| 1. |
- Sandhi, Arifin, 1986-
(författare)
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ARSENIC REMOVAL BY PHYTOFILTRATION AND SILICON TREATMENT : A POTENTIAL SOLUTION FOR LOWERING ARSENIC CONCENTRATIONS IN FOOD CROPS
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Use of arsenic-rich groundwater for crop irrigation can increase the arsenic (As) content in food crops and act as a carcinogen, compromising human health. Using aquatic plant based phytofiltration is a potential eco-technique for removing arsenic from water. The aquatic moss species Warnstorfia fluitans grows naturally in mining areas in northern Sweden, where high concentrations of arsenic occur in lakes and rivers. This species was selected as a model for field, climate chamber and greenhouse studies on factors governing arsenic removal and arsenic phytofiltration of irrigation water. The arsenic and silicon (Si) concentrations in soil, water and plant samples were measured by AAS (atomic absorption spectrophotometry), while arsenite and arsenate species were determined using AAS combined with high pressure liquid chromatography (HPLC) with an anion exchange column. The arsenic content in grains of hybrid and local aromatic rice (Oryza sativa) cultivars with differing arsenic accumulation factor (AF) values was investigated in an arsenic hotspot in Bangladesh. The results showed that arsenic AF was important in identifying arsenic-safer rice cultivars for growing in an arsenic hotspot. The study based on silicon effect on arsenic uptake in lettuce showed that arsenic accumulation in lettuce (Lactuca sativa) could be reduced by silicon addition. The aquatic moss had good phytofiltration capacity, with fast arsenic removal of up to 82% from a medium with low arsenic concentration (1 µM). Extraction analysis showed that inorganic arsenic species were firmly bound inside moss tissue. Absorption of arsenic was relatively higher than adsorption in the moss. Regarding effects of different abiotic factors, plants were stressed at low pH (pH 2.5) and arsenic removal rate was lower from the medium, while arsenic efflux occurred in arsenate-treated medium at low (12°C) and high (30°C) temperature regimes. Besides these factors, low oxygenation increased the efficiency of arsenic removal from the medium. Finally, combining W. fluitans as a phytofilter with a lettuce crop on a constructed wetland significantly reduced the arsenic content in edible parts (leaves) of lettuce. Thus W. fluitans has great potential for use as an arsenic phytofilter in temperate regions.
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| 2. |
- Bergqvist, Claes, 1977-
(författare)
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Arsenic accumulation in plants for food and phytoremediation : Influence by external factors
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Arsenic (As) appears in the environment as various As species, which may vary in plant uptake and toxicity. Moreover, As exposure may vary between habitat due to availability and speciation, both of which are influenced by redox potential. To decrease As uptake, addition of silicate may be a tool.The aim of the study was to investigate how the external factors As availability, plant habitats, silicon and oxygen level, influenced the accumulation and speciation of As in plants for food and phytoremediation in a temperate region. The external factors were chosen due to their previously showed influence on As in plants.The risks with dietary As was investigated by plant As accumulation and speciation in carrot, lettuce and spinach grown in alum shale and glassworks soils, and by the influence of silicon on As accumulation in lettuce in hydroponics. Suitable plants for As phytoremediation was investigated by analysing plants from various habitats, and by the O2 influence on phytofiltration.The results showed that vegetables accumulated more As in soils with higher As extractability, and the As extractability in the rhizosphere was higher than in bulk soil. Also, the As concentration in lettuce was higher in hydroponics than in soil, but silicon reduced the accumulation of As in lettuce in hydroponics. Also, the more toxic inorganic As were the main As species detected in vegetables, compared with the less toxic organic As. For phytoremediation, the results showed a low As accumulation in emergent and terrestrial plants. Submerged plants had had a higher shoot As concentration. In general, the habitat had a major influence on the As accumulation in plants. The results also showed that the As accumulation properties in Elodea canadensis was reduced at higher O2.In conclusion, consumption of vegetables cultivated in As polluted soils can result in an elevated intake of inorganic As, and E. canadensis is a promising candidate for As phytofiltration in a temperate region.
