Remediation of trace element-contaminated sites must consider both the nature of the contaminants and environmental surroundings. This thesis examined treatments for two contamination scenarios. The first study characterized chromium dynamics during the redox-sorption treatment of aqueous hexavalent chromium with the reducing agent sodium dithionite and two iron oxides. Results showed that chromium was successfully removed from solution by precipitation and sorption. The iron oxide derived from ferric chloride had a greater sorption capacity for hexavalent chromium than the oxide derived from ferrous chloride. The second study examined the phytoextraction treatment of soils contaminated with multiple trace elements. Deschampsia caespitosa plants had better early growth in the contaminated high-organic matter soil than three Brassica species. However, D. caespitosa plants did not take up sufficient amounts of trace elements during the study to be considered useful for short-term phytoextraction. These findings are applicable to the development of effective trace element remediation methods.

Per- and polyfluoroalkylated substances (PFASs) are a large group of organic chemicals that have gained an increased attention during recent years. Many of the compounds have shown to be persistent, toxic and bioaccumulating and they are found in water, soils, sediments, biota, animals and humans across the globe. The effects of PFASs to humans and animals are still being debated. It is suspected that the compounds can be carcinogenic, disrupt different hormone systems and have other severe effects. The main transport pathways of PFASs to soil are applied PFAS based firefighting foam, soil improvers and waste from industries producing PFASs or PFAS based products. Once the PFASs find their way to the soil the risk for leaching to drinking water supplies and aquatic ecosystems becomes some of the issues of great concern. In order to be able to evaluate the potential leakage of PFASs from different contaminated soils it is important to know how the PFASs interact with the soil matrix and what parameters that affects these interactions. The objective of this study was to investigate the influence of organic carbon (OC), Ca2+ ions and active carbon (AC) on the n of PFCAs and PFSAs to soil. The PFCAs examined were PFHxA, PFOA, PFNA, PFDA, PFUnDA, PFOcDA, PFHxDA and PFOcDA and the PFSAs examined were PFBS, PFHxS, PFOS and PFDS. Batch experiments were performed on soils with varying concentrations of TOC, Ca2+ and AC. The samples were spiked with PFAS native standard solution containing the 12 target PFASs. All studied parameters showed a positive influence on the sorption of PFASs to soil. The AC was found to have the highest influence on the sorption. The OC was however found to be the most important soil parameter influencing the sorption of PFASs to soil. In order to investigate the influence of aging on the sorption of PFASs, batch experiments were also conducted on soils from four different PFAS contaminated sites. The results showed that the aging positively influenced the strength of the interactions between PFASs and soil. The organic carbon normalized distribution coefficients (Koc) showed a positive correlation with the carbon chain length of the PFAS molecules and also with the substitution of a carboxylic group with a sulfonic group. The log Koc values calculated in this study decreased in the following order PFDS (log Koc3.8 0.3) > PFOS > (log Koc2.8 0.3) > PFUnDA (log Koc 3.2 0.2) > PFDA (log Koc2.7 0.1) > PFNA (log Koc2.0 0.1) > PFHxS (log Koc1.9 0.1) > PFOA (log Koc1.8 0.3) > PFHxA (log Koc1.6 0.3) > PFBS (log Koc 1.5 0.2). The log Koc values found in this study were within the range of previously reported log Kocvalues.

Remediation of trace element-contaminated sites must consider both the nature of the contaminants and environmental surroundings. This thesis examined treatments for two contamination scenarios. The first study characterized chromium dynamics during the redox-sorption treatment of aqueous hexavalent chromium with the reducing agent sodium dithionite and two iron oxides. Results showed that chromium was successfully removed from solution by precipitation and sorption. The iron oxide derived from ferric chloride had a greater sorption capacity for hexavalent chromium than the oxide derived from ferrous chloride. The second study examined the phytoextraction treatment of soils contaminated with multiple trace elements. Deschampsia caespitosa plants had better early growth in the contaminated high-organic matter soil than three Brassica species. However, D. caespitosa plants did not take up sufficient amounts of trace elements during the study to be considered useful for short-term phytoextraction. These findings are applicable to the development of effective trace element remediation methods.

Fertilizer phosphorus (P) can become unavailable to crops due to immobilization of P in acidic soils through forming chemical bonds with iron (Fe) and aluminum (Al) amorphous oxides.  Organic chelating agents form strong bonds with metals in soil and may reduce P binding with Fe and Al.  Ethylenediamine tetraacetic acid (EDTA), hydroxyethyl ethylenediamine triacetic acid (HEEDTA), gluconic acid (GA), and citric acid (CA) were tested to determine their influence on water-soluble P (WSP), Mehlich-1 P and Mehlich-3 P in Loam and Sand soils fertilized with P and incubated for 49 days.  Soil P sorption capacity (PSC) was estimated from an oxalate extraction of Fe and Al, and chelates were applied at rates of 90 percent of the PSC.  The EDTA, HEEDTA, and CA significantly (P<0.05) reduced P sorption in the Loam and Sand when measured by WSP.  In soils without P fertilizer added, EDTA and HEEDTA significantly increased WSP, Mehlich-1, and Mehlich-3 P concentrations.  EDTA and HEEDTA were also applied at 0, 30, 60, 90, 120, and 150 percent PSC to produce a rate response curve for WSP in a second soil incubation.  With increasing chelating rate, there was a linear increase in WSP for both soils, thus indicating higher rates of chelating agents were most efficient at decreasing P sorption. EDTA and HEEDTA were also tested in a 4-week greenhouse study for efficiency at increasing plant available P to corn (Zea mays L.) in two soils.  Phosphorus was added with and without the addition of chelating agents to the center of the pot, simulating a starter band of P.  After 4weeks, soils were analyzed for WSP, Mehlich-1, and Mehlich-3 P and corn above- and below-ground biomass was quantified and analyzed for total P concentration.  Without the presence of chelating agents, concentrations of WSP, Mehlich-1 P, Mehlich-3 P, above- and below-ground biomass, and TKP increased linearly as P fertilizer rates increased at 0, 9.6, 19.3, 28.9, and 38.5 kg P ha-1.  Decreased P sorption using chelating agents was not observed in this experiment.  However, with the results from the soil incubation, chelating agents do show potential for increasing plant available P, but the application and incorporation method needs to be further studied. / Master of Science

