Contamination and Phytoremediation of Arsenic and Other Heavy Metals and Evaluation of Different Drying Process to Determine

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HEAVY METALS IN SEDIMENTS AND REMEDIATION TECHNOLOGIES Contamination and Phytoremediation of Arsenic and Other Heavy Metals and Evaluation of Different Drying Process to Determine Metals in Plant Species Grown in a Mining Impacted Area

H.M. Anawar, M.C. Freitas, N. Canha

Instituto Tecnológico e Nuclear Reactor, Apartado 21, E.N. 10, 2686-953, Sacavém, Portugal, [email protected]

Abstract The magnitude of contamination and dispersion of arsenic (As), antimony (Sb) and other heavy metals in and around the Sao Domingos mining area, Portugal, a copper sulphide mine was assessed by analyzing soils, plants, lichen and moss samples using instru- mental neutron activation analysis (INAA) and µ-PIXE. Furthermore, different drying processes were evaluated to determine metals in plant samples. The concentrations of As and Sb ranged from 2098 to 9120 mg/kg and 388 to 1250 mg/kg for soils, 10.5 to 832.40 and 7.60 to 245.8 mg/kg for plants, 4.3 to 214.1 and 0.5 to 42.0 mg/kg for lichen and moss samples, respectively, and were much higher than the regional background levels. The highest levels were found in the samples collected close to ore processing sites and decreased with distance. Patterns of bioaccumulation of elements in plants throughout the study area were quite similar for widespread pollutants such as As, Sb, Zn, Fe, Br, Co, La, and Cr. Plant species, e.g. Erica andevaleris, Erica australis, Juncus acutus, Eucalyptus comaldulensis, Rumex santalus, Genista polyanthus and Daphnia gnidium with high biomass and exten- sive roots, grown abundantly in the area, maybe potential candidate for the phytostabiliza- tion of mining contaminated soils. In the quantitative analysis of metals and metalloids, freeze-dried and oven-dried plant samples show the higher concentrations when compared to that in ambient air-dried plant biomass. The freeze-drying process is comparatively reliable for determination of metals and metalloids concentrations in plant materials. Key words: Heavy metals, mining area, phytoremediation, drying process, plant samples

Introduction 2000). The plants growing on mine tailings Mining activities in the Sao Domingos have been found to accumulate toxic metals mine, one of the Portuguese massive sul- in their tissues, which could be biomagnified phide deposits, have produced thousands of in the ecological foodchain also. tons of mine waste. The mining district is The mine restoration could benefit located in the northern sector of the Iberian from plantation of different groups of plant Pyrite Belt (IPB), one of the largest metalloge- species. Therefore, selection of appropriate netic provinces of massive sulphides in the plant species which can establish, grow and world with original reserves over 1,700 Mt colonize metal-contaminated soils is impor- (Saez et al., 1999). The sulphide oxidation tant for successful reclamation of degraded processes at Sao Domingos inevitably pro- mine sites (Wong, 2003). Owing to these rea- duces acid mine drainage leachates rich in sons, it is important to make a detailed sulphates, iron and other heavy metals and screening of plant community in Sao Domin- metalloids which are an important source of gos mine in order to find out a group of plant pollution, and hence a threat to the ecologic species that can be revegetated for rehabilita- equilibrium (Abreu et al., 2008). Due to the tion of this sulphide mine. The first objective lack of regulations and environmental educa- of this work was the chemical and mineralog- tion, Sao Domingos is now a residential area ical characterization of mine tailings in Sao suffering from the considerable conse- Domingos in order to assess the adverse envi- quences of poorly regulated mining activities. ronmental impacts. The secondary aim of Phytoremediation is emerging as a new this study was to screen the plant communi- tool for soil remediation by the use of green ty and their potential for phytostabilisation of plants and their associated microbiota, soil mine tailings in Sao Domingos. amendments, and agronomic techniques to Drying treatment of fresh and wet plant remove, contain, or render harmless environ- samples is essential for the measurement of mental contaminants (Raskin and Ensley, metals and metalloids. There are different

