. It is based on extraction in distilled water or in other solutions such as that of magnesium sulfate, alkaline or acidic solutions, etc. under the action of ultrasounds of ions metallic, neutralizing with alkaline solutions when precipitation occurs in the form of water-insoluble hydroxides, centrifugation and measurement of residual metal concentration in supernatant. The precipitate is then redissolved in a solution of nitric acid, further used for metal recovery by electrolysis.

The results of the research made this year 2017 were partly presented orally at scientific events (2 papers at the ISI Conference, SGEM Albena 2017) and published in the conference proceedings . Other results have been published in an international journal with impact factor. Three further papers have been finalized and sent to publish impact, and are currently under evaluation.

Activity 4.1. Performing the laboratory decontamination device

The laboratory installation, which can also be done at the pilot scale, was used in the study decontaminating material from heavy metal waste and arsenic waste dumps (Fig. 1). The working scheme was presented in the previous report.

The laboratory facility, which can also be carried out at a pilot scale, was used in the decontamination of material from heavy metal and arsenic tailings dumps. This technology was schematically presented in the 2016 report (Stage III). It is proposed as a technical solution to solve the decontamination of the Tarniţa area in the Eastern Carpathians, affected by the high concentrations of heavy metals and metalloids from tailings dumps and settling basins. The laboratory decontamination plant involves the extraction in ultrasonic water of metal ions, neutralization with alkaline solutions when precipitating them in the form of water-insoluble hydroxides, centrifugation and measurement of the residual metal concentration of the supernatant. The precipitate is then redissolved in a solution of nitric acid and the obtained solution used for the recovery of metals. We used a simplified plant in which ultrasonic metal extraction takes place separately and supernatants are introduced onto the columns, the centrifugation being also performed separately.

Fig. 1. The part of the polymer-resin extraction of the tailings decontamination facility the dumps in Tarnita. A peristaltic pump purchased through this project sends the supernatant in the columns with ion-exchange resin, and the extract is collected and determined by AAS.

Besides, in the same period, several studies have been carried out on two representative species for this area: fir and beech, and the results were sent to be published in the international Journal of Forestry Research.

II.3. Activity 4.2. Technical feasibility studies for experimental development - Part 2

At the laboratory scale, the decontamination method described in the project was proven to be fully effective, as it results from the analysis of supernatants and solutions that have passed through the ion exchange columns. The heavy metal content was determined in each extract by ICP-OES and AAS. An assessment of Cu, Pb, Zn, Ba, Cr, Mn, Cd, Ni, Ag, As strongly contaminated soils has been performed. The high acidity of the samples (pH 2.04) was correlated with the availability of heavy metals and contamination of surrounding waters and soils by leaching. Although iron oxide fixed metals and they proved to have limited mobility, acidic soil conditions can cause them to move, thus increasing their availability.

Among the dangerous elements found in the Tarniţa forest area, Cu, is known to be toxic to the liver, kidneys and eyes. This element also induces neurological disorders in humans, while lead, Pb, is toxic to the central and peripheral nervous system, but also to circulatory and digestive systems, as well as to the kidneys. Iron, Fe, is harmful to the heart and liver and causes siderosis, whereas nickel, Ni, causes allergic reactions, affects the lungs and kidneys, being also a carcinogen; zinc, Zn, induces epigastric pain, affect the central nervous system, muscles and the cardiovascular system, while manganese, Mn, can cause motor and mental disorders, being involved in Parkinson's pathology. Arsenic, As, causes cardiac dysfunction and skin cancer. Moreover, these elements also affect plant growth: Ni is about 8 times more toxic than Zn on plants. Copper is also highly toxic to plants, Pb exhibits acute toxicity to plants, animals and microorganisms, and Zn reduces biological activity in general.

Although the ecological rehabilitation of Tărnicioara site is carried out in a proportion of about 90% as claimed by the authorities, we consider that the heavy metals should be completely eliminated from the environment, because they can not be degraded as the natural organic compounds. The stabilization and rehabilitation measures of the Tarniţa area did not prevent the pollution of the water in this area, especially the Brăteasa River. Simply building dams or closing pollutants in tailings dumps or tailings ponds does not solve the problem of pollution. Therefore, we attempted extraction of water as the nature of the cause precipitation, precipitation with alkali such as sodium hydroxide or lime environmentally friendly, followed by nitric acid electrolysis, and the precipitate solubilized with recovery and reuse of the metals. On the other hand, samples were taken from 12 wild populations of pulegioides Thymus (thyme, aromatic and medicinal plant) located along the river Bistrita (east of the Carpathians) were analyzed in the course of this year. Phytochemical analysis for various polyphenols was performed by chromatographic and spectrophotometric methods (PhD student Radu Necula, submitted papers). The chemical composition of the essential oils was determined by gas chromatography coupled to mass spectrometry (GC / MS). The content of phenolic and flavonoid acids in plant samples was estimated using a reverse-phase HPLC-UV method. Interpopulational variability in the level of essential oils has also been studied in collaboration with a medicinal plant research team (Stejarul Station, Piatra Neamt). At present, plants are being studied with regard to the accumulation of heavy metals in the Tarniţa area. Studies have been carried out on two representative species for this area: fir and beech.

III.1. Dissemination of the results

Activity 4.3. Participation at scientific meetings in specific project areas (international and national symposia) During the 4th Reporting Stage, 2017, two oral oral presentations were made at the 17th International Multidisciplinary Scientific GeoConference SGEM, Bulgaria, www.sgem.org. There were also some general aspects of pollution at the national forensics conference in Iasi (see list of papers).

All the scientific papers presented orally, published or in the course of evaluation included some of the results of the project and the mention of the project in the presentations, in the published papers or in the corresponding summaries as a source of funding by the Romanian Government and UEFISCDI Bucharest.

The students (master students and PhD students) have been requested to involve theirselves in the scientific research activity, where there are included as co-authors of the scientific papers. Some results will be presented at the Students Scientific Communications Session or at the conference ”Days of A. I Cuza University of Iasi”.

IV. Conclusions

Our field research work has identified sources of continuous pollution, which are the tailings dumps and accumulated lakes of metallic waste, and which should be immediately removed. Soil contamination, as well as the effects of pollutants on vegetation, have also been considered, but they can not lead to immediate practical results related to contamination. Although initially we considered that synthetic resins can be used to remove heavy metals, we later realized that they can be inactivated due to the large concentrations of such pollutants. In other words, the tailings dumps contain too much pirrite, calcopirrite and soluble iron, copper and arsenic ions that must be first precipitated and removed chemically. Chemical decontamination with alkaline solutions is required and only after the chemical treatment these ion exchange resins can be used. Measurements of metal ions concentrations performed using ICP-OES and AAS techniques have shown that water solubilization technology for metal ions and arsenic, followed by their precipitation with alkaline hydroxides and their removal by precipitation and filtration or centrifugation is feasible. The technical element that allowed removal of these metal ions only with distilled water is based on the fact that the pH of the tailings dumps is around 2. However, this treatment does not remove the entire mass of heavy metals but only the solubilized ones. It would be desirable, therefore, to physically remove the pyrite and chalcopyrite from the affected area. The results were published or sent for publication in specialized journals with impact factor or presented orally at international and national conferences.

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