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| 3. |
- Neuschütz, Clara, 1973-
(författare)
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Phytostabilization of mine tailings covered with fly ash and sewage sludge
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Establishing plant communities is essential for the restoration of contaminated land. As potential cover materials, fly ash and sewage sludge can prevent formation of acid mine drainage from sulfidic mine waste. The aim of the thesis was to i) screen for plants that can be established in, and prevent leakage of metals and nutrients from sludge on top of ash and tailings, and ii) investigate root growth into sealing layers of ash and sludge. Analyses were performed under laboratory, greenhouse and field conditions using selected plant species to examine the release of Cd, Cu, Zn, N, and P from the materials. Plant physiological responses and interactions with fly ash were also investigated. The data show that plants can decrease metal and nutrient leakage from the materials, and lower the elemental levels in the leachate, but with varying efficiencies among plant species. Plants capable of taking up both nitrate and ammonium were more efficient in preventing N leakage compared with those taking up primarily ammonium. Fast growing plants could raise the pH in acidic sludge leachate, but the initial pH decrease and N leakage was not counteracted by plants. Germination in fresh sludge was problematic, but enhanced by aeration of the sludge. In general, the accumulation of metals in plant shoots was low, especially if ash was located below the sludge. Fresh ash was phytotoxic (e.g., high alkalinity, salinity and metal levels) and induced the activity of stress-related enzymes in shoots. In sealing layers of aged and cured ash, roots could grow if the penetration resistance was low, or into the surface of stronger layers if the surface had become pulverized. The roots caused dissolution of calcium-rich minerals, possibly by exudation of saccharides. Addition of sludge to an ash layer increased root growth, likely due to decreased bulk density and pH, and nutrient addition. In conclusion, with selected plant species and a properly constructed cover, metal and nutrient leaching from the materials and root growth into the sealing layer can be restricted.
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| 4. |
- Schück, Maria, 1986-
(författare)
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Floating treatment wetlands for stormwater management : Plant species selection and influence of external factors for heavy metal and chloride removal in a cold climate
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Stormwater, which consists of rainwater and snowmelt, often contains pollutants from vehicle traffic, building materials, and industries. These pollutants include chloride and heavy metals, which can cause several environmental issues, such as being toxic to biota at elevated concentrations. A relatively new water treatment method is floating treatment wetlands. These vegetated rafts have given promising results, mainly for nutrient removal in eutrophic watercourses in warmer climates. However, knowledge is lacking about their ability to remove chloride and heavy metals and their performance in a cold climate.The aim was to identify plant species, intended for floating treatment wetlands, which efficiently can remove chloride and the heavy metals Cd, Cu, Pb, and Zn from water in a cold climate such as Sweden and to understand how changes in the environment affect the removal capacity of the plants. This was studied in various conditions by placing plants in water that contained chloride and heavy metals and measuring the concentration of chloride and heavy metals that remained in the water (plant removal capacity; I, III, IV) and the accumulation of removed chloride and heavy metals in the different plant parts (plant accumulation capacity; III, V, VI). In addition, traits of plants capable of high removal and accumulation were identified by correlating their capacity with their morphological characteristics (II, III, VI).The results show that there are Swedish wetland plant species with a high ability to treat water containing chloride and heavy metals, even under varying conditions. Many species effectively reduced the levels of heavy metals in water, and the graminoid species Carex pseudocyperus and Carex riparia distinguished themselves by quickly and significantly decreasing the concentrations of heavy metals in the water (I). Hardly any species were effective chloride removers, but a few, including Phalaris arundinacea, removed large amounts of chloride (III). Species with a high removal and accumulation capacity of chloride and heavy metals generally had high total biomass, a large amount of leaf and thin root biomass, and high transpiration (II, III, VI). The absorbed heavy metals mainly accumulated in the roots, while chloride accumulated in the shoot tissue (III, V, VI). External factors affected the removal and accumulation capacities of the plants to varying degrees. Increased salinity in the water led to lower removal of Cd and Pb, and low temperature decreased the removal of all investigated heavy metals, but some species’ removal capacities were less affected by the salt and the cold (IV). The plant's content of the heavy metals usually equilibrated with the surrounding water. This effect led to increases in the plant's uptake of heavy metals when their concentration in the water increased, but a release of some accumulated heavy metals if the concentration in the water sank (V). Under field conditions, uptake patterns differed (VI). The plants on floating treatment wetlands accumulated the most Cu followed by Zn, Pb, and Cd, and P. arundinacea distinguished itself through high growth and high uptake. The plants accumulated more in one of the stormwater ponds with no clear explanation. This thesis shows that there is potential in a Swedish climate for floating treatment wetlands for the removal of chloride and heavy metals from polluted water. It will be essential to select species expected to achieve high removal capacity in the intended environment, such as P. arundinacea.