15 th ICHMET 483 HEAVY METALS IN SEDIMENTS AND REMEDIATION TECHNOLOGIES of drying treatments, e.g., ambient air-drying shales), iron oxides, pyrite-rich waste dumps, (AAD), hot-air-drying (AD), freeze-drying industrial landfills and leaching tank refuses (FD), oven-drying (OD) and vacuum have degraded the Sao Domingos landscape microwave drying (VMD). The third objective and created the environmental problems of this study was to investigate the effect of within an area around 30 km 2. The acid mine freeze-drying process on the concentrations of drainage production contaminated the soils, metals and metalloids in plant biomass as and stream waters along several km stretch, compared to conventional ambient air-drying possibly affecting ground water and water and oven-drying processes. reservoirs in close vicinity. The total concentrations of heavy met- Materials and Methods als in the soil samples were very high and Soil samples were collected (0-15 cm within the same range as that given for con- depth) in a restricted circle about 60 cm taminated soils from the Spanish Pyrite Belt around the plant species and consisted of a studied by Anawar et al. (2006). Silver (Ag), homogeneous sample (around 4 kg) of four chromium (Cr), mercury (Hg), tin (Sn) and subsample points. After sampling, the soils iron (Fe) concentrations in most of the tailing were dried at room temperature, mixed, samples are higher than the concentrations in homogenized and sieved through a 2 mm control area and the maximum allowable screen. The eighty five plant, lichen and moss value for soils. In the contaminated soils of samples were collected from the different sites Sao Domingos As and Sb attained high con- of the mining affected area. The root, stems, centrations, exceeding 14 and 20 mg/kg, leaves and flowers of plant species were sepa- respectively, the maximum allowable value rated and freeze-dried, ground in Teflon (balls for soils. Arsenic and Sb concentrations and capsule) mills, thoroughly homogenized, ranged 529-6057 mg/kg and 203-2513 mg/kg, and made into 250-mg pellets for neutron respectively in Sao Domingos mine tailings. activation analysis, following the k0-stan- Mercury, in contaminated soils, presented dardized procedure. All elemental determina- concentration values from 2.68 to 38.74 tions of bulk soil and plant samples were car- mg/kg, being the majority above 10 mg/kg. ried out at the Portuguese Research Reactor of These concentrations exceeded the maxi- the Technological and Nuclear Institute (RPI- mum allowed value for soils according to the ITN, Sacavém; maximum nominal power: Portuguese legislation (1.0 mg/kg, Abreu et 1 MW), by k 0-INAA. al., 2008). Silver concentrations ranged from For the experiments to evaluate the dif- 5.99 to 48.61 mg/kg, being the majority above ferent drying processes, the leaves of plant 5 mg/kg exceeding the maximum allowed samples were divided into three parts. One value for soils (5.0 mg/kg, Abreu et al., 1998). portion of samples was processed for air-dry- The results of the metal accumulation ing, another for oven drying and the other for studies indicated wide variations from one freeze drying. The air drying of plant leaves plant species to another. Concentrations of was performed in summer time open air (May elements in the aerial tissues were below the 2009) at ambient temperature (av. 20 oC) toxicity levels referred by Kabata-Pendias and with 70% relative humidity (annual average). Pendias (2001) for most studied elements. The samples were fully air dried for about two However, some plant samples presented As, weeks. The plant leaves were air-dried like Sb, Se and Cr within the excessive or toxic above and subsequently oven-dried at 65 oC limits. The concentration of As accumulation for 4 days. Ground leaf samples were re-dried was found in the order of Erica andevalen- at 85 oC for > 24 h to remove any moisture sis>Erica australis, > Corrigiola telephypho- adsorbed by the sample during the grinding lia > Eritrae pulcheria > Echium plantagium process. For freeze drying, the plant leaves L. > Daphne gnidium, Rumex induratus, were fast frozen in a deep freezer and subse- Carlina corymbosa L., Ulex eriocladus L. quently freeze dried for two days in a laborato- Gramina, Genista hirsutus L., Lavandula ry freeze dryer. luisierra . The high levels of As, a severe con- taminant in Sao Domingos mining area were Results and Discussion found in the aerial parts of the plants indicat- The mining wastes including modern ing tolerance for this element. The aerial part slags, oxidized gossan wastes (gossan coarse of the plants contained between 4.35 and blocks, gossan brittle, gossanized volcanic), 89.45 mg As /kg, which are above the normal country rocks (host volcanics with shales, and range for plants (1-1.7 mg /kg), according to