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

Zugl.: Stuttgart, Univ., Diss., 2008.

Zugl.: Osnabrück, Univ., Diss., 2008

Thesis (Doctoral)--Chalmers tekniska högskola and Göteborgs universitet, Göteborg, Sweden, 1983.

Techn. Hochsch., Diss., 2005--Aachen.

O nitrato (NO3-) é um íon inorgânico que está presente naturalmente no meio ambiente, sendo a forma mais estável do nitrogênio oxidado. Devido a sua alta solubilidade em água, é possivelmente o contaminante das águas subterrâneas mais difundido no mundo, causando problemas de produção de água potável e distúrbios ecológicos. Neste contexto, o objetivo deste estudo consiste em investigar a capacidade de sorção do carvão granular comercial ativado, modificado quimicamente com CaCl2, para remoção de nitrato em soluções aquosas e avaliar a capacidade de regeneração do sorvente em diferentes condições. Com esta finalidade foram realizados ensaios de sorção e de dessorção predeterminando as melhores condições de processo: pH, tempo de residência e concentração de sólido sorvente. Ainda, isotermas de equilíbrio para este sistema foram construídas. Na dessorção do carvão ativado saturado com nitrato foram empregadas soluções de HCl, C6H8O7, NaOH, CaCl2 e H2O. Os ensaios de sorção resultaram nos parâmetros ótimos do processo de sorção: pH 6,0, tempo de 30min e concentração de sorvente igual a 20 g.L-1, utilizando soluções de nitrato com concentração inicial de 20 mg.L-1. Para regeneração, o tempo de residência aplicado foi de 30 min, e foram utilizados 400 mL de solução CaCl2 (2000 mg.L-1). Nestas condições, foi possível realizar vinte ciclos de sorção/regeneração (S/R), obtendo-se 54% de remoção de nitrato ao final destes ciclos. Durante a regeneração foi monitorada a concentração de Ca2+ na solução de CaCl2, objetivando manter a sua concentração inicial. Após 20 ciclos (S/R), o sorvente foi regenerado com 50 mL de solução de HCl 100 mg.L-1 e, em outra batelada, 50 mL de H2O 60ºC. Foram realizados mais 20 ciclos S/R para o sorvente regenerado com HCl e 20 ciclos S/R para o sorvente regenerado com H2O (60ºC). Índices médios de 58% de remoção de nitrato foram alcançados para ambos os processos ao final dos 20 ciclos (S/R). Foram realizados um total de 60 ciclos (S/R) com remoção média de 55% ao final do último ciclo. O modelo de isoterma de sorção que melhor se ajustou os dados experimentais foi o modelo de Langmuir, que forneceu a constante de energia ou afinidade do processo e também a acumulação máxima de nitrato no sorvente. / Nitrate (NO-3) is an inorganic ion which is present naturally in the environment, being the most stable form of oxidized nitrogen. Due to its high solubility in water, it is possibly the groundwater contaminant more widespread in the world, causing problems in the production of drinking water and ecological disturbances. In this context, the objective of this study is to investigate the sorption capacity of the commercial granular activated carbon, chemically modified with CaCl2 to remove nitrate from aqueous solutions and to study the regeneration capacity of the sorbent under different conditions. For this purpose tests of sorption and desorption were carried out, determining the optimal process conditions: pH, residence time and concentration of solid sorbent. Further, equilibrium isotherms for this system were built. In the desorption process of activated carbon saturated with nitrate, water (60°C) and aqueous solutions of HCl, C6H8O7, NaOH, CaCl2 were employed. The best sorption conditions found in the experiments were as follow: pH 6.0, time 30 min and concentration of sorbent 20 g.L-1, using nitrate solutions with initial concentration of 20 mg.L-1. For regeneration tests, the residence time was set as 30 min, using 400 mL of CaCl2 2000 mg.L-1 to keep Ca2+ in solution. Therefore, it was possible to perform twenty cycles of sorption/regeneration (S/R), yielding 54% nitrate removal at the end of these cycles. During regeneration, the concentration of Ca2+ in the CaCl2 solution was monitored. After 20 S/R cycles, the sorbent was regenerated with 50 mL of HCl solution (100 mg.L-1) or 50 mL of H2O at 60°C. Additionally, more 20 cycles (S/R) were performed for the regenerated sorbent with HCl solution or H2O (60°C). Maximum removal values of nitrate (58%) were achieved in both cases at the end of each 20 cycles (S/R). A total of 60 cycles (S/R) were performed, achieving nitrate removal of 55% at the end of the last cycle. The Langmuir sorption isotherm type was found to be the best fit to experimental data, providing the energy constant or affinity of the process and also the maximum accumulation of nitrate in the sorbent.