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| 5. |
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| 6. |
- Göthberg, Agneta, 1946-
(författare)
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Metal fate and sensitivity in the aquatic tropical vegetable Ipomoea aquatica
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aquatic plant Ipomoea aquatica is a popular vegetable in Southeast Asia, often cultivated in nutrient rich and polluted waters. The overall aim of this thesis was to estimate potential risks for human health and reduced plant growth due to accumulation and toxicity of total-Hg, methyl-Hg, Cd and Pb.In plants from cultivations in Thailand, the concentrations of Cd and Pb in the shoots were well beneath recommended maximum values for human consumption, but at some sites the Hg concentrations were high. It was demonstrated that I. aquatica has the capacity to accumulate much higher Cd and Pb concentrations in the shoots than found in field-cultivations, before exhibiting toxic symptoms. The Hg concentrations, however, occasionally reached levels that are toxic for the plant. Up to11% of total-Hg was methyl-Hg, the most toxic Hg species, though at one site it was 50-100%. To study if methyl-Hg is formed in I. aquatica, plants were exposed to inorganic Hg through the roots. Of the Hg that reached the young, metabolically active parts of the shoots, a part was transformed to methyl-Hg. A major proportion of absorbed metals was retained in the roots, which had a high tolerance for high internal metal concentrations. The nutrient level did influence accumulation and effects of Hg, Cd and Pb in I. aquatica. Low external nutrient levels resulted in increased metal accumulation in the shoots and in metal-induced toxic effects in the plant at low external metal levels. A generous supply of sulphur or nitrogen induced formation of thiol-rich peptides in I. aquatica, compounds that have a metal detoxifying effect in plants. To conclude, the levels of Cd and Pb in field cultivated I. aquatica do not pose any apparent threat to human health or risk for reduced plant growth. The levels of Hg however, were high at some sites and could be a health threat, for children and foetuses in particular, and especially considering the presence of methyl-Hg. The use of fertilizers is favourable as it reduces the risk for increased metal concentrations in I. aquatica and for reduced crop yields.
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| 7. |
- Javed, Muhammad Tariq, 1983-
(författare)
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Mechanisms behind pH changes by plant roots and shoots caused by elevated concentration of toxic elements
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Toxic elements are present in polluted water from mines, industrial outlets, storm water etc. Wetland plants take up toxic elements and increase the pH of the medium. In this thesis was investigated how the shoots of submerged plants and roots of emergent plants affected the pH of the surrounding water in the presence of free toxic ions. The aim was to clarify the mechanisms by which these plants change the surrounding water pH in the presence of toxic ions. The influence of Elodea canadensis shoots on the pH of the surrounding water was studied in the presence of cadmium (Cd) at low initial pH (4-5). The involvement of photosynthetic activity in the pH changes was investigated in the presence and absence of Cd. The cytosolic, vacuolar and apoplasmic pH changes as well as cytosolic Cd changes in E. canadensis were monitored. The influence of Eriophorum angustifolium roots on the pH of the surrounding water was investigated in the presence of a combination of Cd, copper, lead, zinc and arsenic at low initial pH (3.5). Eriophorum angustifolium root exudates were analyzed for organic acids. Elodea canadensis shoots increased the pH of the surrounding water, an effect more pronounced with increasing Cd levels and/or increasing plant biomass and increased plant Cd uptake. The pH increase in the presence of free Cd ions was not due to photosynthesis or proton uptake across the plasmalemma or tonoplast. Cadmium was initially sequestered in the apoplasm of E. canadensis and caused its acidosis. Eriophorum angustifolium roots increased the surrounding water pH and this effect was enhanced in the presence of arsenic and metals. This pH increase was found to depend partly on the release of oxalic acid, formic acid and succinic acid by the plants. In conclusion, E. canadensis shoots and E. angustifolium roots were found to increase the low initial pH of the surrounding water. The pH modulation by these species was enhanced by low levels of free toxic ions in the surrounding water.