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Kabata-Pendias and Pendias (2001). The plant species collected from the contaminat- concentration of Sb accumulation was ed mining area; and a few variations in this almost similar to the trend of As that was trend were also observed. Given the advan- found in the order of Erica tages, and disadvantage of the three drying andevalensis>Erica australis, > Corrigiola processes (AAD, FD and OD), the freeze- telephypholia > Echium plantagium L. > drying process is considered to be more con- Eritrae pulcheria > Daphne gnidium, trolled and reliable method for determina- Rumex induratus, Carlina corymbosa L., tion of metals and metalloids in plant mate- Ulex eriocladus L. Gramina, Genista hirsu- rials. tus L., Lavandula luisierra and the concentration of Cr accumulation was found in the Acknowledgements order of Echium plantagium > Lavandula This research work was supported by luisierra > Gramina > Carlina corymbosa > the Fundaçio para Ciencia e Tecnologia Cistus ladanifer > Erica andevalensis, Erica (FCT, Portugal) through research contract australis, Corrigiola telephypholia, Eritrae PTDC/AMB/65462/2006 - HYPERAS. pulcheria, Daphne gnidium, Rumex induratus, Ulex eriocladus, and Genista hirsutus. References Among all the plant samples, higher concen- Abreu MM, Tavares MT, Batista MJ. trations of all the metals were noted in Erica Potential use of Erica andevalensis and Erica andevalensis and Erica australis . australis in phytoremediation of sulphide Considering the size of Sao Domingos mine environments: Sao Domingos, Portu- area (30 km 2) affected by the old mining gal. J Geochem Explor 2008; 96:210-222. processes, the use of high cost remediation Anawar MH, Garcia-Sanchez A, Mur- technologies is not realistic. Therefore, the ciego A, Buyolo T. Exposure and bioavail- phytostabilisation technique, by using spe- ability of arsenic in contaminated soils from cific tolerant plants with or without the the La Parrilla mine, Spain. Environ Geol application of soil amendments, could be a 2006: 50:170-179. promising strategy for this abandoned min- Kabata-Pendias A, Pendias H. Trace ing area. The plant species Erica australis Elements in Soils and Plants (3rd ed.), CRC Lavandula luisierra, Daphne gnidium, Press, Boca Raton, FL, 2001. Rumex induratus, Ulex eriocladus, Juncus Raskin I, Ensley BD (Eds). Phytoreme- and Genista hirsutus may be of major impor- diation of toxic metals using plants to clean tance for the rehabilitation and recovery of the environment, John Wiley & Sons, New the sulphide mining areas. York, 2000. The concentrations of metals and met- Saez R, Pascual E, Toscano M, Almod- alloids in freeze-dried plant biomass showed ovar GR. The Iberian type of volcano-sedi- the highest values, and were relatively high- mentary massive sulphide deposits. Miner- er than those in ambient air-dried plant alium Deposita 1999; 34:549-570. materials, but almost similar with the con- Wong MH. Ecological restoration of centrations found in oven-dried plant sam- mine degraded soils, with emphasis on ples. This trend of metal and metalloid con- metal contaminated soils. Chemosphere centrations were generally found for all the 2003; 50:775-80.

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