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| 8. |
- Schück, Maria, 1986-
(författare)
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Heavy metal removal by floating treatment wetlands: Plant selection
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Elevated levels of heavy metals and chloride are commonly found in stormwater, as a consequence of pollution from traffic, building material and industries, and the use of salt for deicing in wintertime. Floating treatment wetlands (FTWs), consisting of vegetated rafts that can be placed in stormwater ponds, may be able to reduce heavy metal and chloride concentrations, but until this date have mainly been used for nutrient removal in warm climates. Plants are essential in FTWs as pollutants are taken up into plant tissues, adsorbed to exposed plant surfaces, precipitated due to chemical interactions with root exudates or bound to plant litter.The aim of the study was to examine: A) which plant species that should be used on FTWs in a cool climate for efficient heavy metal and chloride removal, and B) to identify plant traits that are connected to high pollutant removal capacity as a help for identification of additional suitable species.Thirty-four wetland plant species, all growing in wild in Sweden, were used in the study. These were all grown hydroponically for 5 days in a solution containing 1.2 µg Cd L–1, 68.5 µg Cu L–1 ¸ 78.4 µg Pb L–1, 559 µg Zn L–1 and 55.4 mg Cl L-1. Carex pseudocyperus and Carex riparia were found to quickly reduce the concentration of all added heavy metals, and keep the concentration low for the remainder of the exposure period. In addition, nine species were able to remove all metals except cadmium quickly. High removal capacity of metals was found to be connected to biomass traits, mainly large fine root and leaf biomass, and to transpiration, which is correlated with to leaf biomass. Twenty-three of the tested species have also been evaluated for their chloride uptake, and Phalaris arundinacea and Glyceria maxima were identified as the species with highest chloride removal capacity. Preliminary analysis show that the correlation between biomass and chloride removal capacity is weaker than for heavy metals.In conclusion, the removal capacity of heavy metals and chloride differs between plant species, which can be explained by differences in the traits of the plants. The findings indicate that removal of both heavy metals and chloride can be achieved by FTWs in cold climates using a combination of native plants.
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| 9. |
- Finnveden, Göran, et al.
(författare)
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Policy Instruments towards a sustainable waste management
- 2016
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Ingår i: Solid waste management: Policy and planning for a sustainable society. - : Apple Academic Press. - 9781771883740 - 9780429091650 ; , s. 185-246, s. 185-246
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 10. |
- Nyquist, Johanna, 1976-
(författare)
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Role of plants in treating metal-polluted waters in wetlands
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim of this thesis was to evaluate the role of wetland plants in wetland treatment of metal-polluted waters. The specific aims were to investigate metal uptake in various wetland plant species; whether and how wetland plants tolerate high metal concentrations in their immediate surroundings, and how the pH and metal concentrations of polluted waters influence metal uptake in wetland plants were also investigated. Acid mine drainage with low pH (3.5) and high metal concentrations, and stormwater with a near neutral pH and lower metal concentrations were the two waters treated. The submerged plant species Elodea canadensis and Sparganium hyperboreum, the floating-leaved plant species Potamogeton natans, and the emergent plant species Carex rostrata, Eriophorum angustifolium, and Phragmites australis were exposed to concentrations of cadmium (Cd), copper (Cu), iron (Fe), lead (Pb), and zinc (Zn) naturally found in these waters. Low pH and high metal concentrations in the polluted waters were demonstrated to have a decreased effect on the treatment efficiency. The presence of submerged and floating-leaved plant species increased the treatment efficiency of a wetland by taking up dissolved metals, while metal uptake by emergent plant species was minor. The wetland plant species displayed only few signs of stress when exposed to Zn, Cu, and Cd. Thiol-rich peptides, increased cell wall binding, and rising pH in the medium are possible mechanisms whereby Cd is detoxified in the plant tissue.The overall conclusion was that using wetlands to treat polluted waters is possible, although treatment efficiency is influenced by the pH and metal concentrations in the polluted water. The role of plants was dependent on the character of the waste water and on the specific plant species used. Wetland plants tolerate metal concentrations in their tissues by activating internal mechanisms that detoxify the metals.
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